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Rexhaj E, Rimoldi SF, Pratali L, Brenner R, Andries D, Soria R, Salinas C, Villena M, Romero C, Allemann Y, Lovis A, Heinzer R, Sartori C, Scherrer U. Sleep-Disordered Breathing and Vascular Function in Patients With Chronic Mountain Sickness and Healthy High-Altitude Dwellers. Chest 2016; 149:991-8. [PMID: 26540612 DOI: 10.1378/chest.15-1450] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 10/02/2015] [Accepted: 10/15/2015] [Indexed: 11/01/2022] Open
Abstract
BACKGROUND Chronic mountain sickness (CMS) is often associated with vascular dysfunction, but the underlying mechanism is unknown. Sleep-disordered breathing (SDB) frequently occurs at high altitude. At low altitude, SDB causes vascular dysfunction. Moreover, in SDB, transient elevations of right-sided cardiac pressure may cause right-to-left shunting in the presence of a patent foramen ovale (PFO) and, in turn, further aggravate hypoxemia and pulmonary hypertension. We speculated that SDB and nocturnal hypoxemia are more pronounced in patients with CMS compared with healthy high-altitude dwellers, and are related to vascular dysfunction. METHODS We performed overnight sleep recordings, and measured systemic and pulmonary artery pressure in 23 patients with CMS (mean ± SD age, 52.8 ± 9.8 y) and 12 healthy control subjects (47.8 ± 7.8 y) at 3,600 m. In a subgroup of 15 subjects with SDB, we assessed the presence of a PFO with transesophageal echocardiography. RESULTS The major new findings were that in patients with CMS, (1) SDB and nocturnal hypoxemia was more severe (P < .01) than in control subjects (apnea-hypopnea index [AHI], 38.9 ± 25.5 vs 14.3 ± 7.8 number of events per hour [nb/h]; arterial oxygen saturation, 80.2% ± 3.6% vs 86.8% ± 1.7%, CMS vs control group), and (2) AHI was directly correlated with systemic blood pressure (r = 0.5216; P = .001) and pulmonary artery pressure (r = 0.4497; P = .024). PFO was associated with more severe SDB (AHI, 48.8 ± 24.7 vs 14.8 ± 7.3 nb/h; P = .013, PFO vs no PFO) and hypoxemia. CONCLUSIONS SDB and nocturnal hypoxemia are more severe in patients with CMS than in control subjects and are associated with systemic and pulmonary vascular dysfunction. The presence of a PFO appeared to further aggravate SDB. Closure of the PFO may improve SDB, hypoxemia, and vascular dysfunction in patients with CMS. TRIAL REGISTRY ClinicalTrials.gov; No.: NCT01182792; URL: www.clinicaltrials.gov.
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Affiliation(s)
- Emrush Rexhaj
- Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland
| | - Stefano F Rimoldi
- Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland
| | | | - Roman Brenner
- Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland
| | - Daniela Andries
- Center for Investigation and Research in Sleep, Lausanne-CHUV, Switzerland
| | - Rodrigo Soria
- Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland
| | - Carlos Salinas
- Instituto Boliviano de Biologia de Altura, La Paz, Bolivia
| | | | | | - Yves Allemann
- Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland
| | - Alban Lovis
- Center for Investigation and Research in Sleep, Lausanne-CHUV, Switzerland
| | - Raphaël Heinzer
- Center for Investigation and Research in Sleep, Lausanne-CHUV, Switzerland
| | - Claudio Sartori
- Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland; Department of Internal Medicine, Lausanne-CHUV, Switzerland
| | - Urs Scherrer
- Department of Cardiology and Clinical Research, Inselspital, University of Bern, Bern, Switzerland; Facultad de Ciencias, Departamento de Biología, Universidad de Tarapacá, Arica, Chile.
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Magnusson J, Cummings KJ. Plasticity in breathing and arterial blood pressure following acute intermittent hypercapnic hypoxia in infant rat pups with a partial loss of 5-HT neurons. Am J Physiol Regul Integr Comp Physiol 2015; 309:R1273-84. [PMID: 26354844 DOI: 10.1152/ajpregu.00241.2015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 09/05/2015] [Indexed: 12/29/2022]
Abstract
The role of serotonin (5-HT) neurons in cardiovascular responses to acute intermittent hypoxia (AIH) has not been studied in the neonatal period. We hypothesized that a partial loss of 5-HT neurons would reduce arterial blood pressure (BP) at rest, increase the fall in BP during hypoxia, and reduce the long-term facilitation of breathing (vLTF) and BP following AIH. We exposed 2-wk-old, 5,7-dihydroxytryptamine-treated and controls to AIH (10% O2; n = 13 control, 14 treated), acute intermittent hypercapnia (5% CO2; n = 12 and 11), or acute intermittent hypercapnic hypoxia (AIHH; 10% O2, 5% CO2; n = 15 and 17). We gave five 5-min challenges of AIH and acute intermittent hypercapnia, and twenty ∼20-s challenges of AIHH to mimic sleep apnea. Systolic BP (sBP), diastolic BP, mean arterial pressure, heart rate (HR), ventilation (V̇e), and metabolic rate (V̇o2) were continuously monitored. 5,7-Dihydroxytryptamine induced an ∼35% loss of 5-HT neurons from the medullary raphe. Compared with controls, pups deficient in 5-HT neurons had reduced resting sBP (∼6 mmHg), mean arterial pressure (∼5 mmHg), and HR (56 beats/min), and experienced a reduced drop in BP during hypoxia. AIHH induced vLTF in both groups, reflected in increased V̇e and V̇e/V̇o2, and decreased arterial Pco2. The sBP of pups deficient in 5-HT neurons, but not controls, was increased 1 h following AIHH. Our data suggest that a relatively small loss of 5-HT neurons compromises resting BP and HR, but has no influence on ventilatory plasticity induced by AIHH. AIHH may be useful for reversing cardiorespiratory defects related to partial 5-HT system dysfunction.
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Affiliation(s)
- Jennifer Magnusson
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, Missouri
| | - Kevin J Cummings
- Department of Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, Missouri
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Abuyassin B, Sharma K, Ayas NT, Laher I. Obstructive Sleep Apnea and Kidney Disease: A Potential Bidirectional Relationship? J Clin Sleep Med 2015; 11:915-24. [PMID: 25845900 PMCID: PMC4513269 DOI: 10.5664/jcsm.4946] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 03/03/2015] [Indexed: 01/02/2023]
Abstract
Chronic kidney disease (CKD) is associated with high mortality rates and heavy economic and social burdens. Nearly 10% of the United States population suffer from CKD, with fatal outcomes increased by 16-40 times even before reaching end-stage renal disease. The prevalence of obstructive sleep apnea (OSA) is between 3% and 7% in the general population, and has increased dramatically during the last 2 decades along with increased rates of obesity. However, the prevalence of OSA is much greater in patients with CKD. In addition, aggressive dialysis improves OSA. The current literature suggests a bidirectional association between CKD and OSA through a number of potential pathological mechanisms, which increase the possibility of both diseases being possible risk factors for each other. CKD may lead to OSA through a variety of mechanisms, including alterations in chemoreflex responsiveness, pharyngeal narrowing due to fluid overload, and accumulation of uremic toxins. It is also being increasingly recognized that OSA can also accelerate loss of kidney function. Moreover, animals exposed to intermittent hypoxia suffer histopathological renal damage. Potential mechanisms of OSA-associated renal dysfunction include renal hypoxia, hypertension, endothelial dysfunction, activation of the sympathetic nervous system, and increased oxidative stress.
