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Mettler SK, Charoenngam N, Jaroenlapnopparat A, Tern C, Xanthavanij N, Economidou S, Strand MJ, Hobbs BD, Moll M, Cho MH. Clinical factors associated with racial differences in the prevalence of occult hypoxemia: a retrospective case-control study. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.03.28.24305036. [PMID: 38585762 PMCID: PMC10996744 DOI: 10.1101/2024.03.28.24305036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
Background Recent studies showed that Black patients more often have falsely normal oxygen saturation on pulse oximetry compared to White patients. However, whether the racial differences in occult hypoxemia are mediated by other clinical differences is unknown. Methods We conducted a retrospective case-control study utilizing two large ICU databases (eICU and MIMIC-IV). We defined occult hypoxemia as oxygen saturation on pulse oximetry within 92-98% despite oxygen saturation on arterial blood gas below 90%. We assessed associations of commonly measured clinical factors with occult hypoxemia using multivariable logistic regression and conducted mediation analysis of the racial effect. Results Among 24,641 patients, there were 1,855 occult hypoxemia cases and 23,786 controls. In both datasets, Black patients were more likely to have occult hypoxemia (unadjusted odds ratio 1.66 [95%-CI: 1.41-1.95] in eICU and 2.00 [95%-CI: 1.22-3.14] in MIMIC-IV). In multivariable models, higher respiratory rate, PaCO2 and creatinine as well as lower hemoglobin were associated with increased odds of occult hypoxemia. Differences in the commonly measured clinical markers accounted for 9.2% and 44.4% of the racial effect on occult hypoxemia in eICU and MIMIC-IV, respectively. Conclusion Clinical differences, in addition to skin tone, might mediate some of the racial differences in occult hypoxemia.
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Affiliation(s)
- Sofia K. Mettler
- Faculty of Medicine, University of Zurich, Zurich, Switzerland
- Mount Auburn Hospital, Cambridge, MA, United States
- Channing Division of Network Medicine, Brigham and Women’s Hospital, Boston, MA, United States
- Harvard Medical School, Boston, MA, United States
| | - Nipith Charoenngam
- Mount Auburn Hospital, Cambridge, MA, United States
- Harvard Medical School, Boston, MA, United States
- Faculty of Medicine, Mahidol University, Bangkok, Thailand
| | | | - Courtney Tern
- Channing Division of Network Medicine, Brigham and Women’s Hospital, Boston, MA, United States
| | - Nutchapon Xanthavanij
- Mount Auburn Hospital, Cambridge, MA, United States
- Harvard Medical School, Boston, MA, United States
| | - Sofia Economidou
- Mount Auburn Hospital, Cambridge, MA, United States
- Harvard Medical School, Boston, MA, United States
| | - Matthew J. Strand
- Division of Biostatistics and Bioinformatics, National Jewish Health, Denver, Colorado, United States
| | - Brian D. Hobbs
- Channing Division of Network Medicine, Brigham and Women’s Hospital, Boston, MA, United States
- Harvard Medical School, Boston, MA, United States
- Division of Pulmonary and Critical Care Medicine, Brigham and Women’s Hospital, Boston, MA, United States
| | - Matthew Moll
- Channing Division of Network Medicine, Brigham and Women’s Hospital, Boston, MA, United States
- Harvard Medical School, Boston, MA, United States
- Division of Pulmonary and Critical Care Medicine, Brigham and Women’s Hospital, Boston, MA, United States
- Pulmonary, Allergy, Sleep and Critical Care Medicine Section, Veterans Affairs Boston Healthcare System, West Roxbury, MA, United States
| | - Michael H. Cho
- Channing Division of Network Medicine, Brigham and Women’s Hospital, Boston, MA, United States
- Harvard Medical School, Boston, MA, United States
- Division of Pulmonary and Critical Care Medicine, Brigham and Women’s Hospital, Boston, MA, United States
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Kohlbrenner D, Marillier M, Randy H, Ghaith A, Furian M, Vergès S. Characterisation of the acute hypoxic response using breathing variability parameters: a pilot study in humans. Respir Physiol Neurobiol 2023:104096. [PMID: 37355056 DOI: 10.1016/j.resp.2023.104096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 06/19/2023] [Accepted: 06/20/2023] [Indexed: 06/26/2023]
Abstract
PURPOSE We aimed to investigate respiratory rate variability (RRV) and tidal volume (Vt) variability during exposure to normobaric hypoxia (i.e., reduction in the fraction of inspired oxygen - FiO2), and the association of the changes in RRV and Vt variability with the changes in pulse oxygen saturation (SpO2). METHODS Thirty healthy human participants (15 females) were exposed to: (1) 15-min normoxia, (2) 10-min hypoxia simulating 2200m, (3) 10-min hypoxia simulating 4000m, (4) 10-min hypoxia simulating 5000m, (5) 15-min recovery in normoxia. Linear regression modelling was applied with SpO2 (dependent variable) and the changes in RRV and Vt variability (independent variables), controlling for FiO2, age, sex, changes in heart rate (HR), changes in HR variability (HRV), and changes in minute ventilation (VE). RESULTS When modelling breathing parameter variability as root-mean-square standard deviation (RMSSD), a significant independent association of the changes in RRV with the changes in SpO2 was found (B=-4.3e-04, 95% CI=-8.3e-04/-2.1e-05, p=0.04). The changes in Vt variability showed no significant association with the changes in SpO2 (B=-1.6, 95% CI=-5.5/2.4, p=0.42). When modelling parameters variability as SD, a significant independent association of the changes in RRV with the changes in SpO2 was found (B=-8.2e-04, 95% CI=-1.5e-03/-9.4e-05, p=0.03). The changes in Vt variability showed no significant association with the changes in SpO2 (B=1.4, 95% CI=-5.8/8.6, p=0.69). CONCLUSION Higher RRV is independently associated with lower SpO2 during acute hypoxic exposure, while Vt variability parameters are not. Therefore, RRV may be a potentially interesting parameter to characterize individual responses to acute hypoxia.
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Affiliation(s)
- Dario Kohlbrenner
- HP2 Laboratory, INSERM, Grenoble Alpes University, Grenoble, France; Faculty of Medicine, University of Zurich, Zurich, Switzerland; Department of Pulmonology, University Hospital Zurich, Zurich, Switzerland.
| | | | - Hugo Randy
- HP2 Laboratory, INSERM, Grenoble Alpes University, Grenoble, France
| | - Abdallah Ghaith
- HP2 Laboratory, INSERM, Grenoble Alpes University, Grenoble, France
| | - Michael Furian
- HP2 Laboratory, INSERM, Grenoble Alpes University, Grenoble, France
| | - Samuel Vergès
- HP2 Laboratory, INSERM, Grenoble Alpes University, Grenoble, France
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Köhler D, Voshaar T, Stais P, Haidl P, Dellweg D. Hypoxische, anämische und kardial bedingte Hypoxämie: Wann beginnt die Hypoxie im Gewebe? Dtsch Med Wochenschr 2023; 148:475-482. [PMID: 36990120 DOI: 10.1055/a-2007-5450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
ZusammenfassungBei einer Hypoxämie ist oft der Sauerstoffgehalt noch im unteren Normbereich, sodass keine
Hypoxie im Gewebe vorliegt. Wird die Hypoxie-Schwelle im Gewebe bei einer hypoxisch, anämisch
und auch kardial bedingten Hypoxämie erreicht, kommt es im Zellstoffwechsel, unabhängig von
der Genese, zu identischen Gegenregulationen. Im klinischen Alltag wird diese
pathophysiologische Tatsache mitunter ignoriert, obwohl je nach Hypoxämie-Ursache die
Beurteilung und die Therapie stark unterschiedlich sind. Während für die anämische Hypoxämie
restriktive und allgemein akzeptierte Regeln in den Transfusionsrichtlinien festgelegt sind,
wird bei einer hypoxischen Hypoxie früh die Indikation zu einer meist invasiven Beatmung
gestellt. Die klinische Beurteilung und Indikationsstellung fokussiert dabei auf die Parameter
Sauerstoffsättigung, Sauerstoffpartialdruck und Oxygenierungsindex. Während der
Corona-Pandemie sind Fehlinterpretationen der Pathophysiologie sichtbar geworden und haben
vermutlich zu überflüssigen Intubationen geführt. Für die Behandlung einer hypoxischen Hypoxie
mittels invasiver Beatmung aber gibt es keine Evidenz. Im vorliegenden Review wird auf die
Pathophysiologie der verschiedenen Hypoxieursachen unter besonderer Berücksichtigung der
Intubation und Beatmung auf der Intensivstation eingegangen.
