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Slow breathing for reducing stress: The effect of extending exhale. Complement Ther Med 2023; 73:102937. [PMID: 36871835 PMCID: PMC10395759 DOI: 10.1016/j.ctim.2023.102937] [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: 01/05/2023] [Revised: 02/17/2023] [Accepted: 02/23/2023] [Indexed: 03/07/2023] Open
Abstract
INTRODUCTION Slow breathing techniques are commonly used to reduce stress. While it is believed by mind-body practitioners that extending the exhale time relative to inhale increases relaxation, this has not been demonstrated. METHODS We conducted a 12-week randomized, single-blinded trial among 100 participants to compare if yoga-based slow breathing with an exhale greater inhale versus an exhale equals inhale produces measurable differences in physiological and psychological stress among healthy adults. RESULTS Participants mean individual instruction attendance was 10.7 ± 1.5 sessions out of 12 offered sessions. The mean weekly home practice was 4.8 ± 1.2 practices per week. There was no statistical difference between treatment groups for frequency of class attendance, home practice, or achieved slow breathing respiratory rate. Participants demonstrated fidelity to assigned breath ratios with home practice as measured by remote biometric assessments through smart garments (HEXOSKIN). Regular slow breathing practice for 12 weeks significantly reduced psychological stress as measured by PROMIS Anxiety (-4.85 S.D. ± 5.53, confidence interval [-5.60, -3.00], but not physiological stress as measured by heart rate variability. Group comparisons showed small effect size differences (d = 0.2) with further reductions in psychological stress and physiological stress from baseline to 12 weeks for exhale greater than inhale versus exhale equals inhale, however these differences were not statistically significant. CONCLUSION While slow breathing significantly reduces psychological stress, breath ratios do not have a significant differential effect on stress reduction among healthy adults.
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Whittle RS, Keller N, Hall EA, Vellore HS, Stapleton LM, Findlay KH, Dunbar BJ, Diaz‐Artiles A. Gravitational Dose‐Response Curves for Acute Cardiovascular Hemodynamics and Autonomic Responses in a Tilt Paradigm. J Am Heart Assoc 2022; 11:e024175. [PMID: 35861832 PMCID: PMC9707822 DOI: 10.1161/jaha.121.024175] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background
The cardiovascular system is strongly dependent on the gravitational environment. Gravitational changes cause mechanical fluid shifts and, in turn, autonomic effectors influence systemic circulation and cardiac control. We implemented a tilt paradigm to (1) investigate the acute hemodynamic response across a range of directions of the gravitational vector, and (2) to generate specific dose‐response relationships of this gravitational dependency.
Methods and Results
Twelve male subjects were tilted from 45° head‐up tilt to 45° head‐down tilt in 15° increments, in both supine and prone postures. We measured the steady‐state hemodynamic response in a range of variables including heart rate, stroke volume, cardiac output, oxygen consumption, total peripheral resistance, blood pressure, and autonomic indices derived from heart rate variability analysis. There is a strong gravitational dependence in almost all variables considered, with the exception of oxygen consumption, whereas systolic blood pressure remained controlled to within ≈3% across the tilt range. Hemodynamic responses are primarily driven by differential loading on the baroreflex receptors, combined with differences in venous return to the heart. Thorax compression in the prone position leads to reduced venous return and increased sympathetic nervous activity, raising heart rate, and systemic vascular resistance while lowering cardiac output and stroke volume.
Conclusions
Gravitational dose‐response curves generated from these data provide a comprehensive baseline from which to assess the efficacy of potential spaceflight countermeasures. Results also assist clinical management of terrestrial surgery in prone posture or head‐down tilt positions.
