Comparison of the Polar S810i monitor and the ECG for the analysis of heart rate variability in the time and frequency domains

Does heart rate variability improve prediction of failed extubation in preterm infants?

Background Prematurity and its respective comorbidities may result in longer periods of mechanical ventilation in intensive care units (ICU). A method for the assessment of organic maturity would be useful for this population. Heart rate variability (HRV), as an indicator of homeostasis, is a well-established tool for this approach. The objective of the study was to assess HRV in intubated preterm infants in ICU immediately prior to extubation and correlate HRV with clinical evaluation outcomes. Methods A total of 46 preterm infants, 13 (28.2%) males, were prospectively studied and divided into a group with failed extubation (FEG: n=11) and a group with successful extubation (SEG: n=35). HRV was evaluated in time, frequency and nonlinear domains with a Polar RS800 device. HRV measurements were assessed with Kubios HRV Premium Software and statistically analyzed with the StatsDirect Statistical Software, version 1.9.2015 (2002). P<0.05 values were considered as statistically significant. Results There were no significant differences between heart rate variables of failed and successful extubation when analyzing the total group. However, the analysis of the sub-group of preterm infants weighing less than 1000 g showed a clear differentiation between the groups, when the nonlinear variables (approximate entropy, sample entropy and multiscale entropy 1, 2 and 3) were used, demonstrating that the group with successful extubation shows greater complexity and, therefore, relatively greater autonomic stability. Conclusion HRV was effective in predicting failed extubation in preterm infants when evaluated in a nonlinear domain and in preterm infants weighing less than 1000 g.

Analysis of Autonomic Modulation in Response to a Session of Aerobic Exercise at Different Intensities in Patients With Moderate and Severe COPD

Despite the many benefits of performing physical exercise in patients with chronic obstructive pulmonary disease (COPD), information on the response of acute cardiac autonomic modulation in subjects with moderate and severe COPD during and after an aerobic exercise session at different intensities is unknown. The aim of this study was to evaluate the response of cardiac autonomic modulation in patients with moderate and severe COPD during and after an aerobic exercise session at different intensities. Twenty-seven patients with COPD, divided into: Moderate Group and Severe Group, underwent an aerobic exercise sessions with intensities equivalent to 60% and 90% of velocity corresponding to peak oxygen consumption. The heart rate variability (HRV) indices were analyzed in the time and frequency domains at the following times: at rest, during exercise, immediately after, and 5, 10, and 15 minutes after exercise. In the comparison analysis between the two groups, no differences were observed in any of the HRV indices at different intensities applied. However, it was observed that the exercise caused autonomic changes when the groups were analyzed separately. Sessions of aerobic exercise influence the autonomic modulation in patients with COPD. However, COPD severity did not influence the autonomic nervous system response to exercise and recovery moments; and there was no difference between the exercise intensities.

Waist-Stature Ratio And Its Relationship With Autonomic Recovery From Aerobic Exercise In Healthy Men

Autonomic modulation and cardiorespiratory variables are influenced by numerous factors, including anthropometric variables. We investigated autonomic recovery following aerobic exercise in healthy men with different waist-stature ratio (WSR) values. The study was conducted with 52 healthy men aged 18 to 30 years, divided into groups according to the WSR: G1 – between 0.40 and 0.449 (N = 19), G2 – between 0.45 and 0.50 (N = 28) and G3 – between 0.5 and 0.56 (N = 5). The subjects endured 15 minutes seated and at rest followed by an aerobic exercise and then remained seated for 60 minutes and at rest during recovery from exercise. Heart rate (HR) variability (HRV) (rMSSD, SD1, HF [ms²]) and cardiorespiratory variables were analyzed before and after exercise. Recovery of respiratory rate, diastolic blood pressure, SD1 and HF indices were delayed in G2. G3 presented delayed recovery after the maximal effort test while no difference with G2 was noted in the moderate intensity. Correlation and linear regression analysis indicated association of WSR, body mass index and waist circumference with HRV indices in the recovery from aerobic exercise (45 to 60 minutes after exercise) in G2. In conclusion, healthy men with higher WSR accomplished delayed autonomic recovery following maximal effort exercise.

Discovery of Causal Paths in Cardiorespiratory Parameters: A Time-Independent Approach in Elite Athletes

Training of elite athletes requires regular physiological and medical monitoring to plan the schedule, intensity and volume of training, and subsequent recovery. In sports medicine, ECG-based analyses are well-established. However, they rarely consider the correspondence of respiratory and cardiac activity. Given such mutual influence, we hypothesize that athlete monitoring might be developed with causal inference and that detailed, time-related techniques should be preceded by a more general, time-independent approach that considers the whole group of participants and parameters describing whole signals. The aim of this study was to discover general causal paths among cardiac and respiratory variables in elite athletes in two body positions (supine and standing), at rest. ECG and impedance pneumography signals were obtained from 100 elite athletes. The mean heart rate, the root-mean-square difference of successive RR intervals (RMSSD), its natural logarithm (lnRMSSD), the mean respiratory rate (RR), the breathing activity coefficients, and the resulting breathing regularity (BR) were estimated. Several causal discovery frameworks were applied, comprising Generalized Correlations (GC), Causal Additive Modeling (CAM), Fast Greedy Equivalence Search (FGES), Greedy Fast Causal Inference (GFCI), and two score-based Bayesian network learning algorithms: Hill-Climbing (HC) and Tabu Search. The discovery of cardiorespiratory paths appears ambiguous. The main, still mild, rules best supported by data are: for supine - tidal volume causes heart activity variation, which causes average heart activity, which causes respiratory timing; and for standing - normalized respiratory activity variation causes average heart activity. The presented approach allows data-driven and time-independent analysis of elite athletes as a particular population, without considering prior knowledge. However, the results seem to be consistent with the medical background. Causality inference is an interesting mathematical approach to the analysis of biological responses, which are complex. One can use it to profile athletes and plan appropriate training. In the next step, we plan to expand the study using time-related causality analyses.

Effect of Ischemic Preconditioning on the Recovery of Cardiac Autonomic Control From Repeated Sprint Exercise

Repeated sprint exercise (RSE) acutely impairs post-exercise heart rate (HR) recovery (HRR) and time-domain heart rate variability (i. e., RMSSD), likely in part, due to lactic acidosis-induced reduction of cardiac vagal reactivation. In contrast, ischemic preconditioning (IPC) mediates cardiac vagal activation and augments energy metabolism efficiency during prolonged ischemia followed by reperfusion. Therefore, we investigated whether IPC could improve recovery of cardiac autonomic control from RSE partially via improved energy metabolism responses to RSE. Fifteen men team-sport practitioners (mean ± SD: 25 ± 5 years) were randomly exposed to IPC in the legs (3 × 5 min at 220 mmHg) or control (CT; 3 × 5 min at 20 mmHg) 48 h, 24 h, and 35 min before performing 3 sets of 6 shuttle running sprints (15 + 15 m with 180° change of direction and 20 s of active recovery). Sets 1 and 2 were followed by 180 s and set 3 by 360 s of inactive recovery. Short-term HRR was analyzed after all sets via linear regression of HR decay within the first 30 s of recovery (T30) and delta from peak HR to 60 s of recovery (HRR60s). Long-term HRR was analyzed throughout recovery from set 3 via first-order exponential regression of HR decay. Moreover, RMSSD was calculated using 30-s data segments throughout recovery from set 3. Energy metabolism responses were inferred via peak pulmonary oxygen uptake (V˙O2peak), peak carbon dioxide output (V˙O2peak), peak respiratory exchange ratio (RERpeak), first-order exponential regression of V˙O2 decay within 360 s of recovery and blood lactate concentration ([Lac-]). IPC did not change T30, but increased HRR60s after all sets (condition main effect: P = 0.03; partial eta square (η²_p) = 0.27, i.e., large effect size). IPC did not change long-term HRR and RMSSD throughout recovery, nor did IPC change any energy metabolism parameter. In conclusion, IPC accelerated to some extent the short-term recovery, but did not change the long-term recovery of cardiac autonomic control from RSE, and such accelerator effect was not accompanied by any IPC effect on surrogates of energy metabolism responses to RSE.