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Doufas AG, Tian L, Kutscher S, Finnsson E, Ágústsson JS, Chung BI, Panousis P. The effect of hyperoxia on ventilation during recovery from general anesthesia: A randomized pilot study for a parallel randomized controlled trial. J Clin Anesth 2022; 83:110982. [PMID: 36265267 DOI: 10.1016/j.jclinane.2022.110982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 09/29/2022] [Accepted: 10/05/2022] [Indexed: 11/06/2022]
Abstract
STUDY OBJECTIVE While supplemental O2 inhalation corrects hypoxemia, its effect on post-anesthesia ventilation remains unknown. This pilot trial tested the hypothesis that hyperoxia increases the time spent with a transcutaneous PCO2 (TcPCO2) > 45 mmHg, compared with standard O2 supplementation. DESIGN Single-blinded, parallel two-arm randomized pilot trial. SETTING University hospital. PATIENTS 20 patients undergoing robotic-assisted laparoscopic nephrectomy. MEASUREMENTS After institutional approval and informed consent, patients were randomized to receive O2 titrated to arterial saturation (SpO2): 90-94% (Conservative O2, N =10), or to SpO2 > 96% (Liberal O2, N = 10) for up to 90 min after anesthesia. Continuous TcPCO2, respiratory inductance plethysmography (RIP), and SpO2, were recorded. We calculated the percentage of time at TcPCO2 > 45 mmHg for each patient and compared the two groups using analysis of covariance, adjusting for sex, age, and body mass index. We also estimated the sample size required to detect the between-group difference observed in this pilot trial. RIP signals were used to calculate apnea/hypopnea index (AHI), which was then compared between two groups. MAIN RESULTS The mean percentage of time with a TcPCO2 > 45 mmHg was 80.6% for the Conservative O2 (N=9) and 61.2% for the Liberal O2 (N=10) group [between-group difference of 19.4% (95% CI: -18.7% to 57.6%), P = 0.140]. With an observed effect size of 0.73, we estimated that 30 participants per group are required, to demonstrate this difference with a power of 80% at a two-sided alpha of 5%. Means SpO2 were 94.5% and 99.9% for the Conservative O2 and the Liberal O2 groups, respectively. AHI was significantly higher in the Conservative O2, compared with the Liberal O2 group (median AHI: 16 vs. 3; P = 0.0014). CONCLUSIONS Hyperoxia in the post-anesthesia period reduced the time spent at TcPCO2 > 45 mmHg and significantly decreased AHI, while mean SpO2 ranged inside the a priori defined limits. TRIAL REGISTRATION ClinicalTrials.gov identifier: NCT04723433.
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Affiliation(s)
- Anthony G Doufas
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, Stanford, CA, United States of America; Center for Sleep and Circadian Sciences, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, United States of America.
| | - Lu Tian
- Department of Biomedical Data Science, Stanford University School of Medicine, Stanford, CA, United States of America
| | - Scott Kutscher
- Department of Psychiatry and Behavioral Sciences, and Center for Sleep Sciences and Medicine, Stanford University School of Medicine, Stanford, CA, United States of America
| | | | | | - Benjamin I Chung
- Department of Urology, Stanford University School of Medicine, Stanford, CA, United States of America
| | - Periklis Panousis
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, Stanford, CA, United States of America
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Oku Y. Temporal variations in the pattern of breathing: techniques, sources, and applications to translational sciences. J Physiol Sci 2022; 72:22. [PMID: 36038825 DOI: 10.1186/s12576-022-00847-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Accepted: 08/12/2022] [Indexed: 11/10/2022]
Abstract
The breathing process possesses a complex variability caused in part by the respiratory central pattern generator in the brainstem; however, it also arises from chemical and mechanical feedback control loops, network reorganization and network sharing with nonrespiratory motor acts, as well as inputs from cortical and subcortical systems. The notion that respiratory fluctuations contain hidden information has prompted scientists to decipher respiratory signals to better understand the fundamental mechanisms of respiratory pattern generation, interactions with emotion, influences on the cortical neuronal networks associated with cognition, and changes in variability in healthy and disease-carrying individuals. Respiration can be used to express and control emotion. Furthermore, respiration appears to organize brain-wide network oscillations via cross-frequency coupling, optimizing cognitive performance. With the aid of information theory-based techniques and machine learning, the hidden information can be translated into a form usable in clinical practice for diagnosis, emotion recognition, and mental conditioning.
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Affiliation(s)
- Yoshitaka Oku
- Division of Physiome, Department of Physiology, Hyogo Medical University, Nishinomiya, Hyogo, 663-8501, Japan.
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6
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Threshold of increase in oxygen demand to predict mechanical ventilation use in novel coronavirus disease 2019: A retrospective cohort study incorporating restricted cubic spline regression. PLoS One 2022; 17:e0269876. [PMID: 35834478 PMCID: PMC9282654 DOI: 10.1371/journal.pone.0269876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 05/29/2022] [Indexed: 12/15/2022] Open
Abstract
Background
Rapid deterioration of oxygenation occurs in novel coronavirus disease 2019 (COVID-19), and prediction of mechanical ventilation (MV) is needed for allocation of patients to intensive care unit. Since intubation is usually decided based on varying clinical conditions, such as required oxygen changes, we aimed to elucidate thresholds of increase in oxygen demand to predict MV use within 12 h.
Methods
A single-center retrospective cohort study using data between January 2020 and January 2021was conducted. Data were retrieved from the hospital data warehouse. Adult patients diagnosed with COVID-19 with a positive polymerase chain reaction (PCR) who needed oxygen during admission were included. Hourly increments in oxygen demand were calculated using two consecutive oxygen values. Covariates were selected from measurements at the closest time points of oxygen data. Prediction of MV use within 12 h by required oxygen changes was evaluated with the area under the receiver operating curves (AUCs). A threshold for increased MV use risk was obtained from restricted cubic spline curves.
Results
Among 66 eligible patients, 1835 oxygen data were analyzed. The AUC was 0.756 for predicting MV by oxygen demand changes, 0.888 by both amounts and changes in oxygen, and 0.933 by the model adjusted with respiratory rate, PCR quantification cycle (Ct), and days from PCR. The threshold of increments of required oxygen was identified as 0.44 L/min/h and the probability of MV use linearly increased afterward. In subgroup analyses, the threshold was lower (0.25 L/min/h) when tachypnea or frequent respiratory distress existed, whereas it was higher (1.00 L/min/h) when viral load is low (Ct ≥20 or days from PCR >7 days).
Conclusions
Hourly changes in oxygen demand predicted MV use within 12 h, with a threshold of 0.44 L/min/h. This threshold was lower with an unstable respiratory condition and higher with a low viral load.
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van den Bosch OFC, Alvarez-Jimenez R, de Grooth HJ, Girbes ARJ, Loer SA. Breathing variability-implications for anaesthesiology and intensive care. Crit Care 2021; 25:280. [PMID: 34353348 PMCID: PMC8339683 DOI: 10.1186/s13054-021-03716-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 07/29/2021] [Indexed: 12/04/2022] Open
Abstract
The respiratory system reacts instantaneously to intrinsic and extrinsic inputs. This adaptability results in significant fluctuations in breathing parameters, such as respiratory rate, tidal volume, and inspiratory flow profiles. Breathing variability is influenced by several conditions, including sleep, various pulmonary diseases, hypoxia, and anxiety disorders. Recent studies have suggested that weaning failure during mechanical ventilation may be predicted by low respiratory variability. This review describes methods for quantifying breathing variability, summarises the conditions and comorbidities that affect breathing variability, and discusses the potential implications of breathing variability for anaesthesia and intensive care.