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Affiliation(s)
- Richard S. Whittle
- Department of Aerospace Engineering Texas A&M University College Station TX
| | - Nathan Keller
- Department of Health and Kinesiology Texas A&M University College Station TX
| | - Eric A. Hall
- Department of Biomedical Engineering Texas A&M University College Station TX
| | | | | | | | - Bonnie J. Dunbar
- Department of Aerospace Engineering Texas A&M University College Station TX
| | - Ana Diaz‐Artiles
- Department of Aerospace Engineering Texas A&M University College Station TX
- Department of Health and Kinesiology Texas A&M University College Station TX
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Jordan J, Limper U, Tank J. Cardiovascular autonomic nervous system responses and orthostatic intolerance in astronauts and their relevance in daily medicine. Neurol Sci 2022; 43:3039-3051. [PMID: 35194757 PMCID: PMC9018660 DOI: 10.1007/s10072-022-05963-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 02/17/2022] [Indexed: 11/12/2022]
Abstract
Background The harsh environmental conditions during space travel, particularly weightlessness, impose a major burden on the human body including the cardiovascular system. Given its importance in adjusting the cardiovascular system to environmental challenges, the autonomic nervous system has been in the focus of scientists and clinicians involved in human space flight. This review provides an overview on human autonomic research under real and simulated space conditions with a focus on orthostatic intolerance. Methods The authors conducted a targeted literature search using Pubmed. Results Overall, 120 articles were identified and included in the review. Conclusions Postflight orthostatic intolerance is commonly observed in astronauts and could pose major risks when landing on another celestial body. The phenomenon likely results from changes in volume status and adaptation of the autonomic nervous system to weightlessness. Over the years, various non-pharmacological and pharmacological countermeasures have been investigated. In addition to enabling safe human space flight, this research may have implications for patients with disorders affecting cardiovascular autonomic control on Earth.
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Affiliation(s)
- Jens Jordan
- Institute of Aerospace Medicine, German Aerospace Center DLR, Linder Hoehe, 51147, Cologne, Germany. .,Aerospace Medicine, Medical Faculty, University of Cologne, Cologne, Germany.
| | - Ulrich Limper
- Institute of Aerospace Medicine, German Aerospace Center DLR, Linder Hoehe, 51147, Cologne, Germany.,Department of Anesthesiology and Intensive Care Medicine, Merheim Medical Center, Hospitals of Cologne, University of Witten/Herdecke, Cologne, Germany
| | - Jens Tank
- Institute of Aerospace Medicine, German Aerospace Center DLR, Linder Hoehe, 51147, Cologne, Germany
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Borovik AS, Orlova EA, Tomilovskaya ES, Tarasova OS, Vinogradova OL. Phase Coupling Between Baroreflex Oscillations of Blood Pressure and Heart Rate Changes in 21-Day Dry Immersion. Front Physiol 2020; 11:455. [PMID: 32508675 PMCID: PMC7253653 DOI: 10.3389/fphys.2020.00455] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 04/09/2020] [Indexed: 11/13/2022] Open
Abstract
Introduction Dry immersion (DI) is a ground-based experimental model which reproduces the effects of microgravity on the cardiovascular system and, therefore, can be used to study the mechanisms of post-flight orthostatic intolerance in cosmonauts. However, the effects of long-duration DI on cardiovascular system have not been studied yet. The aim of this work was to study the effects of 21-day DI on systemic hemodynamics and its baroreflex control at rest and during head-up tilt test (HUTT). Methods Ten healthy young men were exposed to DI for 21 days. The day before, on the 7th, 14th, and 19th day of DI, as well as on the 1st and 5th days of recovery they were subjected to HUTT: 15 min in supine position and then 15 min of orthostasis (60°). ECG, arterial pressure, stroke volume and respiration rate were continuously recorded during the test. Phase synchronization index (PSI) of beat-to-beat mean arterial pressure (MAP) and heart rate (HR) in the frequency band of baroreflex waves (∼0.1 Hz) was used as a quantitative measure of baroreflex activity. Results During DI, strong tachycardia and the reduction of stroke volume were observed both in supine position and during HUTT, these indicators did not recover on post-immersion day 5. In contrast, systolic arterial pressure and MAP decreased during HUTT on 14th day of DI, but then restored to pre-immersion values. Before DI and on day 5 of recovery, a transition from supine position to orthostasis was accompanied by an increase in PSI at the baroreflex frequency. However, PSI did not change in HUTT performed during DI and on post-immersion day 1. The amplitude of MAP oscillations at this frequency were increased by HUTT at all time points, while an increase of respective HR oscillations was absent during DI. Conclusion 21-day DI drastically changed the hemodynamic response to HUTT, while its effect on blood pressure was reduced between days 14 and 19, which speaks in favor of the adaptation to the conditions of DI. The lack of increase in phase synchronization of baroreflex MAP and HR oscillations during HUTT indicates disorders of baroreflex cardiac control during DI.