Inter and Intra-Rater Reliability of Short-Term Measurement of Heart Rate Variability on Rest in Diabetic Type 2 Patients

Heart rate variability (HRV) among other methods can be used to assess diabetic cardiac autonomic neuropathy by cardiac intervals were recorded. However, the amount of error depending on this measurement methodology is unclear. To evaluate the intra- and inter-rater reliability to calculate HRV indices, comparing different times and by different trained examiners in patients with type 2 diabetes mellitus (T2DM). Thirty individuals of both genders, aged between 18 and 45 years, with T2DM. The RR interval (RRi) were recorded during a 10 min period on supine position using a portable heart rate monitor (Polar® S810i model). HRV indices were calculated by the software Kubios® HRV analysis (version 2.2). Linear (Mean RRi; STD RR; Mean HR; rMSSD; RR Tri; TINN LF; HF; total power) and non-linear (SD1; SD2; DFα1; DFα2, ApEn and, SampEn) indices were calculated by two examiners with an interval of one week between them. Substantial to excellent was found for reliability of the intra-examiner, with intraclass correlation coefficient (ICC) values ranging from 0.79 to 0.99, standard error of measurement (SEM) between 0.02 and 123.49 (in percentage: 1.83 and 16.67), and minimum detectable change (MDC) between 0.07 and 342.30. Regarding the inter-examiner reliability, substantial to excellent reliability was found, with ICC values ranging from 0.73 to 0.97, SEM between 0.04 and 178.13 (in percentage: 3.26 and 24.18), and MDC between 0.11 and 493.77. The use of the portable heart rate monitor to measure HRV showed acceptable intra and inter reliability in individuals with T2DM, supporting the use of this method of evaluation in research and clinical practice.

Effects of Cold Stimulation on Cardiac-Vagal Activation in Healthy Participants: Randomized Controlled Trial

Background

The experience of psychological stress has not yet been adequately tackled with digital technology by catering to healthy individuals who wish to reduce their acute stress levels. For the design of digitally mediated solutions, physiological mechanisms need to be investigated that have the potential to induce relaxation with the help of technology. Research has shown that physiological mechanisms embodied in the face and neck regions are effective for diminishing stress-related symptoms. Our study expands on these areas with the design for a wearable in mind. As this study charts new territory in research, it also is a first evaluation of the viability for a wearables concept to reduce stress.

Objective

The objectives of this study were to assess whether (1) heart rate variability would increase and (2) heart rate would decrease during cold stimulation using a thermode device compared with a (nonstimulated) control condition. We expected effects in particular in the neck and cheek regions and less in the forearm area.

Methods

The study was a fully randomized, within-participant design. Volunteer participants were seated in a laboratory chair and tested with cold stimulation on the right side of the body. A thermode was placed on the neck, cheek, and forearm. We recorded and subsequently analyzed participants’ electrocardiogram. The cold stimulation was applied in 16-second intervals over 4 trials per testing location. The control condition proceeded exactly like the cold condition, except we manipulated the temperature variable to remain at the baseline temperature. We measured heart rate as interbeat intervals in milliseconds and analyzed root mean square of successive differences to index heart rate variability. We analyzed data using a repeated-measures ANOVA (analysis of variance) approach with 2 repeated-measures factors: body location (neck, cheek, forearm) and condition (cold, control).

Results

Data analysis of 61 participants (after exclusion of outliers) showed a main effect and an interaction effect for body location and for condition, for both heart rate and heart rate variability. The results demonstrate a pattern of cardiovascular reactivity to cold stimulation, suggesting an increase in cardiac-vagal activation. The effect was significant for cold stimulation in the lateral neck area.

Conclusions

The results confirmed our main hypothesis that cold stimulation at the lateral neck region would result in higher heart rate variability and lower heart rate than in the control condition. This sets the stage for further investigations of stress reduction potential in the neck region by developing a wearable prototype that can be used for cold application. Future studies should include a stress condition, test for a range of temperatures and durations, and collect self-report data on perceived stress levels to advance findings.

Flow mediated vasodilation compared with carotid intima media thickness in the evaluation of early cardiovascular damage in menopausal women and the influence of biological and psychosocial factors

Background

Women after menopause increase risk for cardiovascular disease and several factors may be related. The purpose was to study biological and psychosocial factors associated with early cardiovascular damage in pre- and postmenopausal women, assessed with carotid intima-media thickness vs flow-mediated dilatation.

Methods

Women 45 to 57 years old were grouped in the pre- (n = 60), early (n = 58) and late post-menopause (n = 59). Anthropometric, metabolic and hormonal data were registered, as well as measures of depression, anxiety, submission, perceived stress, and sleep alterations. Heart Rate Variability was recorded to obtain the information regarding sympathovagal balance. Carotid intima-media thickness and flow-mediated dilatation were assessed by ultrasound. Two-way ANOVA and multiple regression model were used.

Results

At late postmenopause, the carotid intima-media was thicker (p < 0.001) and flow-mediated dilatation decreased (p < 0.001). Carotid intima-media thickness was associated positively with age (p < 0.001), submission score (p = 0.029), follicle stimulating hormone levels (p < 0.001), and body mass index (p = 0.009). Flow-mediated dilatation was associated only with age (p < 0.001). Regarding heart rate variability, the time domain pNN50 measurement was higher in premenopausal women (p = 0.001), Low Frequency (LF) was higher in the two groups of postmenopausal (p = 0.001) and High Frequency (HF) higher in the early postmenopausal women (p = 0.042).

Conclusions

Under our conditions carotid intima-media thickness had higher predictive value for early cardiovascular damage at menopause. The finding of the association of the submission score, indicates de influence of stress on vascular damage.

Oral adenosine 5'-triphosphate supplementation improved hemodynamic and autonomic parameters after exercise in hypertensive women

The aim of this study was to verify the autonomic modulation and blood pressure after adenosine-5'-triphosphate (ATP) supplementation associated to acute aerobic exercise in hypertensive women. Eleven hypertensive women (age, 61.8±5.0 years) completed a randomized, double blind trial: ATP supplement condition (ATP=400 mg) or placebo. After 30 min of supplementation or placebo intake, the subjects performed 30 min of aerobic exercise (70%-75% of maximum heart rate). The autonomic modulation was assessed by heart rate variability during rest and recovery (postexercise until 30 min of recovery), the square root of the mean squared difference between adjacent RR intervals (RMSSD), standard deviation of successive values (SDNN), low frequency (LF) and high frequency (HF) were measured. The blood pressure (systolic blood pressure [SBP] and diastolic blood pressure, mmHg) were recorded at rest, immediately postexercise, post-10, post-20, and post-30 min after exercise. For RMSSD, there was statistically significant difference during recovery, with higher RMSSD for ATP compared to placebo (rest=16.4±8.5 vs. placebo=11.6±4.0; ATP=18.5±9.7 msec; P=0.020). When analyzing the delta (recovery minus rest), the RMSSD (ATP=2.1± 7.2 msec vs. placebo=-4.7±7.5 msec; P=0.009), LF (ATP=-19.8±122.7 vs. placebo=-94.1±200.2 msec2; P=0.02), and SDNN (ATP=-2.8±12.2 msec vs. placebo=-10.6±10.5 msec; P=0.010) were higher for ATP than placebo. Furthermore, there was a greater postexercise hypotension at 20 min for ATP (SBP: ATP=-13.2±8.4 mmHg vs. placebo=-6.1±9.9 mmHg; P=0.006). Acute ATP supplementation promoted greater postexercise hypotension for systolic blood pressure and induced faster recovery of heart rate variability in hypertensive women.

Heart Rate Variability During Exercise: A Comparison of Artefact Correction Methods

Giles, DA and Draper, N. Heart rate variability during exercise: a comparison of artefact correction methods. J Strength Cond Res 32(3): 726-735, 2018-There is a need for standard practice in the collection and processing of RR interval data recorded using heart rate monitors (HRMs) in research. This article assessed the validity of RR intervals and heart rate variability (HRV) data obtained using an HRM during incremental exercise and artefact correction methods. Eighteen participants completed an active orthostatic test and incremental running V[Combining Dot Above]O2max test, while simultaneous recordings using a Polar V800 HRM and an electrocardiogram were made. Artefacts were corrected by deletion; degree zero, linear, cubic, and spline interpolation; and Kubios HRV software. Agreement was assessed using percentage bias, effect size (ES), intraclass correlation coefficients (ICC), and Bland-Altman limits of agreement (LoA). Artefacts increased relative to exercise intensity, to a peak of 4.46% during 80-100% V[Combining Dot Above]O2max. Correction of RR intervals was necessary with unacceptably increased bias, LoA, and ES and reduced ICC in all but resting recordings. All correction methods resulted in data with reduced percentage bias and ES for resting and <60% V[Combining Dot Above]O2max recordings. However, at >60% V[Combining Dot Above]O2max, even with correction, large amounts of variation were present in HRV measures of root mean square of the successive difference of intervals, low-to-high frequency ratio, Poincaré dispersion perpendicular to the axis (SD1), and sample entropy. Linear interpolation produced RR intervals with the lowest bias and ES. However, caution should be given to HRV parameters at high exercise intensities, as large amounts of variation were still present. Recommendations for minimizing artefacts are discussed, along with guidelines for their identification, correction, and reporting.