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Affiliation(s)
- Bisher Abuyassin
- Departments of Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Kumar Sharma
- Institute of Metabolomic Medicine and Center for Renal Translational Medicine, University of California, San Diego, La Jolla, CA
| | - Najib T. Ayas
- Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Ismail Laher
- Departments of Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
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54
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The role of high loop gain induced by intermittent hypoxia in the pathophysiology of obstructive sleep apnoea. Sleep Med Rev 2015; 22:3-14. [DOI: 10.1016/j.smrv.2014.10.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Revised: 10/03/2014] [Accepted: 10/07/2014] [Indexed: 02/06/2023]
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El-Chami M, Shaheen D, Ivers B, Syed Z, Badr MS, Lin HS, Mateika JH. Time of day affects the frequency and duration of breathing events and the critical closing pressure during NREM sleep in participants with sleep apnea. J Appl Physiol (1985) 2015; 119:617-26. [PMID: 26183479 DOI: 10.1152/japplphysiol.00346.2015] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 07/15/2015] [Indexed: 12/28/2022] Open
Abstract
We investigated if the number and duration of breathing events coupled to upper airway collapsibility were affected by the time of day. Male participants with obstructive sleep apnea completed a constant routine protocol that consisted of sleep sessions in the evening (10 PM to 1 AM), morning (6 AM to 9 AM), and afternoon (2 PM to 5 PM). On one occasion the number and duration of breathing events was ascertained for each sleep session. On a second occasion the critical closing pressure that demarcated upper airway collapsibility was determined. The duration of breathing events was consistently greater in the morning compared with the evening and afternoon during N1 and N2, while an increase in event frequency was evident during N1. The critical closing pressure was increased in the morning (2.68 ± 0.98 cmH2O) compared with the evening (1.29 ± 0.91 cmH2O; P ≤ 0.02) and afternoon (1.25 ± 0.79; P ≤ 0.01). The increase in the critical closing pressure was correlated to the decrease in the baseline partial pressure of carbon dioxide in the morning compared with the afternoon and evening (r = -0.73, P ≤ 0.005). Our findings indicate that time of day affects the duration and frequency of events, coupled with alterations in upper airway collapsibility. We propose that increases in airway collapsibility in the morning may be linked to an endogenous modulation of baseline carbon dioxide levels and chemoreflex sensitivity (12), which are independent of the consequences of sleep apnea.
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Affiliation(s)
- Mohamad El-Chami
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - David Shaheen
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Blake Ivers
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Ziauddin Syed
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - M Safwan Badr
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan; Department of Biomedical Engineering, Wayne State University Detroit, Michigan
| | - Ho-Sheng Lin
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan; Department of Otolaryngology-Head and Neck Surgery, Wayne State University School of Medicine and Karmanos Cancer Institute, Detroit, Michigan; and
| | - Jason H Mateika
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan; Department of Internal Medicine, Wayne State University School of Medicine, Detroit, Michigan;
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Hermand E, Lhuissier FJ, Larribaut J, Pichon A, Richalet JP. Ventilatory oscillations at exercise: effects of hyperoxia, hypercapnia, and acetazolamide. Physiol Rep 2015; 3:3/6/e12446. [PMID: 26109194 PMCID: PMC4510637 DOI: 10.14814/phy2.12446] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Periodic breathing has been found in patients with heart failure and sleep apneas, and in healthy subjects in hypoxia, during sleep and wakefulness, at rest and, recently, at exercise. To unravel the cardiorespiratory parameters liable to modulate the amplitude and period of ventilatory oscillations, 26 healthy subjects were tested under physiological (exercise) and environmental (hypoxia, hyperoxia, hyperoxic hypercapnia) stresses, and under acetazolamide (ACZ) treatment. A fast Fourier transform spectral analysis of breath-by-breath ventilation evidenced an increase in peak power under hypercapnia (vs. normoxia and hyperoxia, P < 0.001) and a decrease under ACZ (vs. placebo, P < 0.001), whereas it was not modified in hyperoxia. period was shortened by exercise in all conditions (vs. rest, P < 0.01) and by hypercapnia (vs. normoxia, P < 0.05) but remained unchanged under ACZ (vs. placebo). peak power was positively related to cardiac output () and in hyperoxia (P < 0.01), in hypercapnia (P < 0.001) and under ACZ (P < 0.001). period was negatively related to and in hyperoxia (P < 0.01 and P < 0.001, respectively), in hypercapnia (P < 0.05 and P < 0.01, respectively) and under ACZ (P < 0.05 and P < 0.01, respectively). Total respiratory cycle time was the main factor responsible for changes in period. In conclusion, exercise, hypoxia, and hypercapnia increase ventilatory oscillations by increasing and , whereas ACZ decreases ventilatory instability in part by a contrasting action on O2 and CO2 sensing. An intrinsic oscillator might modulate ventilation through a complex system where peripheral chemoreflex would play a key role.
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Affiliation(s)
- Eric Hermand
- Université Paris 13 Sorbonne Paris Cité Laboratoire "Hypoxie et poumon", Bobigny, France
| | - François J Lhuissier
- Université Paris 13 Sorbonne Paris Cité Laboratoire "Hypoxie et poumon", Bobigny, France Assistance Publique-Hôpitaux de Paris, Hôpital Avicenne Service de Physiologie explorations fonctionnelles et médecine du sport, Bobigny, France
| | - Julie Larribaut
- Université Paris 13 Sorbonne Paris Cité Laboratoire "Hypoxie et poumon", Bobigny, France
| | - Aurélien Pichon
- Université Paris 13 Sorbonne Paris Cité Laboratoire "Hypoxie et poumon", Bobigny, France
| | - Jean-Paul Richalet
- Université Paris 13 Sorbonne Paris Cité Laboratoire "Hypoxie et poumon", Bobigny, France Assistance Publique-Hôpitaux de Paris, Hôpital Avicenne Service de Physiologie explorations fonctionnelles et médecine du sport, Bobigny, France
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McEntire DM, Kirkpatrick DR, Kerfeld MJ, Hambsch ZJ, Reisbig MD, Agrawal DK, Youngblood CF. Effect of sedative-hypnotics, anesthetics and analgesics on sleep architecture in obstructive sleep apnea. Expert Rev Clin Pharmacol 2015; 7:787-806. [PMID: 25318836 DOI: 10.1586/17512433.2014.966815] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The perioperative care of obstructive sleep apnea (OSA) patients is currently receiving much attention due to an increased risk for complications. It is established that postoperative changes in sleep architecture occur and this may have pathophysiological implications for OSA patients. Upper airway muscle activity decreases during rapid eye movement sleep (REMS). Severe OSA patients exhibit exaggerated chemoreceptor-driven ventilation during non-rapid eye movement sleep (NREMS), which leads to central and obstructive apnea. This article critically reviewed the literature relevant to preoperative screening for OSA, prevalence of OSA in surgical populations and changes in postoperative sleep architecture relevant to OSA patients. In particular, we addressed three questions in regard to the effects of sedative-hypnotics, anesthetics and analgesics on sleep architecture, the underlying mechanisms and the relevance to OSA. Indeed, these classes of drugs alter sleep architecture, which likely significantly contributes to abnormal postoperative sleep architecture, exacerbation of OSA and postoperative complications.