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Affiliation(s)
- Anatoly S Borovik
- State Research Center of the Russian Federation, Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia
| | - Evgeniya A Orlova
- State Research Center of the Russian Federation, Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia
| | - Elena S Tomilovskaya
- State Research Center of the Russian Federation, Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia
| | - Olga S Tarasova
- State Research Center of the Russian Federation, Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia.,Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Olga L Vinogradova
- State Research Center of the Russian Federation, Institute of Biomedical Problems, Russian Academy of Sciences, Moscow, Russia.,Faculty of Basic Medicine, M.V. Lomonosov Moscow State University, Moscow, Russia
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Limper U, Moestl S, Tank J, Prisk GK, Heusser K, Hoffmann F, Goßmann A, Migeotte PF, Gauger P, Beck LEJ, Schlegel HW, Levine BD, Jordan J. A 20-year evolution of cardiac performance in microgravity in a male astronaut. Clin Auton Res 2020; 31:139-141. [PMID: 31938976 DOI: 10.1007/s10286-019-00657-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 12/09/2019] [Indexed: 11/30/2022]
Affiliation(s)
- Ulrich Limper
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Linder Hoehe, 51147, Cologne, Germany. .,Department of Anesthesiology and Intensive Care Medicine, Merheim Medical Center (CMMC), Witten/Herdecke University, Witten, Germany.
| | - Stefan Moestl
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Linder Hoehe, 51147, Cologne, Germany
| | - Jens Tank
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Linder Hoehe, 51147, Cologne, Germany
| | - Gordon K Prisk
- Departments of Medicine and Radiology, University of California, San Diego, CA, USA
| | - Karsten Heusser
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Linder Hoehe, 51147, Cologne, Germany
| | - Fabian Hoffmann
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Linder Hoehe, 51147, Cologne, Germany.,Department of Internal Medicine III, University of Cologne, Cologne, Germany
| | - Axel Goßmann
- Department of Radiology, Cologne-Merheim Medical Center (CMMC), Witten/Herdecke University, Witten, Germany
| | | | - Peter Gauger
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Linder Hoehe, 51147, Cologne, Germany
| | - Luis E J Beck
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Linder Hoehe, 51147, Cologne, Germany
| | - Hans W Schlegel
- European Space Agency, European Astronaut Centre, Cologne, Germany
| | - Benjamine D Levine
- Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jens Jordan
- German Aerospace Center (DLR), Institute of Aerospace Medicine, Linder Hoehe, 51147, Cologne, Germany.,Chair of Aerospace Medicine, University of Cologne, Cologne, Germany
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Crucian BE, Choukèr A, Simpson RJ, Mehta S, Marshall G, Smith SM, Zwart SR, Heer M, Ponomarev S, Whitmire A, Frippiat JP, Douglas GL, Lorenzi H, Buchheim JI, Makedonas G, Ginsburg GS, Ott CM, Pierson DL, Krieger SS, Baecker N, Sams C. Immune System Dysregulation During Spaceflight: Potential Countermeasures for Deep Space Exploration Missions. Front Immunol 2018; 9:1437. [PMID: 30018614 PMCID: PMC6038331 DOI: 10.3389/fimmu.2018.01437] [Citation(s) in RCA: 191] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 06/11/2018] [Indexed: 12/11/2022] Open
Abstract
Recent studies have established that dysregulation of the human immune system and the reactivation of latent herpesviruses persists for the duration of a 6-month orbital spaceflight. It appears certain aspects of adaptive immunity are dysregulated during flight, yet some aspects of innate immunity are heightened. Interaction between adaptive and innate immunity also seems to be altered. Some crews experience persistent hypersensitivity reactions during flight. This phenomenon may, in synergy with extended duration and galactic radiation exposure, increase specific crew clinical risks during deep space exploration missions. The clinical challenge is based upon both the frequency of these phenomena in multiple crewmembers during low earth orbit missions and the inability to predict which specific individual crewmembers will experience these changes. Thus, a general countermeasure approach that offers the broadest possible coverage is needed. The vehicles, architecture, and mission profiles to enable such voyages are now under development. These include deployment and use of a cis-Lunar station (mid 2020s) with possible Moon surface operations, to be followed by multiple Mars flyby missions, and eventual human Mars surface exploration. Current ISS studies will continue to characterize physiological dysregulation associated with prolonged orbital spaceflight. However, sufficient information exists to begin consideration of both the need for, and nature of, specific immune countermeasures to ensure astronaut health. This article will review relevant in-place operational countermeasures onboard ISS and discuss a myriad of potential immune countermeasures for exploration missions. Discussion points include nutritional supplementation and functional foods, exercise and immunity, pharmacological options, the relationship between bone and immune countermeasures, and vaccination to mitigate herpes (and possibly other) virus risks. As the immune system has sentinel connectivity within every other physiological system, translational effects must be considered for all potential immune countermeasures. Finally, we shall discuss immune countermeasures in the context of their individualized implementation or precision medicine, based on crewmember specific immunological biases.