Influence of Type 1 Diabetes on the Symbolic Analysis and Complexity of Heart Rate Variability in Young Adults

Background

Type 1 diabetes mellitus can cause autonomic changes, which can be assessed by heart rate variability. Among the heart rate variability assessment methods, the symbolic analysis and Shannon entropy, based on the Chaotic dynamics, have gained prominence.

Objective

To compare heart rate variability indexes, obtained through symbolic analysis and Shannon entropy, in young adults with type 1 diabetes mellitus and healthy young individuals, associated with the analysis of linear indexes; and to verify if there are associations between the indexes obtained by the symbolic analysis and by Shannon entropy and linear indexes in diabetic individuals.

Methods

Heart rate variability data from 39 young adults with type 1 diabetes mellitus and 43 healthy young individuals were analyzed, using a cardio-frequency meter. Linear indexes (standard deviation of all normal RR intervals recorded in a time interval expressed in milliseconds; square root of the mean of the squared differences between adjacent normal RR intervals in a time interval expressed in milliseconds; low and high frequency components in millisecond squared; and normalized units and ratio between low and high frequency components) and nonlinear ones (Shannon entropy and symbolic analysis - standard without variation; with one or two variations; and with two different variations) of the heart rate variability were calculated. The statistical significance was set at 5%, and the confidence interval was 95%.

Results

Significantly lower values were observed in the DM1 group compared to healthy young adults for the standard deviation indexes of all normal RR intervals recorded in a time interval [37.30 (29.90) vs. 64.50 (36.20); p = 0.0001], square root of the mean of the squared differences between adjacent normal RR intervals in a time interval [32.73 (17.43) vs. 55.59 (21.60); p = 0.0001], low frequency component [402.00 (531.00) vs. 1,203.00 (1,148.00); p = 0.0001], high frequency component [386.00 (583.00) vs. 963.00 (866.00); p = 0.0001] and the pattern with two different variations [15,33 (9,22) vs. 20.24 (12.73); p = 0.0114], with the effect of this difference being considered large (standard deviation of all normal RR intervals recorded in a time interval, square root of the mean of the squared differences between adjacent normal RR intervals in a time interval and low frequency component), medium (high frequency component) and small (standard with two different variations). The agreement of the associations between the linear and non-linear indexes was considered elevated for the high frequency component index - normalized units (r = -0.776), with the standard index without variation, and moderate for the indexes square root of the mean of the squared differences between adjacent normal RR intervals in a time interval (r = 0.550), standard deviation of all normal RR intervals recorded in a time interval (r = 0.522), high frequency component - normalized units (r = 0.638) with the index standard with two similar variations, as well as for the indexes square root of the mean of the squared differences between adjacent normal RR intervals in a time interval (r = 0.627) and high frequency component - normalized units (r = 0.601) with the index standard with two different variations.

Conclusion

Type 1 diabetes mellitus influenced linear indexes and symbolic analysis, but not yet in the complexity of heart rate variability. Additionally, heart rate variability indexes correlated with the symbolic dynamics.

Effect of the Use of Different Acoustic Stimuli on Cortical Auditory Evoked Potentials and Autonomic Cardiac Modulation

Purpose

The aim of this study was to analyze the relationship between Cortical Auditory Evoked Potentials (CAEPs) measurements and autonomic cardiac modulation in relation to different acoustic stimuli and to verify which of these stimuli have more influence on the autonomic nervous system.

Methods

Sixty healthy women, aged between 18 and 25 years, participated in this study. Prior to the CAEP examination, blood pressure and resting heart rate were measured using a stethoscope, sphygmomanometer, and the Polar RS800CX cardiofrequency measures. After the collection of these measures, the CAEP test was started simultaneously with the HRV collection.

Results

All the HRV indices presented correlations with the components of the CAEPs. During the acoustic stimulation, a predominance of the modulation of the autonomic parasympathetic nervous system was observed. The harmonic and disharmonic stimuli were the ones that presented the most correlations between the measures analyzed in this study.

Conclusions

There was an association between CAEP and cardiac autonomic modulation in relation to different acoustic stimuli. Among the acoustic stimuli used in this study, the ones that most influenced the autonomic cardiac modulation were harmonic and disharmonic stimuli, which are acoustically more complex stimuli.

Postexercise hypotension and autonomic modulation response after full versus split body resistance exercise in trained men

To investigate the effects of full versus split body resistance exercise on postexercise hypotension and autonomic modulation in trained men. Sixteen resistance recreationally trained males (age, 24.9±5.3 years) performed three randomized trials: upper body (UB), lower body (LB), and full body (FB) conditions. Blood pressure and heart rate variability were collected at rest, immediately postexercise, post-10, and post-30 min during recovery. For systolic blood pressure, delta (30 min minus rest) was lower for the FB condition compared to the UB (−10.1±7.4 mmHg [FB] vs. −3.3±12.6 mmHg [LB] vs. −1.9±8.1 mmHg [UB], P=0.004). For diastolic blood pressure (−8.2±10.9 mmHg [FB] vs. −1.5±9.8 mmHg [LB] vs. −8.7±11.4 mmHg [UB], P=0.038) and mean blood pressure delta during recovery (−11.7±14 mmHg [FB] vs. −2.2±10.6 mmHg [LB] vs. −5.2±6.8 mmHg [UB], P=0.045), there were statistically significant lower values in the FB condition in relation to the LB condition. Regarding heart rate variability, there were no significant differences between conditions, however, the square root of the mean squared difference between adjacent RR intervals presented an increase until post-30 during recovery (P<0.001), and there was a higher values of low frequency and lower values of high frequency across time (P<0.001). Postexercise hypotension was influenced by the amount of muscle mass involved in a bout of resistance exercise, with the FB condition inducing lower systolic blood pressure in relation to the UB after exercise, as well as a great decrease in postexercise diastolic and mean blood pressure compared with the LB. The autonomic modulation response was similar between conditions during recovery.

Elastic Tubing Resistance Training and Autonomic Modulation in Subjects with Chronic Obstructive Pulmonary Disease

This study addresses evidence concerning elastic tubing resistance training (ET) on autonomic modulation in patients with chronic obstructive pulmonary disease (COPD). Autonomic dysfunction is common in COPD and contributes to the development of arrhythmias and sudden death. Along with autonomic dysfunction, muscle dysfunction is related to functional limitations and prognosis of the disease. This study investigated the effects of ET on autonomic modulation, muscle strength, and walking distance in COPD. Subjects were divided into two groups, ET (n = 20; 66,5 ± 8,9 y; 25,5 ± 3,5 kg/m2; FEV1/FVC: 50,3 ± 11,0) and conventional training (n = 19; 66,0 ± 6,9; 27,1 ± 4,3; FEV1/FVC: 55,05 ± 9,56). Both groups undertook 24 sessions for 60 minutes, 3 times in a week. The significance level was p ≤ 0,05. Autonomic modulation was evaluated using heart rate variability in the time (rMSSD, ms) and frequency domain (HF, ms). Strength for upper and lower limbs was measured using dynamometry and walking distance was measured using a 6-minute walking test. There were no significant differences in the outcomes between groups. There was an increment to rMSSD [(16,7 ± 11,0 versus 20,8 ± 14,9) versus (14,2 ± 10,0 versus 17,4 ± 12,1)], HF [(141,9 ± 191,3 versus 234,9 ± 335,7) versus (94,1 ± 123,5 versus 177,6 ± 275,5)], shoulder abduction [(50,1 ± 19,6 versus 56,9 ± 20,4) versus (50,5 ± 19,0 versus 56,9 ± 19,3)], knee flexion [(101,9 ± 34,0 versus 116,8 ± 43,3) versus (98,6 ± 21,5 versus 115,1 ± 30,8)], and walking test [(433,0 ± 84,8 versus 468,9 ± 90,8) versus (397,4 ± 99,8 versus 426,3 ± 101,6)] after training for ET and conventional training, respectively. In conclusion, ET improves autonomic modulation in COPD with additional benefits for strength and cardiorespiratory capacity similar to conventional training.

Stress Response and Cognitive Performance Modulation in Classroom versus Natural Environments: A Quasi-Experimental Pilot Study with Children

Stress during childhood can have mental and somatic health influences that track throughout life. Previous research attributes stress-reducing effects to natural environments, but has mainly focused on adults and often following leisurely relaxation in natural environments. This pilot study explores the impact of natural environments on stress response during rest and mental load and cognitive performance in 47 children aged 10–12 years in a school context. Heart rate variability measures indexing tonic, event, and phasic vagal tone and attention scores were compared across classroom and natural environments. Tonic vagal tone was higher in the natural environment than the classrooms, but no differences were found in event or phasic vagal tone or cognitive performance measures. These findings suggest a situational aspect of the conditions under which natural environments may give rise to stress-buffering influences. Further research is warranted to understand the potential benefits in a real-life context, in particular with respect to the underpinning mechanisms and effects of accumulated exposure over time in settings where children spend large proportions of time in natural environments.

