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Burgess A, Andrews G, Colby KME, Lucas SJE, Sprecher K, Donnelly J, Ainslie PN, Basnet AS, Burgess KR. Loop gain response to increased cerebral blood flow at high altitude. Sleep Breath 2024; 28:763-771. [PMID: 38085496 DOI: 10.1007/s11325-023-02956-4] [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: 06/03/2023] [Revised: 11/09/2023] [Accepted: 11/22/2023] [Indexed: 05/31/2024]
Abstract
PURPOSE To compare loop gain (LG) before and during pharmacological increases in cerebral blood flow (CBF) at high altitude (HA). Loop gain (LG) describes stability of a negative-feedback control system; defining the magnitude of response to a disturbance, such as hyperpnea to an apnea in periodic breathing (PB). "Controller-gain" sensitivity from afferent peripheral (PCR) and central-chemoreceptors (CCR) plays a key role in perpetuating PB. Changes in CBF may have a critical role via effects on central chemo-sensitivity during sleep. METHODS Polysomnography (PSG) was performed on volunteers after administration of I.V. Acetazolamide (ACZ-10mg/kg) + Dobutamine (DOB-2-5 μg/kg/min) to increase CBF (via Duplex-ultrasound). Central sleep apnea (CSA) was measured from NREM sleep. The duty ratio (DR) was calculated as ventilatory duration (s) divided by cycle duration (s) (hyperpnea/hyperpnea + apnea), LG = 2π/(2πDR-sin2πDR). RESULTS A total of 11 volunteers were studied. Compared to placebo-control, ACZ/DOB showed a significant increase in the DR (0.79 ± 0.21 vs 0.52 ± 0.03, P = 0.002) and reduction in LG (1.90 ± 0.23 vs 1.29 ± 0.35, P = 0.0004). ACZ/DOB increased cardiac output (CO) (8.19 ± 2.06 vs 6.58 ± 1.56L/min, P = 0.02) and CBF (718 ± 120 vs 526 ± 110ml/min, P < 0.001). There was no significant change in arterial blood gases, minute ventilation (VE), or hypoxic ventilatory response (HVR). However, there was a reduction of hypercapnic ventilatory response (HCVR) by 29% (5.9 ± 2.7 vs 4.2 ± 2.8 L/min, P = 0.1). CONCLUSION Pharmacological elevation in CBF significantly reduced LG and severity of CSA. We speculate the effect was on HCVR "controller gain," rather than "plant gain," because PaCO2 and VE were unchanged. An effect via reduced circulation time is unlikely, as the respiratory-cycle length did not change.
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Affiliation(s)
- Andrew Burgess
- Canberra Sleep Clinic, Canberra, Australian Capital Territory, Australia
| | | | | | | | | | | | | | | | - Keith R Burgess
- Peninsula Sleep Clinic, Sydney, NSW, Australia.
- Macquarie University, Sydney, NSW, Australia.