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Affiliation(s)
- Oscar F C van den Bosch
- Departments of Anesthesiology and Intensive Care, Amsterdam UMC, VUMC, ZH 6F 003, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands.
| | - Ricardo Alvarez-Jimenez
- Departments of Anesthesiology and Intensive Care, Amsterdam UMC, VUMC, ZH 6F 003, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Harm-Jan de Grooth
- Departments of Anesthesiology and Intensive Care, Amsterdam UMC, VUMC, ZH 6F 003, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Armand R J Girbes
- Departments of Anesthesiology and Intensive Care, Amsterdam UMC, VUMC, ZH 6F 003, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Stephan A Loer
- Departments of Anesthesiology and Intensive Care, Amsterdam UMC, VUMC, ZH 6F 003, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
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8
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Effect of nasal airflow on respiratory pattern variability in rats. PHYSIOLOGY AND PHARMACOLOGY 2021. [DOI: 10.52547/phypha.26.1.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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9
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Straus C, Teulier M, Morel S, Wattiez N, Hajage D, Giboin C, Charbit B, Dasque E, Bodineau L, Chenuel B, Straus N, Attali V, Similowski T. Baclofen destabilises breathing during sleep in healthy humans: A randomised, controlled, double-blind crossover trial. Br J Clin Pharmacol 2020; 87:1814-1823. [PMID: 32986891 DOI: 10.1111/bcp.14569] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 08/31/2020] [Accepted: 09/13/2020] [Indexed: 11/29/2022] Open
Abstract
AIMS Periodic breathing is frequent in patients with severe heart failure. Apart from being an indicator of severity, periodic breathing has its own deleterious consequences (sleep-related oxygen desaturations, sleep fragmentation), which justifies attempts to correct it irrespective of the underlying disease. Animal models and human data suggest that baclofen can reconfigure respiratory central pattern generators. We hypothesised that baclofen, a GABAB agonist, may thus be able to correct periodic breathing in humans. METHODS Healthy volunteers were exposed to hypoxia during sleep. Participants who developed periodic breathing (n = 14 [53 screened]) were randomly assigned to double-blind oral baclofen (progressively increased to 60 mg/d) or placebo. The primary outcome was the coefficient of variation (CoVar) of respiratory cycle total time considered as an indicator of breathing irregularity. Secondary outcomes included the CoVar of tidal volume, apnoea-hypopnoea index, sleep fragmentation index and ventilatory complexity (noise limit). RESULTS The analysis was conducted in 9 subjects after exclusion of incomplete datasets. CoVar of respiratory cycle total time significantly increased with baclofen during non-rapid eye movement sleep (median with placebo 56.00% [37.63-78.95]; baclofen 85.42% [68.37-86.40], P = .020; significant difference during the N1-N2 phases of sleep but not during the N3 phase). CoVar of tidal volume significantly increased during N1-N2 sleep. The apnoea-hypopnoea index, sleep fragmentation index and ventilatory complexity were not significantly different between placebo and baclofen. CONCLUSION Baclofen did not stabilise breathing in our model. On the contrary, it increased respiratory variability. Baclofen should probably not be used in patients with or at risk of periodic breathing.
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Affiliation(s)
- Christian Straus
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale (INSERM), UMRS1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Paris, France.,AP-HP, Groupe Hospitalier APHP-Sorbonne Université, Hôpital Pitié-Salpêtrière, Département R3S, Service des Explorations Fonctionnelles de la Respiration, de l'Exercice et de la Dyspnée, Paris, France
| | - Marion Teulier
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale (INSERM), UMRS1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Paris, France
| | - Sébastien Morel
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale (INSERM), UMRS1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Paris, France
| | - Nicolas Wattiez
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale (INSERM), UMRS1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Paris, France
| | - David Hajage
- Institut National de la Santé et de la Recherche Médicale (INSERM), Institut Pierre Louis d'Epidémiologie et de Santé Publique, AP-HP. Sorbonne Université, Hôpital Pitié Salpêtrière, Département de Santé Publique, Unité de Recherche Clinique Salpêtrière-Charles Foix, Centre de Pharmacoépidémiologie (Cephepi), Sorbonne Université, Paris, France
| | - Caroline Giboin
- AP-HP, Groupe Hospitalier APHP-Sorbonne Université, Hôpital Pitié-Salpêtrière, Unité de Recherche Clinique Salpêtrière-Charles Foix, Paris, France
| | - Beny Charbit
- INSERM and AP-HP, CIC-1901 module Paris-Est, Groupe Hospitalier Universitaire APHP-Sorbonne Université, site Pitié-Salpêtrière, Paris, France.,Department of Anesthesiology and Intensive Care, CHU Reims, Hôpital Robert Debré, Reims, France
| | - Eric Dasque
- INSERM and AP-HP, CIC-1901 module Paris-Est, Groupe Hospitalier Universitaire APHP-Sorbonne Université, site Pitié-Salpêtrière, Paris, France
| | - Laurence Bodineau
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale (INSERM), UMRS1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Paris, France
| | - Bruno Chenuel
- CHRU de Nancy, Service des Explorations Fonctionnelles Respiratoires et Centre Universitaire de Médecine du Sport et Activité Physique Adaptée, Vandoeuvre-lès-Nancy, France.,Faculté de Médecine de Nancy, EA DevAH - Universié de Lorraine, Vandoeuvre-lès-Nancy, France
| | - Nicolas Straus
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale (INSERM), UMRS1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Paris, France
| | - Valérie Attali
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale (INSERM), UMRS1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Paris, France.,AP-HP, Groupe Hospitalier APHP-Sorbonne Université, Hôpital Pitié-Salpêtrière, Hôpital Pitié-Salpêtrière, Département R3S, Service des Pathologies du Sommeil, Paris, France
| | - Thomas Similowski
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale (INSERM), UMRS1158 Neurophysiologie Respiratoire Expérimentale et Clinique, Paris, France.,AP-HP, Groupe Hospitalier APHP-Sorbonne Université, Hôpital Pitié-Salpêtrière, Hôpital Pitié-Salpêtrière, Département R3S, Service de Pneumologie, Médecine Intensive et Réanimation, Paris, France
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Tobin MJ, Laghi F, Jubran A. Why COVID-19 Silent Hypoxemia Is Baffling to Physicians. Am J Respir Crit Care Med 2020; 202:356-360. [PMID: 32539537 PMCID: PMC7397783 DOI: 10.1164/rccm.202006-2157cp] [Citation(s) in RCA: 353] [Impact Index Per Article: 88.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 06/15/2020] [Indexed: 02/07/2023] Open
Abstract
Patients with coronavirus disease (COVID-19) are described as exhibiting oxygen levels incompatible with life without dyspnea. The pairing-dubbed happy hypoxia but more precisely termed silent hypoxemia-is especially bewildering to physicians and is considered as defying basic biology. This combination has attracted extensive coverage in media but has not been discussed in medical journals. It is possible that coronavirus has an idiosyncratic action on receptors involved in chemosensitivity to oxygen, but well-established pathophysiological mechanisms can account for most, if not all, cases of silent hypoxemia. These mechanisms include the way dyspnea and the respiratory centers respond to low levels of oxygen, the way the prevailing carbon dioxide tension (PaCO2) blunts the brain's response to hypoxia, effects of disease and age on control of breathing, inaccuracy of pulse oximetry at low oxygen saturations, and temperature-induced shifts in the oxygen dissociation curve. Without knowledge of these mechanisms, physicians caring for patients with hypoxemia free of dyspnea are operating in the dark, placing vulnerable patients with COVID-19 at considerable risk. In conclusion, features of COVID-19 that physicians find baffling become less strange when viewed in light of long-established principles of respiratory physiology; an understanding of these mechanisms will enhance patient care if the much-anticipated second wave emerges.