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Affiliation(s)
- Dan M McEntire
- Department of Anesthesiology and the Center for Clinical and Translational Science, Creighton University School of Medicine, 601 N. 30th Street, Suite 3222, Omaha, NE 68131, USA
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58
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Bloch KE, Latshang TD, Ulrich S. Patients with Obstructive Sleep Apnea at Altitude. High Alt Med Biol 2015; 16:110-6. [DOI: 10.1089/ham.2015.0016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- Konrad E. Bloch
- Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Switzerland
- Center for Human Integrative Physiology, and Zurich Center for Interdisciplinary Sleep Research, University of Zurich, Switzerland
| | - Tsogyal D. Latshang
- Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Switzerland
- Center for Human Integrative Physiology, and Zurich Center for Interdisciplinary Sleep Research, University of Zurich, Switzerland
| | - Silvia Ulrich
- Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Switzerland
- Center for Human Integrative Physiology, and Zurich Center for Interdisciplinary Sleep Research, University of Zurich, Switzerland
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Hoiland RL, Ainslie PN, Wildfong KW, Smith KJ, Bain AR, Willie CK, Foster G, Monteleone B, Day TA. Indomethacin-induced impairment of regional cerebrovascular reactivity: implications for respiratory control. J Physiol 2015; 593:1291-306. [PMID: 25641262 PMCID: PMC4358685 DOI: 10.1113/jphysiol.2014.284521] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 12/03/2014] [Indexed: 01/20/2023] Open
Abstract
Cerebrovascular reactivity impacts CO₂-[H(+)] washout at the central chemoreceptors and hence has marked influence on the control of ventilation. To date, the integration of cerebral blood flow (CBF) and ventilation has been investigated exclusively with measures of anterior CBF, which has a differential reactivity from the vertebrobasilar system and perfuses the brainstem. We hypothesized that: (1) posterior versus anterior CBF would have a stronger relationship to central chemoreflex magnitude during hypercapnia, and (2) that higher posterior reactivity would lead to a greater hypoxic ventilatory decline (HVD). End-tidal forcing was used to induce steady-state hyperoxic (300 mmHg P ET ,O₂) hypercapnia (+3, +6 and +9 mmHg P ET ,CO₂) and isocapnic hypoxia (45 mmHg P ET ,O₂) before and following pharmacological blunting (indomethacin; INDO; 1.45 ± 0.17 mg kg(-1)) of resting CBF and reactivity. In 22 young healthy volunteers, ventilation, intra-cranial arterial blood velocities and extra-cranial blood flows were measured during these challenges. INDO-induced blunting of cerebrovascular flow responsiveness (CVR) to CO₂ was unrelated to variability in ventilatory sensitivity during hyperoxic hypercapnia. Further results in a sub-group of volunteers (n = 9) revealed that elevations of P ET,CO₂ via end-tidal forcing reduce arterial-jugular venous gradients, attenuating the effect of CBF on chemoreflex responses. During isocapnic hypoxia, vertebral artery CVR was related to the magnitude of HVD (R(2) = 0.27; P < 0.04; n = 16), suggesting that CO₂-[H(+)] washout from central chemoreceptors modulates hypoxic ventilatory dynamics. No relationships were apparent with anterior CVR. As higher posterior, but not anterior, CVR was linked to HVD, our study highlights the importance of measuring flow in posterior vessels to investigate CBF and ventilatory integration.
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Affiliation(s)
- Ryan L Hoiland
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Kevin W Wildfong
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Kurt J Smith
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Anthony R Bain
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Chris K Willie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Glen Foster
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British ColumbiaKelowna, British Columbia, Canada
| | - Brad Monteleone
- Faculty of Medicine, University of British Columbia OkanaganKelowna, British Columbia, Canada
| | - Trevor A Day
- Department of Biology, Faculty of Science and Technology, Mount Royal UniversityCalgary, Alberta, Canada
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60
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El-Chami M, Shaheen D, Ivers B, Syed Z, Badr MS, Lin HS, Mateika JH. Time of day affects chemoreflex sensitivity and the carbon dioxide reserve during NREM sleep in participants with sleep apnea. J Appl Physiol (1985) 2014; 117:1149-56. [PMID: 25213638 DOI: 10.1152/japplphysiol.00681.2014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Our investigation was designed to determine whether the time of day affects the carbon dioxide reserve and chemoreflex sensitivity during non-rapid eye movement (NREM) sleep. Ten healthy men with obstructive sleep apnea completed a constant routine protocol that consisted of sleep sessions in the evening (10 PM to 1 AM), morning (6 AM to 9 AM), and afternoon (2 PM to 5 PM). Between sleep sessions, the participants were awake. During each sleep session, core body temperature, baseline levels of carbon dioxide (PET(CO2)) and minute ventilation, as well as the PET(CO2) that demarcated the apneic threshold and hypocapnic ventilatory response, were measured. The nadir of core body temperature during sleep occurred in the morning and was accompanied by reductions in minute ventilation and PetCO2 compared with the evening and afternoon (minute ventilation: 5.3 ± 0.3 vs. 6.2 ± 0.2 vs. 6.1 ± 0.2 l/min, P < 0.02; PET(CO2): 39.7 ± 0.4 vs. 41.4 ± 0.6 vs. 40.4 ± 0.6 Torr, P < 0.02). The carbon dioxide reserve was reduced, and the hypocapnic ventilatory response increased in the morning compared with the evening and afternoon (carbon dioxide reserve: 2.1 ± 0.3 vs. 3.6 ± 0.5 vs. 3.5 ± 0.3 Torr, P < 0.002; hypocapnic ventilatory response: 2.3 ± 0.3 vs. 1.6 ± 0.2 vs. 1.8 ± 0.2 l·min(-1)·mmHg(-1), P < 0.001). We conclude that time of day affects chemoreflex properties during sleep, which may contribute to increases in breathing instability in the morning compared with other periods throughout the day/night cycle in individuals with sleep apnea.
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Affiliation(s)
- Mohamad El-Chami
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - David Shaheen
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Blake Ivers
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - Ziauddin Syed
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - M Safwan Badr
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan; Department of Biomedical Engineering, Wayne State University Detroit, Michigan
| | - Ho-Sheng Lin
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan; Department of Otolaryngology-Head & Neck Surgery, Wayne State University School of Medicine and Karmanos Cancer Institute, Detroit, Michigan; and
| | - Jason H Mateika
- John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan; Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan; Department of Internal Medicine, Wayne State University School of Medicine, Detroit, Michigan;
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Abstract
Respiration during sleep is determined by metabolic demand; respiratory drive is determined by a central respiratory generator. Changes in pharyngeal dilator muscle tone resulting in increased upper airway resistance and collapsibility contribute to hypoventilation. Relative hypotonia of respiratory muscles, body posture changes, and altered ventilatory control result in additional physiologic changes contributing to hypoventilation. This article reviews mechanisms of central control of respiration and normal upper and lower airway physiology. Understanding sleep-related changes in respiratory physiology will help in developing new therapies to prevent hypoventilation in susceptible populations.
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Affiliation(s)
- Mudiaga Sowho
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, Johns Hopkins University, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA
| | - Jason Amatoury
- Neuroscience Research Australia, Barker Street, Randwick, New South Wales 2031, Australia; Ludwig Engel Centre for Respiratory Research, Westmead Millennium Institute, and Sydney Medical School, University of Sydney at Westmead Hospital, Hawkesbury Road, Westmead, New South Wales 2145, Australia
| | - Jason P Kirkness
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, Johns Hopkins University, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA
| | - Susheel P Patil
- Division of Pulmonary, Critical Care, and Sleep Medicine, Department of Medicine, Johns Hopkins University, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA.
