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Djientcheu DFY, Azabji-Kenfack M, Kameni PM, Bilanda DC, Femoe MU, Ngoungoure MC, Kamtchouing P, Dzeufiet DPD. Analysis of Sinus Variability in a Group of Cameroonian Athletes. JOURNAL OF SPORTS MEDICINE (HINDAWI PUBLISHING CORPORATION) 2024; 2024:1752677. [PMID: 38572353 PMCID: PMC10987244 DOI: 10.1155/2024/1752677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 02/24/2024] [Accepted: 02/26/2024] [Indexed: 04/05/2024]
Abstract
Background Heart rate variability (HRV) analysis is a useful method for assessing the heart's ability to adapt to endogenous and exogenous loads. Data from African population on HRV are scarce and even more so in sports populations. This study aimed to compare cardiac autonomic modulation response in Cameroonian athletes and sedentary. Methodology. We conducted a prospective and analytical study in sports teams in the city of Yaoundé, Cameroon. The participants in our study were divided in three groups; people who practiced little or no sporting activity (sedentary as group 1) or who were regularly physically active as part of a sports team (footballers or handballers as second and third groups). They had to be aged 18 or over and have given their informed consent. Heart rate (HR) was continuously recorded at rest for ten minutes and then transferred to a computer equipped with Kubios HRV Standard software for analysis. Means ± mean standard errors were compared using the one-way ANOVA test, followed by Tukey's post-test. The significance threshold was set at 0.05. Results Of the 60 people selected to participate to our study, 75.0% were sportsmen (40.0% handball players and 35.0% footballers). The resting HR of sedentary people was higher (p < 0.001) than that of footballers and handball players. The SDNN, RMSSD, and pNN50 of sedentary people (16.22 ± 1.04; 9.97 ± 0.46; and 0.16 ± 0.06) were lower than those of footballers (30.13 ± 2.93; 20.61 ± 2.46; and 2.99 ± 0.63, with p < 0.001) and handball players (29.00 ± 1.86; 16.44 ± 1.16; and 2.15 ± 0.38, with p < 0.001 and p < 0.05 respectively). Absolute and relative very-low-frequency (VLF) power, absolute low and high-frequency (LF and HF) power, as well as total power (TP) were lower in sedentary people (3.66 ± 0.08 and 16.21 ± 0.64; 5.04 ± 0.15 and 2.50 ± 0.16 and 246.40 ± 18.04) compared to footballers (5.09 ± 0.24 and 26.87 ± 1.76; 5.85 ± 0.32 and 3.92 ± 0.22 and 836.10 ± 103.70, with p < 0.001, p < 0.01, and p < 0.001) and handball players (4.86 ± 0.16 and 30.82 ± 2.67; 6.03 ± 0.19 and 3.46 ± 0.16 and 927.30 ± 94.12, with p < 0.001, p < 0.05, p < 0.01, and p < 0.001). The LF/HF ratio was 12.1% and 20.1% lower in sedentary people (7.55 ± 0.58) compared with footballers (8.46 ± 0.50) and handball players (9.07 ± 0.60), respectively. Conclusion Sportsmen showed greater parasympathetic and global modulation when compared to sedentary people.
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Affiliation(s)
- Deugoue F. Y. Djientcheu
- Laboratory of Animal Physiology, Faculty of Sciences, University of Yaoundé I, Yaoundé, Cameroon
- Laboratory of Physiology, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon
| | - M. Azabji-Kenfack
- Laboratory of Physiology, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon
| | - Poumeni M. Kameni
- Laboratory of Animal Physiology, Faculty of Sciences, University of Yaoundé I, Yaoundé, Cameroon
| | - D. C. Bilanda
- Laboratory of Animal Physiology, Faculty of Sciences, University of Yaoundé I, Yaoundé, Cameroon
| | - Membe U. Femoe
- Laboratory of Animal Physiology, Faculty of Sciences, University of Yaoundé I, Yaoundé, Cameroon
| | - M. C. Ngoungoure
- Laboratory of Animal Physiology, Faculty of Sciences, University of Yaoundé I, Yaoundé, Cameroon
| | - P. Kamtchouing
- Laboratory of Animal Physiology, Faculty of Sciences, University of Yaoundé I, Yaoundé, Cameroon
| | - Djomeni P. D. Dzeufiet
- Laboratory of Animal Physiology, Faculty of Sciences, University of Yaoundé I, Yaoundé, Cameroon
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Sadeghian F, Divsalar DN, Fadil R, Tavakolian K, Blaber AP. Canadian aging and inactivity study: Spaceflight-inspired exercises during head-down tilt bedrest blunted reductions in muscle-pump but not cardiac baroreflex in older persons. Front Physiol 2022; 13:943630. [PMID: 36213230 PMCID: PMC9532525 DOI: 10.3389/fphys.2022.943630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 08/18/2022] [Indexed: 11/13/2022] Open
Abstract
As part of the first Canadian aging and inactivity study (CAIS) we assessed the efficacy of space-based exercise countermeasures for maintenance of cardiac and muscle-pump baroreflex in older persons during bedrest. An initiative of the Canadian Space Agency, Canadian Institutes of Health Research and the Canadian Frailty Network, CAIS involved 14 days of 6-degree head-down tilt bedrest (HDBR) with (Exercise) or without (Control) combined upper and lower body strength, aerobic, and high-intensity interval training exercise countermeasures. Twenty healthy men and women aged 55 to 65, randomly divided into control and exercise groups (male control (MC, n = 5), male exercise (ME, n = 5), female control (FC, n = 6), female exercise (FE, n = 4)) (age: 58.7 ± 0.5 years, height: 1.67 ± 0.02 m, body mass: 70.2 ± 3.2 kg; mean ± SEM), completed the study. Cardiac and muscle-pump baroreflex activity were assessed with supine-to-stand tests. Wavelet transform coherence was used to characterise cardiac and muscle-pump baroreflex fraction time active (FTA) and gain values, and convergent cross-mapping was used to investigate causal directionality between blood pressure (BP) and heart rate, as well as BP and lower leg muscle electromyography (EMG). Seven of the twenty participants were unable to stand for 6 minutes after HDBR, with six of those being female. Our findings showed that 2 weeks of bedrest impaired skeletal muscle’s ability to return blood to the venous circulation differently across various sexes and intervention groups. Comparing values after bed rest with before bed rest values, there was a significant increase in heart rates (∆ of +25%; +17% in MC to +33% in FC; p < 0.0001), beat-to-beat EMG decreased (∆ of −43%; −25% in ME to −58% in MC; p < 0.02), while BP change was dependent on sex and intervention groups. Unlike their male counterparts, in terms of muscle-pump baroreflex, female participants had considerably decreased FTA after HDBR (p < 0.01). All groups except female control demonstrated parallel decreases in cardiac active gain and causality, while the FC demonstrated an increase in cardiac causality despite a similar decline in cardiac active gain. Results showed that the proposed exercises may alleviate muscle-pump baroreflex declines but could not influence the cardiac baroreflex decline from 14 days of inactivity in older adults.
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Affiliation(s)
- Farshid Sadeghian
- Department of Biomedical Physiology and Kinesiology, Aerospace Physiology Laboratory, Simon Fraser University, Burnaby, Canada
| | - Donya Naz Divsalar
- Department of Biomedical Physiology and Kinesiology, Aerospace Physiology Laboratory, Simon Fraser University, Burnaby, Canada
| | - Rabie Fadil
- Biomedical Engineering Program, University of North Dakota, Grand Forks, ND, United States
| | - Kouhyar Tavakolian
- Biomedical Engineering Program, University of North Dakota, Grand Forks, ND, United States
| | - Andrew P. Blaber
- Department of Biomedical Physiology and Kinesiology, Aerospace Physiology Laboratory, Simon Fraser University, Burnaby, Canada
- Biomedical Engineering Program, University of North Dakota, Grand Forks, ND, United States
- *Correspondence: Andrew P. Blaber,
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Mollura M, Salerni C, Lehman LW, Barbieri R. Characterization of Physiologic Patients' Response to Fluid Interventions in the Intensive Care Unit. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2022; 2022:1402-1405. [PMID: 36086234 DOI: 10.1109/embc48229.2022.9871512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Fluid administration is one of the most common therapies performed on intensive care patients. However, no clinical evidence is available to establish optimal strategies for fluid management as well as characterizing the effects on the cardiovascular system after therapy initiation. Moreover, fluid overload showed a correlation with worse clinical outcomes. This study aims at characterizing the response to the fluid intervention of intensive care unit patients. We extracted a population of 57 subjects with available electrocardiogram and arterial blood pressure recordings from the MIMIC-III database and evaluated the induced changes in cardiovascular and autonomic indices. We compare autonomic indices obtained from a statistical model of heartbeat dynamics before and after the intervention. Results show significant differences in RR interval, blood pressure, autonomic and Baroreflex activities up to 60 minutes after fluid administration. Specifically, we observed a median increase in RR interval, Baroreflex activity, and overall activity both in pressure and RR time series, as well as a reduction in systolic blood pressure. Specifically, a subgroup of survived patients shows an imbalance toward sympathetic activity, whereas non-survivors have a persistent vagal state after fluid administration. Clinical relevance - The observed differences in autonomic response after fluid administration, together with the assessment of their correlation with patients' mortality, paves the way for the inclusion of heart rate variability indices as markers for assessing fluid responsiveness as associated with ICU patients' state.
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Sedentary behavior is associated with reduced cardiovagal baroreflex sensitivity in healthy adults. Hypertens Res 2022; 45:1193-1202. [DOI: 10.1038/s41440-022-00904-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 01/24/2022] [Accepted: 02/18/2022] [Indexed: 11/08/2022]
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Leonardi-Figueiredo MM, de Queiroz Davoli GB, Avi AE, Crescêncio JC, Moura-Tonello SC, Manso PH, Júnior LG, Martinez EZ, Catai AM, Mattiello-Sverzut AC. Cardiac Autonomic Modulation of Heart Rate Recovery in Children with Spina Bifida. Int J Sports Med 2021; 42:1113-1121. [PMID: 33890263 DOI: 10.1055/a-1393-6472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
We aimed to analyse cardiac autonomic control by assessing the post-exercise heart rate recovery (HRR) and physical fitness in children and adolescents with spina bifida (SB), compared to participants with typical development. A total of 124 participants, 42 with spina bifida (SB group) and 82 typical developmental controls (CO group) performed the arm cranking exercise test with a gas analysis system. HRR was determined at the first (HRR_1) and second (HRR_2) minute at recovery phase. Data are shown as [mean difference (95% CI)]. The SB group showed reduced HR reserve [14.5 (7.1-22.0) bmp, P<0.01], slower HRR_1 [12.4 (7.4-17.5) bpm, P<0.01] and HRR_2 [16.3 (10.6-21.9) bpm; P<0.01], lower VO2peak [VO2peak relative: 7.3 (4.2-10.3) mL·min-1·kg-1, P<0.01; VO2peak absolute: 0.42 (0.30-0.54) L·min-1, P<0.01], and lower O2 pulse [2.5 (1.8-3.2) mL·bpm, P<0.01] and ventilatory responses [13.5 (8.8-18.1) L·min-1, P<0.01] than the CO group. VE/VO2 was not different between groups [-2.82 (-5.77- -0.12); P=0.06], but the VE/VCO2 [-2.59 (-4.40-0.78); P<0.01] and the values of the anaerobic threshold corrected by body mass [-3.2 (-5.8- -0.6) mL·min-1·kg-1, P=0.01] were higher in the SB group than in the CO group. We concluded that children and adolescents with SB have reduced physical fitness and a slower HRR response after maximal effort.