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Affiliation(s)
- Martin J Tobin
- Division of Pulmonary and Critical Care Medicine, Hines Veterans Affairs Hospital and Loyola University of Chicago Stritch School of Medicine, Hines, Illinois
| | - Franco Laghi
- Division of Pulmonary and Critical Care Medicine, Hines Veterans Affairs Hospital and Loyola University of Chicago Stritch School of Medicine, Hines, Illinois
| | - Amal Jubran
- Division of Pulmonary and Critical Care Medicine, Hines Veterans Affairs Hospital and Loyola University of Chicago Stritch School of Medicine, Hines, Illinois
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11
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Jiang Y, Costello JT, Williams TB, Panyapiean N, Bhogal AS, Tipton MJ, Corbett J, Mani AR. A network physiology approach to oxygen saturation variability during normobaric hypoxia. Exp Physiol 2020; 106:151-159. [DOI: 10.1113/ep088755] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 07/02/2020] [Indexed: 02/02/2023]
Affiliation(s)
- Yuji Jiang
- Network Physiology Laboratory UCL Division of Medicine University College London London UK
| | - Joseph T. Costello
- Extreme Environments Laboratory School of Sport, Health and Exercise Science University of Portsmouth Portsmouth UK
| | - Thomas B. Williams
- Extreme Environments Laboratory School of Sport, Health and Exercise Science University of Portsmouth Portsmouth UK
| | - Nawamin Panyapiean
- Network Physiology Laboratory UCL Division of Medicine University College London London UK
| | - Amar S. Bhogal
- Network Physiology Laboratory UCL Division of Medicine University College London London UK
| | - Michael J. Tipton
- Extreme Environments Laboratory School of Sport, Health and Exercise Science University of Portsmouth Portsmouth UK
| | - Jo Corbett
- Extreme Environments Laboratory School of Sport, Health and Exercise Science University of Portsmouth Portsmouth UK
| | - Ali R. Mani
- Network Physiology Laboratory UCL Division of Medicine University College London London UK
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12
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Affiliation(s)
- Martin J Tobin
- Division of Pulmonary and Critical Care MedicineHines Veterans Affairs Hospital and Loyola University of Chicago Stritch School of Medicine Hines, Illinois
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Young BP, Loparo KA, Dick TE, Jacono FJ. Ventilatory pattern variability as a biometric for severity of acute lung injury in rats. Respir Physiol Neurobiol 2019; 265:161-171. [PMID: 30928542 PMCID: PMC9994622 DOI: 10.1016/j.resp.2019.03.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 03/05/2019] [Accepted: 03/26/2019] [Indexed: 01/27/2023]
Abstract
We hypothesize that ventilatory pattern variability (VPV) varies with the magnitude of acute lung injury (ALI). In adult male rats, we instilled a low- or high- dose of bleomycin or saline (PBS) intratracheally. While representative samples of pulmonary tissue indicated graded lung injury, coefficient of variation (CV) of TTOT did not differ among the 3 groups. Broncho-alveolar lavage fluid (BALF), respiratory rate (fR), mutual information were greater in ALI than sham rats; but did not differ between bleomycin doses. However, nonlinear complexity index (NLCI), which is the difference in sample entropy between original and surrogate data sets was greater for high- versus low- dose; but did not differ between low-dose and sham groups. Further, NLCI correlated to an injury index based on protein concentration of BALF and failure to gain weight. Finally, Receiver Operator Curves (ROCs) indicated that both mutual information and NLCI had greater sensitivity and specificity than fR and CVTTOT in identifying ALI. Thus, nonlinear analyses of VPV can distinguish ALI and out performs fR as a biometric.
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Affiliation(s)
- Benjamin P Young
- Division of Pulmonary, Critical Care, & Sleep Medicine, Department of Medicine, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Kenneth A Loparo
- Department of Electrical Engineering and Computer Science, School of Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Thomas E Dick
- Division of Pulmonary, Critical Care, & Sleep Medicine, Department of Medicine, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; Department of Neurosciences, School of Medicine Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Frank J Jacono
- Division of Pulmonary, Critical Care, & Sleep Medicine, Department of Medicine, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Louis Stokes VA Medical Center, Cleveland, OH 44106, USA
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Satalin J, Habashi NM, Nieman GF. Never give the lung the opportunity to collapse. TRENDS IN ANAESTHESIA AND CRITICAL CARE 2018. [DOI: 10.1016/j.tacc.2018.05.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Shalish W, Kanbar LJ, Rao S, Robles-Rubio CA, Kovacs L, Chawla S, Keszler M, Precup D, Brown K, Kearney RE, Sant'Anna GM. Prediction of Extubation readiness in extremely preterm infants by the automated analysis of cardiorespiratory behavior: study protocol. BMC Pediatr 2017; 17:167. [PMID: 28716018 PMCID: PMC5512825 DOI: 10.1186/s12887-017-0911-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 06/29/2017] [Indexed: 11/10/2022] Open
Abstract
Background Extremely preterm infants (≤ 28 weeks gestation) commonly require endotracheal intubation and mechanical ventilation (MV) to maintain adequate oxygenation and gas exchange. Given that MV is independently associated with important adverse outcomes, efforts should be made to limit its duration. However, current methods for determining extubation readiness are inaccurate and a significant number of infants fail extubation and require reintubation, an intervention that may be associated with increased morbidities. A variety of objective measures have been proposed to better define the optimal time for extubation, but none have proven clinically useful. In a pilot study, investigators from this group have shown promising results from sophisticated, automated analyses of cardiorespiratory signals as a predictor of extubation readiness. The aim of this study is to develop an automated predictor of extubation readiness using a combination of clinical tools along with novel and automated measures of cardiorespiratory behavior, to assist clinicians in determining when extremely preterm infants are ready for extubation. Methods In this prospective, multicenter observational study, cardiorespiratory signals will be recorded from 250 eligible extremely preterm infants with birth weights ≤1250 g immediately prior to their first planned extubation. Automated signal analysis algorithms will compute a variety of metrics for each infant, and machine learning methods will then be used to find the optimal combination of these metrics together with clinical variables that provide the best overall prediction of extubation readiness. Using these results, investigators will develop an Automated system for Prediction of EXtubation (APEX) readiness that will integrate the software for data acquisition, signal analysis, and outcome prediction into a single application suitable for use by medical personnel in the neonatal intensive care unit. The performance of APEX will later be prospectively validated in 50 additional infants. Discussion The results of this research will provide the quantitative evidence needed to assist clinicians in determining when to extubate a preterm infant with the highest probability of success, and could produce significant improvements in extubation outcomes in this population. Trial registration Clinicaltrials.gov identifier: NCT01909947. Registered on July 17 2013. Trial sponsor: Canadian Institutes of Health Research (CIHR). Electronic supplementary material The online version of this article (doi:10.1186/s12887-017-0911-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Wissam Shalish
- Department of Pediatrics, Division of Neonatology, Montreal Children's Hospital, McGill University, 1001 Boul. Décarie, room B05.2714. Montreal, Quebec, H4A 3J1, Canada
| | - Lara J Kanbar
- Department of Biomedical Engineering, McGill University, Montreal, Quebec, H3A 2B4, Canada
| | - Smita Rao
- Department of Pediatrics, Division of Neonatology, Montreal Children's Hospital, McGill University, 1001 Boul. Décarie, room B05.2714. Montreal, Quebec, H4A 3J1, Canada
| | - Carlos A Robles-Rubio
- Department of Biomedical Engineering, McGill University, Montreal, Quebec, H3A 2B4, Canada
| | - Lajos Kovacs
- Department of Neonatology, Jewish General Hospital, Montreal, Quebec, H3T 1E2, Canada
| | - Sanjay Chawla
- Division of Neonatal-Perinatal Medicine, Hutzel Women's Hospital, Wayne State University, Detroit, MI, 48201, USA
| | - Martin Keszler
- Department of Pediatrics, Women and Infants Hospital of Rhode Island, Brown University, Providence, RI, 02905, USA
| | - Doina Precup
- Department of Computer Science, McGill University, Montreal, Quebec, H3A 0E9, Canada
| | - Karen Brown
- Department of Anesthesia, Montreal Children's Hospital, McGill University Health Center, Montreal, Quebec, H4A 3J1, Canada
| | - Robert E Kearney
- Department of Biomedical Engineering, McGill University, Montreal, Quebec, H3A 2B4, Canada
| | - Guilherme M Sant'Anna
- Department of Pediatrics, Division of Neonatology, Montreal Children's Hospital, McGill University, 1001 Boul. Décarie, room B05.2714. Montreal, Quebec, H4A 3J1, Canada.
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BuSha BF, Banis G. A stochastic and integrative model of breathing. Respir Physiol Neurobiol 2017; 237:51-56. [DOI: 10.1016/j.resp.2016.12.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 12/21/2016] [Accepted: 12/28/2016] [Indexed: 12/17/2022]
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Goto Y, Katayama S, Shono A, Mori Y, Miyazaki Y, Sato Y, Ozaki M, Kotani T. Roles of neurally adjusted ventilatory assist in improving gas exchange in a severe acute respiratory distress syndrome patient after weaning from extracorporeal membrane oxygenation: a case report. J Intensive Care 2016; 4:26. [PMID: 27057312 PMCID: PMC4823850 DOI: 10.1186/s40560-016-0153-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 03/31/2016] [Indexed: 02/06/2023] Open
Abstract
Background Patient-ventilator asynchrony is a major cause of difficult weaning from mechanical ventilation. Neurally adjusted ventilatory assist (NAVA) is reported useful to improve the synchrony in patients with sustained low lung compliance. However, the role of NAVA has not been fully investigated. Case presentation The patient was a 63-year-old Japanese man with acute respiratory distress syndrome secondary to respiratory infection. He was treated with extracorporeal membrane oxygenation for 7 days and survived. Dynamic compliance at withdrawal of extracorporeal membrane oxygenation decreased to 20 ml/cmH2O or less, but gas exchange was maintained by full support with assist/control mode. However, weaning from mechanical ventilation using a flow trigger failed repeatedly because of patient-ventilator asynchrony with hypercapnic acidosis during partial ventilator support despite using different types of ventilators and different trigger levels. Weaning using NAVA restored the regular respiration and stable and normal acid-base balance. Electromyographic analysis of the diaphragm clearly showed improved triggering of both the start and the end of spontaneous inspiration. Regional ventilation monitoring using electrical impedance tomography showed an increase in tidal volume and a ventilation shift to the dorsal regions during NAVA, indicating that NAVA could deliver gas flow to the dorsal regions to adjust for the magnitude of diaphragmatic excursion. NAVA was applied for 31 days, followed by partial ventilatory support with a conventional flow trigger. The patient was discharged from the intensive care unit on day 110 and has recovered enough to be able to live without a ventilatory support for 5 h per day. Conclusion Our experience showed that NAVA improved not only patient-ventilator synchrony but also regional ventilation distribution in an acute respiratory distress patient with sustained low lung compliance.