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2
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Bird JD, Sands SA, Alex RM, Shing CLH, Shafer BM, Jendzjowsky NG, Wilson RJA, Day TA, Foster GE. Sex-related Differences in Loop Gain during High-Altitude Sleep-disordered Breathing. Ann Am Thorac Soc 2023; 20:1192-1200. [PMID: 37000675 PMCID: PMC10405604 DOI: 10.1513/annalsats.202211-918oc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 03/31/2023] [Indexed: 04/01/2023] Open
Abstract
Rationale: Central sleep apnea (CSA) is pervasive during sleep at high altitude, disproportionately impacting men and associated with increased peripheral chemosensitivity. Objectives: We aimed to assess whether biological sex affects loop gain (LGn) and CSA severity during sleep over 9-10 days of acclimatization to 3,800 m. We hypothesized that CSA severity would worsen with acclimatization in men but not in women because of greater increases in LGn in men. Methods: Sleep studies were collected from 20 (12 male) healthy participants at low altitude (1,130 m, baseline) and after ascent to (nights 2/3, acute) and residence at high altitude (nights 9/10, prolonged). CSA severity was quantified as the respiratory event index (REI) as a surrogate of the apnea-hypopnea index. LGn, a measure of ventilatory control instability, was quantified using a ventilatory control model fit to nasal flow. Linear mixed models evaluated effects of time at altitude and sex on respiratory event index and LGn. Data are presented as contrast means with 95% confidence intervals. Results: REI was comparable between men and women at acute altitude (4.1 [-9.3, 17.5] events/h; P = 0.54) but significantly greater in men at prolonged altitude (23.7 [10.3, 37.1] events/h; P = 0.0008). Men had greater LGn than did women for acute (0.08 [0.001, 0.15]; P = 0.047) and prolonged (0.17 [0.10, 0.25]; P < 0.0001) altitude. The change in REI per change in LGn was significantly greater in men than in women (107 ± 46 events/h/LGn; P = 0.02). Conclusions: The LGn response to high altitude differed between sexes and contributed to worsening of CSA over time in men but not in women. This sex difference in acclimatization appears to protect females from high altitude-related CSA. These data provide fundamental sex-specific physiological insight into high-altitude acclimatization in healthy individuals and may help to inform sex differences in sleep-disordered breathing pathogenesis in patients with cardiorespiratory disease.
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Affiliation(s)
- Jordan D. Bird
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
- Faculty of Science and Technology, Department of Biology, Mount Royal University, Calgary, Alberta, Canada
| | - Scott A. Sands
- Division of Sleep Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
| | - Raichel M. Alex
- Division of Sleep Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
| | - Conan L. H. Shing
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Brooke M. Shafer
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Nicholas G. Jendzjowsky
- Respiratory Medicine and Exercise Physiology, The Lundquist Institute for Biomedical Innovation, Harbor University of California Los Angeles Medical Center, West Carson, California; and
| | - Richard J. A. Wilson
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children’s Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Trevor A. Day
- Faculty of Science and Technology, Department of Biology, Mount Royal University, Calgary, Alberta, Canada
| | - Glen E. Foster
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
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Casarrubios AM, Pérez-Atencio LF, Martín C, Ibarz JM, Mañas E, Paul DL, Barrio LC. Neural bases for the genesis and CO 2 therapy of periodic Cheyne-Stokes breathing in neonatal male connexin-36 knockout mice. Front Neurosci 2023; 17:1045269. [PMID: 36845442 PMCID: PMC9944137 DOI: 10.3389/fnins.2023.1045269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 01/16/2023] [Indexed: 02/11/2023] Open
Abstract
Periodic Cheyne-Stokes breathing (CSB) oscillating between apnea and crescendo-decrescendo hyperpnea is the most common central apnea. Currently, there is no proven therapy for CSB, probably because the fundamental pathophysiological question of how the respiratory center generates this form of breathing instability is still unresolved. Therefore, we aimed to determine the respiratory motor pattern of CSB resulting from the interaction of inspiratory and expiratory oscillators and identify the neural mechanism responsible for breathing regularization induced by the supplemental CO2 administration. Analysis of the inspiratory and expiratory motor pattern in a transgenic mouse model lacking connexin-36 electrical synapses, the neonatal (P14) Cx36 knockout male mouse, with a persistent CSB, revealed that the reconfigurations recurrent between apnea and hyperpnea and vice versa result from cyclical turn on/off of active expiration driven by the expiratory oscillator, which acts as a master pacemaker of respiration and entrains the inspiratory oscillator to restore ventilation. The results also showed that the suppression of CSB by supplemental 12% CO2 in inhaled air is due to the stabilization of coupling between expiratory and inspiratory oscillators, which causes the regularization of respiration. CSB rebooted after washout of CO2 excess when the inspiratory activity depressed again profoundly, indicating that the disability of the inspiratory oscillator to sustain ventilation is the triggering factor of CSB. Under these circumstances, the expiratory oscillator activated by the cyclic increase of CO2 behaves as an "anti-apnea" center generating the crescendo-decrescendo hyperpnea and periodic breathing. The neurogenic mechanism of CSB identified highlights the plasticity of the two-oscillator system in the neural control of respiration and provides a rationale base for CO2 therapy.