Evaluation of the beat-to-beat detection accuracy of PulseOn wearable optical heart rate monitor

Heart rate variability (HRV) provides significant information about the health status of an individual. Optical heart rate monitoring is a comfortable alternative to ECG based heart rate monitoring. However, most available optical heart rate monitoring devices do not supply beat-to-beat detection accuracy required by proper HRV analysis. We evaluate the beat-to-beat detection accuracy of a recent wrist-worn optical heart rate monitoring device, PulseOn (PO). Ten subjects (8 male and 2 female; 35.9±10.3 years old) participated in the study. HRV was recorded with PO and Firstbeat Bodyguard 2 (BG2) device, which was used as an ECG based reference. HRV was recorded during sleep. As compared to BG2, PO detected on average 99.57% of the heartbeats (0.43% of beats missed) and had 0.72% extra beat detection rate, with 5.94 ms mean absolute error (MAE) in beat-to-beat intervals (RRI) as compared to the ECG based RRI BG2. Mean RMSSD difference between PO and BG2 derived HRV was 3.1 ms. Therefore, PO provides an accurate method for long term HRV monitoring during sleep.

Heart rate variability in patients with bipolar disorder: From mania to euthymia

Bipolar Disorder (BD) is characterized by the occurrence of mania alternating with euthymia. The aim of the present study was to investigate the impact of BD on the autonomic nervous system, as indicated by heart rate variability (HRV). The study was registered in the Clinical Trials Registration (NCT01272518). Nineteen hospitalized, male patients (age: 34.0 ± 12.3 years) with type I BD were assessed during mania and at discharge on euthymia. HRV data were collected during 20- minutes in supine position at rest, on spontaneous breathing, using the Polar RS 800 CX frequencymeter. HRV measures included variables in time, frequency and non-linear domains. Psychiatric conditions were evaluated by the Mini International Neuropsychiatric Interview (MINI) and the Bech-Rafaelsen mania scale (BRMS). Time domain measures of RMSSD (Cohen's d = 0.668) and pNN50 (Cohen's d = 0.688) increased from first to second assessments. The high-frequency component (HFms2) also increased (Cohen's d = 0.586), while the LF/HF ratio decreased (Cohen's d = 0.785). Non-linear domain measures including the SD1 component (Cohen's d = 0.668), and the SD1/SD2 ratio (Cohen's d = 1.2934) extracted from the Poincare plot analysis increased from first to second assessment. The variables Lmean (Cohen's d = 0.9627), Lmax (Cohen's d = 1.2164), REC% (Cohen's d = 1.0595) and EntShannon (Cohen's d = 1.0607) were higher in mania. By contrast, ApEn (Cohen's d = 0.995) and EntSample (Cohen's d = 1.189) were less during mania, all reflecting ANS improvement. Findings are interpreted in the context of recently published models relating to neurovisceral integration across the continuum of time, and the implications for the future health and wellbeing of patients are considered.

Evaluation of accuracy and reliability of PulseOn optical heart rate monitoring device

PulseOn is a wrist-worn optical heart rate (HR) monitor based on photoplethysmography. It utilizes multi-wavelength technology and optimized sensor geometry to monitor blood flow at different depths of skin tissue, and it dynamically adapts to an optimal measurement depth in different conditions. Movement artefacts are reduced by adaptive movement-cancellation algorithms and optimized mechanics, which stabilize the sensor-to-skin contact. In this paper, we evaluated the accuracy and reliability of PulseOn technology against ECG-derived HR in laboratory conditions during a wide range of physical activities and also during outdoor sports. In addition, we compared the performance to another on-the-shelf wrist-worn consumer product Mio LINK(®). The results showed PulseOn reliability (% of time with error <;10bpm) of 94.5% with accuracy (100% - mean absolute percentage error) 96.6% as compared to ECG (vs 86.6% and 94.4% for Mio LINK(®), correspondingly) during laboratory protocol. Similar or better reliability and accuracy was seen during normal outdoor sports activities. The results show that PulseOn provides reliability and accuracy similar to traditional chest strap ECG HR monitors during cardiovascular exercise.

Validity and Reliability of the Apple Watch for Measuring Heart Rate During Exercise

We examined the validity and reliability of the Apple Watch heart rate sensor during and in recovery from exercise. Twenty-one males completed treadmill exercise while wearing two Apple Watches (left and right wrists) and a Polar S810i monitor (criterion). Exercise involved 5-min bouts of walking, jogging, and running at speeds of 4 km.h ⁻¹ , 7 km.h ⁻¹ , and 10 km.h ⁻¹ , followed by 11 min of rest between bouts. At all exercise intensities the mean bias was trivial. There were very good correlations with the criterion during walking (L: r=0.97; R: r=0.97), but good (L: r=0.93; R: r=0.92) and poor/good (L: r=0.81; R: r=0.86) correlations during jogging and running. Standardised typical error of the estimate was small, moderate, and moderate to large. There were good correlations following walking, but poor correlations following jogging and running. The percentage of heart rates recorded reduced with increasing intensity but increased over time. Intra-device standardised typical errors decreased with intensity. Inter-device standardised typical errors were small to moderate with very good to nearly perfect intraclass correlations. The Apple Watch heart rate sensor has very good validity during walking but validity decreases with increasing intensity.

Risk Assessment of Diabetes Mellitus by Chaotic Globals to Heart Rate Variability via Six Power Spectra

Background: The priniciple objective here is to analyze cardiovascular dynamics in diabetic subjects by actions related to heart rate variability (HRV). The correlation of chaotic globals is vital to evaluate the probability of dynamical diseases.

Methods: Forty-six adults were split equally. The autonomic evaluation consisted of recording HRV for 30 minutes in supine position without any additional stimuli. “Chaotic globals” are then able to statistically determine which series of interbeat intervals are diabetic and which are not. Two of these chaotic globals, spectral Entropy and spectral Detrended fluctuation analysis were derived from six alternative power spectra: Welch, Multi-Taper Method, Covariance, Burg, Yule-Walker and the Periodogram. We then compared results to observe which power spectra provided the greatest significance by three statistical tests: One-way analysis of variance (ANOVA1); Kruskal-Wallis technique and the multivariate technique, principal component analysis (PCA).

Results: The Chaotic Forward Parameter One (CFP1) applying all three parameters is proven the most robust algorithm with Welch and MTM spectra enforced. This was proven following two tests for normality where ANOVA1 (p=0.09) and Kruskal-Wallis (p=0.03). Multivariate analysis revealed that two principal components represented 99.8% of total variance, a steep scree plot, with CFP1 the most influential parameter.

Conclusion: Diabetes reduced the chaotic response.

Heart rate variability based on risk stratification for type 2 diabetes mellitus

Objective

To evaluate heart rate variability among adults with different risk levels for type 2 diabetes mellitus.

Methods

The risk for type 2 diabetes mellitus was assessed in 130 participants (89 females) based on the questionnaire Finnish Diabetes Risk Score and was classified as low risk (n=26), slightly elevated risk (n=41), moderate risk (n=27) and high risk (n=32). To measure heart rate variability, a heart-rate monitor Polar S810i^® was employed to obtain RR series for each individual, at rest, for 5 minutes, followed by analysis of linear and nonlinear indexes.

Results

The groups at higher risk of type 2 diabetes mellitus had significantly lower linear and nonlinear heart rate variability indexes.

Conclusion

The individuals at high risk for type 2 diabetes mellitus have lower heart rate variability.

Effects of creatine supplementation on cardiac autonomic functions in bodybuilders

Bodybuilder-type workouts may affect heart rate variability (HRV), which has considerable potential to assess the role of autonomic nervous system (ANS). A scientifically designed approach is necessary for bodybuilders to achieve better results while protecting their health. In this study, we aimed to investigate HRV parameters in bodybuilders compared to healthy control subjects and effects of creatine supplementation. A total of 48 male participants (16 controls, 16 supplement (-), 16 supplement (+)) were evaluated in our study. Bodybuilders who were taking creatine supplementation were enrolled in supplement (+) group. HRV parameters were measured from 24-hour Holter recordings of all participants. When mean heart rates were compared with control group (71.5 ± 12.6 beats/min), statistically significant difference was revealed in supplement (-) group (61.8 ± 6.8 beats/min; P = 0.022) unlike supplement (+) group (69.63 ± 14.1 beats/min; P = 0.650). HRV analyses revealed significant parasympathetic shift in supplement (-) group. No significant difference was demonstrated on HRV parameters, except high frequency (P = 0.029) in supplement (+) group. Conclusively, elevated parasympathetic modulation, which is favorable cardiovascular outcome of exercise, was demonstrated in bodybuilders. However, our study also revealed that creatine supplementation attenuates this favorable effect in ANS by limiting elevation of parasympathetic modulation. Although the sympathetic slight shift is attributed to creatine supplementation, it cannot be discriminated from the effects of over training.