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Gederi E, Nemati S, Edwards BA, Clifford GD, Malhotra A, Wellman A. Model-based estimation of loop gain using spontaneous breathing: a validation study. Respir Physiol Neurobiol 2014; 201:84-92. [PMID: 25038522 DOI: 10.1016/j.resp.2014.07.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 06/16/2014] [Accepted: 07/02/2014] [Indexed: 10/25/2022]
Abstract
Non-invasive assessment of ventilatory control stability or loop gain (which is a key contributor in a number of sleep-related breathing disorders) has proven to be cumbersome. We present a novel multivariate autoregressive model that we hypothesize will enable us to make time-varying measurements of loop gain using nothing more than spontaneous fluctuations in ventilation and CO2. The model is adaptive to changes in the feedback control loop and therefore can account for system non-stationarities (e.g. changes in sleep state) and it is resistant to artifacts by using a signal quality measure. We tested this method by assessing its ability to detect a known increase in loop gain induced by proportional assist ventilation (PAV). Subjects were studied during sleep while breathing on continuous positive airway pressure (CPAP) alone (to stabilize the airway) or on CPAP+PAV. We show that the method tracked the PAV-induced increase in loop gain, demonstrating its time-varying capabilities, and it remained accurate in the face of measurement related artifacts. The model was able to detect a statistically significant increase in loop gain from 0.14±10 on CPAP alone to 0.21±0.13 on CPAP+PAV (p<0.05). Furthermore, our method correctly detected that the PAV-induced increase in loop gain was predominantly driven by an increase in controller gain. Taken together, these data provide compelling evidence for the validity of this technique.
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Affiliation(s)
- Elnaz Gederi
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK.
| | - Shamim Nemati
- Harvard School of Engineering and Applied Sciences, 33 Oxford Street, Cambridge, MA 02138, USA
| | - Bradley A Edwards
- Division of Sleep Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Gari D Clifford
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, UK; Division of Sleep Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA; Department of Biomedical Informatics, School of Medicine, Emory University, Atlanta, GA 30322, USA; Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Atul Malhotra
- Division of Sleep Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA; Pulmonary and Critical Care Division, University of California, San Diego, CA 92037, USA
| | - Andrew Wellman
- Division of Sleep Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
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Patz DS, Patz MD, Hackett PH. Dead space mask eliminates central apnea at altitude. High Alt Med Biol 2014; 14:168-74. [PMID: 23795738 DOI: 10.1089/ham.2012.1111] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Travelers to high altitude may have disturbed sleep due to periodic breathing with frequent central apneas. We tested whether a mask with added dead space could reduce the central apneas of altitude. 16 subjects were recruited, age 18-35, residing at 4600 ft (1400 m). They each slept one night with full polysomnographic monitoring, including end tidal CO2, in a normobaric hypoxia tent simulating 12,000 ft. (3658 m) altitude. Those who had a central apnea index (CAI) >20/h returned for a night in the tent for dead space titration, during which they slept with increasing amounts of dead space, aiming for a CAI <5/h or <10% of baseline. Then each subject slept another night with the titrated amount of dead space. Of the 16 subjects, 5 had a central apnea index >20/h mean 49.1, range 21.4-131.5/hr. In each of the 5, the dead space mask reduced the CAI by at least 88% to a mean of 3.1, range 0.9-7.1/h, (p=0.04). Hypopnea index was unchanged. Three subjects required 500 cc of dead space or less. One subject required 860 cc, and one required 2.1 L. Morning symptoms and arousal index were not significantly affected by the dead space mask. Dead space did not appear to increase the CO2 reserve. At 12,000 ft., central apneas can be effectively reduced with a dead space mask, but clinical utility will require further evaluation.
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Affiliation(s)
- David S Patz
- St. Mary's Hospital, Grand Junction, CO 81507, USA.
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64
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Skow RJ, Tymko MM, MacKay CM, Steinback CD, Day TA. The effects of head-up and head-down tilt on central respiratory chemoreflex loop gain tested by hyperoxic rebreathing. PROGRESS IN BRAIN RESEARCH 2014; 212:149-72. [DOI: 10.1016/b978-0-444-63488-7.00009-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Abstract
There is a growing public awareness that hormones can have a significant impact on most biological systems, including the control of breathing. This review will focus on the actions of two broad classes of hormones on the neuronal control of breathing: sex hormones and stress hormones. The majority of these hormones are steroids; a striking feature is that both groups are derived from cholesterol. Stress hormones also include many peptides which are produced primarily within the paraventricular nucleus of the hypothalamus (PVN) and secreted into the brain or into the circulatory system. In this article we will first review and discuss the role of sex hormones in respiratory control throughout life, emphasizing how natural fluctuations in hormones are reflected in ventilatory metrics and how disruption of their endogenous cycle can predispose to respiratory disease. These effects may be mediated directly by sex hormone receptors or indirectly by neurotransmitter systems. Next, we will discuss the origins of hypothalamic stress hormones and their relationship with the respiratory control system. This relationship is 2-fold: (i) via direct anatomical connections to brainstem respiratory control centers, and (ii) via steroid hormones released from the adrenal gland in response to signals from the pituitary gland. Finally, the impact of stress on the development of neural circuits involved in breathing is evaluated in animal models, and the consequences of early stress on respiratory health and disease is discussed.
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Affiliation(s)
- Mary Behan
- Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin, USA.
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66
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Abstract
Neurophysiologically, central apnea is due to a temporary failure in the pontomedullary pacemaker generating breathing rhythm. As a polysomnographic finding, central apneas occur in many pathophysiological conditions. Depending on the cause or mechanism, central apneas may not be clinically significant, for example, those that occur normally at sleep onset. In contrast, central apneas occur in a number of disorders and result in pathophysiological consequences. Central apneas occur commonly in high-altitude sojourn, disrupt sleep, and cause desaturation. Central sleep apnea also occurs in number of disorders across all age groups and both genders. Common causes of central sleep apnea in adults are congestive heart failure and chronic use of opioids to treat pain. Under such circumstances, diagnosis and treatment of central sleep apnea may improve quality of life, morbidity, and perhaps mortality. The mechanisms of central sleep apnea have been best studied in congestive heart failure and hypoxic conditions when there is increased CO2 sensitivity below eupnea resulting in lowering eupneic PCO2 below apneic threshold causing cessation of breathing until the PCO2 rises above the apneic threshold when breathing resumes. In many other disorders, the mechanism of central sleep apnea (CSA) remains to be investigated.
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Affiliation(s)
- S Javaheri
- University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.
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Sankari A, Bascom AT, Chowdhuri S, Badr MS. Tetraplegia is a risk factor for central sleep apnea. J Appl Physiol (1985) 2013; 116:345-53. [PMID: 24114704 DOI: 10.1152/japplphysiol.00731.2013] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Sleep-disordered breathing (SDB) is highly prevalent in patients with spinal cord injury (SCI); the exact mechanism(s) or the predictors of disease are unknown. We hypothesized that patients with cervical SCI (C-SCI) are more susceptible to central apnea than patients with thoracic SCI (T-SCI) or able-bodied controls. Sixteen patients with chronic SCI, level T6 or above (8 C-SCI, 8 T-SCI; age 42.5 ± 15.5 years; body mass index 25.9 ± 4.9 kg/m(2)) and 16 matched controls were studied. The hypocapnic apneic threshold and CO2 reserve were determined using noninvasive ventilation. For participants with spontaneous central apnea, CO2 was administered until central apnea was abolished, and CO2 reserve was measured as the difference in end-tidal CO2 (PetCO2) before and after. Steady-state plant gain (PG) was calculated from PetCO2 and VE ratio during stable sleep. Controller gain (CG) was defined as the ratio of change in VE between control and hypopnea or apnea to the ΔPetCO2. Central SDB was more common in C-SCI than T-SCI (63% vs. 13%, respectively; P < 0.05). Mean CO2 reserve for all participants was narrower in C-SCI than in T-SCI or control group (-0.4 ± 2.9 vs.-2.9 ± 3.3 vs. -3.0 ± 1.2 l·min(-1)·mmHg(-1), respectively; P < 0.05). PG was higher in C-SCI than in T-SCI or control groups (10.5 ± 2.4 vs. 5.9 ± 2.4 vs. 6.3 ± 1.6 mmHg·l(-1)·min(-1), respectively; P < 0.05) and CG was not significantly different. The CO2 reserve was an independent predictor of apnea-hypopnea index. In conclusion, C-SCI had higher rates of central SDB, indicating that tetraplegia is a risk factor for central sleep apnea. Sleep-related hypoventilation may play a significant role in the mechanism of SDB in higher SCI levels.