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Affiliation(s)
- Ana M. Casarrubios
- Units of Experimental Neurology and Sleep Apnea, Hospital “Ramón y Cajal” (IRYCIS), Madrid, Spain,Ph.D. Program in Neuroscience, Autonoma de Madrid University-Cajal Institute, Madrid, Spain
| | - Leonel F. Pérez-Atencio
- Units of Experimental Neurology and Sleep Apnea, Hospital “Ramón y Cajal” (IRYCIS), Madrid, Spain
| | - Cristina Martín
- Units of Experimental Neurology and Sleep Apnea, Hospital “Ramón y Cajal” (IRYCIS), Madrid, Spain
| | - José M. Ibarz
- Units of Experimental Neurology and Sleep Apnea, Hospital “Ramón y Cajal” (IRYCIS), Madrid, Spain
| | - Eva Mañas
- Sleep Apnea Unit, Respiratory Department, Hospital “Ramón y Cajal” (IRYCIS), Madrid, Spain
| | - David L. Paul
- Department of Neurobiology, Medical School, Harvard University, Boston, MA, United States
| | - Luis C. Barrio
- Units of Experimental Neurology and Sleep Apnea, Hospital “Ramón y Cajal” (IRYCIS), Madrid, Spain,Center for Biomedical Technology, Universidad Politécnica de Madrid, Madrid, Spain,*Correspondence: Luis C. Barrio, ; orcid.org/0000-0002-9016-3510
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4
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Pal A, Martinez F, Akey MA, Aysola RS, Henderson LA, Malhotra A, Macey PM. Breathing rate variability in obstructive sleep apnea during wakefulness. J Clin Sleep Med 2022; 18:825-833. [PMID: 34669569 PMCID: PMC8883075 DOI: 10.5664/jcsm.9728] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
STUDY OBJECTIVES Obstructive sleep apnea (OSA) is defined by pauses in breathing during sleep, but daytime breathing dysregulation may also be present. Sleep may unmask breathing instability in OSA that is usually masked by behavioral influences during wakefulness. A breath-hold (BH) challenge has been used to demonstrate breathing instability. One measure of breathing stability is breathing rate variability (BRV). We aimed to assess BRV during rest and in response to BH in OSA. METHODS We studied 62 participants (31 with untreated OSA: respiratory event index [mean ± SD] 20 ± 15 events/h, 12 females, age 51 ± 14 years, body mass index [BMI] 32 ± 8 kg/m2; 31 controls: 17 females, age 47 ± 13 years; BMI 26 ± 4 kg/m2). Breathing movements were collected using a chest belt for 5 minutes of rest and during a BH protocol (60 seconds baseline, 30 seconds BH, 90 seconds recovery, 3 repeats). From the breathing movements, we calculated median breathing rate (BR) and interquartile BRV at rest. We calculated change in BRV during BH recovery from baseline. Group comparisons of OSA vs control were conducted using analysis of covariance with age, sex, and BMI as covariates. RESULTS We found 10% higher BRV in OSA vs controls (P < .05) during rest. In response to BH, BRV increased 7% in OSA vs 1% in controls (P < .001). Resting BR was not significantly different in OSA and controls, and sex and age did not have any significant interaction effects. BMI was associated with BR at rest (P < .05) and change in BRV with BH (P < .001), but no significant BMI-by-group interaction effect was observed. CONCLUSIONS The findings suggest breathing instability as reflected by BRV is high in OSA during wakefulness, both at rest and in response to a stimulus. Breathing instability together with high blood pressure variability in OSA may reflect a compromised cardiorespiratory consequence in OSA during wakefulness. CITATION Pal A, Martinez F, Akey MA, et al. Breathing rate variability in obstructive sleep apnea during wakefulness. J Clin Sleep Med. 2022;18(3):825-833.