Sensitivity, Specificity and Predictive Value of Heart Rate Variability Indices in Type 1 Diabetes Mellitus

Background

Heart rate variability (HRV) indices may detect autonomic changes with good diagnostic accuracy. Type diabetes mellitus (DM) individuals may have changes in autonomic modulation; however, studies of this nature in this population are still scarce.

Objective

To compare HRV indices between and assess their prognostic value by measurements of sensitivity, specificity and predictive values in young individuals with type 1 DM and healthy volunteers.

Methods

In this cross-sectional study, physical and clinical assessment was performed in 39 young patients with type 1 DM and 43 young healthy controls. For HRV analysis, beat-to-beat heart rate variability was measured in dorsal decubitus, using a Polar S810i heart rate monitor, for 30 minutes. The following indices were calculated: SDNN, RMSSD, PNN50, TINN, RRTri, LF ms², HF ms², LF un, HF un, LF/HF, SD1, SD2, SD1/SD2, and ApEn.

Results

Type 1 DM subjects showed a decrease in sympathetic and parasympathetic activities, and overall variability of autonomic nervous system. The RMSSD, SDNN, PNN50, LF ms², HF ms², RRTri, SD1 and SD2 indices showed greater diagnostic accuracy in discriminating diabetic from healthy individuals.

Conclusion

Type 1 DM individuals have changes in autonomic modulation. The SDNN, RMSSD, PNN50, RRtri, LF ms², HF ms², SD1 and SD2 indices may be alternative tools to discriminate individuals with type 1 DM.

Evaluation of frequency of positive exercise-induced bronchospasm between swimmers and sedentary individuals

Abstract Introduction: Despite the prevalence of prescribed asthma, there is uncertainty about the incidence of exercise-induced bronchospasm (EIB). Objective: Compare the frequency of EIB between swimmers and sedentary individuals, and observe heart rate variability during bronchial activity. Methods: In total, 18 swimmers (group 1) and 18 sedentary individuals (group 2) were included. The participants rested for 30 minutes for evaluation of HRV. Blood pressure (PA), respiratory rate (RR), and pulse oxygen saturation (SpO2) were measured. The volunteers remained seated for the spirometry test (maneuver of forced vital capacity - FVC). This was repeated 5, 10, 15, 20, and 30 minutes after the exercise test. The statistical analysis used the Student t, Mann Whitney, and Shapiro-Wilks tests. The significance level was p <0.05. Results: The spirometry findings showed 3 sedentary individuals and 10 swimmers with obstructive ventilatory disorder (OVD). Only 2 of the sedentary and none of the swimmer group demonstrated positive bronchial provocation. A key criterion for diagnosing OVD, the relationship between forced expiratory volume in one second and FVC (FEV1/FVC), was statistically lower in the swimmer group. The measures of the root mean square of the successive differences between adjacent normal RR intervals, in a time interval (RMSSD), and the standard deviation of all normal RR intervals recorded in a time interval (SDNN) were significantly higher among the athletes. Conclusion: The bronchial provocation test identified a higher prevalence of bronchospasm among sedentary individuals. However, there was a reduction in the FEV1/FVC ratio and higher HRV in the group of swimmers.

Transcranial direct current stimulation in individuals with spinal cord injury: Assessment of autonomic nervous system activity

BACKGROUND

We hypothesized in this study that transcranial direct current stimulation (tDCS) of primary motor cortex could exert top-down modulation over subcortical systems associated with autonomic control and thus be useful to revert some of the dysfunctional changes found in the autonomic nervous system (ANS) of subjects with spinal cord injuries (SCI).

OBJECTIVE

To explore the acute effect of tDCS on ANS indexed by Heart Rate Variability (HRV) in individuals with SCI and analyze whether this effect depends on the gender, degree, level and time of injury.

METHODS

In this randomized, placebo-controlled, crossover, double-blinded study, 18 adults with SCI (32.9±7.9 years old) were included; the intervention consisted of a single 12-minute session of active tDCS (anodal, 2 mA) and a control session of sham tDCS applied over Cz (bihemispheric motor cortex). HRV was calculated using spectral analysis. Low-frequency (LF), high-frequency (HF), and LF/HF ratio variables were evaluated before, during, and post tDCS.

RESULTS

A two-way repeated measures ANOVA showed that after active (anodal) stimulation, LF/HF ratio was significantly increased (P = 0.013). There was a trend for an interaction between time and stimulation for both LF and HF (P = 0.052). Paired exploratory t-tests reported effects on the difference of time [post-pre] between stimulation conditions for LF (P = 0.052), HF (P = 0.052) and LF/HF (P = 0.003).

CONCLUSION

Anodal tDCS of the motor cortex modulated ANS activity in individuals with SCI independent of gender, type and time of lesion. These changes were in the direction of normalization of ANS parameters, thus confirming our initial hypothesis that an enhancement of cortical excitability by tDCS could at least partially restore some of the dysfunctional activity in the ANS system of subjects with SCI.

Birth Weight and Its Relationship with the Cardiac Autonomic Balance in Healthy Children

Several studies indicate that the fetal environment plays a significant role in the development of cardiometabolic disease later in life. However, a few studies present conflicting data about the correlation between birth weight and the impairment of cardiac autonomic modulation. The purpose of the present study was to provide further knowledge to elucidate this contradictory relationship. One hundred children aged 5 and 14 years had anthropometric parameters, body composition and blood pressure levels determined. Heart rate variability (HRV) was evaluated by heart rate monitoring, including measurements of both the time and frequency domains. The results showed inverse correlation between the HRV parameters with BMI (RMSSD: P = 0.047; PNN50: P = 0.021; HF: P = 0.041), systolic (RMSSD: P = 0.023; PNN50: P = 0.032) and diastolic (PNN50: P = 0.030) blood pressure levels. On the other hand, there were consistent positive correlations between the HRV parameters and birth weight (RMSSD: P = 0.001; PNN50: P = 0.001; HF: P = 0.002). To determine the effect of birth weight on HRV parameters, we perform multivariate linear regression analysis adjusted for potentially confounding factors (prematurity, gender, age, BMI, physical activity index and SBP levels). These findings were preserved even after adjusting for these confounders. Our results suggested that impaired cardiac autonomic modulation characterized by a reduction in the parasympathetic activity occurs in children with low birth weight. One possible interpretation for these data is that a vagal withdrawal, rather than a sympathetic overactivity, could precede the development of hypertension and other cardiometabolic diseases in children with low birth weight. However, long-term studies should be performed to investigate this possibility.

Association of cardiac autonomic modulation with physical and clinical features of young people with type 1 diabetes

OBJECTIVE

The objective of this study was to verify possible associations between heart rate variability indices and physical activity, body composition, and metabolic and cardiovascular parameters in individuals with type 1 diabetes.

METHOD

A total of 39 young patients with type 1 diabetes were included. Body composition, physical activity, cardiovascular parameters, and metabolic parameters were assessed. For the heart rate variability analysis, heart rate was recorded beat-by-beat using a Polar S810i heart rate monitor for 30 minutes, with the volunteers in the supine position; subsequently, the following indices were considered: standard deviation of all normal RR intervals; root-mean square of differences between adjacent normal RR intervals in a time interval; percentage of adjacent RR intervals with a difference of duration >50 ms; high frequency component in milliseconds squared; high frequency component in normalised units; standard deviation of the instantaneous variability beat-to-beat; and standard deviation of the long-term variability. The association between the heart rate variability indices and independent variables was verified through linear regression in unadjusted and adjusted models (considering gender and age). The statistical significance was set at 5% and the confidence interval at 95%.

RESULTS

High values of at-rest heart rate were associated with reduced parasympathetic activity and global heart rate variability, and higher values of waist-to-hip ratio were related to lower parasympathetic activity, independent of age or gender.

CONCLUSION

For young patients with type 1 diabetes, increases in at-rest heart rate values are associated with reduced parasympathetic activity and global heart rate variability, whereas higher waist-to-hip ratio values are related to lower parasympathetic activity, both independent of age and gender.