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Affiliation(s)
- Yuya Goto
- Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan
| | - Shinshu Katayama
- Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan
| | - Atsuko Shono
- Department of Anesthesiology, Shimane University, Shimane, 693-8501 Japan
| | - Yosuke Mori
- Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan
| | - Yuya Miyazaki
- Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan
| | - Yoko Sato
- Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan
| | - Makoto Ozaki
- Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan
| | - Toru Kotani
- Department of Anesthesiology and Intensive Care Medicine, Tokyo Women's Medical University, Tokyo, 162-8666 Japan
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Hermand E, Pichon A, Lhuissier FJ, Richalet JP. Periodic breathing in healthy humans at exercise in hypoxia. J Appl Physiol (1985) 2014; 118:115-23. [PMID: 25554800 DOI: 10.1152/japplphysiol.00832.2014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Periodic breathing is frequent in heart failure or ventilatory disorders during sleep, and common during sleep at high altitude, but has been rarely studied in wakefulness and during exercise. A retrospective analysis of ventilation from hypoxia exercise tests was realized in 82 healthy subjects separated into two groups with either high or low ventilatory response to hypoxia at exercise (HVRe). A fast Fourier transform spectral analysis of the breath-by-breath ventilation (V̇e) signal, O2 saturation, and end-tidal PCO2 evidenced a periodic pattern with a period of 11.1 to 12.0 s. The peak power of the V̇e spectrum was higher in the high HVRe group (P < 0.001). A prospective study (25 subjects) was performed to evaluate the influence of cardiorespiratory factors on the amplitude and period of oscillations in various conditions of exercise (20 to 40% maximal aerobic power) and hypoxia (0 to 4,000 m altitude). The period of V̇e was shorter at exercise (vs. rest, P < 0.001) and hypoxia (vs. normoxia, P < 0.001), and inversely related with cardiac output and V̇e (P < 0.001). V̇e peak power was higher at exercise (P < 0.001) and hypoxia (P < 0.001), and was positively related with cardiac output and V̇e (P < 0.001). V̇e peak power in hypoxia was positively related with the ventilatory response to CO2 (HCVR). This novel observation suggests that healthy subjects demonstrate a spontaneous periodic breathing, not clearly observable at rest and in normoxia, but triggered by hypoxic exercise. The periodic pattern is enhanced in subjects with high HVRe and high HCVR, suggesting that oxygen and CO2 play synergistic roles in the modulation of these oscillations.
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Affiliation(s)
- Eric Hermand
- Université Paris 13, Sorbonne Paris Cité, Laboratoire Hypoxie et poumon, Bobigny, France; and
| | - Aurélien Pichon
- Université Paris 13, Sorbonne Paris Cité, Laboratoire Hypoxie et poumon, Bobigny, France; and
| | - François J Lhuissier
- Université Paris 13, Sorbonne Paris Cité, Laboratoire Hypoxie et poumon, Bobigny, France; and Assistance Publique-Hôpitaux de Paris, Hôpital Avicenne, Service de Physiologie, explorations fonctionnelles et médecine du sport, Bobigny, France
| | - Jean-Paul Richalet
- Université Paris 13, Sorbonne Paris Cité, Laboratoire Hypoxie et poumon, Bobigny, France; and Assistance Publique-Hôpitaux de Paris, Hôpital Avicenne, Service de Physiologie, explorations fonctionnelles et médecine du sport, Bobigny, France
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Tobin MJ, Laghi F, Jubran A. Ventilatory failure, ventilator support, and ventilator weaning. Compr Physiol 2013; 2:2871-921. [PMID: 23720268 DOI: 10.1002/cphy.c110030] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The development of acute ventilatory failure represents an inability of the respiratory control system to maintain a level of respiratory motor output to cope with the metabolic demands of the body. The level of respiratory motor output is also the main determinant of the degree of respiratory distress experienced by such patients. As ventilatory failure progresses and patient distress increases, mechanical ventilation is instituted to help the respiratory muscles cope with the heightened workload. While a patient is connected to a ventilator, a physician's ability to align the rhythm of the machine with the rhythm of the patient's respiratory centers becomes the primary determinant of the level of rest accorded to the respiratory muscles. Problems of alignment are manifested as failure to trigger, double triggering, an inflationary gas-flow that fails to match inspiratory demands, and an inflation phase that persists after a patient's respiratory centers have switched to expiration. With recovery from disorders that precipitated the initial bout of acute ventilatory failure, attempts are made to discontinue the ventilator (weaning). About 20% of weaning attempts fail, ultimately, because the respiratory controller is unable to sustain ventilation and this failure is signaled by development of rapid shallow breathing. Substantial advances in the medical management of acute ventilatory failure that requires ventilator assistance are most likely to result from research yielding novel insights into the operation of the respiratory control system.
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Affiliation(s)
- Martin J Tobin
- Division of Pulmonary and Critical Care Medicine, Edward Hines Jr. Veterans Affairs Hospital and Loyola University of Chicago Stritch School of Medicine, Hines, Illinois, USA.
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Control of ventilation in COPD and lung injury. Respir Physiol Neurobiol 2013; 189:371-6. [PMID: 23856486 DOI: 10.1016/j.resp.2013.07.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2013] [Revised: 06/27/2013] [Accepted: 07/04/2013] [Indexed: 11/23/2022]
Abstract
Breathing occurs in single breaths and in patterns which are altered by the onset, progression and resolution of respiratory diseases. Through modulations of rate, depth, and patterning of breathing, the ventilatory control system maintains numerous critical variables within their homeostatic ranges. A dynamic respiratory control system is critical to successful adaptation in the face of progressive pulmonary pathology. The objective of this review, is to illustrate functional changes and compensatory mechanisms which occur with the onset and progression of acute and chronic lung disease. Chronic obstructive pulmonary disease (COPD) will be considered as a model of a slowly progressive pulmonary process, where destruction of lung parenchyma and airway obstruction leads to hypoxemia and hypercapnia. Over time, adaptations of the respiratory control system to this disease include changes in the intrinsic properties of respiratory muscles, chemoreceptor signaling, and central respiratory drive which increase motor output to the respiratory muscles. In contrast, acute respiratory distress syndrome (ARDS) is an exemplar of an acute pulmonary process. The result of severe lung injury, ARDS is characterized by lung infiltrates, rapidly progressive hypoxemic respiratory failure, and possible progression to pulmonary fibrosis. Changes in breathing patterns result from these functional changes, as well as altered processing of afferent feedback by the central controller, possibly influenced by brainstem inflammation. Taken together, these disease models highlight the plasticity of the respiratory control system in response to the development and progression of lung disease.
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Jacono FJ, Mayer CA, Hsieh YH, Wilson CG, Dick TE. Lung and brainstem cytokine levels are associated with breathing pattern changes in a rodent model of acute lung injury. Respir Physiol Neurobiol 2011; 178:429-38. [PMID: 21569869 PMCID: PMC3170447 DOI: 10.1016/j.resp.2011.04.022] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Revised: 04/22/2011] [Accepted: 04/27/2011] [Indexed: 02/07/2023]
Abstract
Acute lung injury evokes a pulmonary inflammatory response and changes in the breathing pattern. The inflammatory response has a centrally mediated component which depends on the vagi. We hypothesize that the central inflammatory response, complimentary to the pulmonary inflammatory response, is expressed in the nuclei tractus solitarii (nTS) and that the expression of cytokines in the nTS is associated with breathing pattern changes. Adult, male Sprague-Dawley rats (n=12) received intratracheal instillation of either bleomycin (3units in 120μl of saline) or saline (120μl). Respiratory pattern changed by 24h. At 48h, bronchoalveolar lavage fluid and lung tissue had increased IL-1β and TNF-α levels, but not IL-6. No changes in these cytokines were noted in serum. Immunocytochemical analysis of the brainstem indicated increased expression of IL-1β in the nTS commissural subnucleus that was localized to neurons. We conclude that breathing pattern changes in acute lung injury were associated with increased levels of IL-1β in brainstem areas which integrate cardio-respiratory sensory input.