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Affiliation(s)
| | | | - Amanda Evangelista Avi
- Departamento Ciências da Saúde, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Julio Cesar Crescêncio
- Departamento Clínica Médica, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | | | - Paulo Henrique Manso
- Departamento de Puericultura e Pediatria, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Lourenço Gallo Júnior
- Departamento de Medicina Social, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Edson Zangiacomi Martinez
- Departamento de Medicina Social, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Aparecida Maria Catai
- Departamento de Fisioterapia, Universidade Federal de São Carlos, São Carlos, Brazil
| | - Ana Claudia Mattiello-Sverzut
- Departamento Ciências da Saúde, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
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6
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Tomoto T, Repshas J, Zhang R, Tarumi T. Midlife aerobic exercise and dynamic cerebral autoregulation: associations with baroreflex sensitivity and central arterial stiffness. J Appl Physiol (1985) 2021; 131:1599-1612. [PMID: 34647828 PMCID: PMC8616602 DOI: 10.1152/japplphysiol.00243.2021] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 10/04/2021] [Accepted: 10/11/2021] [Indexed: 12/20/2022] Open
Abstract
Midlife aerobic exercise may significantly impact age-related changes in the cerebro- and cardiovascular regulations. This study investigated the associations of midlife aerobic exercise with dynamic cerebral autoregulation (dCA), cardiovagal baroreflex sensitivity (BRS), and central arterial stiffness. Twenty middle-aged athletes (MA) who had aerobic training for >10 yr were compared with 20 young (YS) and 20 middle-aged sedentary (MS) adults. Beat-to-beat cerebral blood flow velocity, blood pressure (BP), and heart rate were measured at rest and during forced BP oscillations induced by repeated sit-stand maneuvers at 0.05 Hz. Transfer function analysis was used to calculate dCA and BRS parameters. Carotid distensibility was measured by ultrasonography. MA had the highest peak oxygen uptake (V̇o2peak) among all groups. During forced BP oscillations, MS showed lower BRS gain than YS, but this age-related reduction was absent in MA. Conversely, dCA was similar among all groups. At rest, BRS and dCA gains at low frequency (∼0.1 Hz) were higher in the MA than in MS and YS groups. Carotid distensibility was similar between MA and YS groups, but it was lower in the MS. Across all subjects, V̇o2peak was positively associated with BRS gains at rest and during forced BP oscillations (r = 0.257∼0.382, P = 0.003∼0.050) and carotid distensibility (r = 0.428∼0.490, P = 0.001). Furthermore, dCA gain at rest and carotid distensibility were positively correlated with BRS gain at rest in YS and MA groups (all P < 0.05). These findings suggest that midlife aerobic exercise improves central arterial elasticity and BRS, which may contribute to cerebral blood flow (CBF) regulation through dCA.NEW & NOTEWORTHY Middle-aged athletes (MA) showed intact dynamic cerebral autoregulation (dCA) during sit-stand maneuvers when compared with young (YS) and middle-aged sedentary (MS) adults. Conversely, MA showed the significant attenuation of age-related carotid distensibility and baroreflex sensitivity (BRS) impairments. In MA and YS groups, BRS was positively associated with dCA gain at rest and carotid distensibility. Our findings suggest that midlife aerobic exercise improves BRS by reducing central arterial stiffness, which contributes to CBF regulation through dCA.
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Affiliation(s)
- Tsubasa Tomoto
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Justin Repshas
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
| | - Rong Zhang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Takashi Tarumi
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas
- Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
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7
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Möstl S, Orter S, Hoffmann F, Bachler M, Hametner B, Wassertheurer S, Rabineau J, Mulder E, Johannes B, Jordan J, Tank J. Limited Effect of 60-Days Strict Head Down Tilt Bed Rest on Vascular Aging. Front Physiol 2021; 12:685473. [PMID: 34122149 PMCID: PMC8194311 DOI: 10.3389/fphys.2021.685473] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 05/04/2021] [Indexed: 11/13/2022] Open
Abstract
Background Cardiovascular risk may be increased in astronauts after long term space flights based on biomarkers indicating premature vascular aging. We tested the hypothesis that 60 days of strict 6° head down tilt bed rest (HDTBR), an established space analog, promotes vascular stiffening and that artificial gravity training ameliorates the response. Methods We studied 24 healthy participants (8 women, 24–55 years, BMI = 24.3 ± 2.1 kg/m2) before and at the end of 60 days HDTBR. 16 subjects were assigned to daily artificial gravity. We applied echocardiography to measure stroke volume and isovolumetric contraction time (ICT), calculated aortic compliance (stroke volume/aortic pulse pressure), and assessed aortic distensibility by MRI. Furthermore, we measured brachial-femoral pulse wave velocity (bfPWV) and pulse wave arrival times (PAT) in different vascular beds by blood pressure cuffs and photoplethysmography. We corrected PAT for ICT (cPAT). Results In the pooled sample, diastolic blood pressure (+8 ± 7 mmHg, p < 0.001), heart rate (+7 ± 9 bpm, p = 0.002) and ICT (+8 ± 13 ms, p = 0.036) increased during HDTBR. Stroke volume decreased by 14 ± 15 ml (p = 0.001). bfPWV, aortic compliance, aortic distensibility and all cPAT remained unchanged. Aortic area tended to increase (p = 0.05). None of the parameters showed significant interaction between HDTBR and artificial gravity training. Conclusion 60 days HDTBR, while producing cardiovascular deconditioning and cephalad fluid shifts akin to weightlessness, did not worsen vascular stiffness. Artificial gravity training did not modulate the response.
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Affiliation(s)
- Stefan Möstl
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany
| | - Stefan Orter
- Center for Health and Bioresources, AIT Austrian Institute of Technology, Vienna, Austria
| | - Fabian Hoffmann
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany.,Department of Cardiology, University Hospital Cologne, Cologne, Germany
| | - Martin Bachler
- Center for Health and Bioresources, AIT Austrian Institute of Technology, Vienna, Austria
| | - Bernhard Hametner
- Center for Health and Bioresources, AIT Austrian Institute of Technology, Vienna, Austria
| | | | - Jérémy Rabineau
- Laboratory of Physics and Physiology, University of Brussels, Brussels, Belgium
| | - Edwin Mulder
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany
| | - Bernd Johannes
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany
| | - Jens Jordan
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany.,Chair of Aerospace Medicine, University Hospital Cologne, Cologne, Germany
| | - Jens Tank
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany
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Whittle RS, Diaz-Artiles A. Modeling individual differences in cardiovascular response to gravitational stress using a sensitivity analysis. J Appl Physiol (1985) 2021; 130:1983-2001. [PMID: 33914657 DOI: 10.1152/japplphysiol.00727.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The human cardiovascular (CV) system elicits a physiological response to gravitational environments, with significant variation between different individuals. Computational modeling can predict CV response, however model complexity and variation of physiological parameters in a normal population makes it challenging to capture individual responses. We conducted a sensitivity analysis on an existing 21-compartment lumped-parameter hemodynamic model in a range of gravitational conditions to 1) investigate the influence of model parameters on a tilt test CV response and 2) to determine the subset of those parameters with the most influence on systemic physiological outcomes. A supine virtual subject was tilted to upright under the influence of a constant gravitational field ranging from 0 g to 1 g. The sensitivity analysis was conducted using a Latin hypercube sampling/partial rank correlation coefficient methodology with subsets of model parameters varied across a normal physiological range. Sensitivity was determined by variation in outcome measures including heart rate, stroke volume, central venous pressure, systemic blood pressures, and cardiac output. Results showed that model parameters related to the length, resistance, and compliance of the large veins and parameters related to right ventricular function have the most influence on model outcomes. For most outcome measures considered, parameters related to the heart are dominant. Results highlight which model parameters to accurately value in simulations of individual subjects' CV response to gravitational stress, improving the accuracy of predictions. Influential parameters remain largely similar across gravity levels, highlighting that accurate model fitting in 1 g can increase the accuracy of predictive responses in reduced gravity.NEW & NOTEWORTHY Computational modeling is used to predict cardiovascular responses to altered gravitational environments. However, considerable variation between subjects and model complexity makes accurate parameter assignment for individuals challenging. This computational effort studies sensitivity in cardiovascular model outcomes due to varying parameters across a normal physiological range. This allows determination of which parameters have the largest influence on outcomes, i.e., which parameters must be most carefully selected to give accurate predictions of individual responses.
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Affiliation(s)
- Richard S Whittle
- Department of Aerospace Engineering, Texas A&M University, College Station, Texas
| | - Ana Diaz-Artiles
- Department of Aerospace Engineering, Texas A&M University, College Station, Texas.,Department of Health and Kinesiology, Texas A&M University, College Station, Texas
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Solbiati S, Martin-Yebra A, Vaïda P, Caiani EG. Evaluation of Cardiac Circadian Rhythm Deconditioning Induced by 5-to-60 Days of Head-Down Bed Rest. Front Physiol 2021; 11:612188. [PMID: 33519517 PMCID: PMC7838678 DOI: 10.3389/fphys.2020.612188] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 12/16/2020] [Indexed: 12/14/2022] Open
Abstract
Head-down tilt (HDT) bed rest elicits changes in cardiac circadian rhythms, generating possible adverse health outcomes such as increased arrhythmic risk. Our aim was to study the impact of HDT duration on the circadian rhythms of heart beat (RR) and ventricular repolarization (QTend) duration intervals from 24-h Holter ECG recordings acquired in 63 subjects during six different HDT bed rest campaigns of different duration (two 5-day, two 21-day, and two 60-day). Circadian rhythms of RR and QTend intervals series were evaluated by Cosinor analysis, resulting in a value of midline (MESOR), oscillation amplitude (OA) and acrophase (φ). In addition, the QTc (with Bazett correction) was computed, and day-time, night-time, maximum and minimum RR, QTend and QTc intervals were calculated. Statistical analysis was conducted, comparing: (1) the effects at 5 (HDT5), 21 (HDT21) and 58 (HDT58) days of HDT with baseline (PRE); (2) trends in recovery period at post-HDT epochs (R) in 5-day, 21-day, and 60-day HDT separately vs. PRE; (3) differences at R + 0 due to bed rest duration; (4) changes between the last HDT acquisition and the respective R + 0 in 5-day, 21-day, and 60-day HDT. During HDT, major changes were observed at HDT5, with increased RR and QTend intervals' MESOR, mostly related to day-time lengthening and increased minima, while the QTc shortened. Afterward, a progressive trend toward baseline values was observed with HDT progression. Additionally, the φ anticipated, and the OA was reduced during HDT, decreasing system's ability to react to incoming stimuli. Consequently, the restoration of the orthostatic position elicited the shortening of RR and QTend intervals together with QTc prolongation, notwithstanding the period spent in HDT. However, the magnitude of post-HDT changes, as well as the difference between the last HDT day and R + 0, showed a trend to increase with increasing HDT duration, and 5/7 days were not sufficient for recovering after 60-day HDT. Additionally, the φ postponed and the OA significantly increased at R + 0 compared to PRE after 5-day and 60-day HDT, possibly increasing the arrhythmic risk. These results provide evidence that continuous monitoring of astronauts' circadian rhythms, and further investigations on possible measures for counteracting the observed modifications, will be key for future missions including long periods of weightlessness and gravity transitions, for preserving astronauts' health and mission success.
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Affiliation(s)
- Sarah Solbiati
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy.,Institute of Electronics, Computer and Telecommunication Engineering, Consiglio Nazionale delle Ricerche, Milan, Italy
| | - Alba Martin-Yebra
- Centro de Investigación Biomédica en Red - Bioingeniería, Biomateriales y Nanomedicina, BSICoS Group, Universidad de Zaragoza, Zaragoza, Spain
| | - Pierre Vaïda
- College of Health Sciences, University of Bordeaux, Bordeaux, France
| | - Enrico G Caiani
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy.,Institute of Electronics, Computer and Telecommunication Engineering, Consiglio Nazionale delle Ricerche, Milan, Italy
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Hossein A, Rabineau J, Gorlier D, Pinki F, van de Borne P, Nonclercq A, Migeotte PF. Effects of acquisition device, sampling rate, and record length on kinocardiography during position-induced haemodynamic changes. Biomed Eng Online 2021; 20:3. [PMID: 33407507 PMCID: PMC7788803 DOI: 10.1186/s12938-020-00837-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 12/10/2020] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Kinocardiography (KCG) is a promising new technique used to monitor cardiac mechanical function remotely. KCG is based on ballistocardiography (BCG) and seismocardiography (SCG), and measures 12 degrees-of-freedom (DOF) of body motion produced by myocardial contraction and blood flow through the cardiac chambers and major vessels. RESULTS The integral of kinetic energy ([Formula: see text]) obtained from the linear and rotational SCG/BCG signals was computed over each dimension over the cardiac cycle, and used as a marker of cardiac mechanical function. We tested the hypotheses that KCG metrics can be acquired using different sensors, and at 50 Hz. We also tested the effect of record length on the ensemble average on which the metrics were computed. Twelve healthy males were tested in the supine, head-down tilt, and head-up tilt positions to expand the haemodynamic states on which the validation was performed. CONCLUSIONS KCG metrics computed on 50 Hz and 1 kHz SCG/BCG signals were very similar. Most of the metrics were highly similar when computed on different sensors, and with less than 5% of error when computed on record length longer than 60 s. These results suggest that KCG may be a robust and non-invasive method to monitor cardiac inotropic activity. Trial registration Clinicaltrials.gov, NCT03107351. Registered 11 April 2017, https://clinicaltrials.gov/ct2/show/NCT03107351?term=NCT03107351&draw=2&rank=1 .
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Affiliation(s)
- Amin Hossein
- LPHYS, Université Libre de Bruxelles, Brussels, Belgium.