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Affiliation(s)
- Abdulghani Sankari
- Sleep Research Laboratory, John D. Dingell Veterans Affairs Medical Center, Wayne State University, Detroit, Michigan
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Wang D, Eckert DJ, Grunstein RR. Drug effects on ventilatory control and upper airway physiology related to sleep apnea. Respir Physiol Neurobiol 2013; 188:257-66. [PMID: 23685318 DOI: 10.1016/j.resp.2013.05.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 05/05/2013] [Accepted: 05/08/2013] [Indexed: 12/30/2022]
Abstract
Understanding the inter-relationship between pharmacological agents, ventilatory control, upper airway physiology and their consequent effects on sleep-disordered breathing may provide new directions for targeted drug therapy. Where available, this review focuses on human studies that contain both drug effects on sleep-disordered breathing and measures of ventilatory control or upper airway physiology. Many of the existing studies are limited in sample size or comprehensive methodology. At times, the presence of paradoxical findings highlights the complexity of drug therapy for OSA. The existing studies also highlight the importance of considering inter-individual pharmacokinetics and underlying causes of sleep apnea in interpreting drug effects on sleep-disordered breathing. Practical ways to assess an individual's ventilatory control and how it interacts with upper airway physiology is required for future targeted pharmacotherapy in sleep apnea.
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Affiliation(s)
- David Wang
- Woolcock Institute of Medical Research, University of Sydney, Glebe Point Road, Glebe, 2037 NSW, Australia; Department of Respiratory & Sleep Medicine, Royal Prince Alfred Hospital, Missenden Road, Camperdown, NSW 2050, Australia.
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van Hulsteijn LT, van Duinen N, Ninaber MK, Romijn JA, van Dijk JG, van Kralingen KW, Havekes B, Smid L, Lammers GJ, Jansen JC, Smit JW, Thijs RD, Corssmit EPM. Carotid body tumors are not associated with an increased risk for sleep-disordered breathing. Sleep Breath 2013; 18:103-9. [PMID: 23657666 DOI: 10.1007/s11325-013-0855-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 04/18/2013] [Indexed: 01/28/2023]
Abstract
PURPOSE Tumors in the carotid bodies may interfere with their function as peripheral chemoreceptors. An altered control of ventilation may predispose to sleep-disordered breathing. This study aimed to assess whether patients with unilateral or bilateral carotid body tumors (uCBT or bCBT, respectively) or bilateral CBT resection (bCBR) display sleep-disordered breathing and to evaluate the global contribution of the peripheral chemoreceptor to the hypercapnic ventilatory response. METHODS Eight uCBT, eight bCBT, and nine bCBR patients and matched controls underwent polysomnography. The peripheral chemoreflex drive was assessed using euoxic and hyperoxic CO2 rebreathing tests. Daytime sleepiness and fatigue were assessed with the Epworth Sleepiness Scale and the Multidimensional Fatigue Index. RESULTS All patient groups reported significant fatigue-related complaints, but no differences in excessive daytime sleepiness (EDS) were found. The apnea/hypopnea index (AHI) did not differ significantly between patient groups and controls. Only in bCBT patients, a trend towards a higher AHI was observed, but this did not reach significance (p=0.06). No differences in the peripheral chemoreflex drive were found between patients and controls. CONCLUSIONS Patients with (resection of) CBTs have more complaints of fatigue but are not at risk for EDS. The presence or resection of CBTs is neither associated with an altered peripheral chemoreflex drive nor with sleep-disordered breathing.
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Affiliation(s)
- L T van Hulsteijn
- Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, PO Box 9600, 2300 RC, Leiden, the Netherlands,
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Gavlak JC, Stocks J, Laverty A, Fettes E, Bucks R, Sonnappa S, Cooper J, Grocott MP, Levett DZ, Martin DS, Imray CH, Kirkham FJ. The Young Everest Study: preliminary report of changes in sleep and cerebral blood flow velocity during slow ascent to altitude in unacclimatised children. Arch Dis Child 2013; 98:356-62. [PMID: 23471157 PMCID: PMC3625826 DOI: 10.1136/archdischild-2012-302512] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND Cerebral blood flow velocity (CBFV) and sleep physiology in healthy children exposed to hypoxia and hypocarbia are under-researched. AIM To investigate associations between sleep variables, daytime end-tidal carbon dioxide (EtCO2) and CBFV in children during high-altitude ascent. METHODS Vital signs, overnight cardiorespiratory sleep studies and transcranial Doppler were undertaken in nine children (aged 6-13 years) at low altitude (130 m), and then at moderate (1300 m) and high (3500 m) altitude during a 5-day ascent. RESULTS Daytime (130 m: 98%; 3500 m: 90%, p=0.004) and mean (130 m: 97%, 1300 m: 94%, 3500: 87%, p=0.0005) and minimum (130 m: 92%, 1300 m: 84%, 3500 m: 79%, p=0.0005) overnight pulse oximetry oxyhaemoglobin saturation decreased, and the number of central apnoeas increased at altitude (130 m: 0.2/h, 1300 m: 1.2/h, 3500 m: 3.5/h, p=0.2), correlating inversely with EtCO2 (R(2) 130 m: 0.78; 3500 m: 0.45). Periodic breathing occurred for median (IQR) 0.0 (0; 0.3)% (130 m) and 0.2 (0; 1.2)% (3500 m) of total sleep time. At 3500 m compared with 130 m, there were increases in middle (MCA) (mean (SD) left 29.2 (42.3)%, p=0.053; right 9.9 (12)%, p=0.037) and anterior cerebral (ACA) (left 65.2 (69)%, p=0.024; right 109 (179)%; p=0.025) but not posterior or basilar CBFV. The right MCA CBFV increase at 3500 m was predicted by baseline CBFV and change in daytime SpO2 and EtCO2 at 3500 m (R(2) 0.92); these associations were not seen on the left. CONCLUSIONS This preliminary report suggests that sleep physiology is disturbed in children even with slow ascent to altitude. The regional variations in CBFV and their association with hypoxia and hypocapnia require further investigation.
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Affiliation(s)
- Johanna C Gavlak
- Department of Paediatric Respiratory Medicine, Great Ormond Street Hospital for Children NHS Trust, Walrus Ward Level 1, Morgan Stanley Clinical Building, Great Ormond Street, London WC1N 3JH, UK.