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Affiliation(s)
- Frank J Jacono
- Division of Pulmonary, Critical Care and Sleep Medicine, CWRU School of Medicine and University Hospitals Case Medical Center, United States.
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23
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Lower interbreath interval complexity is associated with extubation failure in mechanically ventilated patients during spontaneous breathing trials. ACTA ACUST UNITED AC 2010; 68:1310-6. [PMID: 20539175 DOI: 10.1097/ta.0b013e3181da90db] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To determine whether lower complexity of interbreath interval as measured with nonlinear analysis techniques will identify patients who fail to separate from mechanical ventilation after 30-minute spontaneous breathing trials (SBTs). METHODS Respiratory waveforms from SBT of patients in surgical or burn intensive care units were recorded for later analysis. The decision to extubate was made by attending physician. Extubated patients were observed for 48 hours; during this time, reintubation or noninvasive positive pressure ventilation was considered as a failure. Analysis of waveform data by software was performed post hoc. Sample entropy (SampEn) and other nonlinear measures were 48 hours of extubation. RESULTS Thirty-two patients (24 burn, 8 trauma/surgical admissions; mean age, 40.2 +/- 16.9 years; 26 men and 6 women) who were intubated >24 hours were extubated after SBT. Twenty-four patients were successfully separated from mechanical ventilation and eight failed. Age, gender, and mechanism of injury did not influence outcome. SampEn calculated for the two groups presented in this study was different with the cohort that failed extubation having a lower mean value (1.35 +/- 0.39 vs. 1.87 +/- 0.27; p < 0.001). Other nonlinear metrics were moved in concert with SampEn. The stationarity in the respiratory signal was not different between groups. CONCLUSION In intubated patients, the interbreath interval in those who were successfully separated from mechanical ventilation was more irregular than those who failed, as measured by nonlinear techniques. When available at bedside, these metrics may be useful markers of pulmonary health and assist in clinical decision making.
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Goldman LJ, Jarabo RM, Gómez RG. Airway pressure alters wavelet fractal dynamics and short-range dependence of respiratory variability. Respir Physiol Neurobiol 2008; 161:29-40. [DOI: 10.1016/j.resp.2007.11.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2006] [Revised: 11/24/2007] [Accepted: 11/26/2007] [Indexed: 11/25/2022]
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Mangin L, Fiamma MN, Straus C, Derenne JP, Zelter M, Clerici C, Similowski T. Source of human ventilatory chaos: lessons from switching controlled mechanical ventilation to inspiratory pressure support in critically ill patients. Respir Physiol Neurobiol 2008; 161:189-96. [PMID: 18387347 DOI: 10.1016/j.resp.2008.02.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2007] [Revised: 01/30/2008] [Accepted: 02/08/2008] [Indexed: 11/15/2022]
Abstract
Ventilatory flow measured at the airway opening in humans exhibits a complex dynamics that has the features of chaos. Currently available data point to a neural origin of this feature, but the role of respiratory mechanics has not been specifically assessed. In this aim, we studied 17 critically ill mechanically ventilated patients during a switch form an entirely machine-controlled assistance mode (assist-controlled ventilation ACV) to a patient-driven mode (inspiratory pressure support IPS). Breath-by-breath respiratory variability was assessed with the coefficient of variation of tidal volume, total cycle time, inspiratory time, expiratory time, mean inspiratory flow, duty cycle. The detection of chaos was performed with the noise titration technique. When present, chaos was characterized with numerical indexes (correlation dimension, irregularity; largest Lyapunov exponent, sensitivity to initial conditions). Expectedly, the coefficients of variations of the respiratory variables were higher during IPS than during ACV. During ACV, noise titration failed to detect nonlinearities in 12 patients who did not exhibit signs of spontaneous respiratory activity. This indicates that the mechanical properties of the respiratory system were not sufficient to produce ventilatory chaos in the presence of a nonlinear command (ventilator clock). A positive noise limit was found in the remaining 5 cases, but these patients exhibited signs of active expiratory control (highly variable expiratory time, respiratory frequency higher than the set frequency). A positive noise limit was also observed in 16/17 patients during IPS (p<0.001). These observations suggest that ventilatory chaos predominantly has a neural origin (intrinsic to the respiratory central pattern generators, resulting from their perturbation by respiratory afferents, or both), with little contribution of respiratory mechanics, if any.
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Affiliation(s)
- Laurence Mangin
- Université Paris 7 and Service de Physiologie-Explorations fonctionnelles, Hôpital Bichat, AP-HP, Paris, France.
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Jubran A, Tobin MJ. Noninvasive Respiratory Monitoring. Crit Care Med 2008. [DOI: 10.1016/b978-032304841-5.50015-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Giraldo BF, Chaparro J, Ballesteros D, Lopez-Rodriguez L, Geat D, Benito S, Caminal P. Study of the respiratory pattern variability in patients during weaning trials. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2007; 2004:3909-12. [PMID: 17271151 DOI: 10.1109/iembs.2004.1404093] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Mechanical ventilators are used to provide life support in patients with respiratory failure. One of the challenges in intensive care is the process of weaning from mechanical ventilation. We studied the differences in respiratory pattern variability between patients capable of maintaining spontaneous breathing during weaning trials and patients that fail to maintain spontaneous breathing. The respiratory pattern was characterized by the following time series: inspiratory time (T(I)), expiratory time (T(E)), breath duration (T(Tot)), tidal volume (V(T)), fractional inspiratory time (T(I)/T(Tot)), mean inspiratory flow (V(T)/T(I)), respiratory frequency (f), and rapid shallow breathing index (f/V(T)). The variational activity of breathing was partitioned into autoregressive, periodic and white noise fractions. Patients with unsuccessful trial presented a tendency to higher values of gross variability of V(T)/T(I) and f/V(T), and lower values of T(I). The autocorrelation coefficients tended to present higher values for T(I), T(I)/T(Tot) and V(T)/T(I). During both successful and unsuccessful T-tube test uncorrelated random behavior constituted > 75% of the variance of each time breath components and represented 50 to 70% in the breath component related to V(T). Correlated behavior represented 6 to 21% in time components and 28 to 50% in component related to V(T).
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Affiliation(s)
- B F Giraldo
- Biomedical Engineering Research Centre (CREB), Department ESAII, Technical University of Catalonia, Barcelona, Spain
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Rameckers H, Kohl J, Boutellier U. The influence of a mouthpiece and noseclip on breathing pattern at rest is reduced at high altitude. Respir Physiol Neurobiol 2007; 156:165-70. [PMID: 17011245 DOI: 10.1016/j.resp.2006.09.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2006] [Accepted: 09/03/2006] [Indexed: 11/27/2022]
Abstract
The effects of the instrumentation by a mouthpiece (MP) and a noseclip (NC) on the ventilatory response to short time hypobaric hypoxia were studied in 10 healthy volunteers at rest. The subjects were exposed to simulated altitude of 500 m, 3000 m, 4000 m and again 500 m, each altitude being applied for 30 min in a hypobaric chamber. Resting minute ventilation (VE), tidal volume (VT) and respiratory frequency (fR) using inductive plethysmography were continuously measured in all subjects in a standardized half lying position. The recordings were carried out at each altitude during the first 10 min without MP and NC, then 10 min with them, and the last 10 min again without them. At 500 m during MP+NC breathing VE and VT were increased, whereas fR was not significantly changed. At 3000 m, the VE increase with MP+NC was no more significant and fR was decreased. These effects of MP+NC on respiration disappeared at 4000 m and reappeared after the descent to 500 m. Furthermore, with and without MP and NC the variability of VE at 4000 m was significantly higher than at 500 m before ascent, and in all altitudes the variability of VT was significantly reduced by the MP+NC. It is concluded that the influence of MP+NC on VE, VT and fR is reduced or even abolished at high altitude, whereas the hypoxia induced increase of VE variability is not affected by the instrumentation.