- BEAMS, Université Libre de Bruxelles, Brussels, Belgium.
| | | | | | - Farhana Pinki
- LPHYS, Université Libre de Bruxelles, Brussels, Belgium
| | - Philippe van de Borne
- Department of Cardiology, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
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11
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Impaired cerebral blood flow regulation in chronic traumatic brain injury. Brain Res 2020; 1743:146924. [DOI: 10.1016/j.brainres.2020.146924] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Revised: 05/28/2020] [Accepted: 06/01/2020] [Indexed: 01/26/2023]
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12
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Cardio-postural interactions and muscle-pump baroreflex are severely impacted by 60-day bedrest immobilization. Sci Rep 2020; 10:12042. [PMID: 32694819 PMCID: PMC7374578 DOI: 10.1038/s41598-020-68962-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 06/26/2020] [Indexed: 02/07/2023] Open
Abstract
To understand fundamental mechanisms associated with post-flight orthostatic intolerance we investigated the interaction between the cardiovascular and postural functions before and after 60 days of head down bedrest (HDBR). Twenty healthy young males (35.0 ± 1.7 years) were subjected to 60-day HDBR at 6˚ to simulate spaceflight-induced fluid shifts. A supine-to-stand (STS) test was conducted to evaluate cardio-postural control before and after (R) HDBR while an assessment of cardiovascular function was performed during HDBR. Beat-to-beat heart period, systolic blood pressure, and electromyography impulses were derived for wavelet transform coherence and causality analyses of the cardio-postural control and used to assess changes in the muscle-pump baroreflex. During quiet stand of the STS test, compared to baseline, heart rate was 50% higher on the day of exit from bedrest (R0) and 20% higher eight days later (R8). There was a 50% increase in deoxygenated hemoglobin on R0 and R8. Leg muscle activity reduced, and postural sway increased after HDBR. Causality of the muscle-pump baroreflex was reduced on R0 (0.73 ± 0.2) compared to baseline (0.87 ± 0.2) with complete recovery by R8. The muscle-pump baroreflex also had decreased gain and fraction time active following HDBR. Overall, our data show a significantly impaired muscle-pump baroreflex following bedrest.
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13
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Kermorgant M, Nasr N, Czosnyka M, Arvanitis DN, Hélissen O, Senard JM, Pavy-Le Traon A. Impacts of Microgravity Analogs to Spaceflight on Cerebral Autoregulation. Front Physiol 2020; 11:778. [PMID: 32719617 PMCID: PMC7350784 DOI: 10.3389/fphys.2020.00778] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 06/15/2020] [Indexed: 12/16/2022] Open
Abstract
It is well known that exposure to microgravity in astronauts leads to a plethora physiological responses such as headward fluid shift, body unloading, and cardiovascular deconditioning. When astronauts return to Earth, some encounter problems related to orthostatic intolerance. An impaired cerebral autoregulation (CA), which could be compromised by the effects of microgravity, has been proposed as one of the mechanisms responsible for orthostatic intolerance. CA is a homeostatic mechanism that maintains cerebral blood flow for any variations in cerebral perfusion pressure by adapting the vascular tone and cerebral vessel diameter. The ground-based models of microgravity are useful tools for determining the gravitational impact of spaceflight on human body. The head-down tilt bed rest (HDTBR), where the subject remains in supine position at −6 degrees for periods ranging from few days to several weeks is the most commonly used ground-based model of microgravity for cardiovascular deconditioning. head-down bed rest (HDBR) is able to replicate cephalic fluid shift, immobilization, confinement, and inactivity. Dry immersion (DI) model is another approach where the subject remains immersed in thermoneutral water covered with an elastic waterproof fabric separating the subject from the water. Regarding DI, this analog imitates absence of any supporting structure for the body, centralization of body fluids, immobilization and hypokinesia observed during spaceflight. However, little is known about the impact of microgravity on CA. Here, we review the fundamental principles and the different mechanisms involved in CA. We also consider the different approaches in order to assess CA. Finally, we focus on the effects of short- and long-term spaceflight on CA and compare these findings with two specific analogs to microgravity: HDBR and DI.
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Affiliation(s)
- Marc Kermorgant
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France
| | - Nathalie Nasr
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France.,Department of Neurology, Institute for Neurosciences, Toulouse University Hospital, Toulouse, France
| | - Marek Czosnyka
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge University Hospital, Cambridge, United Kingdom.,Institute of Electronic Systems, Warsaw University of Technology, Warsaw, Poland
| | - Dina N Arvanitis
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France
| | - Ophélie Hélissen
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France
| | - Jean-Michel Senard
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France.,Department of Clinical Pharmacology, Toulouse University Hospital, Toulouse, France
| | - Anne Pavy-Le Traon
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France.,Department of Neurology, Institute for Neurosciences, Toulouse University Hospital, Toulouse, France
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14
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Ding K, Tarumi T, Wang C, Vernino S, Zhang R, Zhu DC. Central autonomic network functional connectivity: correlation with baroreflex function and cardiovascular variability in older adults. Brain Struct Funct 2020; 225:1575-1585. [PMID: 32350644 DOI: 10.1007/s00429-020-02075-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 04/18/2020] [Indexed: 12/30/2022]
Abstract
Baroreflex regulates short-term cardiovascular variability via the autonomic neural system. The contributions of the central autonomic system to the baroreflex regulations of arterial blood pressure (BP) and heart rate have been reported in young healthy adults, but not in older adults. Therefore, we investigated the association between the high-level central autonomic network (CAN) connectivity and baroreflex sensitivity (BRS) under a resting condition in a healthy older population. Twenty-two older adults (68 ± 8 years old) underwent BRS assessment using the modified Oxford and transfer function methods. Resting-state brain functional MRI was performed to assess the CAN functional connectivity at rest. We found that the functional connectivity (FC) between the left amygdala and left medial frontal gyrus (MeFG), bilateral postcentral gyri and bilateral paracentral lobules (PCL) is associated with BRS and R-R interval (RRI) variability in the low-frequency (LF) range. Compared to the left amygdala, the FC map of the right amygdala only showed significant associations with BRS in the anterior cingulate cortex (ACC) and with RRI variability in the left occipital region. In addition, post hoc analysis of the functionally defined left insula sub-region confirmed the association between CAN and BRS. Overall, our study demonstrates that CAN and its related brain regions may be involved, likely in a left-lateral manner, in peripheral cardiac autonomic regulation at rest. The results highlight the potential importance of brain neural network function in maintaining cardiovascular homeostasis in older adults.
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Affiliation(s)
- Kan Ding
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA
| | - Takashi Tarumi
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA.,Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 8200 Walnut Hill Ln, Dallas, TX, 75231, USA.,Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
| | - Ciwen Wang
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA
| | - Steven Vernino
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA
| | - Rong Zhang
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA.,Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 8200 Walnut Hill Ln, Dallas, TX, 75231, USA
| | - David C Zhu
- Departments of Radiology and Psychology and Cognitive Imaging Research Center, Michigan State University, Radiology Building, 846 Service Road, East Lansing, MI, 48824, USA.
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15
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Manou-Stathopoulou V, Korbonits M, Ackland GL. Redefining the perioperative stress response: a narrative review. Br J Anaesth 2019; 123:570-583. [PMID: 31547969 DOI: 10.1016/j.bja.2019.08.011] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 07/21/2019] [Accepted: 08/11/2019] [Indexed: 12/13/2022] Open
Abstract
The systemic stress response triggered by surgical trauma is characterised by sterile inflammation preceding metabolic and neuroendocrine dysregulation. However, the relevance of the classically described 'stress response' is now highly questionable in an era where profound physiological deconditioning is common in older, frail surgical patients. Commonly used assessment techniques do not accurately reflect hypothalamic-pituitary-adrenal axis integrity after major surgery. Clinical interpretation of plasma concentrations of cortisol, the prototypical stress hormone, is rarely accurate, because of study heterogeneity, the inherently dynamic characteristics of cortisol production, and assay variability. Before surgery, chronic psychosocial stress and common cardiorespiratory co-morbidities are clinically relevant modifiers of neuroendocrine activation to acute stress/inflammation. The frequent development of multi-morbidity after major surgery further clouds the compartmentalised, discrete model of neuroendocrine activation after initial tissue injury. Starvation, impaired mobility, and sepsis after surgery generate distinct neuroendocrine profiles that challenge the conventional model of neuroendocrine activation. Basic science studies suggest that high circulating levels of cortisol may directly cause organ injury. Conversely, randomised controlled clinical trials investigating glucocorticoid supplementation have delivered contrasting results, with some suggesting a protective effect in the perioperative period. Here, we consider many of the confounding factors that have emerged to challenge the conventional model of the surgical stress response, and suggest that a more nuanced understanding of changes in hypothalamic-pituitary-adrenal axis physiology is warranted to advance perioperative medicine. Re-examining the perioperative stress response presents opportunities for improving outcomes through enhancing the understanding of the neuroendocrine aspects of preparation for and recovery from surgery.
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Affiliation(s)
- Vasiliki Manou-Stathopoulou
- Translational Medicine and Therapeutics, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Márta Korbonits
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Gareth L Ackland
- Translational Medicine and Therapeutics, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK.
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16
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Gerber B, Singh JL, Zhang Y, Liou W. A computer simulation of short-term adaptations of cardiovascular hemodynamics in microgravity. Comput Biol Med 2018; 102:86-94. [PMID: 30253272 DOI: 10.1016/j.compbiomed.2018.09.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 09/11/2018] [Accepted: 09/15/2018] [Indexed: 12/01/2022]
Abstract
Astronauts in the microgravity environment experience significant changes in their cardiovascular hemodynamics. In this study, a system-level numerical model has been utilized to simulate the short-term adaptations of hemodynamic parameters due to the gravitational removal in space. The effect of lower body negative pressure (LBNP) as a countermeasure has also been simulated. The numerical model was built upon a lumped-parameter Windkessel model by incorporating gravity-induced hydrostatic pressure and transcapillary fluid exchange modules. The short-term (in the time scale of seconds and minutes) adaptations of the cardiac functions, blood pressure, and fluid volumes have been analyzed and compared with physiological data. The simulation results suggest microgravity induces a decrease in aortic pressure, heart rate, lower body capillary pressure and volume, and an increase in stroke volume, upper body capillary pressure and volume. The activation of LBNP causes an immediate increase in lower body blood volume and a gradual decrease in upper body blood volume. As a result, the fluid shift due to microgravity could be reversed by the LBNP application. LBNP also counters the impacts of microgravity on the cardiac functions, including heart rate and stroke volume. The simulation results have been validated using available physiological data obtained from spaceflight and parabolic flight experiments.
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Affiliation(s)
- Benjamin Gerber
- Department Electrical and Computer Engineering, North Dakota State University, Fargo, ND, USA
| | - John-Luke Singh
- Department of Mechanical Engineering, North Dakota State University, Fargo, ND, USA
| | - Yan Zhang
- Department of Mechanical Engineering, North Dakota State University, Fargo, ND, USA.
| | - William Liou
- Department of Mechanical and Aerospace Engineering, Western Michigan University, Kalamazoo, MI, USA
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17
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Leonardi-Figueiredo MM, de Souza HCD, Martins EJ, Squiaveto M, Mattiello-Sverzut AC. Damaged cardiovascular autonomic control in wheelchair-using children and adolescents with myelomeningocele: a case-control study. Braz J Phys Ther 2018; 23:27-32. [PMID: 30243858 DOI: 10.1016/j.bjpt.2018.09.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 08/08/2018] [Accepted: 09/04/2018] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Cardiovascular autonomic dysfunction is associated with the development of cardiovascular diseases, but little is known about it in children and adolescents with myelomeningocele. OBJECTIVE This study investigated the cardiovascular autonomic function in wheelchair-using children and adolescents with myelomeningocele. METHODS Twenty-two participants were assigned to one of two groups: myelomeningocele group (n=11) and Control group (n=11). Heart rate variability and systolic blood pressure variability were collected in supine resting position using spectral analyses. Spontaneous baroreflex sensitivity was collected by time-domain through the sequence method. RESULTS At rest, heart rate was higher in myelomeningocele group when compared to Control group (mean difference 22.1, 95% CI 4.82-39.40; p=0.01). The heart rate and systolic blood pressure variability parameters did not show differences between groups. However, myelomeningocele showed lower gain mean in baroreflex sensitivity (mean difference -4.5, 95% CI -8.47 to -0.60; p=0.02), when compared to Control. CONCLUSION Wheelchair-using children and adolescents with myelomeningocele presented differences in the autonomic cardiovascular function. This may be associated with hypomobility due to wheelchair dependence, and venous muscle pump insufficiency due to paraplegia.
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Affiliation(s)
| | - Hugo Celso Dutra de Souza
- Department of Healthy Sciences, Ribeirão Preto Medical School, Universidade de São Paulo (USP), Ribeirão Preto, SP, Brazil
| | - Emanuela Juvenal Martins
- Department of Healthy Sciences, Ribeirão Preto Medical School, Universidade de São Paulo (USP), Ribeirão Preto, SP, Brazil
| | - Monalisa Squiaveto
- Department of Healthy Sciences, Ribeirão Preto Medical School, Universidade de São Paulo (USP), Ribeirão Preto, SP, Brazil
| | - Ana Claudia Mattiello-Sverzut
- Department of Healthy Sciences, Ribeirão Preto Medical School, Universidade de São Paulo (USP), Ribeirão Preto, SP, Brazil.