| | - Janet Stocks
- Portex Respiratory Unit, UCL Institute of Child Health, London, UK
| | - Aidan Laverty
- Department of Paediatric Respiratory Medicine, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Emma Fettes
- Department of Paediatric Respiratory Medicine, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Romola Bucks
- Department of Psychology, University of Western Australia, Perth, Australia
| | - Samatha Sonnappa
- Department of Paediatric Respiratory Medicine, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK,Portex Respiratory Unit, UCL Institute of Child Health, London, UK
| | - Janine Cooper
- Developmental Neuroscience Unit, UCL Institute of Child Health, London, UK
| | - Michael P Grocott
- Centre for Altitude Space and Extreme Environment Medicine, UCL Institute of Child Health, London, UK,Anaesthesia and Critical Care Research Unit, University Hospitals Southampton NHS Foundation Trust, Southampton, UK,Department of Clinical and Experimental Sciences, University of Southampton, Southampton, UK
| | - Denny Z Levett
- Centre for Altitude Space and Extreme Environment Medicine, UCL Institute of Child Health, London, UK
| | - Daniel S Martin
- Centre for Altitude Space and Extreme Environment Medicine, UCL Institute of Child Health, London, UK
| | - Christopher H Imray
- Department of Vascular Surgery, University Hospitals Coventry and Warwickshire NHS Trust, Warwick Medical School, Coventry, UK
| | - Fenella J Kirkham
- Department of Clinical and Experimental Sciences, University of Southampton, Southampton, UK,Neurosciences Units, UCL Institute of Child Health, London, UK,Department of Child Health, University Hospitals Southampton NHS Foundation Trust, Southampton, UK
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71
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The effects of a single mild dose of morphine on chemoreflexes and breathing in obstructive sleep apnea. Respir Physiol Neurobiol 2013. [DOI: 10.1016/j.resp.2012.11.014] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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72
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Fiamma MN, O'Connor ET, Roy A, Zuna I, Wilson RJA. The essential role of peripheral respiratory chemoreceptor inputs in maintaining breathing revealed when CO2 stimulation of central chemoreceptors is diminished. J Physiol 2013; 591:1507-21. [PMID: 23359670 DOI: 10.1113/jphysiol.2012.247304] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Central sleep apnoea is a condition characterized by oscillations between apnoea and hyperpnoea during sleep. Studies in sleeping dogs suggest that withdrawal of peripheral chemoreceptor (carotid body) activation following transient ventilatory overshoots plays an essential role in causing apnoea, raising the possibility that sustaining carotid body activity during ventilatory overshoots may prevent apnoea. To test whether sustained peripheral chemoreceptor activation is sufficient to drive breathing, even in the absence of central chemoreceptor stimulation and vagal feedback, we used a vagotomized, decerebrate dual-perfused in situ rat preparation in which the central and peripheral chemoreceptors are independently and artificially perfused with gas-equilibrated medium. At varying levels of carotid body stimulation (CB PO2/PCO2: 40/60, 100/40, 200/15, 500/15 Torr), we decreased the brainstem perfusate PCO2 in 5 Torr steps while recording phrenic nerve activity to determine the central apnoeic thresholds. The central apnoeic thresholds decreased with increased carotid body stimulation. When the carotid bodies were strongly stimulated (CB 40/60), the apnoeic threshold was 3.6 ± 1.4 Torr PCO2 (mean ± SEM, n = 7). Stimulating carotid body afferent activity with either hypercapnia (60 Torr PCO2) or the neuropeptide pituitary adenylate cyclase-activating peptide restored phrenic activity during central apnoea. We conclude that peripheral stimulation shifts the central apnoeic threshold to very hypocapnic levels that would likely increase the CO2 reserve and have a protective effect on breathing. These data demonstrate that peripheral respiratory chemoreceptors are sufficient to stave off central apnoeas when the brainstem is perfused with low to no CO2.
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Affiliation(s)
- Marie-Noëlle Fiamma
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
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74
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Anholm JD, Foster GP. The 17th International Hypoxia Symposium: Hypoxia and Cancer, February 15-20, 2011. High Alt Med Biol 2012; 12:285-9. [PMID: 21962073 DOI: 10.1089/ham.2011.1032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- James D Anholm
- Pulmonary and Critical Care Section, Veterans Administration Loma Linda Healthcare System, Loma Linda, California 92357, USA.
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75
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Abstract
Central chemoreception traditionally refers to a change in ventilation attributable to changes in CO2/H(+) detected within the brain. Interest in central chemoreception has grown substantially since the previous Handbook of Physiology published in 1986. Initially, central chemoreception was localized to areas on the ventral medullary surface, a hypothesis complemented by the recent identification of neurons with specific phenotypes near one of these areas as putative chemoreceptor cells. However, there is substantial evidence that many sites participate in central chemoreception some located at a distance from the ventral medulla. Functionally, central chemoreception, via the sensing of brain interstitial fluid H(+), serves to detect and integrate information on (i) alveolar ventilation (arterial PCO2), (ii) brain blood flow and metabolism, and (iii) acid-base balance, and, in response, can affect breathing, airway resistance, blood pressure (sympathetic tone), and arousal. In addition, central chemoreception provides a tonic "drive" (source of excitation) at the normal, baseline PCO2 level that maintains a degree of functional connectivity among brainstem respiratory neurons necessary to produce eupneic breathing. Central chemoreception responds to small variations in PCO2 to regulate normal gas exchange and to large changes in PCO2 to minimize acid-base changes. Central chemoreceptor sites vary in function with sex and with development. From an evolutionary perspective, central chemoreception grew out of the demands posed by air versus water breathing, homeothermy, sleep, optimization of the work of breathing with the "ideal" arterial PCO2, and the maintenance of the appropriate pH at 37°C for optimal protein structure and function.
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Affiliation(s)
- Eugene Nattie
- Dartmouth Medical School, Department of Physiology, Lebanon, New Hampshire, USA.
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76
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Abstract
Central chemoreception traditionally refers to a change in ventilation attributable to changes in CO2/H(+) detected within the brain. Interest in central chemoreception has grown substantially since the previous Handbook of Physiology published in 1986. Initially, central chemoreception was localized to areas on the ventral medullary surface, a hypothesis complemented by the recent identification of neurons with specific phenotypes near one of these areas as putative chemoreceptor cells. However, there is substantial evidence that many sites participate in central chemoreception some located at a distance from the ventral medulla. Functionally, central chemoreception, via the sensing of brain interstitial fluid H(+), serves to detect and integrate information on (i) alveolar ventilation (arterial PCO2), (ii) brain blood flow and metabolism, and (iii) acid-base balance, and, in response, can affect breathing, airway resistance, blood pressure (sympathetic tone), and arousal. In addition, central chemoreception provides a tonic "drive" (source of excitation) at the normal, baseline PCO2 level that maintains a degree of functional connectivity among brainstem respiratory neurons necessary to produce eupneic breathing. Central chemoreception responds to small variations in PCO2 to regulate normal gas exchange and to large changes in PCO2 to minimize acid-base changes. Central chemoreceptor sites vary in function with sex and with development. From an evolutionary perspective, central chemoreception grew out of the demands posed by air versus water breathing, homeothermy, sleep, optimization of the work of breathing with the "ideal" arterial PCO2, and the maintenance of the appropriate pH at 37°C for optimal protein structure and function.
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Affiliation(s)
- Eugene Nattie
- Dartmouth Medical School, Department of Physiology, Lebanon, New Hampshire, USA.
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77
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Yokhana SS, Gerst DG, Lee DS, Badr MS, Qureshi T, Mateika JH. Impact of repeated daily exposure to intermittent hypoxia and mild sustained hypercapnia on apnea severity. J Appl Physiol (1985) 2011; 112:367-77. [PMID: 22052874 DOI: 10.1152/japplphysiol.00702.2011] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined whether exposure to intermittent hypoxia (IH) during wakefulness impacted on the apnea/hypopnea index (AHI) during sleep in individuals with sleep apnea. Participants were exposed to twelve 4-min episodes of hypoxia in the presence of sustained mild hypercapnia each day for 10 days. A control group was exposed to sustained mild hypercapnia for a similar duration. The intermittent hypoxia protocol was completed in the evening on day 1 and 10 and was followed by a sleep study. During all sleep studies, the change in esophageal pressure (ΔPes) from the beginning to the end of an apnea and the tidal volume immediately following apneic events were used to measure respiratory drive. Following exposure to IH on day 1 and 10, the AHI increased above baseline measures (day 1: 1.95 ± 0.42 fraction of baseline, P ≤ 0.01, vs. day 10: 1.53 ± 0.24 fraction of baseline, P < 0.06). The indexes were correlated to the hypoxic ventilatory response (HVR) measured during the IH protocol but were not correlated to the magnitude of ventilatory long-term facilitation (vLTF). Likewise, ΔPes and tidal volume measures were greater on day 1 and 10 compared with baseline (ΔPes: -8.37 ± 0.84 vs. -5.90 ± 1.30 cmH(2)0, P ≤ 0.04; tidal volume: 1,193.36 ± 101.85 vs. 1,015.14 ± 119.83 ml, P ≤ 0.01). This was not the case in the control group. Interestingly, the AHI on day 10 (0.78 ± 0.13 fraction of baseline, P ≤ 0.01) was significantly less than measures obtained during baseline and day 1 in the mild hypercapnia control group. We conclude that enhancement of the HVR initiated by exposure to IH may lead to increases in the AHI during sleep and that initiation of vLTF did not appear to impact on breathing stability. Lastly, our results suggest that repeated daily exposure to mild sustained hypercapnia may lead to a decrease in breathing events.