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Affiliation(s)
- Brian E. Crucian
- Biomedical Research and Environmental Sciences Division, NASA Johnson Space Center, Houston, TX, United States
| | - Alexander Choukèr
- Laboratory of Translational Research “Stress and Immunity”, Department of Anesthesiology, Hospital of the Ludwig-Maximilians-University, Munich, Germany
| | - Richard J. Simpson
- Department of Nutritional Sciences, The University of Arizona, Tucson, AZ, United States
- Department of Pediatrics, The University of Arizona, Tucson, AZ, United States
- Department of Immunobiology, The University of Arizona, Tucson, AZ, United States
| | | | - Gailen Marshall
- University of Mississippi Medical Center, Jackson, MS, United States
| | - Scott M. Smith
- Biomedical Research and Environmental Sciences Division, NASA Johnson Space Center, Houston, TX, United States
| | - Sara R. Zwart
- University of Texas Medical Branch, Galveston, TX, United States
| | - Martina Heer
- Institute of Nutritional and Food Sciences, University of Bonn, Bonn, Germany
| | | | | | - Jean P. Frippiat
- Stress Immunity Pathogens Laboratory, EA7300, Lorraine University, Nancy, France
| | - Grace L. Douglas
- Human Systems Engineering and Development Division, NASA Johnson Space Center, Houston, TX, United States
| | | | - Judith-Irina Buchheim
- Laboratory of Translational Research “Stress and Immunity”, Department of Anesthesiology, Hospital of the Ludwig-Maximilians-University, Munich, Germany
| | | | - Geoffrey S. Ginsburg
- Duke Center for Applied Genomics and Precision Medicine, Durham, NC, United States
| | - C. Mark Ott
- Biomedical Research and Environmental Sciences Division, NASA Johnson Space Center, Houston, TX, United States
| | - Duane L. Pierson
- Biomedical Research and Environmental Sciences Division, NASA Johnson Space Center, Houston, TX, United States
| | | | - Natalie Baecker
- Institute of Nutritional and Food Sciences, University of Bonn, Bonn, Germany
| | - Clarence Sams
- Biomedical Research and Environmental Sciences Division, NASA Johnson Space Center, Houston, TX, United States
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Klassen SA, De Abreu S, Greaves DK, Kimmerly DS, Arbeille P, Denise P, Hughson RL, Normand H, Shoemaker JK. Long-duration bed rest modifies sympathetic neural recruitment strategies in male and female participants. J Appl Physiol (1985) 2018; 124:769-779. [PMID: 29212669 PMCID: PMC5899270 DOI: 10.1152/japplphysiol.00640.2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 11/09/2017] [Accepted: 12/04/2017] [Indexed: 01/07/2023] Open
Abstract
To understand the impact of physical deconditioning with head-down tilt bed rest (HDBR) on the malleability of sympathetic discharge patterns, we studied 1) baseline integrated muscle sympathetic nerve activity (MSNA; microneurography) from 13 female participants in the WISE-2005 60-day HDBR study (retrospective analysis), 2) integrated MSNA and multiunit action potential (AP) analysis in 13 male participants performed on data collected at baseline and during physiological stress imposed by end-inspiratory apnea in a new 60-day HDBR study, and 3) a repeatability study (control; n = 6, retrospective analysis, 4 wk between tests). Neither baseline integrated burst frequency nor incidence were altered with HDBR (both P > 0.35). However, baseline integrated burst latency increased in both HDBR studies (male: 1.35 ± 0.02 to 1.39 ± 0.02 s, P < 0.01; female: 1.23 ± 0.02 to 1.29 ± 0.02 s, P < 0.01), whereas controls exhibited no change across two visits (1.25 ± 0.02 to 1.25 ± 0.02 s, group-by-time interaction, P = 0.02). With the exception of increased AP latency ( P = 0.03), male baseline AP data did not change with HDBR (all P > 0.19). The change in AP frequency on going from baseline to apnea (∆94 ± 25 to ∆317 ± 55 AP/min, P < 0.01) and the