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Affiliation(s)
- Amrita Pal
- UCLA School of Nursing, University of California, Los Angeles, Los Angeles, California
| | - Fernando Martinez
- UCLA School of Nursing, University of California, Los Angeles, Los Angeles, California
| | - Margaret A. Akey
- UCLA School of Nursing, University of California, Los Angeles, Los Angeles, California
| | - Ravi S. Aysola
- Division of Pulmonary and Critical Care, David Geffen School of Medicine at UCLA, University of California, Los Angeles, Los Angeles, California
| | - Luke A. Henderson
- Brain and Mind Centre, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Atul Malhotra
- Department of Pulmonary Critical Care and Sleep Medicine, University of California, San Diego, San Diego, California
| | - Paul M. Macey
- UCLA School of Nursing, University of California, Los Angeles, Los Angeles, California,Address correspondence to: Paul M. Macey, PhD, UCLA School of Nursing, 700 Tiverton Avenue, Los Angeles, CA 90095-1702; Tel: (424) 234-3244;
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Toraldo DM, Arigliani M, De Benedetto M. Depressed ventilatory drive for respiratory muscle weakness and chemo-responsiveness as a pathophysiological mechanism of CSA after surgery for obstructive sleep apnoea. ACTA ACUST UNITED AC 2021; 40:311-312. [PMID: 33100342 PMCID: PMC7586187 DOI: 10.14639/0392-100x-n0443] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 12/03/2019] [Indexed: 11/24/2022]
Affiliation(s)
- Domenico Maurizio Toraldo
- Department of Rehabilitation "V. Fazzi" Hospital, Cardio-Respiratory Unit Care, ASL/Lecce, San Cesario di Lecce, Lecce, Italy
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Orr JE, Ayappa I, Eckert DJ, Feldman JL, Jackson CL, Javaheri S, Khayat RN, Martin JL, Mehra R, Naughton MT, Randerath WJ, Sands SA, Somers VK, Badr MS. Research Priorities for Patients with Heart Failure and Central Sleep Apnea. An Official American Thoracic Society Research Statement. Am J Respir Crit Care Med 2021; 203:e11-e24. [PMID: 33719931 PMCID: PMC7958519 DOI: 10.1164/rccm.202101-0190st] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Background: Central sleep apnea (CSA) is common among patients with heart failure and has been strongly linked to adverse outcomes. However, progress toward improving outcomes for such patients has been limited. The purpose of this official statement from the American Thoracic Society is to identify key areas to prioritize for future research regarding CSA in heart failure. Methods: An international multidisciplinary group with expertise in sleep medicine, pulmonary medicine, heart failure, clinical research, and health outcomes was convened. The group met at the American Thoracic Society 2019 International Conference to determine research priority areas. A statement summarizing the findings of the group was subsequently authored using input from all members. Results: The workgroup identified 11 specific research priorities in several key areas: 1) control of breathing and pathophysiology leading to CSA, 2) variability across individuals and over time, 3) techniques to examine CSA pathogenesis and outcomes, 4) impact of device and pharmacological treatment, and 5) implementing CSA treatment for all individuals Conclusions: Advancing care for patients with CSA in the context of heart failure will require progress in the arenas of translational (basic through clinical), epidemiological, and patient-centered outcome research. Given the increasing prevalence of heart failure and its associated substantial burden to individuals, society, and the healthcare system, targeted research to improve knowledge of CSA pathogenesis and treatment is a priority.