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Affiliation(s)
- Sanar S Yokhana
- Department of Physiology, Wayne State University School of Medicine, Wayne State University, Detroit, Michigan, USA
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WANG DAVID, MARSHALL NATHANIELS, DUFFIN JAMES, YEE BRENDONJ, WONG KEITHK, NOORI NARGIS, NG SUSANNASW, GRUNSTEIN RONALDR. Phenotyping interindividual variability in obstructive sleep apnoea response to temazepam using ventilatory chemoreflexes during wakefulness. J Sleep Res 2011; 20:526-32. [DOI: 10.1111/j.1365-2869.2011.00931.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Nussbaumer-Ochsner Y, Latshang TD, Ulrich S, Kohler M, Thurnheer R, Bloch KE. Patients with obstructive sleep apnea syndrome benefit from acetazolamide during an altitude sojourn: a randomized, placebo-controlled, double-blind trial. Chest 2011; 141:131-138. [PMID: 21659435 DOI: 10.1378/chest.11-0375] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
BACKGROUND Many patients with obstructive sleep apnea syndrome (OSA) are unable or unwilling to use continuous positive airway pressure (CPAP) therapy when traveling to the mountains for work or recreation even though they risk pronounced hypoxemia and exacerbation of sleep apnea. Because the treatment of OSA at altitude has not been established, we tested the hypothesis that acetazolamide improves hypoxemia, sleep, and breathing disturbances in otherwise untreated patients with OSA at altitude. METHODS Forty-five patients with OSA on long-term CPAP, median age 64 years, living at < 600 m underwent a placebo-controlled, double-blind, crossover trial randomized for the sequence of drug and altitude exposure (490 m, 1,860 m, and 2,590 m). Patients spent two 3-day periods at altitude and a 2-week wash-out period at < 600 m. At altitude, patients discontinued CPAP and received acetazolamide 2 × 250 mg daily or placebo. Polysomnography, vigilance, and symptoms were evaluated. RESULTS At 490 m, off CPAP, median nocturnal oxygen saturation was 93%, and the apnea/hypopnea index was 51.2/h. On placebo at 1,860 m and 2,590 m, the corresponding values were 89% and 85% and 63.6/h and 86.2/h, respectively (P < .01 vs 490 m, both instances). On acetazolamide at 1,860 m and 2,590 m, oxygen saturation was higher (91% and 88%) and apnea/hypopnea indices were lower (48.0/h and 61.4/h) than on placebo (P < .01 all instances). Acetazolamide reduced nocturnal transcutaneous Pco(2), improved sleep efficiency and subjective insomnia, and prevented excessive BP elevations at altitude. CONCLUSIONS In patients with OSA discontinuing CPAP during an altitude sojourn, acetazolamide improves oxygenation, breathing disturbances, and sleep quality by stimulating ventilation. Therefore, patients with OSA may benefit from acetazolamide at altitude if CPAP therapy is not feasible. TRIAL REGISTRY ClinicalTrials.gov; No.: NCT00714740; URL: www.clinicaltrials.gov.
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Affiliation(s)
- Yvonne Nussbaumer-Ochsner
- Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Center for Human Integrative Physiology, University of Zurich, Zurich
| | - Tsogyal D Latshang
- Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Center for Human Integrative Physiology, University of Zurich, Zurich
| | - Silvia Ulrich
- Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Center for Human Integrative Physiology, University of Zurich, Zurich
| | - Malcolm Kohler
- Center for Human Integrative Physiology, University of Zurich, Zurich
| | - Robert Thurnheer
- Pulmonary Division, Cantonal Hospital Munsterlingen, Munsterlingen, Switzerland
| | - Konrad E Bloch
- Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Center for Human Integrative Physiology, University of Zurich, Zurich.
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81
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Xie A, Bedekar A, Skatrud JB, Teodorescu M, Gong Y, Dempsey JA. The heterogeneity of obstructive sleep apnea (predominant obstructive vs pure obstructive apnea). Sleep 2011; 34:745-50. [PMID: 21629362 PMCID: PMC3099495 DOI: 10.5665/sleep.1040] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
STUDY OBJECTIVES To compare the breathing instability and upper airway collapsibility between patients with pure OSA (i.e. 100% of apneas are obstructive) and patients with predominant OSA (i.e., coexisting obstructive and central apneas). DESIGN A cross-sectional study with data scored by a fellow being blinded to the subjects' classification. The results were compared between the 2 groups with unpaired student t-test. SETTING AND INTERVENTIONS Standard polysomnography technique was used to document sleep-wake state. Ventilator in pressure support mode was used to introduce hypocapnic apnea during CO(2) reserve measurement. CPAP with both positive and negative pressures was used to produce obstructive apnea during upper airway collapsibility measurement. PARTICIPANTS 21 patients with OSA: 12 with coexisting central/mixed apneas and hypopneas (28% ± 6% of total), and 9 had pure OSA. MEASUREMENTS The upper airway collapsibility was measured by assessing the critical closing pressure (Pcrit). Breathing stability was assessed by measuring CO(2) reserve (i.e., ΔPCO(2) [eupnea-apnea threshold]) during NREM sleep. RESULTS There was no difference in Pcrit between the 2 groups (pure OSA vs. predominant OSA: 2.0 ± 0.4 vs. 2.7 ± 0.4 cm H(2)O, P = 0.27); but the CO(2) reserve was significantly smaller in predominant OSA group (1.6 ± 0.7 mm Hg) than the pure OSA group (3.8 ± 0.6 mm Hg) (P = 0.02). CONCLUSIONS The present data indicate that breathing stability rather than upper airway collapsibility distinguishes OSA patients with a combination of obstructive and central events from those with pure OSA.
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Affiliation(s)
- Ailiang Xie
- Population Health Sciences, University of Wisconsin, Madison, WI, USA.