Reproducibility for Heart Rate Variability Analysis during 6-Min Walk Test in Patients with Heart Failure and Agreement between Devices

Heart rate variability (HRV) analysis is a useful method to assess abnormal functioning in the autonomic nervous system and to predict cardiac events in patients with heart failure (HF). HRV measurements with heart rate monitors have been validated with an electrocardiograph in healthy subjects but not in patients with HF. We explored the reproducibility of HRV in two consecutive six-minute walk tests (6MW), 60-minute apart, using a heart rate monitor (PolarS810i) and a portable electrocardiograph (called Holter) in 50 HF patients (mean age 59 years, NYHA II, left ventricular ejection fraction ~35%). The reproducibility for each device was analysed using a paired t-test or the Wilcoxon signed-rank test. Additionally, we assessed the agreement between the two devices based on the HRV indices at rest, during the 6MW and during recovery using concordance correlation coefficients (CCC), 95% confidence intervals and Bland-Altman plots. The test-retest for the HRV analyses was reproducible using Holter and PolarS810i at rest but not during recovery. In the second 6MW, patients showed significant increases in rMSSD and walking distance. The PolarS810i measurements had remarkably high concordance correlation [0.86 Collapse

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MESH Headings

• Aged
• Electrocardiography
• Female
• Heart Failure/diagnosis
• Heart Failure/physiopathology
• Heart Rate
• Humans
• Male
• Reproducibility of Results
• Walk Test

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Grants

• Fundação de Amparo à Pesquisa do Estado de São Paulo

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Affiliation(s)

Lays Magalhães Braga Department of Physiotherapy, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
Gustavo Faibischew Prado Pulmonary Division of Heart Institute (InCor) do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
Iracema Ioco Kikuchi Umeda Dante Pazzanese Institute of Cardiology São Paulo State, São Paulo, Brazil
Tatiana Satie Kawauchi Department of Physiotherapy, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
Adriana Marques Fróes Taboada Dante Pazzanese Institute of Cardiology São Paulo State, São Paulo, Brazil
Raymundo Soares Azevedo Department of Pathology, University of São Paulo Medical School, São Paulo, Brazil
Horacio Gomes Pereira Filho Cardiology Division of Heart Institute (InCor) do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
César José Grupi Cardiology Division of Heart Institute (InCor) do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
Hayala Cristina Cavenague Souza Dante Pazzanese Institute of Cardiology São Paulo State, São Paulo, Brazil
Dalmo Antônio Ribeiro Moreira Dante Pazzanese Institute of Cardiology São Paulo State, São Paulo, Brazil
Naomi Kondo Nakagawa Department of Physiotherapy, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil

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Support Schemas Influence Reactivity for Adult Survivors of Childhood Maltreatment

Adult survivors of childhood maltreatment can be resilient when they have adequate psychosocial resources to cope with maltreatment-related sequelae; however, interpersonal problems may influence the effectiveness of such resources. This study used a schema activation experimental paradigm to test the benefit of social support cognitions on emotional reactivity in adult survivors, while also testing for the moderating role of interpersonal problems and the mediating role of stress appraisal. Young women (N = 126, ages = 18-23) with histories of childhood maltreatment were administered an anger provocation stressor task while their cardiac activity, state anger, and stress appraisals were assessed. Prior to the stressor, women were randomly assigned to either a support schema condition or an acquaintance schema (control) condition, in which they were asked to think and write about either a supportive person or casual acquaintance. The support schema condition demonstrated the least emotional reactivity as evidenced by subjective anger and heart-rate variability, and this outcome was strongest for those with high interpersonal problems. Also, stress appraisals, particularly feeling intimidated, partially mediated the support schema and emotional reactivity relationship. These findings suggest that maltreated women can regulate anger by activating their social support schema. Moreover, support schema may be an important focus of intervention for adult survivors with high interpersonal problems.

Impact of Diabetes Type 1 in Children on Autonomic Modulation at Rest and in Response to the Active Orthostatic Test

Introduction

Cardiovascular autonomic neuropathy is one of the most common complications of diabetes mellitus type 1 (DM1), of which one of the first subclinical manifestations is changes in heart rate variability (HRV). Thus, analysis of HRV associated with the autonomic active orthostatic test is important in this population.

Objectives

To analyze the autonomic modulation responses induced by the implementation of the active orthostatic test, in children with DM1, and study the autonomic modulation by means of HRV indices.

Method

Data of 35 children were analyzed, of both sexes, aged between 7 and 15 years, who were divided into two groups: Diabetic (n = 16) and Control (n = 19). The following variables were collected initially: weight, height, body fat percentage, heart rate, blood pressure and casual blood glucose. Subsequently, for analysis of autonomic modulation, the beat-to-beat heart rate was captured by a heart rate monitor in the supine position for 30 minutes and after 10 minutes standing during performance of the active orthostatic test. HRV indices were calculated in the time and frequency domains. For data analysis, covariance analysis was used to compare groups and ANOVA for repeated measures to compare the effects of the active orthostatic test. These data were adjusted for age, sex, ethnicity, body fat percentage and casual blood glucose, with a 5% significance level.

Results

The results suggested that diabetic children at rest present a decrease in SDNN (50.4 vs. 75.2), rMSSD (38.7 vs 57.6) and LF [ms²] (693.6 vs 1874.6). During the active orthostatic test the children in both groups demonstrated a reduction in SDNN, RMSSD and LF [ms²] compared to the resting position, and this response was less pronounced in the diabetic group.

Conclusion

We conclude that regardless of age, sex, ethnicity, body fat percentage and casual blood glucose, performing the active orthostatic test promoted increased sympathetic modulation and reduced parasympathetic modulation in both groups, and this response was less pronounced in diabetic children, who presented reduced overall variability and parasympathetic modulation.

Dynamics of heart rate variability analysed through nonlinear and linear dynamics is already impaired in young type 1 diabetic subjects

BACKGROUND

Autonomic diabetic neuropathy is one of the most common complications of type 1 diabetes mellitus, and studies using heart rate variability to investigate these individuals have shown inconclusive results regarding autonomic nervous system activation. Aims To investigate the dynamics of heart rate in young subjects with type 1 diabetes mellitus through nonlinear and linear methods of heart rate variability.

METHODS

We evaluated 20 subjects with type 1 diabetes mellitus and 23 healthy control subjects. We obtained the following nonlinear indices from the recurrence plot: recurrence rate (REC), determinism (DET), and Shanon entropy (ES), and we analysed indices in the frequency (LF and HF in ms2 and normalised units - nu - and LF/HF ratio) and time domains (SDNN and RMSSD), through analysis of 1000 R-R intervals, captured by a heart rate monitor.

RESULTS

There were reduced values (p<0.05) for individuals with type 1 diabetes mellitus compared with healthy subjects in the following indices: DET, REC, ES, RMSSD, SDNN, LF (ms2), and HF (ms2). In relation to the recurrence plot, subjects with type 1 diabetes mellitus demonstrated lower recurrence and greater variation in their plot, inter-group and intra-group, respectively.

CONCLUSION

Young subjects with type 1 diabetes mellitus have autonomic nervous system behaviour that tends to randomness compared with healthy young subjects. Moreover, this behaviour is related to reduced sympathetic and parasympathetic activity of the autonomic nervous system.

Effects of transcutaneous electrical diaphragmatic stimulation on the cardiac autonomic balance in healthy individuals: a randomized clinical trial

ABSTRACT The transcutaneous electrical diaphragmatic stimulation (TEDS) is a technique of respiratory muscle activation that affects breathing pattern and rhythm. In an attempt to evaluate changes in cardiac autonomic balance in response to TEDS in healthy individuals, we used a well-established TEDS model. Twenty-two volunteers aged between 22 and 35 years old, with no cardiac pathology history, were randomized into two groups (control, n = 8; TEDS, n = 14). The individuals were allowed to rest in supine position and were then subjected to the electrical stimulation protocol. The control group was subjected to electrical stimulation at perceptive level, whereas for the TEDS group the electric stimulus generated diaphragm contraction. Cardiac intervals (CI) were sampled by a Polar RS800CX monitor. Cardiac interval variability was studied in the time and frequency domains. In the control group, electrical stimulation did not change cardiac interval length and variability (CI: 761±44 vs. 807±39 ms; RMSSD: 37±9 vs. 42±13 ms ; LF: 69±6 vs. 67±5 nu; HF: 31±6 vs. 33±5 nu; all comparisons versus baseline). Nevertheless, as compared to baseline, TEDS group showed decreased sympathetic cardiac modulation (LF: 43±3 vs. 63±4 nu) and increased parasympathetic cardiac modulation (RMSSD: 109±10 vs. 41±6 ms; HF: 57±3 vs. 37±4 nu) during diaphragmatic stimulation. However, cardiac interval length was not changed by electrical stimulation (CI: 686±59 vs. 780±31 ms). It can be suggested that the use of TEDS stimulus leads to pronounced changes in the cardiac sympathovagal balance, with higher parasympathetic cardiac modulation, possibly induced by increased diaphragmatic excursion.