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18
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Edgell H, Grinberg A, Beavers KR, Gagné N, Hughson RL. Efficacy of fluid loading as a countermeasure to the hemodynamic and hormonal changes of 28-h head-down bed rest. Physiol Rep 2018; 6:e13874. [PMID: 30298552 PMCID: PMC6175712 DOI: 10.14814/phy2.13874] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Accepted: 08/26/2018] [Indexed: 11/24/2022] Open
Abstract
After exposure to microgravity, or head-down bed rest (HDBR), fluid loading is often used with the intent of increasing plasma volume and maintaining mean arterial pressure during orthostatic stress. Nine men (aged 18-32 years) underwent three randomized trials with lower body negative pressure (LBNP) before and after: (1) 4-h of sitting with fluid loading (1 g sodium chloride/125 mL of water starting 2.5-h before LBNP), (2) 28-h of 6-degree HDBR without fluid loading, and (3) 28-h of 6-degree HDBR with fluid loading. LBNP was progressive from 0 to -40 mmHg. After 28-h HDBR, fluid loading did not protect against the loss of plasma volume (-280 ± 64 mL without fluid loading, -207 ± 86 with fluid loading, P = 0.472) nor did it protect against a drop of mean arterial pressure (P = 0.017) during LBNP (Post-28 h HDBR response from 0 to -40 mmHg LBNP: 88 ± 4 to 85 ± 4 mmHg without fluid loading and 93 ± 4 to 88 ± 5 mmHg with fluid loading, P = 0.557 between trials). However, fluid loading did protect against the loss of stroke volume index and central venous pressure observed after 28-h HDBR. Fluid loading also attenuated the increase of angiotensin II seen after 28-h HDBR and throughout the LBNP protocol (Post-28 h HDBR response from 0 to -40 mmHg LBNP: 16.6 ± 3.4 to 23.7 ± 5.0 pg/mL without fluid loading and 6.1 ± 0.8 to 12.2 ± 2.3 pg/mL with fluid loading, P < 0.001 between trials). Our results indicate that fluid loading did not protect against plasma volume loss due to HDBR or change blood pressure responses to LBNP. However, changes in central venous pressure, stroke volume and fluid regulatory hormones could potentially influence longer duration studies and those with more severe orthostatic stress.
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Affiliation(s)
- Heather Edgell
- Faculty of Applied Health SciencesUniversity of WaterlooWaterlooOntarioCanada
- School of Kinesiology and Health SciencesYork UniversityTorontoOntarioCanada
| | - Anna Grinberg
- Faculty of Applied Health SciencesUniversity of WaterlooWaterlooOntarioCanada
| | - Keith R. Beavers
- Faculty of Applied Health SciencesUniversity of WaterlooWaterlooOntarioCanada
| | - Nathalie Gagné
- Faculty of Applied Health SciencesUniversity of WaterlooWaterlooOntarioCanada
| | - Richard L. Hughson
- Faculty of Applied Health SciencesUniversity of WaterlooWaterlooOntarioCanada
- Schlegel‐University of Waterloo Research Institute for AgingWaterlooOntarioCanada
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19
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Valenza G, Faes L, Citi L, Orini M, Barbieri R. Instantaneous Transfer Entropy for the Study of Cardiovascular and Cardiorespiratory Nonstationary Dynamics. IEEE Trans Biomed Eng 2017; 65:1077-1085. [PMID: 28816654 DOI: 10.1109/tbme.2017.2740259] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE Measures of transfer entropy (TE) quantify the direction and strength of coupling between two complex systems. Standard approaches assume stationarity of the observations, and therefore are unable to track time-varying changes in nonlinear information transfer with high temporal resolution. In this study, we aim to define and validate novel instantaneous measures of TE to provide an improved assessment of complex nonstationary cardiorespiratory interactions. METHODS We here propose a novel instantaneous point-process TE (ipTE) and validate its assessment as applied to cardiovascular and cardiorespiratory dynamics. In particular, heartbeat and respiratory dynamics are characterized through discrete time series, and modeled with probability density functions predicting the time of the next physiological event as a function of the past history. Likewise, nonstationary interactions between heartbeat and blood pressure dynamics are characterized as well. Furthermore, we propose a new measure of information transfer, the instantaneous point-process information transfer (ipInfTr), which is directly derived from point-process-based definitions of the Kolmogorov-Smirnov distance. RESULTS AND CONCLUSION Analysis on synthetic data, as well as on experimental data gathered from healthy subjects undergoing postural changes confirms that ipTE, as well as ipInfTr measures are able to dynamically track changes in physiological systems coupling. SIGNIFICANCE This novel approach opens new avenues in the study of hidden, transient, nonstationary physiological states involving multivariate autonomic dynamics in cardiovascular health and disease. The proposed method can also be tailored for the study of complex multisystem physiology (e.g., brain-heart or, more in general, brain-body interactions).
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20
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Gerdt AM, Shutov AM, Menzorov MV, Gubareva EA. [Causal relationships in stroke and kidney injury]. TERAPEVT ARKH 2017; 89:62-68. [PMID: 28745691 DOI: 10.17116/terarkh201789662-68] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
AIM To assess the frequency, severity, and causes of acute kidney injury (AKI) in patients with stroke. SUBJECTS AND METHODS 272 patients (143 men and 129 women) (mean age, 66.7±11.6 years) with stroke were examined. The 2008 European Stroke Organization (ESO) guidelines were used to diagnose stroke, to determine indications for and contraindications to thrombolytic therapy, and to evaluate its efficiency. Hemorrhagic and ischemic strokes (HS and IS) were diagnosed in 52 (19%) and 220 (81%) patients, respectively. AKI was diagnosed and classified according to the 2012 Kidney Disease: Improving Global Outcomes (KDIGO) guidelines. RESULTS AKI was diagnosed in 89 (33%) patients: 19 (36.5%) with HS and 70 (31.8%) with IS. The relative risk of death in patients with AKI-associated stroke was 2.6 (95% confidence interval (CI) 1.6-4.0). A poor outcome (the combined endpoint of death or Rankin scale scores of 4-5) was noted in 56 (62.9%) patients with AKI and in 70 (38.2 %) without AKI (χ2=14.6; p=0.0002). The relative risk of a poor outcome in patients with AKI-associated with stroke was 1.64 (95% CI 1.3-2.0). Forty-five (50.6%) patients with stroke developed AKI in the prehospital period. CONCLUSION AKI complicates stroke in every three patients and increases death rates. 50% of cases develop AKI in the prehospital period due to the common causes of stroke and AKI.
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Affiliation(s)
- A M Gerdt
- Ulyanovsk State University, Ulyanovsk, Russia; V.V. Banykin Tolyatti City Hospital Two, Tolyatti, Russia
| | - A M Shutov
- Ulyanovsk State University, Ulyanovsk, Russia
| | | | - E A Gubareva
- V.V. Banykin Tolyatti City Hospital Two, Tolyatti, Russia
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21
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Yadav K, Singh A, Badhwar S, Jaryal AK, Coshic P, Chatterjee K, Deepak KK. Decreased Spontaneous Baroreflex Sensitivity as an Early Marker for Progression of Haemorrhage. High Blood Press Cardiovasc Prev 2017; 24:275-281. [PMID: 28497338 DOI: 10.1007/s40292-017-0205-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 04/28/2017] [Indexed: 11/25/2022] Open
Abstract
INTRODUCTION Blood donation provides an ideal setup for assessment of cardiovascular responses to mild hypovolemia for understanding the underlying mechanisms. AIM To evaluate cardiovascular responses in time and magnitude by estimating the spontaneous baroreflex sensitivity (BRS) during and after donation of 450 ml of blood. METHODS Continuous beat-to-beat blood pressure and lead II ECG was recorded before, during and after blood donation in 54 healthy volunteers (age 34.7 ± 5.08 years; weight 77.9 ± 8.20 kg), followed by offline analyses of baroreflex sensitivity. RESULTS The systolic, diastolic or mean blood pressures did not change during or after the blood donation. Decrease in pulse pressure and increase in heart rate was observed post donation. The spontaneous BRS decreased during [8.68 (6.038-12.69) ms/mmHg] and after blood donation [9.401 (6.396-11.59) ms/mmHg] as compared to the baseline [12.83 (6.884-18.18) ms/mmHg] with a significant decrease in α-HF on spectral analysis. CONCLUSION Mild blood loss (450 ml) results in non-hypotensive haemorrhage with a decrease in spontaneous BRS before the rise of heart rate during blood donation.
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Affiliation(s)
- Kavita Yadav
- Department of Physiology, All India Institute of Medical Sciences, Room No. 2009, Teaching Block, Second Floor, Ansari Nagar, New Delhi, India
| | - Akanksha Singh
- Department of Physiology, All India Institute of Medical Sciences, Room No. 2009, Teaching Block, Second Floor, Ansari Nagar, New Delhi, India
| | - Smriti Badhwar
- Department of Physiology, All India Institute of Medical Sciences, Room No. 2009, Teaching Block, Second Floor, Ansari Nagar, New Delhi, India
| | - Ashok Kumar Jaryal
- Department of Physiology, All India Institute of Medical Sciences, Room No. 2009, Teaching Block, Second Floor, Ansari Nagar, New Delhi, India.
| | - Poonam Coshic
- Department of Transfusion Medicine (Blood Bank), All India Institute of Medical Sciences, Ground Floor, Main Blood Bank Unit 1, Ansari Nagar, New Delhi, India
| | - Kabita Chatterjee
- Department of Transfusion Medicine (Blood Bank), All India Institute of Medical Sciences, Ground Floor, Main Blood Bank Unit 1, Ansari Nagar, New Delhi, India
| | - K K Deepak
- Department of Physiology, All India Institute of Medical Sciences, Room No. 2009, Teaching Block, Second Floor, Ansari Nagar, New Delhi, India
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22
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Xing CY, Tarumi T, Meijers RL, Turner M, Repshas J, Xiong L, Ding K, Vongpatanasin W, Yuan LJ, Zhang R. Arterial Pressure, Heart Rate, and Cerebral Hemodynamics Across the Adult Life Span. Hypertension 2017; 69:712-720. [PMID: 28193707 DOI: 10.1161/hypertensionaha.116.08986] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Revised: 01/08/2017] [Accepted: 01/19/2017] [Indexed: 01/15/2023]
Abstract
Age-related alterations in systemic and cerebral hemodynamics are not well understood. The purpose of this study is to characterize age-related alterations in beat-to-beat oscillations in arterial blood pressure (BP), heart rate (HR), cerebral blood flow (CBF), cardiac baroreflex sensitivity, and dynamic cerebral autoregulation across the adult life span. We studied 136 healthy adults aged 21 to 80 years (60% women). Beat-to-beat BP, HR, and CBF velocity were measured at rest and during sit-stand maneuvers to mimic effects of postural changes on BP and CBF. Transfer function analysis was used to assess baroreflex sensitivity and dynamic cerebral autoregulation. Carotid-femoral pulse wave velocity was measured to assess central arterial stiffness. Advanced aging was associated with elevated carotid-femoral pulse wave velocity, systolic and pulse BP, cerebrovascular resistance, and CBF pulsatility, but reduced mean CBF velocity. Compared with the young and middle-aged, older adults had lower beat-to-beat BP, HR, and CBF variability in the low-frequency ranges at rest, but higher BP and CBF variability during sit-stand maneuvers. Baroreflex sensitivity was reduced, whereas dynamic cerebral autoregulation gain was elevated at rest in older adults. Multiple linear regression analysis indicated that systolic BP variability is correlated positively with carotid-femoral pulse wave velocity independent of HR variability. In conclusion, advanced aging is associated with elevated pulsatility in BP and CBF; reduced beat-to-beat low-frequency oscillations in BP, HR, and CBF; and impaired baroreflex sensitivity and dynamic cerebral autoregulation at rest. The augmented BP and CBF variability in older adults during sit-stand maneuvers indicate diminished cardiovascular regulatory capability and increased hemodynamic stress on the cerebral circulation with aging.