number of active sympathetic clusters per burst (∆0 ± 0.2 to ∆1 ± 0.2 clusters/burst, P = 0.02) were greater post- compared with pre-HDBR. The change in total clusters with apnea was ∆0 ± 0.5 clusters pre- and ∆2 ± 0.7 clusters post-HDBR ( P = 0.07). These data indicate that 60-day HDBR modified discharge characteristics in baseline burst latency and sympathetic neural recruitment during apneic stress. NEW & NOTEWORTHY Long-duration bed rest did not modify baseline sympathetic burst frequency in male and female participants, but examination of additional features of the multiunit signal provided novel evidence to suggest augmented synaptic delays or processing times at baseline for all sympathetic action potentials. Furthermore, long-duration bed rest increased reflex-sympathetic arousal to apneic stress in male participants primarily by mechanisms involving an augmented firing rate of action potential clusters active at baseline.
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Affiliation(s)
- Stephen A Klassen
- Neurovascular Research Laboratory, School of Kinesiology, University of Western Ontario , London, Ontario , Canada
| | | | - Danielle K Greaves
- Schlegel-University of Waterloo Research Institute for Aging , Waterloo, Ontario , Canada
| | - Derek S Kimmerly
- Division of Kinesiology, School of Health and Human Performance, Dalhousie University , Halifax, Nova Scotia , Canada
| | - Philippe Arbeille
- UMPS-CERCOM, School of Medicine, University of Tours , Tours , France
| | - Pierre Denise
- Normandie Université, Unicaen, INSERM, Caen , France
| | - Richard L Hughson
- Schlegel-University of Waterloo Research Institute for Aging , Waterloo, Ontario , Canada
| | - Hervé Normand
- Normandie Université, Unicaen, INSERM, Caen , France
| | - J Kevin Shoemaker
- Neurovascular Research Laboratory, School of Kinesiology, University of Western Ontario , London, Ontario , Canada
- Department of Physiology and Pharmacology, University of Western Ontario , London, Ontario , Canada
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Eckberg DL. Reply from Dwain L. Eckberg and the Neurolab Autonomic Team. J Physiol 2017; 595:2199-2200. [DOI: 10.1113/jp273846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Dwain L. Eckberg
- Departments of Medicine and Physiology Hunter Holmes McGuire Department of Veterans Affairs Medical Center and Virginia Commonwealth University School of Medicine Richmond VA USA
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Eckberg DL, Cooke WH, Diedrich A, Biaggioni I, Buckey JC, Pawelczyk JA, Ertl AC, Cox JF, Kuusela TA, Tahvanainen KUO, Mano T, Iwase S, Baisch FJ, Levine BD, Adams-Huet B, Robertson D, Blomqvist CG. Respiratory modulation of human autonomic function on Earth. J Physiol 2016; 594:5611-27. [PMID: 27028958 PMCID: PMC5043049 DOI: 10.1113/jp271654] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 03/14/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS We studied healthy supine astronauts on Earth with electrocardiogram, non-invasive arterial pressure, respiratory carbon dioxide concentrations, breathing depth and sympathetic nerve recordings. The null hypotheses were that heart beat interval fluctuations at usual breathing frequencies are baroreflex mediated, that they persist during apnoea, and that autonomic responses to apnoea result from changes of chemoreceptor, baroreceptor or lung stretch receptor inputs. R-R interval fluctuations at usual breathing frequencies are unlikely to be baroreflex mediated, and disappear during apnoea. The subjects' responses to apnoea could not be attributed to changes of central chemoreceptor activity (hypocapnia prevailed); altered arterial baroreceptor input (vagal baroreflex gain declined and muscle sympathetic nerve burst areas, frequencies and probabilities increased, even as arterial pressure climbed to new levels); or