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7
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Zeineddine S, Badr MS. Treatment-Emergent Central Apnea: Physiologic Mechanisms Informing Clinical Practice. Chest 2021; 159:2449-2457. [PMID: 33497650 DOI: 10.1016/j.chest.2021.01.036] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Revised: 12/11/2020] [Accepted: 01/14/2021] [Indexed: 11/26/2022] Open
Abstract
The purpose of this review was to describe our management approach to patients with treatment-emergent central sleep apnea (TECSA). The emergence of central sleep apnea during positive airway pressure therapy occurs in approximately 8% of titration studies for OSA, and it has been associated with several demographic, clinical, and polysomnographic factors, as well as factors related to the titration study itself. TECSA shares similar pathophysiology with central sleep apnea. In fact, central and OSA pathophysiologic mechanisms are inextricably intertwined, with ventilatory instability and upper airway narrowing occurring in both entities. TECSA is a "dynamic" process, with spontaneous resolution with ongoing positive airway pressure therapy in most patients, persistence in some, or appearing de novo in a minority of patients. Management strategy for TECSA aims to eliminate abnormal respiratory events, stabilize sleep architecture, and improve the underlying contributing medical comorbidities. CPAP therapy remains a standard therapy for TECSA. Expectant management is appropriate given its transient nature in most cases, whereas select patients would benefit from an early switch to an alternative positive airway pressure modality. Other treatment options include supplemental oxygen and pharmacologic therapy.
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Affiliation(s)
- Salam Zeineddine
- John D. Dingell VA Medical Center, Detroit, MI; Department of Medicine, Wayne State University, Detroit, MI
| | - M Safwan Badr
- John D. Dingell VA Medical Center, Detroit, MI; Department of Medicine, Wayne State University, Detroit, MI.
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Harman K, Weichard AJ, Davey MJ, Horne RS, Nixon GM, Edwards BA. Assessing ventilatory control stability in children with and without an elevated central apnoea index. Respirology 2019; 25:214-220. [DOI: 10.1111/resp.13606] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 04/06/2019] [Accepted: 05/01/2019] [Indexed: 01/10/2023]
Affiliation(s)
- Katherine Harman
- Department of PaediatricsMonash University Melbourne VIC Australia
- The Ritchie Centre, Hudson Institute of Medical Research Melbourne VIC Australia
- Melbourne Children's Sleep CentreMonash Children's Hospital Melbourne VIC Australia
| | - Aidan J. Weichard
- Department of PaediatricsMonash University Melbourne VIC Australia
- The Ritchie Centre, Hudson Institute of Medical Research Melbourne VIC Australia
| | - Margot J. Davey
- Department of PaediatricsMonash University Melbourne VIC Australia
- The Ritchie Centre, Hudson Institute of Medical Research Melbourne VIC Australia
- Melbourne Children's Sleep CentreMonash Children's Hospital Melbourne VIC Australia
| | - Rosemary S.C. Horne
- Department of PaediatricsMonash University Melbourne VIC Australia
- The Ritchie Centre, Hudson Institute of Medical Research Melbourne VIC Australia
| | - Gillian M. Nixon
- Department of PaediatricsMonash University Melbourne VIC Australia
- The Ritchie Centre, Hudson Institute of Medical Research Melbourne VIC Australia
- Melbourne Children's Sleep CentreMonash Children's Hospital Melbourne VIC Australia
| | - Bradley A. Edwards
- Sleep and Circadian Medicine Laboratory, Department of Physiology and School of Psychological Sciences, Faculty of Medicine, Nursing and Health SciencesMonash University Melbourne VIC Australia
- School of Psychological Sciences and Turner Institute for Brain and Mental HealthMonash University Melbourne VIC Australia
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9
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Landry SA, Andara C, Terrill PI, Joosten SA, Leong P, Mann DL, Sands SA, Hamilton GS, Edwards BA. Ventilatory control sensitivity in patients with obstructive sleep apnea is sleep stage dependent. Sleep 2019; 41:4944421. [PMID: 29741725 DOI: 10.1093/sleep/zsy040] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Indexed: 11/14/2022] Open
Abstract
Study Objectives The severity of obstructive sleep apnea (OSA) is known to vary according to sleep stage; however, the pathophysiology responsible for this robust observation is incompletely understood. The objective of the present work was to examine how ventilatory control system sensitivity (i.e. loop gain) varies during sleep in patients with OSA. Methods Loop gain was estimated using signals collected from standard diagnostic polysomnographic recordings performed in 44 patients with OSA. Loop gain measurements associated with nonrapid eye movement (NREM) stage 2 (N2), stage 3 (N3), and REM sleep were calculated and compared. The sleep period was also split into three equal duration tertiles to investigate how loop gain changes over the course of sleep. Results Loop gain was significantly lower (i.e. ventilatory control more stable) in REM (Mean ± SEM: 0.51 ± 0.04) compared with N2 sleep (0.63 ± 0.04; p = 0.001). Differences in loop gain between REM and N3 (p = 0.095), and N2 and N3 (p = 0.247) sleep were not significant. Furthermore, N2 loop gain was significantly lower in the first third (0.57 ± 0.03) of the sleep period compared with later second (0.64 ± 0.03, p = 0.012) and third (0.64 ± 0.03, p = 0.015) tertiles. REM loop gain also tended to increase across the night; however, this trend was not statistically significant [F(2, 12) = 3.49, p = 0.09]. Conclusions These data suggest that loop gain varies between REM and NREM sleep and modestly increases over the course of sleep. Lower loop gain in REM is unlikely to contribute to the worsened OSA severity typically observed in REM sleep, but may explain the reduced propensity for central sleep apnea in this sleep stage.