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Affiliation(s)
- Chang-Yang Xing
- From the Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas (C.-Y.X., T.T., R.L.M., M.T., J.R., R.Z.); Department of Internal Medicine (C.-Y.X., W.V., R.Z.) and Department of Neurology and Neurotherapeutics (T.T., K.D., R.Z.), University of Texas Southwestern Medical Center, Dallas; Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (C.-Y.X., L.-J.Y.); Department of Geriatric Medicine, Radboud University Nijmegen Medical Centre, The Netherlands (R.L.M.); and Department of Medicine and Therapeutics, Chinese University of Hong Kong, China (L.X.)
| | - Takashi Tarumi
- From the Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas (C.-Y.X., T.T., R.L.M., M.T., J.R., R.Z.); Department of Internal Medicine (C.-Y.X., W.V., R.Z.) and Department of Neurology and Neurotherapeutics (T.T., K.D., R.Z.), University of Texas Southwestern Medical Center, Dallas; Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (C.-Y.X., L.-J.Y.); Department of Geriatric Medicine, Radboud University Nijmegen Medical Centre, The Netherlands (R.L.M.); and Department of Medicine and Therapeutics, Chinese University of Hong Kong, China (L.X.)
| | - Rutger L Meijers
- From the Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas (C.-Y.X., T.T., R.L.M., M.T., J.R., R.Z.); Department of Internal Medicine (C.-Y.X., W.V., R.Z.) and Department of Neurology and Neurotherapeutics (T.T., K.D., R.Z.), University of Texas Southwestern Medical Center, Dallas; Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (C.-Y.X., L.-J.Y.); Department of Geriatric Medicine, Radboud University Nijmegen Medical Centre, The Netherlands (R.L.M.); and Department of Medicine and Therapeutics, Chinese University of Hong Kong, China (L.X.)
| | - Marcel Turner
- From the Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas (C.-Y.X., T.T., R.L.M., M.T., J.R., R.Z.); Department of Internal Medicine (C.-Y.X., W.V., R.Z.) and Department of Neurology and Neurotherapeutics (T.T., K.D., R.Z.), University of Texas Southwestern Medical Center, Dallas; Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (C.-Y.X., L.-J.Y.); Department of Geriatric Medicine, Radboud University Nijmegen Medical Centre, The Netherlands (R.L.M.); and Department of Medicine and Therapeutics, Chinese University of Hong Kong, China (L.X.)
| | - Justin Repshas
- From the Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas (C.-Y.X., T.T., R.L.M., M.T., J.R., R.Z.); Department of Internal Medicine (C.-Y.X., W.V., R.Z.) and Department of Neurology and Neurotherapeutics (T.T., K.D., R.Z.), University of Texas Southwestern Medical Center, Dallas; Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (C.-Y.X., L.-J.Y.); Department of Geriatric Medicine, Radboud University Nijmegen Medical Centre, The Netherlands (R.L.M.); and Department of Medicine and Therapeutics, Chinese University of Hong Kong, China (L.X.)
| | - Li Xiong
- From the Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas (C.-Y.X., T.T., R.L.M., M.T., J.R., R.Z.); Department of Internal Medicine (C.-Y.X., W.V., R.Z.) and Department of Neurology and Neurotherapeutics (T.T., K.D., R.Z.), University of Texas Southwestern Medical Center, Dallas; Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (C.-Y.X., L.-J.Y.); Department of Geriatric Medicine, Radboud University Nijmegen Medical Centre, The Netherlands (R.L.M.); and Department of Medicine and Therapeutics, Chinese University of Hong Kong, China (L.X.)
| | - Kan Ding
- From the Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas (C.-Y.X., T.T., R.L.M., M.T., J.R., R.Z.); Department of Internal Medicine (C.-Y.X., W.V., R.Z.) and Department of Neurology and Neurotherapeutics (T.T., K.D., R.Z.), University of Texas Southwestern Medical Center, Dallas; Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (C.-Y.X., L.-J.Y.); Department of Geriatric Medicine, Radboud University Nijmegen Medical Centre, The Netherlands (R.L.M.); and Department of Medicine and Therapeutics, Chinese University of Hong Kong, China (L.X.)
| | - Wanpen Vongpatanasin
- From the Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas (C.-Y.X., T.T., R.L.M., M.T., J.R., R.Z.); Department of Internal Medicine (C.-Y.X., W.V., R.Z.) and Department of Neurology and Neurotherapeutics (T.T., K.D., R.Z.), University of Texas Southwestern Medical Center, Dallas; Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (C.-Y.X., L.-J.Y.); Department of Geriatric Medicine, Radboud University Nijmegen Medical Centre, The Netherlands (R.L.M.); and Department of Medicine and Therapeutics, Chinese University of Hong Kong, China (L.X.)
| | - Li-Jun Yuan
- From the Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas (C.-Y.X., T.T., R.L.M., M.T., J.R., R.Z.); Department of Internal Medicine (C.-Y.X., W.V., R.Z.) and Department of Neurology and Neurotherapeutics (T.T., K.D., R.Z.), University of Texas Southwestern Medical Center, Dallas; Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (C.-Y.X., L.-J.Y.); Department of Geriatric Medicine, Radboud University Nijmegen Medical Centre, The Netherlands (R.L.M.); and Department of Medicine and Therapeutics, Chinese University of Hong Kong, China (L.X.)
| | - Rong Zhang
- From the Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas (C.-Y.X., T.T., R.L.M., M.T., J.R., R.Z.); Department of Internal Medicine (C.-Y.X., W.V., R.Z.) and Department of Neurology and Neurotherapeutics (T.T., K.D., R.Z.), University of Texas Southwestern Medical Center, Dallas; Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China (C.-Y.X., L.-J.Y.); Department of Geriatric Medicine, Radboud University Nijmegen Medical Centre, The Netherlands (R.L.M.); and Department of Medicine and Therapeutics, Chinese University of Hong Kong, China (L.X.).
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23
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Pichon AP, Connes P, Robach P. Effects of acute and chronic hematocrit modulations on blood viscosity in endurance athletes. Clin Hemorheol Microcirc 2016; 64:115-123. [DOI: 10.3233/ch-162050] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Aurélien P. Pichon
- Laboratory Mobility, aging & exercise (MOVE) - EA 6314, Faculty of Sport Sciences, University of Poitiers, Poitiers, France
- Laboratory Hypoxia & Lung - EA 2363, UFR SMBH, University Paris 13, Bobigny, France
- Association pour la Recherche en Physiologie de l’Environnement (ARPE), UFR de Médecine, 74 rue Marcel Cachin, Bobigny, France
| | - Philippe Connes
- Institut Universitaire de France, Paris, France
- Laboratoire CRIS EA647 –Section “Vascular biology and red blood cell”, University of Lyon 1, Villeurbanne, France
- Laboratoire d’Excellence GR-Ex, Paris, France
| | - Paul Robach
- Département Médical, Ecole Nationale des Sports de Montagne, site de l’Ecole Nationale de Ski et d’Alpinisme, Chamonix, France
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24
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Yadav K, Singh A, Jaryal AK, Coshic P, Chatterjee K, Deepak KK. Modulation of cardiac autonomic tone in non-hypotensive hypovolemia during blood donation. J Clin Monit Comput 2016; 31:739-746. [PMID: 27484693 DOI: 10.1007/s10877-016-9912-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 07/25/2016] [Indexed: 11/25/2022]
Abstract
Non-hypotensive hypovolemia, observed during mild haemorrhage or blood donation leads to reflex readjustment of the cardiac autonomic tone. In the present study, the cardiac autonomic tone was quantified using heart rate and blood pressure variability during and after non-hypotensive hypovolemia of blood donation. 86 voluntary healthy male blood donors were recruited for the study (age 35 ± 9 years; weight 78 ± 12 kg; height 174 ± 6 cms). Continuous lead II ECG and beat-to-beat blood pressure was recorded before, during and after blood donation followed by offline time and frequency domain analysis of HRV and BPV. The overall heart rate variability (SDNN and total power) did not change during or after blood donation. However, there was a decrease in indices that represent the parasympathetic component (pNN50 %, SDSD and HF) while an increase was observed in sympathetic component (LF) along with an increase in sympathovagal balance (LF:HF ratio) during blood donation. These changes were sustained for the period immediately following blood donation. No fall of blood pressure was observed during the period of study. The blood pressure variability showed an increase in the SDNN, CoV and RMSSD time domain measures in the post donation period. These results suggest that mild hypovolemia produced by blood donation is non-hypotensive but is associated with significant changes in the autonomic tone. The increased blood pressure variability and heart rate changes that are seen only in the later part of donation period could be because of the progressive hypovolemia associated parasympathetic withdrawal and sympathetic activation that manifest during the course of blood donation.
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Affiliation(s)
- Kavita Yadav
- Department of Physiology, All India Institute of Medical Sciences, Room No. 2009, Teaching Block, Second Floor, Ansari Nagar, New Delhi, India
| | - Akanksha Singh
- Department of Physiology, All India Institute of Medical Sciences, Room No. 2009, Teaching Block, Second Floor, Ansari Nagar, New Delhi, India
| | - Ashok Kumar Jaryal
- Department of Physiology, All India Institute of Medical Sciences, Room No. 2009, Teaching Block, Second Floor, Ansari Nagar, New Delhi, India.
| | - Poonam Coshic
- Transfusion Medicine (Blood Bank), All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
| | - Kabita Chatterjee
- Transfusion Medicine (Blood Bank), All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
| | - K K Deepak
- Department of Physiology, All India Institute of Medical Sciences, Room No. 2009, Teaching Block, Second Floor, Ansari Nagar, New Delhi, India
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25
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Watenpaugh DE. Analogs of microgravity: head-down tilt and water immersion. J Appl Physiol (1985) 2016; 120:904-14. [DOI: 10.1152/japplphysiol.00986.2015] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 02/04/2016] [Indexed: 01/26/2023] Open
Abstract
This article briefly reviews the fidelity of ground-based methods used to simulate human existence in weightlessness (spaceflight). These methods include horizontal bed rest (BR), head-down tilt bed rest (HDT), head-out water immersion (WI), and head-out dry immersion (DI; immersion with an impermeable elastic cloth barrier between subject and water). Among these, HDT has become by far the most commonly used method, especially for longer studies. DI is less common but well accepted for long-duration studies. Very few studies exist that attempt to validate a specific simulation mode against actual microgravity. Many fundamental physical, and thus physiological, differences exist between microgravity and our methods to simulate it, and between the different methods. Also, although weightlessness is the salient feature of spaceflight, several ancillary factors of space travel complicate Earth-based simulation. In spite of these discrepancies and complications, the analogs duplicate many responses to 0 G reasonably well. As we learn more about responses to microgravity and spaceflight, investigators will continue to fine-tune simulation methods to optimize accuracy and applicability.
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Affiliation(s)
- Donald E. Watenpaugh
- Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas
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26
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Schmitt L, Regnard J, Millet GP. Monitoring Fatigue Status with HRV Measures in Elite Athletes: An Avenue Beyond RMSSD? Front Physiol 2015; 6:343. [PMID: 26635629 PMCID: PMC4652221 DOI: 10.3389/fphys.2015.00343] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 11/04/2015] [Indexed: 11/27/2022] Open
Abstract
Among the tools proposed to assess the athlete's “fatigue,” the analysis of heart rate variability (HRV) provides an indirect evaluation of the settings of autonomic control of heart activity. HRV analysis is performed through assessment of time-domain indices, the square root of the mean of the sum of the squares of differences between adjacent normal R-R intervals (RMSSD) measured during short (5 min) recordings in supine position upon awakening in the morning and particularly the logarithm of RMSSD (LnRMSSD) has been proposed as the most useful resting HRV indicator. However, if RMSSD can help the practitioner to identify a global “fatigue” level, it does not allow discriminating different types of fatigue. Recent results using spectral HRV analysis highlighted firstly that HRV profiles assessed in supine and standing positions are independent and complementary; and secondly that using these postural profiles allows the clustering of distinct sub-categories of “fatigue.” Since, cardiovascular control settings are different in standing and lying posture, using the HRV figures of both postures to cluster fatigue state embeds information on the dynamics of control responses. Such, HRV spectral analysis appears more sensitive and enlightening than time-domain HRV indices. The wealthier information provided by this spectral analysis should improve the monitoring of the adaptive training-recovery process in athletes.
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Affiliation(s)
- Laurent Schmitt
- Centre National de Ski Nordique et de Moyenne Montagne, Ecole Nationale des Sports de Montagne Prémanon, France ; Faculty of Biology and Medicine, Institute of Sport Sciences, University of Lausanne Lausanne, Switzerland
| | - Jacques Regnard
- Unité de Recherche EA3920, Marqueurs Pronostiques et Facteurs de Régulations des Pathologies Cardiaques et Vasculaires, Hôpital Universitaire de Besançon, Université de Franche-Comté Besançon, France
| | - Grégoire P Millet
- Faculty of Biology and Medicine, Institute of Sport Sciences, University of Lausanne Lausanne, Switzerland
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27
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Orthostatic Intolerance Is Independent of the Degree of Autonomic Cardiovascular Adaptation after 60 Days of Head-Down Bed Rest. BIOMED RESEARCH INTERNATIONAL 2015; 2015:896372. [PMID: 26425559 PMCID: PMC4573436 DOI: 10.1155/2015/896372] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Revised: 08/12/2015] [Accepted: 08/19/2015] [Indexed: 11/17/2022]
Abstract
Spaceflight and head-down bed rest (HDBR) can induce the orthostatic intolerance (OI); the mechanisms remain to be clarified. The aim of this study was to determine whether or not OI after HDBR relates to the degree of autonomic cardiovascular adaptation. Fourteen volunteers were enrolled for 60 days of HDBR. A head-up tilt test (HUTT) was performed before and after HDBR. Our data revealed that, in all nonfainters, there was a progressive increase in heart rate over the course of HDBR, which remained higher until 12 days of recovery. The mean arterial pressure gradually increased until day 56 of HDBR and returned to baseline after 12 days of recovery. Respiratory sinus arrhythmia and baroreflex sensitivity decreased during HDBR and remained suppressed until 12 days of recovery. Low-frequency power of systolic arterial pressure increased during HDBR and remained elevated during recovery. Three subjects fainted during the HUTT after HDBR, in which systemic vascular resistance did not increase and remained lower until syncope. None of the circulatory patterns significantly differed between the fainters and the nonfainters at any time point. In conclusion, our data indicate that the impaired orthostatic tolerance after HDBR could not be distinguished by estimation of normal hemodynamic and/or neurocardiac data.