Effects of elevation change on mental stress in high-voltage transmission tower construction workers

High-voltage transmission tower construction is a high-risk operation due to the construction site locations, extreme climatic factors, elevated working surfaces, and narrow working space. To comprehensively enhance our understanding of the psychophysiological phenomena of workers in extremely high tower constructions, we carried out a series of field experiments to test and compare three working surface heights in terms of frequency-domain heart rate variability (HRV) measurements. Twelve experienced male workers participated in this experiment. The dependent variables, namely, heart rate (HR), normalized low-frequency power (nLF), normalized high-frequency power (nHF), and LF-to-HF power ratio (LF/HF), were measured with the Polar RS800CX heart rate monitor. The experimental results indicated that the task workload was similar between working surface heights. Tower construction workers perceived an increased level of mental stress as working surface height increased.

At the heart of morality lies neuro-visceral integration: lower cardiac vagal tone predicts utilitarian moral judgment

To not harm others is widely considered the most basic element of human morality. The aversion to harm others can be either rooted in the outcomes of an action (utilitarianism) or reactions to the action itself (deontology). We speculated that the human moral judgments rely on the integration of neural computations of harm and visceral reactions. The present research examined whether utilitarian or deontological aspects of moral judgment are associated with cardiac vagal tone, a physiological proxy for neuro-visceral integration. We investigated the relationship between cardiac vagal tone and moral judgment by using a mix of moral dilemmas, mathematical modeling and psychophysiological measures. An index of bipolar deontology-utilitarianism was correlated with resting heart rate variability (HRV)-an index of cardiac vagal tone-such that more utilitarian judgments were associated with lower HRV. Follow-up analyses using process dissociation, which independently quantifies utilitarian and deontological moral inclinations, provided further evidence that utilitarian (but not deontological) judgments were associated with lower HRV. Our results suggest that the functional integration of neural and visceral systems during moral judgments can restrict outcome-based, utilitarian moral preferences. Implications for theories of moral judgment are discussed.

Effects of functional training on geometric indices of heart rate variability

BACKGROUND

Geometric methods provide an analysis of autonomic modulation using the geometric properties of the resulting pattern, and represent an interesting tool in the analysis of heart rate variability (HRV). The aim of this study was to evaluate the impact of functional training on cardiac autonomic modulation in healthy young women using the geometric indices of HRV.

METHODS

Data were analyzed from 29 women, and were stratified into a functional training group (FTG, n = 13; 23.00 ± 2.51 years; 21.90 ± 2.82 kg/m²) and a control group (CG, n = 16; 20.56 ± 1.03 years; 22.12 ± 3.86 kg/m²). The FTG received periodized functional training for 12 weeks. The cardiac autonomic modulation of both groups was evaluated before and after this training, and a qualitative analysis was performed using the Poincaré plot.

RESULTS

There was a significant increase in the difference of the triangular index (RRTri), SD1, SD2, and RR intervals in the FTG as compared to the CG, and the qualitative analysis from the Poincaré plot showed an increase in the dispersion of beat-to-beat and long-term RR intervals in the functional group after training. No changes were observed in the triangular interpolation of RR interval histogram (TINN) or SD1/SD2.

CONCLUSION

Functional training had a beneficial impact on autonomic modulation, as characterized by increased parasympathetic activity and overall variability, thus highlighting the clinical usefulness of this type of training.

Changes in disgust and heart rate during exposure for Obsessive Compulsive Disorder: A case series

BACKGROUND AND OBJECTIVES

The emotion of disgust has been suggested as a factor contributing to a poor response to Cognitive Behaviour Therapy (CBT) in the treatment of Obsessive Compulsive Disorder (OCD). However, only limited information is available about the phenomenology of disgust in clinical OCD and the physiological mechanisms involved. This case series was designed to explore the phenomenology of OCD and the physiological activity associated with the emotion of disgust.

METHODS

State disgust and heart rate was measured in eleven participants attending treatment for OCD during exposure relevant to their individual formulation.

RESULTS

All participants with contamination and most patients with blood and injury related fears experienced a prominent increase in state disgust during exposure. These participants also had absent heart rate acceleration during exposure. Disgust response correlated with heart rate response (r = -0.63, p < 0.01) and Root Mean Square of Successive Differences (RMSSD) (r = 0.52, p < 0.01).

LIMITATIONS

The design using ecologically valid stimuli and the limited number of participants did not allow between subject comparisons or more detailed analysis of relationship between trait and state disgust and between disgust and severity of OCD.

CONCLUSIONS

Our findings show that a large proportion of our case series with OCD experience prominent disgust with signs of increased vagal tonus during their exposure. Such experiences differ from the concept of adrenergic activation used for psychoeducation in CBT and appraisals of harm and this may result in poorer therapeutic outcome.

Influence of Smoking Consumption and Nicotine Dependence Degree in Cardiac Autonomic Modulation

Background

Smoking consumption alters cardiac autonomic function.

Objective

Assess the influence of the intensity of smoking and the nicotine dependence degree in cardiac autonomic modulation evaluated through index of heart rate variability (HRV).

Methods

83 smokers, of both genders, between 50 and 70 years of age and with normal lung function were divided according to the intensity of smoking consumption (moderate and severe) and the nicotine dependency degree (mild, moderate and severe). The indexes of HRV were analyzed in rest condition, in linear methods in the time domain (TD), the frequency domain (FD) and through the Poincaré plot. For the comparison of smoking consumption, unpaired t test or Mann-Whitney was employed. For the analysis between the nicotine dependency degrees, we used the One-way ANOVA test, followed by Tukey's post test or Kruskal-Wallis followed by Dunn's test. The significance level was p < 0,05.

Results

Differences were only found when compared to the different intensities of smoking consumption in the indexes in the FD. LFun (62.89 ± 15.24 vs 75.45 ± 10.28), which corresponds to low frequency spectrum component in normalized units; HFun (37.11 ± 15.24 vs 24.55 ± 10.28), which corresponds to high frequency spectrum component in normalized units and in the LF/HF ratio (2.21 ± 1.47 vs 4.07 ± 2.94). However, in the evaluation of nicotine dependency, significant differences were not observed (p > 0.05).

Conclusion

Only the intensity of smoking consumption had an influence over the cardiac autonomic modulation of the assessed tobacco smokers. Tobacco smokers with severe intensity of smoking consumption presented a lower autonomic modulation than those with moderate intensity.

The role of heart rate variability in sports physiology

Heart rate variability (HRV) is a relevant marker reflecting cardiac modulation by sympathetic and vagal components of the autonomic nervous system (ANS). Although the clinical application of HRV is mainly associated with the prediction of sudden cardiac death and assessing cardiovascular and metabolic illness progression, recent observations have suggested its applicability to physical exercise training. HRV is becoming one of the most useful tools for tracking the time course of training adaptation/maladaptation of athletes and in setting the optimal training loads leading to improved performances. However, little is known regarding the role of HRV and the internal effects of physical exercise on an athlete, which may be useful in designing fitness programs ensuring sufficient training load that may correspond with the specific ability of the athlete. In this review, we offer a comprehensive assessment of investigations concerning the interrelation between HRV and ANS, and examine how the application of HRV to physical exercise may play a role in sports physiology.

Virtual reality cue exposure for the relapse prevention of tobacco consumption: a study protocol for a randomized controlled trial

Background

Successful interventions have been developed for smoking cessation, but the success of smoking relapse prevention interventions has been limited. In particular, cognitive behavioural therapy (CBT) has been hampered by a high relapse rate. Because relapses can be due to the presence of conditions associated with tobacco consumption (such as drinking in bars with friends), virtual reality exposure therapy (VRET) can generate synthetic environments that represent risk situations for the patient in the context of relapse prevention. The primary objective of this study is to evaluate the effectiveness of CBT coupled with VRET, in comparison to CBT alone, in the prevention of smoking relapse. The secondary objectives are to assess the impact of CBT coupled with VRET on anxiety, depression, quality of life, self-esteem and addictive comorbidities (such as alcohol, cannabis, and gambling). A third objective examines the feasibility and acceptability of VR use considering elements such as presence, cybersickness and number of patients who complete the VRET program.