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Affiliation(s)
- Shane A Landry
- Sleep and Circadian Medicine Laboratory, Department of Physiology, Monash University, Melbourne, VIC, Australia.,School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Monash University, Melbourne, VIC, Australia
| | - Christopher Andara
- Sleep and Circadian Medicine Laboratory, Department of Physiology, Monash University, Melbourne, VIC, Australia.,School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Monash University, Melbourne, VIC, Australia
| | - Philip I Terrill
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Australia
| | - Simon A Joosten
- Monash Lung and Sleep, Monash Medical Centre, Clayton, VIC, Australia.,School of Clinical Sciences, Monash University, Melbourne, VIC, Australia.,Monash Partners - Epworth, Victoria, Australia
| | - Paul Leong
- Monash Lung and Sleep, Monash Medical Centre, Clayton, VIC, Australia
| | - Dwayne L Mann
- School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Australia
| | - Scott A Sands
- Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA.,The Alfred and Monash University, Melbourne, VIC, Australia
| | - Garun S Hamilton
- Monash Lung and Sleep, Monash Medical Centre, Clayton, VIC, Australia.,School of Clinical Sciences, Monash University, Melbourne, VIC, Australia.,Monash Partners - Epworth, Victoria, Australia
| | - Bradley A Edwards
- Sleep and Circadian Medicine Laboratory, Department of Physiology, Monash University, Melbourne, VIC, Australia.,School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Monash University, Melbourne, VIC, Australia
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10
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de Melo CM, Taranto-Montemurro L, Butler JP, White DP, Loring SH, Azarbarzin A, Marques M, Berger PJ, Wellman A, Sands SA. Stable Breathing in Patients With Obstructive Sleep Apnea Is Associated With Increased Effort but Not Lowered Metabolic Rate. Sleep 2017; 40:4004820. [PMID: 28977669 PMCID: PMC5805127 DOI: 10.1093/sleep/zsx128] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Study objectives In principle, if metabolic rate were to fall during sleep in a patient with obstructive sleep apnea (OSA), ventilatory requirements could be met without increased respiratory effort thereby favoring stable breathing. Indeed, most patients achieve periods of stable flow-limited breathing without respiratory events for periods during the night for reasons that are unclear. Thus, we tested the hypothesis that in patients with OSA, periods of stable breathing occur when metabolic rate (VO2) declines. Methods Twelve OSA patients (apnea-hypopnea index >15 events/h) completed overnight polysomnography including measurements of VO2 (using ventilation and intranasal PO2) and respiratory effort (esophageal pressure). Results Contrary to our hypothesis, VO2 did not differ between stable and unstable breathing periods in non-REM stage 2 (208 ± 20 vs. 213 ± 18 mL/min), despite elevated respiratory effort during stable breathing (26 ± 2 versus 23 ± 2 cmH2O, p = .03). However, VO2 was lowered during deeper sleep (244 to 179 mL/min from non-REM stages 1 to 3, p = .04) in conjunction with more stable breathing. Further analysis revealed that airflow obstruction curtailed metabolism in both stable and unstable periods, since CPAP increased VO2 by 14% in both cases (p = .02, .03, respectively). Patients whose VO2 fell most during sleep avoided an increase in PCO2 and respiratory effort. Conclusions OSA patients typically convert from unstable to stable breathing without lowering metabolic rate. During sleep, OSA patients labor with increased respiratory effort but fail to satisfy metabolic demand even in the absence of overt respiratory events.