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28
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Horsman HM, Peebles KC, Tzeng YC. Interactions between breathing rate and low-frequency fluctuations in blood pressure and cardiac intervals. J Appl Physiol (1985) 2015. [PMID: 26205543 DOI: 10.1152/japplphysiol.00525.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Evidence derived from spontaneous measures of cardiovagal baroreflex sensitivity (BRS) suggests that slow breathing at 6 breaths/min augments BRS. However, increases in BRS associated with slow breathing may simply reflect the frequency-dependent nature of the baroreflex rather than the modulation of baroreflex function by changes in breathing rate per se. To test this hypothesis we employed a crossover study design (n = 14) wherein breathing rate and systolic arterial blood pressure (SAP) oscillation induced via the application of oscillating lower body negative pressure (OLBNP) were independently varied at fixed frequencies. Breathing rate was controlled at 6 or 10 breaths/min with the aid of a metronome, and SAP oscillations were driven at 0.06 Hz and 0.1 Hz using OLBNP. The magnitudes of SAP and R-R interval (cardiac period) oscillations were quantified using power spectral analysis, and the transfer function gain between SAP and R-R interval was used to estimate BRS. Linear mixed-effects models were used to examine the main effects and interactions between breathing rate and OLBNP frequency. There was no statistical interaction between breathing and OLBNP frequency (P = 0.59), indicating that the effect of breathing rate on BRS did not differ according to OLBNP frequency (and vice versa). Additionally, there was no main effect for breathing rate (P = 0.28). However, we observed a significant main effect for OLBNP frequency (P = 0.01) consistent with the frequency-dependent nature of baroreflex. These findings suggest that increases in spectral indices of BRS reflect the frequency dependence of the baroreflex and are not due to slow breathing per se.
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Affiliation(s)
- H M Horsman
- Cardiovascular Systems Laboratory and Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - K C Peebles
- Cardiovascular Systems Laboratory and Centre for Translational Physiology, University of Otago, Wellington, New Zealand; Department of Physiology, University of Otago, Dunedin, New Zealand; and Department of Health Professions, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, Australia
| | - Y C Tzeng
- Cardiovascular Systems Laboratory and Centre for Translational Physiology, University of Otago, Wellington, New Zealand;
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29
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Preventive Cardiology: The Effects of Exercise. Coron Artery Dis 2015. [DOI: 10.1007/978-1-4471-2828-1_28] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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30
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Horsman HM, Tzeng YC, Galletly DC, Peebles KC. The repeated sit-to-stand maneuver is a superior method for cardiac baroreflex assessment: a comparison with the modified Oxford method and Valsalva maneuver. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1345-52. [DOI: 10.1152/ajpregu.00376.2014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Baroreflex assessment has diagnostic and prognostic utility in the clinical and research environments, and there is a need for a reliable, simple, noninvasive method of assessment. The repeated sit-to-stand method induces oscillatory changes in blood pressure (BP) at a desired frequency and is suitable for assessing dynamic baroreflex sensitivity (BRS). However, little is known about the reliability of this method and its ability to discern fundamental properties of the baroreflex. In this study we sought to: 1) evaluate the reliability of the sit-to-stand method for assessing BRS and compare its performance against two established methods (Oxford method and Valsalva maneuver), and 2) examine whether the frequency of the sit-to-stand method influences hysteresis. Sixteen healthy participants underwent three trials of each method. For the sit-to-stand method, which was performed at 0.1 and 0.05 Hz, BRS was quantified as an integrated response (BRSINT) and in response to falling and rising BP (BRSDOWN and BRSUP, respectively). Test retest reliability was assessed using the intraclass correlation coefficient (ICC). Irrespective of frequency, the ICC for BRSINT during the sit-to-stand method was ≥0.88. The ICC for a rising BP evoked by phenylephrine (PEGAIN) in the Oxford method was 0.78 and ≤0.5 for the remaining measures. During the sit-to-stand method, hysteresis was apparent in all participants at 0.1 Hz but was absent at 0.05 Hz. These findings indicate the sit-to-stand method is a statistically reliable BRS assessment tool and suitable for the examination of baroreflex hysteresis. Using this approach we showed that baroreflex hysteresis is a frequency-dependent phenomenon.
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Affiliation(s)
- H. M. Horsman
- Cardiovascular Systems Laboratory
- Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - Y. C. Tzeng
- Cardiovascular Systems Laboratory
- Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - D. C. Galletly
- Cardiovascular Systems Laboratory
- Centre for Translational Physiology, University of Otago, Wellington, New Zealand
| | - K. C. Peebles
- Cardiovascular Systems Laboratory
- Centre for Translational Physiology, University of Otago, Wellington, New Zealand
- Department of Physiology, University of Otago, Dunedin, New Zealand; and
- Department of Human Sciences, Macquarie University, Sydney, Australia
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31
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Wang L, Zhao M, Ma J, Tian S, Xiang P, Yao W, Fan Y. Effect of combining traction and vibration on back muscles, heart rate and blood pressure. Med Eng Phys 2014; 36:1443-8. [PMID: 25263929 DOI: 10.1016/j.medengphy.2014.08.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 06/19/2014] [Accepted: 08/20/2014] [Indexed: 10/24/2022]
Abstract
Eighty-five percent of the population has experienced low back pain (LBP), which may result in decreasing muscle strength and endurance, functional capacity of the spine, and so on. Traction and vibration are commonly used to relieve the low back pain. The effect of the combing traction and vibration on back muscles, heart rate (HR) and blood pressure (BP) was investigated in this study. Thirty healthy subjects participated in 12 trials lying supine on the spine-combing bed with different tilt angle (0°, 10°, 20° and 30°) and vibration modes (along with the sagittal and coronal axis with 0 Hz, 2 Hz and 12 Hz separately). EMG was recorded during each trial. Power spectral frequency analysis was applied to evaluate muscle fatigue by the shift of median power frequency (MPF). Pulse pressure (PP) was calculated from BP. HR and PP were used to estimate the effect of the combination of traction and vibration on the cardio-vascular system. It was shown that vibration could increase HR and decrease PP. The combination of traction and vibration (2 Hz vibration along Z-axis and 12 Hz vibration along Y-axis) had no significant effect on the cardio-vascular system. The MPF of lumbar erector spinae (LES) and upper trapezius (UT) decreased significantly when the angle reached 20° under the condition of 2 Hz vibration along Z-axis compared with it of 0°. Furthermore, the MPF also decreased significantly compared with it of static mode at 20° for LES and at 30° for UT. However at 12 Hz vibration along Y-axis, the MPF had significant increase when the angle reached 20° in LES and 30° in UT compared to 0°. For LES, the MPF also had significant difference when the angle was increased from 10° to 20°. Therefore, combining 2 Hz vibration along Z-axis and traction (tilt angles that less than 20°) may to reduce muscle fatigue both for LES and UT compared with either vibration or traction alone. The combination of 12 Hz vibration along Y-axis and traction (tilt angles greater than 10° for LES and more than 20° for UT) could provide good treatment of lower muscle fatigue for back pain compared with either vibration or traction alone. It is helpful to provide biomechanical quantitative basis for the selection of the clinical treatment methods.
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Affiliation(s)
- Lizhen Wang
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, 100191 Beijing, China; International Joint Research Center of Aerospace Biotechnology and Medical Engineering, Ministry of Science and Technology of China, 100191 Beijing, China
| | - Meiya Zhao
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, 100191 Beijing, China; International Joint Research Center of Aerospace Biotechnology and Medical Engineering, Ministry of Science and Technology of China, 100191 Beijing, China
| | - Jian Ma
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, 100191 Beijing, China; International Joint Research Center of Aerospace Biotechnology and Medical Engineering, Ministry of Science and Technology of China, 100191 Beijing, China
| | - Shan Tian
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, 100191 Beijing, China; International Joint Research Center of Aerospace Biotechnology and Medical Engineering, Ministry of Science and Technology of China, 100191 Beijing, China
| | - Pin Xiang
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, 100191 Beijing, China; International Joint Research Center of Aerospace Biotechnology and Medical Engineering, Ministry of Science and Technology of China, 100191 Beijing, China
| | - Wei Yao
- Bioengineering Unit, Department of Biomedical Engineering, University of Strathclyde, Glasgow G4 0NW, UK
| | - Yubo Fan
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, 100191 Beijing, China; International Joint Research Center of Aerospace Biotechnology and Medical Engineering, Ministry of Science and Technology of China, 100191 Beijing, China.
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32
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Yanagida R, Ogawa Y, Ueda K, Aoki K, Iwasaki KI. Sustained mild hypergravity reduces spontaneous cardiac baroreflex sensitivity. Auton Neurosci 2014; 185:123-8. [PMID: 25156804 DOI: 10.1016/j.autneu.2014.07.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Revised: 07/07/2014] [Accepted: 07/08/2014] [Indexed: 10/24/2022]
Abstract
Head-to-foot gravitational force >1G (+Gz hypergravity) augments venous pooling in the lower body and reduces central blood volume during exposure, compared with 1Gz. Central hypovolemia has been reported to reduce spontaneous cardiac baroreflex sensitivity. However, no investigations have examined spontaneous cardiac baroreflex sensitivity during exposure to sustained mild +Gz hypergravity. We therefore hypothesized that mild +Gz hypergravity would reduce spontaneous cardiac baroreflex sensitivity, compared with 1Gz. To test this hypothesis, we examined spontaneous cardiac baroreflex sensitivity in 16 healthy men during exposure to mild +Gz hypergravity using a short-arm centrifuge. Beat-to-beat arterial blood pressure (tonometry) and R-R interval (electrocardiography) were obtained during 1Gz and 1.5Gz exposures. Spontaneous cardiac baroreflex sensitivity was assessed by sequence slope and transfer function gain. Stroke volume was calculated from the arterial pressure waveform using a three-element model. All indices of spontaneous cardiac baroreflex sensitivity decreased significantly (up slope: 18.6±2.3→12.7±1.6ms/mmHg, P<0.001; down slope: 19.0±2.5→13.2±1.3ms/mmHg, P=0.002; transfer function gain in low frequency: 14.4±2.2→10.1±1.1ms/mmHg, P=0.004; transfer function gain in high frequency: 22.2±7.5→12.4±3.5ms/mmHg, P<0.001). Stroke volume decreased significantly (88±5→80±6ml, P=0.025). Moreover, although systolic arterial pressure variability increased, R-R interval variability did not increase. These results suggest that even mild +Gz hypergravity reduces spontaneous cardiac baroreflex sensitivity, increasing the risk of cardiovascular disturbance during the exposure.
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Affiliation(s)
- Ryo Yanagida
- Division of Hygiene, Department of Social Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Yojiro Ogawa
- Division of Hygiene, Department of Social Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Kaname Ueda
- Department of Anesthesiology, Nihon University School of Medicine, Tokyo, Japan
| | - Ken Aoki
- Division of Hygiene, Department of Social Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Ken-ichi Iwasaki
- Division of Hygiene, Department of Social Medicine, Nihon University School of Medicine, Tokyo, Japan.
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Bartels-Ferreira R, de Sousa ÉD, Trevizani GA, Silva LP, Nakamura FY, Forjaz CLM, Lima JRP, Peçanha T. Can a first-order exponential decay model fit heart rate recovery after resistance exercise? Clin Physiol Funct Imaging 2014; 35:98-103. [PMID: 24494748 DOI: 10.1111/cpf.12132] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 01/03/2014] [Indexed: 12/01/2022]
Abstract
The time-constant of postexercise heart rate recovery (HRRτ ) obtained by fitting heart rate decay curve by a first-order exponential fitting has being used to assess cardiac autonomic recovery after endurance exercise. The feasibility of this model was not tested after resistance exercise (RE). The aim of this study was to test the goodness of fit of the first-order exponential decay model to fit heart rate recovery (HRR) after RE. Ten healthy subjects participated in the study. The experimental sessions occurred in two separated days and consisted of performance of 1 set of 10 repetitions at 50% or 80% of the load achieved on the one-repetition maximum test [low-intensity (LI) and high-intensity (HI) sessions, respectively]. Heart rate (HR) was continuously registered before and during exercise and also for 10 min of recovery. A monoexponential equation was used to fit the HRR curve during the postexercise period using different time windows (i.e. 30, 60, 90, … 600 s). For each time window, (i) HRRτ was calculated and (ii) variation of HR explained by the model (R(2) goodness of fit index) was assessed. The HRRτ showed stabilization from 360 and 420 s on LI and HI, respectively. Acceptable R(2) values were observed from the 360 s on LI (R(2) > 0.65) and at all tested time windows on HI (R(2) > 0.75). In conclusion, this study showed that using a minimum length of monitoring (~420 s) HRR after RE can be adequately modelled by a first-order exponential fitting.