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Vallverdú M, Tibaduisa O, Hoyer D, Giraldo B, Benito S, Caminal P. Analysis of the nonlinear autodependencies of respiratory pattern in patients on weaning trials. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2007; 2006:542-5. [PMID: 17271733 DOI: 10.1109/iembs.2004.1403214] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Traditional time domain techniques of data analysis are often not sufficient to characterize the nonlinear dynamics of respiration. In this study, the respiratory pattern variability was analyzed using auto mutual information measures. These provide access to nonlinear statistical autodependencies of respiratory pattern variability. A group of 20 patients on weaning trials from mechanical ventilation were studied at two different pressure support ventilation levels, in order to obtain respiratory volume signals with different variability. Time series of breathing duration, inspiratory time, fractional inspiratory time, tidal volume and mean inspiratory flow were analyzed. Different measures based on auto-mutual information were studied to characterize the respiratory pattern variability with regard to its complex organization.
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Affiliation(s)
- M Vallverdú
- Biomedical Engineering Research Centre, Department ESAII, Univ. Politècnica de Catalunya, Spain
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Wysocki M, Cracco C, Teixeira A, Mercat A, Diehl JL, Lefort Y, Derenne JP, Similowski T. Reduced breathing variability as a predictor of unsuccessful patient separation from mechanical ventilation. Crit Care Med 2006; 34:2076-83. [PMID: 16755257 DOI: 10.1097/01.ccm.0000227175.83575.e9] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES To compare descriptors of the breath-to-breath respiratory variability during a 60-min spontaneous breathing trial in patients successfully and unsuccessfully separated from the ventilator and the endotracheal tube and to assess the usefulness of these predictors in discriminating these two categories of patients. DESIGN Prospective observational study. SETTING Four general intensive care units in university hospitals. PATIENTS A total of 51 consecutive patients mechanically ventilated for >24 hrs. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS Tidal volume, respiratory period, inspiratory time, expiratory time, mean inspiratory flow (tidal volume/inspiratory time), and duty cycle (inspiratory time/respiratory period) were obtained from the flow signal. Breath-by-breath variability was expressed in terms of their coefficients of variation (CV), the number of breaths among which a significant correlation was found (lag), and the autocorrelation coefficient between one breath and the following one. Five patients were excluded because of nonstationarity of the data, leaving 46 cases for analysis. Between-group comparison was conducted with the Mann-Whitney test, and a nonparametric classification and regression tree was used to identify variables discriminating "success" (n = 32) and "failure" patients (n = 14). All coefficients of variation were significantly higher in success patients, who also exhibited significantly less respiratory autocorrelation (shorter "short memory"). The classification and regression tree analysis allocated all success patients to a group defined by a coefficient of variation of tidal volume/inspiratory time of > or =19% and a coefficient of variation of inspiratory time/respiratory period of > or =10% that did not contain any failure patient. All failure patients belonged to a group with coefficient of variation of tidal volume/inspiratory time of <19%, a lag tidal volume of > or =11, and that contained no success patient. CONCLUSIONS In intensive care unit patients undergoing a spontaneous breathing trial, breathing variability is greater in patients successfully separated from the ventilator and the endotracheal tube. Variability indices are sufficient to separate success from failure cases.
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Affiliation(s)
- Marc Wysocki
- UPRES EA 2397, Université Paris VI Pierre et Marie Curie, Paris, France
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Caminal P, Vallverdú M, Giraldo B, Benito S, Vázquez G, Voss A. Optimized Symbolic Dynamics Approach for the Analysis of the Respiratory Pattern. IEEE Trans Biomed Eng 2005; 52:1832-9. [PMID: 16285386 DOI: 10.1109/tbme.2005.856293] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Traditional time domain techniques of data analysis are often not sufficient to characterize the complex dynamics of respiration. In this paper, the respiratory pattern variability is analyzed using symbolic dynamics. A group of 20 patients on weaning trials from mechanical ventilation are studied at two different pressure support ventilation levels, in order to obtain respiratory volume signals with different variability. Time series of inspiratory time, expiratory time, breathing duration, fractional inspiratory time, tidal volume and mean inspiratory flow are analyzed. Two different symbol alphabets, with three and four symbols, are considered to characterize the respiratory pattern variability. Assessment of the method is made using the 40 respiratory volume signals classified using clinical criteria into two classes: low variability (LV) or high variability (HV). A discriminant analysis using single indexes from symbolic dynamics has been able to classify the respiratory volume signals with an out-of-sample accuracy of 100%.
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Affiliation(s)
- P Caminal
- ESAII Department, Catalonian Bioengineering Research Centre (CREBEC), Technical University of Catalonia (UPC), Barcelona, Spain.
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Brack T, Jubran A, Laghi F, Tobin MJ. Fluctuations in end-expiratory lung volume during Cheyne-Stokes respiration. Am J Respir Crit Care Med 2005; 171:1408-13. [PMID: 15778489 DOI: 10.1164/rccm.200503-409oc] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
We hypothesized that patients with Cheyne-Stokes respiration exhibit periodic increases in end-expiratory lung volume, mediated by changes in breath components, postinspiratory inspiratory muscle activity, or both. Calibrated inductive plethysmography revealed that 12 of 12 patients with Cheyne-Stokes respiration experienced increases in end-expiratory volume during hyperpnea: maximum 412 +/- 112 (SE) ml (range 75-1,543 ml). Compared with quiet breathing, the breath with largest increase in end-expiratory volume had larger tidal volume (867 +/- 107 vs. 567 +/- 38 ml, p < 0.01) and shorter expiratory time (1.25 +/- 0.11 vs. 1.66 +/- 0.15 seconds, p < 0.05). During decrescendo, the breath with largest decrease in end-expiratory volume had smaller tidal volume (p < 0.01) and longer expiratory time (p < 0.01). Cross-correlation of time series revealed that end-expiratory volume was related to both breath components (p < 0.0001). Bipolar needle electrodes revealed that scalene muscle activity at end-expiration was 50.7 +/- 14.0% higher at highest increase in lung volume than during preceding apnea (p < 0.05). Time series for scalene activity and end-expiratory volume were cross-correlated (p < 0.008). Increase in tonic scalene activity at end-expiration, however, was equivalent during crescendo and decrescendo phases: 50.6 +/- 22.1 versus 42.0 +/- 12.9% (p = 0.48). In conclusion, patients with Cheyne-Stokes respiration exhibit fluctuations in end-expiratory lung volume, primarily because of alterations in tidal volume and expiratory time rather than postinspiratory inspiratory muscle activity.
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Affiliation(s)
- Thomas Brack
- Division of Pulmonary and Critical Care Medicine, Edward Hines Jr. VA Hospital, 111N, 5th Avenue and Roosevelt Road, Hines, IL 60141, USA
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Jubran A, Grant BJB, Laghi F, Parthasarathy S, Tobin MJ. Weaning prediction: esophageal pressure monitoring complements readiness testing. Am J Respir Crit Care Med 2005; 171:1252-9. [PMID: 15764727 DOI: 10.1164/rccm.200503-356oc] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Several variables are recommended for identifying if a patient is ready for a trial of weaning from mechanical ventilation, but there is no agreement as to whether monitoring any variable during the trial enhances patient management. To determine whether repeated measurements of esophageal pressure throughout a trial are more reliable than measurements of esophageal pressure or frequency-to-VT ratio during the first minute of the trial, we studied 60 patients. A trend index that quantified esophageal pressure swings over time was more reliable than the first-minute measurements: sensitivity, 0.91, and specificity, 0.89. Area under receiver operating characteristic curve for trend index (0.94) was greater than for first-minute measurement of esophageal pressure (0.44, p < 0.05) and tended to be greater than that for frequency-to-VT ratio (0.78, p = 0.13). The likelihood ratio was highest for the trend index (8.2, p < 0.05). The advantage of the trend index may be related to the progressive increase in esophageal pressure throughout a failed weaning trial, whereas breathing pattern changed little after 2 minutes of spontaneous breathing. In conclusion, continuous monitoring of esophageal pressure swings during a spontaneous breathing trial provides additional guidance in patient management over tests used for deciding when to initiate weaning.
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Affiliation(s)
- Amal Jubran
- Division of Pulmonary and Critical Care Medicine, Edward Hines Jr. VA Hospital, 111N 5th Avenue and Roosevelt Road, Hines, IL 60141, USA.