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Affiliation(s)
- Camila M de Melo
- Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA
- Department of Psychobiology, Universidade Federal de Sao Paulo UNIFESP, Sao Paulo, SP, Brazil
| | - Luigi Taranto-Montemurro
- Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA
| | - James P Butler
- Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA
| | - David P White
- Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA
| | - Stephen H Loring
- Department of Anesthesia and Critical Care, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA
| | - Ali Azarbarzin
- Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA
| | - Melania Marques
- Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA
- Sleep Laboratory, Pulmonary Division, Heart Institute (Incor), Hospital das Clínicas HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
| | - Philip J Berger
- The Ritchie Centre, Hudson Institute of Medical Research, Monash University, Melbourne, VIC, Australia
| | - Andrew Wellman
- Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA
| | - Scott A Sands
- Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA
- Department of Allergy Immunology and Respiratory Medicine and Central Clinical School, The Alfred and Monash University, Melbourne, VIC, Australia
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11
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Sands SA, Mebrate Y, Edwards BA, Nemati S, Manisty CH, Desai AS, Wellman A, Willson K, Francis DP, Butler JP, Malhotra A. Resonance as the Mechanism of Daytime Periodic Breathing in Patients with Heart Failure. Am J Respir Crit Care Med 2017; 195:237-246. [PMID: 27559818 DOI: 10.1164/rccm.201604-0761oc] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE In patients with chronic heart failure, daytime oscillatory breathing at rest is associated with a high risk of mortality. Experimental evidence, including exaggerated ventilatory responses to CO2 and prolonged circulation time, implicates the ventilatory control system and suggests feedback instability (loop gain > 1) is responsible. However, daytime oscillatory patterns often appear remarkably irregular versus classic instability (Cheyne-Stokes respiration), suggesting our mechanistic understanding is limited. OBJECTIVES We propose that daytime ventilatory oscillations generally result from a chemoreflex resonance, in which spontaneous biological variations in ventilatory drive repeatedly induce temporary and irregular ringing effects. Importantly, the ease with which spontaneous biological variations induce irregular oscillations (resonance "strength") rises profoundly as loop gain rises toward 1. We tested this hypothesis through a comparison of mathematical predictions against actual measurements in patients with heart failure and healthy control subjects. METHODS In 25 patients with chronic heart failure and 25 control subjects, we examined spontaneous oscillations in ventilation and separately quantified loop gain using dynamic inspired CO2 stimulation. MEASUREMENTS AND MAIN RESULTS Resonance was detected in 24 of 25 patients with heart failure and 18 of 25 control subjects. With increased loop gain-consequent to increased chemosensitivity and delay-the strength of spontaneous oscillations increased precipitously as predicted (r = 0.88), yielding larger (r = 0.78) and more regular (interpeak interval SD, r = -0.68) oscillations (P < 0.001 for all, both groups combined). CONCLUSIONS Our study elucidates the mechanism underlying daytime ventilatory oscillations in heart failure and provides a means to measure and interpret these oscillations to reveal the underlying chemoreflex hypersensitivity and reduced stability that foretells mortality in this population.