altered pulmonary stretch receptor activity (major breathing frequency and tidal volume changes did not alter vagal tone or sympathetic activity). Apnoea responses of healthy subjects may result from changes of central respiratory motoneurone activity. ABSTRACT We studied eight healthy, supine astronauts on Earth, who followed a simple protocol: they breathed at fixed or random frequencies, hyperventilated and then stopped breathing, as a means to modulate and expose to view important, but obscure central neurophysiological mechanisms. Our recordings included the electrocardiogram, finger photoplethysmographic arterial pressure, tidal volume, respiratory carbon dioxide concentrations and peroneal nerve muscle sympathetic activity. Arterial pressure, vagal tone and muscle sympathetic outflow were comparable during spontaneous and controlled-frequency breathing. Compared with spontaneous, 0.1 and 0.05 Hz breathing, however, breathing at usual frequencies (∼0.25 Hz) lowered arterial baroreflex gain, and provoked smaller arterial pressure and R-R interval fluctuations, which were separated by intervals that were likely to be too short and variable to be attributed to baroreflex physiology. R-R interval fluctuations at usual breathing frequencies disappear during apnoea, and thus cannot provide evidence for the existence of a central respiratory oscillation. Apnoea sets in motion a continuous and ever changing reorganization of the relations among stimulatory and inhibitory inputs and autonomic outputs, which, in our study, could not be attributed to altered chemoreceptor, baroreceptor, or pulmonary stretch receptor activity. We suggest that responses of healthy subjects to apnoea are driven importantly, and possibly prepotently, by changes of central respiratory motoneurone activity. The companion article extends these observations and asks the question, Might terrestrial responses to our 20 min breathing protocol find expression as long-term neuroplasticity in serial measurements made over 20 days during and following space travel?
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Affiliation(s)
- Dwain L Eckberg
- Departments of Medicine and Physiology, Hunter Holmes McGuire Department of Veterans Affairs, Medical Center and Virginia Commonwealth University School of Medicine, Richmond, VA, USA.
| | - William H Cooke
- Department of Kinesiology, Health, and Nutrition, University of Texas at San Antonio, San Antonio, TX, USA
| | - André Diedrich
- Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, TN, USA
| | - Italo Biaggioni
- Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, TN, USA
| | - Jay C Buckey
- Dartmouth Hitchcock Medical Center, Lebanon, NH, USA
| | - James A Pawelczyk
- Department of Physiology, Pennsylvania State University, University Park and Hershey, PA, USA
| | - Andrew C Ertl
- Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, TN, USA
| | - James F Cox
- Departments of Medicine and Physiology, Hunter Holmes McGuire Department of Veterans Affairs, Medical Center and Virginia Commonwealth University School of Medicine, Richmond, VA, USA
| | - Tom A Kuusela
- Department of Physics, University of Turku, Turku, Finland
| | - Kari U O Tahvanainen
- Department of Clinical Physiology and Nuclear Medicine, South Karelia Central Hospital, Lappeenranta, Finland
| | - Tadaaki Mano
- Gifu University of Medical Science, 795-1 Nagamine Ichihiraga, Seki, Gifu, 501-3892, Japan
| | - Satoshi Iwase
- Department of Physiology, Aichi Medical University, Aichi, Japan
| | | | - Benjamin D Levine
- Department of Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, TX, USA
| | | | - David Robertson
- Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, TN, USA
| | - C Gunnar Blomqvist
- Department of Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA
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