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Affiliation(s)
- Rhenan Bartels-Ferreira
- Biomedical Engineering Program, COPPE, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
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Horsman HM, Peebles KC, Galletly DC, Tzeng YC. Cardiac baroreflex gain is frequency dependent: insights from repeated sit-to-stand maneuvers and the modified Oxford method. Appl Physiol Nutr Metab 2013; 38:753-9. [DOI: 10.1139/apnm-2012-0444] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Helen M. Horsman
- Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, 23A Mein Street, Wellington South, New Zealand
- Department of Surgery and Anaesthesia, University of Otago, Wellington South, New Zealand
| | - Karen C. Peebles
- Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, 23A Mein Street, Wellington South, New Zealand
- Department of Surgery and Anaesthesia, University of Otago, Wellington South, New Zealand
- Department of Physiology, University of Otago, Wellington South, New Zealand
| | - Duncan C. Galletly
- Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, 23A Mein Street, Wellington South, New Zealand
| | - Yu-Chieh Tzeng
- Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, 23A Mein Street, Wellington South, New Zealand
- Department of Surgery and Anaesthesia, University of Otago, Wellington South, New Zealand
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35
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Adami A, Pizzinelli P, Bringard A, Capelli C, Malacarne M, Lucini D, Simunič B, Pišot R, Ferretti G. Cardiovascular re-adjustments and baroreflex response during clinical reambulation procedure at the end of 35-day bed rest in humans. Appl Physiol Nutr Metab 2013; 38:673-80. [DOI: 10.1139/apnm-2012-0396] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During the reambulation procedure after 35-day head-down tilt bed rest (HDTBR) for 9 men, we recorded for the first time heart rate (HR; with electrocardiogram) and arterial pressure profiles (fingertip plethysmography) for 5 min in HDTBR and horizontal (SUP) positions, followed by 12 min in standing position, during which 4 subjects fainted (intolerant, INT) and were laid horizontal again (Recovery). We computed: mean arterial pressure (P¯; pressure profiles integral mean), stroke volume (SV; obtained with Modelflow method), and cardiac output (Q̇; SV × HR). All cardiovascular data remained stable in HDTBR and SUP for both groups (EXP). Taking the upright posture, EXP showed a decrease in SV and an increase in HR, becoming significantly different from SUP within 1 min. Further evolution of these parameters kept Q̇ stable in both groups until the second minute of standing. Afterward, in INT, P̄ precipitated without further HR increases: SV stopped being corrected and Q̇ reached 2.9 ± 0.4 L·min−1 at the last 15 s of standing. Sudden drop in P̄ allowed identification of a low-pressure threshold in INT (70.7 ± 12.9 mm Hg), after which syncope occurred within 80 s. During Recovery, baroreflex curves showed a flat phase (P̄ increase, HR stable), followed by a steep phase (P̄ increased, HR decreased, starting when P̄ was 84.5 ± 12.5 mm Hg and Q̇ was 9.6 ± 1.5 L·min−1). INT, in contrast with tolerant subjects, did not sustain standing because HR was unable to correct for the P̄ drop. These results indicate a major role for impaired arterial baroreflexes in the onset of orthostatic intolerance.
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Affiliation(s)
- Alessandra Adami
- Département de Neuroscience Fondamentales, Centre Médical Universitaire, Université de Genève, 1 Rue Michel Servet, CH-1211 Genève 4, Switzerland
| | - Paolo Pizzinelli
- Dipartimento di Scienze Cliniche, Ospedale L. Sacco, Università di Milano, via GB. Grassi 74, Milano, Italia
| | - Aurélien Bringard
- Département de Neuroscience Fondamentales, Centre Médical Universitaire, Université de Genève, 1 Rue Michel Servet, CH-1211 Genève 4, Switzerland
| | - Carlo Capelli
- Dipartimento di Scienze Neurologiche, Neuropsicologiche, Morfologiche e Motorie, Facoltà di Scienze Motorie, Università di Verona, via F. Casorati, 54, 37100 Verona, Italia
| | - Mara Malacarne
- Dipartimento di Scienze Cliniche, Ospedale L. Sacco, Università di Milano, via GB. Grassi 74, Milano, Italia
| | - Daniela Lucini
- Dipartimento di Scienze Cliniche, Ospedale L. Sacco, Università di Milano, via GB. Grassi 74, Milano, Italia
| | - Boštjan Simunič
- Institute of Kinesiology Research, Science and Research Center, University of Primorska, Koper, Garibaldijeva street 1, 6000 Koper, Slovenia
| | - Rado Pišot
- Institute of Kinesiology Research, Science and Research Center, University of Primorska, Koper, Garibaldijeva street 1, 6000 Koper, Slovenia
| | - Guido Ferretti
- Département de Neuroscience Fondamentales, Centre Médical Universitaire, Université de Genève, 1 Rue Michel Servet, CH-1211 Genève 4, Switzerland
- Dipartimento di Scienze Biomediche e Biotecnologie, Facoltà di Medicina, Università di Brescia, Viale Europa 11, 25123 Brescia, Italia
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Stewart JM. Update on the theory and management of orthostatic intolerance and related syndromes in adolescents and children. Expert Rev Cardiovasc Ther 2013; 10:1387-99. [PMID: 23244360 DOI: 10.1586/erc.12.139] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Orthostasis means standing upright. One speaks of orthostatic intolerance (OI) when signs, such as hypotension, and symptoms, such as lightheadedness, occur when upright and are relieved by recumbence. The experience of transient mild OI is part of daily life. 'Initial orthostatic hypotension' on rapid standing is a normal form of OI. However, other people experience OI that seriously interferes with quality of life. These include episodic acute OI, in the form of postural vasovagal syncope, and chronic OI, in the form of postural tachycardia syndrome. Less common is neurogenic orthostatic hypotension, which is an aspect of autonomic failure. Normal orthostatic physiology and potential mechanisms for OI are discussed, including forms of sympathetic hypofunction, forms of sympathetic hyperfunction and OI that results from regional blood volume redistribution. General and specific treatment options are proposed.
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Affiliation(s)
- Julian M Stewart
- Departments of Pediatrics, Physiology and Medicine, The Maria Fareri Childrens Hospital and New York Medical College, Valhalla, NY, USA.
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Faes L, Masè M, Nollo G, Chon KH, Florian JP. Measuring postural-related changes of spontaneous baroreflex sensitivity after repeated long-duration diving: frequency domain approaches. Auton Neurosci 2013; 178:96-102. [PMID: 23587978 DOI: 10.1016/j.autneu.2013.03.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 02/28/2013] [Accepted: 03/12/2013] [Indexed: 11/29/2022]
Abstract
Sustained water immersion is thought to modulate orthostatic tolerance to an extent dependent on the duration and repetition over consecutive days of the diving sessions. We tested this hypothesis investigating in ten healthy subjects the potential changes in the cardiovascular response to head-up tilt induced by single and multiple resting air dives. Parametric cross-spectral analysis of spontaneous RR interval and systolic arterial pressure variability was performed in three experimental sessions: before diving (BD), after single 6-hour dive (ASD), and after multiple 6-hour dives (AMD, 5 consecutive days with 18-hour surface interval). From this analysis, baroreflex sensitivity (BRS) was computed as spectral power ratio (αBRS), non-causal transfer function gain (tfBRS) and causal transfer function gain (γBRS) evaluated at low frequency (0.04-0.14Hz) in the supine position (su) as well as in the standing upright position in the early tilt (et) and late tilt (lt) epochs. We found that, while αBRS decreased significantly in et and lt compared to su during all sessions, tfBRS and γBRS decreased during ASD and AMD but not during BD; moreover γBRS evidenced a progressive decrease from BD to ASD and to AMD in both et and lt epochs. These results indicate the necessity of following a causal approach for the estimation of BRS in the frequency domain, and suggest a progressive impairment of the baroreflex response to postural stress after single and multiple dives, which may reflect symptoms of increasing orthostatic intolerance.
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Affiliation(s)
- Luca Faes
- Department Physics and BIOtech Center, University of Trento, Trento, Italy.
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Arzeno NM, Stenger MB, Lee SMC, Ploutz-Snyder R, Platts SH. Sex differences in blood pressure control during 6° head-down tilt bed rest. Am J Physiol Heart Circ Physiol 2013; 304:H1114-23. [PMID: 23396455 DOI: 10.1152/ajpheart.00391.2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Spaceflight-induced orthostatic intolerance has been studied for decades. Although ∼22% of the astronaut corps are women, most mechanistic studies use mostly male subjects, despite known sex differences in autonomic control and postflight orthostatic intolerance. We studied adrenergic, baroreflex, and autonomic indexes during continuous infusions of vasoactive drugs in men and women during a 60-day head-down bed rest. Volunteers were tested before bed rest (20 men and 10 women) and around day 30 (20 men and 10 women) and day 60 (16 men and 8 women) of bed rest. Three increasing doses of phenylephrine (PE) and sodium nitroprusside were infused for 10 min after an infusion of normal saline. A 20-min rest period separated the phenylephrine and sodium nitroprusside infusions. Autonomic activity was approximated by spectral indexes of heart rate and blood pressure variability, and baroreflex sensitivity was measured by the spontaneous baroreflex slope. Parasympathetic modulation and baroreflex sensitivity decreased with bed rest, with women experiencing a larger decrease in baroreflex sensitivity by day 30 than men. The sympathetic activation of men and parasympathetic responsiveness of women in blood pressure control during physiological stress were preserved throughout bed rest. During PE infusions, women experienced saturation of the R-R interval at high frequency, whereas men did not, revealing a sex difference in the parabolic relationship between high-frequency R-R interval, a measurement of respiratory sinus arrhythmia, and R-R interval. These sex differences in blood pressure control during simulated microgravity reveal the need to study sex differences in long-duration spaceflight to ensure the health and safety of the entire astronaut corps.
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Affiliation(s)
- Natalia M Arzeno
- Wyle Science, Technology and Engineering Group, Houston, Texas, USA
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Ogawa Y, Aoki K, Kato J, Iwasaki KI. Differential effects of mild central hypovolemia with furosemide administration vs. lower body suction on dynamic cerebral autoregulation. J Appl Physiol (1985) 2012. [PMID: 23195631 DOI: 10.1152/japplphysiol.00741.2012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Diuretic-induced mild hypovolemia with hemoconcentration reportedly improves dynamic cerebral autoregulation, whereas central hypovolemia without hemoconcentration induced by lower body negative pressure (LBNP) has no effect or impairs dynamic cerebral autoregulation. This discrepancy may be explained by different blood properties, by degrees of central hypovolemia, or both. We investigated the effects of equivalent central hypovolemia induced by furosemide administration or LBNP application on dynamic cerebral autoregulation to test our hypothesis that mild central hypovolemia due to furosemide administration enhances dynamic cerebral autoregulation in contrast to LBNP. Seven healthy male subjects received 0.4 mg/kg furosemide and LBNP, with equivalent decreases in central venous pressure (CVP). Dynamic cerebral autoregulation was assessed by spectral and transfer function analysis between beat-to-beat mean arterial blood pressure (MAP) and mean cerebral blood flow velocity (MCBFV). CVP decreased by ∼3-4 mmHg with both furosemide administration (∼26 mg) and LBNP (approximately -20 mmHg). Steady state MCBFV remained unchanged with both techniques, whereas MAP increased significantly with furosemide administration. Coherence and transfer function gain in the low and high frequency ranges with hypovolemia due to furosemide administration were significantly lower than those due to LBNP (ANOVA interaction effects, P < 0.05), although transfer function gain in the very low frequency range did not change. Our results suggest that although the decreases in CVP were equivalent between furosemide administration and LBNP, the resultant central hypovolemia differentially affected dynamic cerebral autoregulation. Mild central hypovolemia with hemoconcentration resulting from furosemide administration may enhance dynamic cerebral autoregulation compared with LBNP.
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Affiliation(s)
- Yojiro Ogawa
- Division of Hygiene, Department of Social Medicine, Nihon University School of Medicine, Tokyo 173-8610, Japan
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40
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Schmitt L, Millet GP. Ineffective normobaric LHTL: room confinement or inappropriate training intensity? J Appl Physiol (1985) 2012; 112:527; author reply 528. [PMID: 22302933 DOI: 10.1152/japplphysiol.01431.2011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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41
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Ichinose M, Sala-Mercado JA, Coutsos M, Li Z, Ichinose TK, Dawe E, Fano D, O'Leary DS. Dynamic cardiac output regulation at rest, during exercise, and muscle metaboreflex activation: impact of congestive heart failure. Am J Physiol Regul Integr Comp Physiol 2012; 303:R757-68. [PMID: 22855278 DOI: 10.1152/ajpregu.00119.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We tested whether mild and moderate dynamic exercise and muscle metaboreflex activation (MMA) affect dynamic baroreflex control of heart rate (HR) and cardiac output (CO), and the influence of stroke volume (SV) fluctuations on CO regulation in normal (N) and pacing-induced heart failure (HF) dogs by employing transfer function analyses of the relationships between spontaneous changes in left ventricular systolic pressure (LVSP) and HR, LVSP and CO, HR and CO, and SV and CO at low and high frequencies (Lo-F, 0.04-0.15 Hz; Hi-F, 0.15-0.6 Hz). In N dogs, both workloads significantly decreased the gains for LVSP-HR and LVSP-CO in Hi-F, whereas only moderate exercise also reduced the LVSP-CO gain in Lo-F. MMA during mild exercise further decreased the gains for LVSP-HR in both frequencies and for LVSP-CO in Lo-F. MMA during moderate exercise further reduced LVSP-HR gain in Lo-F. Coherence for HR-CO in Hi-F was decreased by exercise and MMA, whereas that in Lo-F was sustained at a high level (>0.8) in all settings. HF significantly decreased dynamic HR and CO regulation in all situations. In HF, the coherence for HR-CO in Lo-F decreased significantly in all settings; the coherence for SV-CO in Lo-F was significantly higher. We conclude that dynamic exercise and MMA reduces dynamic baroreflex control of HR and CO, and these are substantially impaired in HF. In N conditions, HR modulation plays a major role in CO regulation. In HF, influence of HR modulation wanes, and fluctuations of SV dominate in CO variations.