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Lanini B, Bianchi R, Romagnoli I, Coli C, Binazzi B, Gigliotti F, Pizzi A, Grippo A, Scano G. Chest wall kinematics in patients with hemiplegia. Am J Respir Crit Care Med 2003; 168:109-13. [PMID: 12714347 DOI: 10.1164/rccm.200207-745oc] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Owing to difficulties in measuring ventilation symmetry, good evidence of different right/left respiratory movements has not yet been provided. We investigated VT differences between paretic and healthy sides during quiet breathing, voluntary hyperventilation, and hypercapnic stimulation in patients with hemiparesis. We studied eight patients with hemiparesis and nine normal sex- and age-matched subjects. Right- and left-sided VT was reconstructed using optoelectronic plethysmography. In control subjects, no asymmetry was found in the study conditions. VTs of paretic and healthy sides were similar during quiet breathing, but paretic VT was lower during voluntary hyperventilation in six patients and higher during hypercapnic stimulation in eight patients (p = 0.02). The ventilatory response to hypercapnic stimulation was higher on the paretic than on the healthy side (p = 0.012). In conclusion, hemiparetic stroke produces asymmetric ventilation with an increase in carbon dioxide sensitivity and a decrease in voluntary ventilation on the paretic side.
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Affiliation(s)
- Barbara Lanini
- Fondazione Don C. Gnocchi (IRCCS), Via Imprunetana, 124 50020 Pozzolatico, Florence, Italy.
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Mitrouska I, Kondili E, Prinianakis G, Siafakas N, Georgopoulos D. Effects of theophylline on ventilatory poststimulus potentiation in patients with brain damage. Am J Respir Crit Care Med 2003; 167:1124-30. [PMID: 12531775 DOI: 10.1164/rccm.200206-552oc] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Patients with brain damage, in contrast to normal subjects, exhibit a significant ventilatory undershoot when brief hypocapnic hypoxia is terminated abruptly by hyperoxia. This has been attributed to an impairment of activation of short-term potentiation, a brain stem mechanism promoting breathing stability. We hypothesized that in these patients theophylline, a drug that stabilizes breathing, may affect short-term potentiation. Eight stable patients with brain damage and 10 normal adults were studied. Activation of short-term potentiation was examined by brief exposure to hypoxia followed by hyperoxia after pretreatment with placebo or theophylline. Both in patients and normal subjects at the end of hypoxia ventilation increased to a similar magnitude with and without theophylline. In normal subjects independent of pretreatment, when hypoxia was terminated abruptly by hyperoxia, ventilation declined slowly to baseline without an undershoot, indicating activation of short-term potentiation. In patients with placebo, ventilation upon switching to hyperoxia exhibited a significant undershoot. This undershoot was significantly attenuated by theophylline, although compared with normal subjects, a slight hypoventilation was observed. We conclude that in patients with brain damage, theophylline largely prevents the hyperoxic drop of ventilation, presumably by affecting the activation of short-term potentiation. This may underlie the beneficial effect of theophylline on breathing stability.
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Affiliation(s)
- Ioanna Mitrouska
- Department of Intensive Care Medicine, University Hospital of Heraklion, University of Crete, Greece
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Brack T, Jubran A, Tobin MJ. Dyspnea and decreased variability of breathing in patients with restrictive lung disease. Am J Respir Crit Care Med 2002; 165:1260-4. [PMID: 11991875 DOI: 10.1164/rccm.2201018] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Patients with restrictive lung disease are typically dyspneic and have an increase in overall respiratory center drive, as a result of increased lung elasticity. When we subjected healthy volunteers to external elastic loads, their variability of breathing was lessened. Accordingly, we hypothesized that patients with restrictive lung disease display decreased variability of breathing and, also, that decreased variability of breathing is related to dyspnea. Breathing pattern was measured nonobtrusively over 1 hour in 10 patients with restrictive lung disease and in 7 healthy subjects. On a separate occasion, dyspnea was measured while all subjects copied different tidal volumes and frequencies. Compared with healthy subjects, the random fraction of breath variability was reduced in patients with restrictive lung disease: 27 times for expiratory time, 12 times for tidal volume, and 6 times for inspiratory time (p < 0.01 in each instance). Conversely, the nonrandom, correlated fraction for tidal volume was increased almost 3-fold in the patients (p < 0.01). Small variations from average resting tidal volume caused marked increases in dyspnea in patients, and the relationship was parabolic (r2 = 0.97; p < 0.001). In conclusion, patients with restrictive lung disease adopt a tightly constrained breathing pattern, probably as a strategy for avoiding dyspnea.
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Affiliation(s)
- Thomas Brack
- Division of Pulmonary and Critical Care Medicine, Edward Hines Jr., Veterans Affairs Hospital, Hines, Illinois 60141, USA
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Van den Aardweg JG, Karemaker JM. Influence of chemoreflexes on respiratory variability in healthy subjects. Am J Respir Crit Care Med 2002; 165:1041-7. [PMID: 11956042 DOI: 10.1164/ajrccm.165.8.2104100] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The background of this study was the hypothesis that respiratory variability is influenced by chemoreflex regulation. In search for periodicities in the variability due to instability of the respiratory control system, spectral analysis was applied to breath-to-breath variables in 19 healthy subjects at rest. During room-air breathing, coherent oscillations in end-tidal CO2 (PET(CO2)) and mean inspiratory flow (VI/TI) were found in 15 subjects with frequencies mostly below 0.15 cycles per breath. Coherent oscillations in PET(CO2) and VI/TI were expressed by gain (0.13 to 0.34 L/second small middle dot kPa) and phase (-170 degrees to +8 degrees ). The oscillations in VI/TI were in phase with inspiratory volume (VI). A model that describes the effects of chemoreflex feedback to noise in the system could explain these gains and phases, whereas a model without chemoreflex could not. During 100% O2 breathing, only eight subjects had coherent oscillations in PET(CO2) and VI/TI. The coherent oscillations in PET(CO2) and VI/TI were interpreted as a manifestation of chemoreflex activity. We conclude that respiratory variability is not a random process but contains information on chemoreflex properties, such as the chemoreflex gain. The analysis of respiratory variability therefore provides a new tool to study the action of the chemoreflexes without application of external stimuli.
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Tobin MJ. Sleep-disordered breathing, control of breathing, respiratory muscles, pulmonary function testing, nitric oxide, and bronchoscopy in AJRCCM 2000. Am J Respir Crit Care Med 2001; 164:1362-75. [PMID: 11704580 DOI: 10.1164/ajrccm.164.8.2108124] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
- M J Tobin
- Division of Pulmonary and Critical Care Medicine, Loyola University of Chicago Stritch School of Medicine and Hines Veterans Affairs Hospital, Hines, Illinois 60141, USA.
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Preas HL, Jubran A, Vandivier RW, Reda D, Godin PJ, Banks SM, Tobin MJ, Suffredini AF. Effect of endotoxin on ventilation and breath variability: role of cyclooxygenase pathway. Am J Respir Crit Care Med 2001; 164:620-6. [PMID: 11520726 DOI: 10.1164/ajrccm.164.4.2003031] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
To evaluate the effects of endotoxemia on respiratory controller function, 12 subjects were randomized to receive endotoxin or saline; six also received ibuprofen, a cyclooxygenase inhibitor, and six received placebo. Administration of endotoxin produced fever, increased respiratory frequency, decreased inspiratory time, and widened alveolar-arterial oxygen tension gradient (all p < or = 0.001); these responses were blocked by ibuprofen. Independent of ibuprofen, endotoxin produced dyspnea, and it increased fractional inspiratory time, minute ventilation, and mean inspiratory flow (all p < or = 0.025). Endotoxin altered the autocorrelative behavior of respiratory frequency by increasing its autocorrelation coefficient at a lag of one breath, the number of breath lags with significant serial correlations, and its correlated fraction (all p < 0.05); these responses were blocked by ibuprofen. Changes in correlated behavior of respiratory frequency were related to changes in arterial carbon dioxide tension (r = 0.86; p < 0.03). Endotoxin decreased the oscillatory fraction of inspiratory time in both the placebo (p < 0.05) and ibuprofen groups (p = 0.06). In conclusion, endotoxin produced increases in respiratory motor output and dyspnea independent of fever and symptoms, and it curtailed the freedom to vary respiratory timing-a response that appears to be mediated by the cyclooxygenase pathway.
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Affiliation(s)
- H L Preas
- Critical Care Medicine Department, Warren G. Magnuson Clinical Center, National Institutes of Health, Bethesda, Maryland, USA
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