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Affiliation(s)
- Scott A Sands
- 1 Division of Sleep and Circadian Disorders and.,2 Department of Allergy, Immunology and Respiratory Medicine and Central Clinical School, The Alfred and Monash University, Melbourne, Victoria, Australia
| | - Yoseph Mebrate
- 3 International Center for Circulatory Health, National Heart and Lung Institute, Imperial College London, London, United Kingdom.,4 Department of Clinical Engineering, Royal Brompton Hospital, London, United Kingdom
| | - Bradley A Edwards
- 1 Division of Sleep and Circadian Disorders and.,5 Sleep and Circadian Medicine Laboratory, Department of Physiology, and.,6 School of Psychological Sciences and Monash Institute of Cognitive and Clinical Neurosciences, Monash University, Melbourne, Victoria, Australia
| | | | - Charlotte H Manisty
- 7 Institute of Cardiovascular Sciences, University College London, London, United Kingdom; and
| | - Akshay S Desai
- 8 Division of Cardiovascular Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | | | - Keith Willson
- 3 International Center for Circulatory Health, National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | - Darrel P Francis
- 3 International Center for Circulatory Health, National Heart and Lung Institute, Imperial College London, London, United Kingdom
| | | | - Atul Malhotra
- 1 Division of Sleep and Circadian Disorders and.,9 Division of Pulmonary and Critical Care Medicine, University of California San Diego, La Jolla, California
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Orr JE, Deacon N, Ravits J. Sleep Apnea in Familial Dysautonomia: A Reflection of Apnea Pathogenesis. J Clin Sleep Med 2016; 12:1583-1584. [PMID: 27855745 DOI: 10.5664/jcsm.6334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 11/03/2016] [Indexed: 11/13/2022]
Affiliation(s)
- Jeremy E Orr
- Division of Pulmonary, Critical Care, and Sleep Medicine, University of California, San Diego, CA
| | - Naomi Deacon
- Division of Pulmonary, Critical Care, and Sleep Medicine, University of California, San Diego, CA
| | - John Ravits
- Department of Neurology, University of California, San Diego, CA
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13
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Orr JE, Malhotra A, Sands SA. Pathogenesis of central and complex sleep apnoea. Respirology 2016; 22:43-52. [PMID: 27797160 DOI: 10.1111/resp.12927] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 09/22/2016] [Accepted: 10/03/2016] [Indexed: 12/01/2022]
Abstract
Central sleep apnoea (CSA) - the temporary absence or diminution of ventilatory effort during sleep - is seen in a variety of forms including periodic breathing in infancy and healthy adults at altitude and Cheyne-Stokes respiration in heart failure. In most circumstances, the cyclic absence of effort is paradoxically a consequence of hypersensitive ventilatory chemoreflex responses to oppose changes in airflow, that is elevated loop gain, leading to overshoot/undershoot ventilatory oscillations. Considerable evidence illustrates overlap between CSA and obstructive sleep apnoea (OSA), including elevated loop gain in patients with OSA and the presence of pharyngeal narrowing during central apnoeas. Indeed, treatment of OSA, whether via continuous positive airway pressure (CPAP), tracheostomy or oral appliances, can reveal CSA, an occurrence referred to as complex sleep apnoea. Factors influencing loop gain include increased chemosensitivity (increased controller gain), reduced damping of blood gas levels (increased plant gain) and increased lung to chemoreceptor circulatory delay. Sleep-wake transitions and pharyngeal dilator muscle responses effectively raise the controller gain and therefore also contribute to total loop gain and overall instability. In some circumstances, for example apnoea of infancy and central congenital hypoventilation syndrome, central apnoeas are the consequence of ventilatory depression and defective ventilatory responses, that is low loop gain. The efficacy of available treatments for CSA can be explained in terms of their effects on loop gain, for example CPAP improves lung volume (plant gain), stimulants reduce the alveolar-inspired PCO2 difference and supplemental oxygen lowers chemosensitivity. Understanding the magnitude of loop gain and the mechanisms contributing to instability may facilitate personalized interventions for CSA.
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Affiliation(s)
- Jeremy E Orr
- Division of Pulmonary and Critical Care Medicine, University of California San Diego, La Jolla, California, USA
| | - Atul Malhotra
- Division of Pulmonary and Critical Care Medicine, University of California San Diego, La Jolla, California, USA
| | - Scott A Sands
- Division of Sleep and Circadian Disorders, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.,Department of Allergy Immunology and Respiratory Medicine and Central Clinical School, The Alfred and Monash University, Melbourne, Victoria, Australia
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