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Affiliation(s)
- Masashi Ichinose
- Dept. of Physiology, Wayne State Univ. School of Medicine, Detroit, MI 48201, USA
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Yanagida R, Ogawa Y, Mizuochi F, Suzuki T, Takahashi M, Iwasaki K. [Relationship between baroreflex function and training effects on altitude training]. Nihon Eiseigaku Zasshi 2012; 67:417-22. [PMID: 22781017 DOI: 10.1265/jjh.67.417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Altitude training is frequently used for athletes requiring competitive endurance in an attempt to improve their sea-level performance. However, there has been no study in which the mechanisms by which spontaneous arterial-cardiac baroreflex function changes was examined in responders or nonresponders of altitude training. The purpose of this study was to clarify the different effects of altitude training on baroreflex function between responders and nonresponders. METHODS Twelve university student cross-country skiers (6 men, 6 women; age, 19±1 years) participated in the altitude training in a camp for 3 weeks, which was carried out in accordance with the method of Living High-Training Low. Baroreflex function was estimated by transfer function analysis before and after the training. RESULTS The responders of the training were 3 men and 2 women, and the nonresponders were 3 men and 4 women. In the responders, the transfer function gain in the high-frequency range significantly increased after the training (28.9→46.5 ms/mmHg p=0.021). On the other hand, no significant change in this index was observed in the nonresponders (25.9→21.2 ms/mmHg p=0.405). CONCLUSION As indicated by the results of transfer function gain in the high-frequency range, the baroreflex function in the responders increased significantly after the altitude training, whereas no significant change was observed in the nonresponders.
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Affiliation(s)
- Ryo Yanagida
- Department of Social Medicine, Nihon University School of Medicine, Japan
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Aletti F, Ferrario M, Xu D, Greaves DK, Shoemaker JK, Arbeille P, Baselli G, Hughson RL. Short-term variability of blood pressure: effects of lower-body negative pressure and long-duration bed rest. Am J Physiol Regul Integr Comp Physiol 2012; 303:R77-85. [DOI: 10.1152/ajpregu.00050.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mild lower-body negative pressure (LBNP) has been utilized to selectively unload cardiopulmonary baroreceptors, but there is evidence that arterial baroreceptors can be transiently unloaded after the onset of mild LBNP. In this paper, a black box mathematical model for the prediction of diastolic blood pressure (DBP) variability from multiple inputs (systolic blood pressure, R-R interval duration, and central venous pressure) was applied to interpret the dynamics of blood pressure maintenance under the challenge of LBNP and in long-duration, head-down bed rest (HDBR). Hemodynamic recordings from seven participants in the WISE (Women's International Space Simulation for Exploration) Study collected during an experiment of incremental LBNP (−10 mmHg, −20 mmHg, −30 mmHg) were analyzed before and on day 50 of a 60-day-long HDBR campaign. Autoregressive spectral analysis focused on low-frequency (LF, ∼0.1 Hz) oscillations of DBP, which are related to fluctuations in vascular resistance due to sympathetic and baroreflex regulation of vasomotor tone. The arterial baroreflex-related component explained 49 ± 13% of LF variability of DBP in spontaneous conditions, and 89 ± 9% ( P < 0.05) on day 50 of HDBR, while the cardiopulmonary baroreflex component explained 17 ± 9% and 12 ± 4%, respectively. The arterial baroreflex-related variability was significantly increased in bed rest also for LBNP equal to −20 and −30 mmHg. The proposed technique provided a model interpretation of the proportional effect of arterial baroreflex vs. cardiopulmonary baroreflex-mediated components of blood pressure control and showed that arterial baroreflex was the main player in the mediation of DBP variability. Data during bed rest suggested that cardiopulmonary baroreflex-related effects are blunted and that blood pressure maintenance in the presence of an orthostatic stimulus relies mostly on arterial control.
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Affiliation(s)
- Federico Aletti
- Dipartimento di Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Manuela Ferrario
- Dipartimento di Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Da Xu
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, Ontario, Canada
| | - Danielle K. Greaves
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, Ontario, Canada
| | - J. Kevin Shoemaker
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada; and
| | - Philippe Arbeille
- Unité Médecine et Physiologie Spatiale CEntre de Recherche COeur et Maladies vasculaires, University Hospital Trousseau, Tours, France
| | - Giuseppe Baselli
- Dipartimento di Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Richard L. Hughson
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, Ontario, Canada
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Abstract
Sympathetic circulatory control is key to the rapid cardiovascular adjustments that occur within seconds of standing upright (orthostasis) and which are required for bipedal stance. Indeed, patients with ineffective sympathetic adrenergic vasoconstriction rapidly develop orthostatic hypotension, prohibiting effective upright activities. One speaks of orthostatic intolerance (OI) when signs, such as hypotension, and symptoms, such as lightheadedness, occur when upright and are relieved by recumbence. The experience of transient mild OI is part of daily life. However, many people experience episodic acute OI as postural faint or chronic OI in the form of orthostatic tachycardia and orthostatic hypotension that significantly reduce the quality of life. Potential mechanisms for OI are discussed including forms of sympathetic hypofunction, forms of sympathetic hyperfunction, and OI that results from regional blood volume redistribution attributable to regional adrenergic hypofunction.
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Affiliation(s)
- Julian M Stewart
- Departments of Physiology, Pediatrics and Medicine, New York Medical College, Valhalla, NY, USA. mail:
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Sumi K, Katayama Y, Otaka T, Obuchi T, Kano T, Kobayashi K, Oshima H, Fukaya C, Yamamoto T, Ogawa Y, Iwasaki K. Effect of Subthalamic Nucleus Deep Brain Stimulation on the Autonomic Nervous System in Parkinsons Disease Patients Assessed by Spectral Analyses of R-R Interval Variability and Blood Pressure Variability. Stereotact Funct Neurosurg 2012; 90:248-54. [DOI: 10.1159/000338090] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2011] [Accepted: 02/27/2012] [Indexed: 11/19/2022]
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Siebenmann C, Robach P, Jacobs RA, Rasmussen P, Nordsborg N, Diaz V, Christ A, Olsen NV, Maggiorini M, Lundby C. "Live high-train low" using normobaric hypoxia: a double-blinded, placebo-controlled study. J Appl Physiol (1985) 2011; 112:106-17. [PMID: 22033534 DOI: 10.1152/japplphysiol.00388.2011] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The combination of living at altitude and training near sea level [live high-train low (LHTL)] may improve performance of endurance athletes. However, to date, no study can rule out a potential placebo effect as at least part of the explanation, especially for performance measures. With the use of a placebo-controlled, double-blinded design, we tested the hypothesis that LHTL-related improvements in endurance performance are mediated through physiological mechanisms and not through a placebo effect. Sixteen endurance cyclists trained for 8 wk at low altitude (<1,200 m). After a 2-wk lead-in period, athletes spent 16 h/day for the following 4 wk in rooms flushed with either normal air (placebo group, n = 6) or normobaric hypoxia, corresponding to an altitude of 3,000 m (LHTL group, n = 10). Physiological investigations were performed twice during the lead-in period, after 3 and 4 wk during the LHTL intervention, and again, 1 and 2 wk after the LHTL intervention. Questionnaires revealed that subjects were unaware of group classification. Weekly training effort was similar between groups. Hb mass, maximal oxygen uptake (VO(2)) in normoxia, and at a simulated altitude of 2,500 m and mean power output in a simulated, 26.15-km time trial remained unchanged in both groups throughout the study. Exercise economy (i.e., VO(2) measured at 200 W) did not change during the LHTL intervention and was never significantly different between groups. In conclusion, 4 wk of LHTL, using 16 h/day of normobaric hypoxia, did not improve endurance performance or any of the measured, associated physiological variables.
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Affiliation(s)
- Christoph Siebenmann
- Center for Integrative Human Physiology, Institute of Physiology, University of Zurich, Zurich, Switzerland
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Thijssen DHJ, Green DJ, Hopman MTE. Blood vessel remodeling and physical inactivity in humans. J Appl Physiol (1985) 2011; 111:1836-45. [PMID: 21737819 DOI: 10.1152/japplphysiol.00394.2011] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Physical inactivity is associated with an increase in cardiovascular risk that cannot be fully explained by traditional or novel risk factors. Inactivity is also associated with changes in hemodynamic stimuli, which exert direct effects on the vasculature leading to remodeling and a proatherogenic phenotype. In this review, we synthesize and summarize in vivo evidence relating to the impact of local and systemic models of physical inactivity on conduit arteries, resistance vessels, and the microcirculation in humans. Taken together, the literature suggests that a rapid inward structural remodeling of vessels occurs in response to physical inactivity. The magnitude of this response is dependent on the "dose" of inactivity. Moreover, changes in vascular function are found at resistance and microvessel levels in humans. In conduit arteries, a strong interaction between vascular function and structure is present, which results in conflicting data regarding the impact of inactivity on conduit artery function. While much of the cardioprotective effect of exercise is related to the nitric oxide pathway, deconditioning may primarily be associated with activation of vasoconstrictor pathways. The effects of deconditioning on the vasculature are therefore not simply the opposite of those in response to exercise training. Given the importance of sedentary behavior, future studies should provide further insight into the impact of inactivity on the vasculature and other (novel) markers of vascular health. Moreover, studies should examine the role of (hemodynamic) stimuli that underlie the characteristic vascular adaptations during deconditioning. Our review concludes with some suggestions for future research directions.
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Affiliation(s)
- Dick H J Thijssen
- Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom.
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Niizeki K, Tominaga T, Saitoh T, Nishidate I, Takahashi T, Uchida K. Effects of lower-leg rhythmic cuff inflation on cardiovascular autonomic responses during quiet standing in healthy subjects. Am J Physiol Heart Circ Physiol 2011; 300:H1923-9. [PMID: 21378141 DOI: 10.1152/ajpheart.01288.2010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To determine the effects of muscle pump function on cardiac autonomic activity in response to quiet standing, we simulated the muscle pump effect by rhythmic lower-leg cuff inflation (RCI) with four cuff pressures of 0 (sham), 40, 80, and 120 mmHg at 5 cycles/min. The R-R interval (RRI) and beat-to-beat blood pressure (BP) were acquired in healthy subjects (6 males and 5 females, aged 21-24 yr). From the continuous BP measurement, stroke volume (SV) was calculated by a pulse-contour method. Using spectral and cross-spectral analysis, RRI and systolic BP variability as well as the gain of spontaneous cardiac baroreflex sensitivity (sBRS) were estimated for the low- and high-frequency (HF) bands. Compared with the sham condition, RCI with cuff pressures of 80 and 120 mmHg led to increases in the mean RRI (P < 0.01) and HF power of RRI fluctuation (P < 0.05 for 80 mmHg and P < 0.01 for 120 mmHg) during quiet standing. Reduction in SV during standing was suppressed, and the sBRS of the HF band for standing were increased by RCI for either cuff pressure (P < 0.05 for 80 mmHg and P < 0.01 for 120 mmHg). However, at 40 mmHg RCI, these remained unchanged. These results suggest that, during standing, RCI of the lower leg increases cardiac vagal outflow when the cuff pressure is raised enough to oppose the hydrostatic-induced venous pressure in the calf.
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Affiliation(s)
- Kyuichi Niizeki
- Department of Bio-System Engineering, Graduate School of Science and Technology, Yamagata University, Yonezawa, Japan.
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Baskin KK, Taegtmeyer H. Taking pressure off the heart: the ins and outs of atrophic remodelling. Cardiovasc Res 2011; 90:243-50. [PMID: 21354996 DOI: 10.1093/cvr/cvr060] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Our work on atrophic remodelling of the heart has led us to appreciate the simple principles in biology: (i) the dynamic nature of intracellular protein turnover, (ii) the return to the foetal gene programme when the heart remodels, and (iii) the adaptive changes of cardiac metabolism. Although the molecular mechanisms of cardiac hypertrophy are many, much less is known regarding the molecular mechanisms of cardiac atrophy. We state the case that knowing more about mechanisms of atrophic remodelling may provide insights into cellular consequences of metabolic and haemodynamic unloading of the stressed heart. Overall we strive to find an answer to the question: 'What makes the failing heart shrink and become stronger?' We speculate that signals arising from intermediary metabolism of energy-providing substrates are likely candidates.
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Affiliation(s)
- Kedryn K Baskin
- Department of Internal Medicine, Division of Cardiology, The University of Texas School of Medicine at Houston, 6431 Fannin, MSB 1.246, Houston, TX 77030, USA
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Artificial gravity with ergometric exercise as a countermeasure against cardiovascular deconditioning during 4 days of head-down bed rest in humans. Eur J Appl Physiol 2011; 111:2315-25. [DOI: 10.1007/s00421-011-1866-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Accepted: 02/03/2011] [Indexed: 10/18/2022]
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