Method/design

The present study is a 14-month (2 months of therapy followed by 12 months of follow-up), prospective, comparative, randomized and open clinical trial, involving two parallel groups (CBT coupled with VRET versus CBT alone). The primary outcome is the proportion of individuals with tobacco abstinence at 6 months after the end of the therapy. Abstinence is defined by the total absence of tobacco consumption assessed during a post-test interview and with an apparatus that measures the carbon monoxide levels expired. A total of 60 individuals per group will be included.

Discussion

This study is the first to examine the efficacy of CBT coupled with VRET in the prevention of smoking relapse. Because VRET is simple to use and has a low cost, this interactive therapeutic method might be easily implemented in clinical practice if the study confirms its efficacy.

Trial registration

ClinicalTrials.gov Identifier: NCT02205060 (registered 25 July 2014).

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-016-1224-5) contains supplementary material, which is available to authorized users.

[Options and limitations of heart rate measurement and analysis of heart rate variability by mobile devices: A systematic review]

BACKGROUND

Heart rate (HR) and heart rate variability (HRV) have been established in the last few years as a non-invasive method for recording the demands on the cardiovascular system. The development enables us today to measure the interbeat intervals with different technologies for calculating HR and HRV.

MATERIALS AND METHODS

This review is based on a systematic literature search in PubMed for validity of different measurement techniques and their pros and cons for the measurement of HR and the analysis of HRV.

RESULTS

Measurement equipment for recording of interbeat intervals should have a high storage capacity and a sampling rate of 1000 Hz ideally. The quality criteria of freedom of feedback (small, little disruptive), robustness and a non-invasive measurement (e. g. freeze-electrodes or sensors) have to be fulfilled. In addition to the Holter ECG, several portable heart rate watch and chest belt systems provide adequate validity and good applicability.

DISCUSSION

The Holter ECG is still the gold standard for the measurement of NN intervals and for the analysis of HRV. Modern heart rate watches show a good correlation with the conformance of freedom from discomfort, robustness and non-invasive measurement and are a good alternative due to the lower disturbance of test persons.

Validity of the Polar V800 heart rate monitor to measure RR intervals at rest

Purpose

To assess the validity of RR intervals and short-term heart rate variability (HRV) data obtained from the Polar V800 heart rate monitor, in comparison to an electrocardiograph (ECG).

Method

Twenty participants completed an active orthostatic test using the V800 and ECG. An improved method for the identification and correction of RR intervals was employed prior to HRV analysis. Agreement of the data was assessed using intra-class correlation coefficients (ICC), Bland–Altman limits of agreement (LoA), and effect size (ES).

Results

A small number of errors were detected between ECG and Polar RR signal, with a combined error rate of 0.086 %. The RR intervals from ECG to V800 were significantly different, but with small ES for both supine corrected and standing corrected data (ES <0.001). The bias (LoA) were 0.06 (−4.33 to 4.45 ms) and 0.59 (−1.70 to 2.87 ms) for supine and standing intervals, respectively. The ICC was >0.999 for both supine and standing corrected intervals. When analysed with the same HRV software no significant differences were observed in any HRV parameters, for either supine or standing; the data displayed small bias and tight LoA, strong ICC (>0.99) and small ES (≤0.029).

Conclusions

The V800 improves over previous Polar models, with narrower LoA, stronger ICC and smaller ES for both the RR intervals and HRV parameters. The findings support the validity of the Polar V800 and its ability to produce RR interval recordings consistent with an ECG. In addition, HRV parameters derived from these recordings are also highly comparable.

COMPARAÇÃO DA MODULAÇÃO AUTONÔMICA CARDÍACA DURANTE ESFORÇO DE FUMANTES E NÃO FUMANTES

Introdução O tabagismo é uma das principais causas de morbimortalidade em todo o mundo. Indivíduos fumantes têm risco aumentado de desenvolver disfunção autonômica, a qual pode ser avaliada tanto pela variabilidade da frequência cardíaca (VFC) como pela frequência cardíaca de recuperação (FCRec). A maioria dos estudos envolvendo esta análise é realizada em adultos de idade avançada e na condição de repouso. Objetivos Comparar a atividade autonômica cardíaca em repouso e esforço, em homens jovens, fumantes e não fumantes. Métodos Trinta e dois jovens voluntários, (idade 22,0 ± 2,8 anos) foram distribuídos em dois grupos: o grupo fumante (GF; n=15) e o não fumante (GNF; n=17). Realizou-se o teste de Cooper, com análise da VFC pelo cardiofrequencímetro Polar(r)s810i, em repouso e durante o esforço e FCRec. Resultados No GF, 73% foram classificados com nível de dependência nicotínica "muito baixa" segundo questionário de Fargeström. A classificação de ativos e muito ativos pelo questionário IPAQ correspondeu a mais de 50% da amostra em ambos os grupos. Não se observou diferenças significativas entre os grupos na VFC, tanto no repouso quanto no esforço. Entretanto, em cada grupo, notou-se diferença na maioria dos índices de VFC do repouso para o esforço. No teste de Cooper não foram observadas diferenças significativas na FCmédia, FCpico e de FCRec entre os grupos, mas notou-se uma melhor capacidade funcional no GNF pela distância caminhada (2050,2 ± 300,0 vs. 1780,3 ± 390,4 m, p=0,036). Conclusão O GF apresentou menor capacidade funcional e ativação parassimpática durante o esforço, além de menores índices de VFC durante repouso, o que pode sugerir um comprometimento precoce na modulação autonômica cardíaca.

Effects of 12 weeks of aerobic training on autonomic modulation, mucociliary clearance, and aerobic parameters in patients with COPD

Introduction

Patients with chronic obstructive pulmonary disease (COPD) exhibit aerobic function, autonomic nervous system, and mucociliary clearance alterations. These parameters can be attenuated by aerobic training, which can be applied with continuous or interval efforts. However, the possible effects of aerobic training, using progressively both continuous and interval sessions (ie, linear periodization), require further investigation.

Aim

To analyze the effects of 12-week aerobic training using continuous and interval sessions on autonomic modulation, mucociliary clearance, and aerobic function in patients with COPD.

Methods

Sixteen patients with COPD were divided into an aerobic (continuous and interval) training group (AT) (n=10) and a control group (CG) (n=6). An incremental test (initial speed of 2.0 km·h⁻¹, constant slope of 3%, and increments of 0.5 km·h⁻¹ every 2 minutes) was performed. The training group underwent training for 4 weeks at 60% of the peak velocity reached in the incremental test (vVO_2peak) (50 minutes of continuous effort), followed by 4 weeks of sessions at 75% of vVO_2peak (30 minutes of continuous effort), and 4 weeks of interval training (5×3-minute effort at vVO_2peak, separated by 1 minute of passive recovery). Intensities were adjusted through an incremental test performed at the end of each period.

Results

The AT presented an increase in the high frequency index (ms²) (P=0.04), peak oxygen uptake (VO_2peak) (P=0.01), vVO_2peak (P=0.04), and anaerobic threshold (P=0.02). No significant changes were observed in the CG (P>0.21) group. Neither of the groups presented changes in mucociliary clearance after 12 weeks (AT: P=0.94 and CG: P=0.69).

Conclusion

Twelve weeks of aerobic training (continuous and interval sessions) positively influenced the autonomic modulation and aerobic parameters in patients with COPD. However, mucociliary clearance was not affected by aerobic training.

Impact of obesity on autonomic modulation, heart rate and blood pressure in obese young people

INTRODUCTION

Obesity can be understood as a comorbidity of increasing systemic impact, including a deficit in the autonomic nervous system.

OBJECTIVE

To analyze cardiac autonomic behavior and hemodynamic parameters in obese young people.

METHODS

92 individuals (20.58±1.48 years) were evaluated, divided into two groups: obese and eutrophic. Heart rate (HR) was captured for 30 min in the supine position whilst breathing spontaneously. Blood pressure (BP) values were obtained prior to performance of the protocol. For the autonomic analysis, 1000 beats were used for the calculation of heart rate variability indices in the time (Mean RR, SDNN and RMSSD) and frequency (LF, HF and LF/HF) domains, in addition to the Poincaré plot (SD1, SD2, SD1/SD2 and qualitative visual analysis).

RESULTS

The obese group presented higher baseline BP and HR values compared to the eutrophic. Regarding autonomic modulation a significant decrease was observed in the RMSSD; SD1, HFms and HFnu indices in the obese group, indicating a decrease in vagal activity and reduced SDNN and SD2 rates, with statistical significance for the former, suggesting a reduction in overall variability. The high value of the LFnu index and decrease in Mean RR in the obese group pointed to relative sympathetic predominance in these individuals. The visual analysis of the Poincaré plot showed less dispersion of the points in the obese group.

CONCLUSION

The obese group presented higher BP and HR values at rest and autonomic impairment, characterized by a reduction in parasympathetic activity and relative predominance of sympathetic activity.