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82
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Yun CH, Thomas RJ. Effect of Zolpidem and Enhanced Expiratory Rebreathing Space on Complex Sleep Apnea. SLEEP MEDICINE RESEARCH 2011. [DOI: 10.17241/smr.2011.2.1.35] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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83
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Nemati S, Edwards BA, Sands SA, Berger PJ, Wellman A, Verghese GC, Malhotra A, Butler JP. Model-based characterization of ventilatory stability using spontaneous breathing. J Appl Physiol (1985) 2011; 111:55-67. [PMID: 21474696 DOI: 10.1152/japplphysiol.01358.2010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cyclic ventilatory instabilities are widely attributed to an increase in the sensitivity or loop gain of the chemoreflex feedback loop controlling ventilation. A major limitation in the conventional characterization of this feedback loop is the need for labor-intensive methodologies. To overcome this limitation, we developed a method based on trivariate autoregressive modeling using ventilation, end-tidal Pco(2) and Po(2); this method provides for estimation of the overall "loop gain" of the respiratory control system and its components, chemoreflex gain and plant gain. Our method was applied to recordings of spontaneous breathing in 15 anesthetized, tracheostomized, newborn lambs before and after administration of domperidone (a dopamine D(2)-receptor antagonist that increases carotid body sensitivity). We quantified the known increase in hypoxic ventilatory sensitivity in response to domperidone; controller gain for O(2) increased from 0.06 (0.03, 0.09) l·min(-1)·mmHg(-1) to 0.09 (0.08, 0.13) l·min(-1)·mmHg(-1); median (interquartile-range). We also report that domperidone increased the loop gain of the control system more than twofold [0.14 (0.12, 0.22) to 0.40 (0.15, 0.57)]. We observed no significant changes in CO(2) controller gain, or plant gains for O(2) and CO(2). Furthermore, our estimate of the cycle duration of periodic breathing compared favorably with that observed experimentally [measured: 7.5 (7.2, 9.1) vs. predicted: 7.9 (7.0, 9.2) breaths]. Our results demonstrate that model-based analysis of spontaneous breathing can 1) characterize the dynamics of the respiratory control system, and 2) provide a simple tool for elucidating an individual's propensity for ventilatory instability, in turn allowing potential therapies to be directed at the underlying mechanisms.
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Affiliation(s)
- Shamim Nemati
- Massachusetts Institute of Technology, Cambridge, MA, USA.
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84
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Chami HA, Resnick HE, Quan SF, Gottlieb DJ. Association of incident cardiovascular disease with progression of sleep-disordered breathing. Circulation 2011; 123:1280-6. [PMID: 21403097 DOI: 10.1161/circulationaha.110.974022] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Prospective data suggest that sleep-disordered breathing enhances risk for incident and recurrent cardiovascular disease (CVD). However, a reverse causal pathway whereby incident CVD causes or worsens sleep-disordered breathing has not been studied. METHODS AND RESULTS A total of 2721 Sleep Heart Health Study participants (mean age 62, standard deviation=10 years; 57% women; 23% minority) without CVD at baseline underwent 2 polysomnograms 5 years apart. Incident CVD events, including myocardial infarction, congestive heart failure, and stroke, were ascertained and adjudicated. The relation of incident CVD to change in apnea-hypopnea index between the 2 polysomnograms was tested with general linear models, with adjustment for age, sex, race, study center, history of diabetes mellitus, change in body mass index, change in neck circumference, percent sleep time spent in supine sleep, and time between the 2 polysomnograms. Incident CVD occurred in 95 participants between the first and second polysomnograms. Compared with participants without incident CVD, those with incident CVD experienced larger increases in apnea-hypopnea index between polysomnograms. The difference in adjusted mean apnea-hypopnea index change between subjects with and without incident CVD was 2.75 events per hour (95% confidence interval, 0.26 to 5.24; P=0.032). This association persisted after subjects with central sleep apnea were excluded. Compared with participants without incident CVD, participants with incident CVD had greater increases in both mean obstructive and central apnea indices, by 1.75 events per hour (95% confidence interval, 0.10 to 1.75; P=0.04) and by 1.07 events per hour (95% confidence interval, 0.40 to 1.74; P=0.001), respectively. CONCLUSIONS In a diverse, community-based sample of middle-aged and older adults, incident CVD was associated with worsening sleep-disordered breathing over 5 years.
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Affiliation(s)
- Hassan A Chami
- The Pulmonary Center, Boston University School of Medicine, 72 E Concord Street, Boston, MA 02118, USA
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85
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Schäffer T. Respiratory physiology in sleep and wakefulness. HANDBOOK OF CLINICAL NEUROLOGY 2011; 98:371-81. [PMID: 21056199 DOI: 10.1016/b978-0-444-52006-7.00024-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Thorsten Schäffer
- Medical Faculty, Ruhr-University Bochum and Institute of Clinical Physiology, Helios Klinik Hagen-Ambrock, Germany.
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86
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Gilmartin G, McGeehan B, Vigneault K, Daly RW, Manento M, Weiss JW, Thomas RJ. Treatment of positive airway pressure treatment-associated respiratory instability with enhanced expiratory rebreathing space (EERS). J Clin Sleep Med 2010; 6:529-538. [PMID: 21206741 PMCID: PMC3014237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
STUDY OBJECTIVES Hypocapnia is an important mediator of sleep-dependent respiratory instability. Positive pressure-associated ventilatory control instability results in poor control of sleep apnea and persistent sleep fragmentation. We tested the adjunctive efficacy of low volumes of dead space (enhanced expiratory rebreathing space [EERS]) using a non-vented mask to minimize sleep hypocapnia. DESIGN Retrospective chart review. SETTING American Academy of Sleep Medicine accredited sleep center and laboratory. INTERVENTION Enhanced expiratory rebreathing space MEASUREMENTS AND RESULTS 204 patients diagnosed with continuous positive pressure (CPAP)-refractory sleep apnea between 1/1/04 and 7/1/06 were included in this retrospective review. All patients had in-lab attended polysomnography for diagnosis, conventional CPAP titration, and further assessments of added EERS. EERS volume was titrated to control of disease, which was typically obtained when end-tidal (ET) CO₂ during sleep was 1-2 mm Hg above wake eupneic CO₂ levels. The clinic records were reviewed for clinical outcomes. Poor laboratory response to, and initial clinical abandonment of CPAP, was very common (89.2%) in this group of patients, who as a group demonstrated mild resting wake hypocapnia (ETCO₂ = 38.1 ± 3.1 mm Hg). Minimizing sleep hypocapnia by adding 100-150 mL EERS (mean ETCO₂) at optimal therapy 38.6 ± 2.9 mm Hg) markedly improved polysomnographic control of sleep apnea, without inducing tachypnea or tachycardia. Follow-up (range 30-1872 days) showed improved clinical tolerance, compliance, and sustained clinical improvement. Leak and sleep fragmentation modified clinical outcomes. CONCLUSIONS EERS is a potentially useful adjunctive therapy for positive pressure-associated respiratory instability and salvage of some CPAP treatment failures.
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Affiliation(s)
- Geoffrey Gilmartin
- Division of Pulmonary, Critical Care and Sleep Medicine, Beth Israel Deaconess Medical Center, Boston, MA
| | | | | | | | - Megan Manento
- Division of Pulmonary, Critical Care and Sleep Medicine, Beth Israel Deaconess Medical Center, Boston, MA
| | - J. Woodrow Weiss
- Division of Pulmonary, Critical Care and Sleep Medicine, Beth Israel Deaconess Medical Center, Boston, MA
| | - Robert Joseph Thomas
- Division of Pulmonary, Critical Care and Sleep Medicine, Beth Israel Deaconess Medical Center, Boston, MA
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87
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Biomechanics of the upper airway: Changing concepts in the pathogenesis of obstructive sleep apnea. Int J Oral Maxillofac Surg 2010; 39:1149-59. [DOI: 10.1016/j.ijom.2010.09.007] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2010] [Accepted: 09/13/2010] [Indexed: 11/19/2022]
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88
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Abstract
Sleep is a phase during which the respiratory system undergoes major changes. These changes lead to greater vulnerability and a greater risk of abnormalities, even in normal individuals. In the transition from wakefulness to sleep, there is commonly an increase in upper airway resistance and impairment of various protective responses and reflexes, which are efficient in promoting and maintaining upper airway patency during wakefulness. In individuals who present risk factors, such as anatomical abnormalities in the upper airway, these sleep-related changes cannot be efficaciously compensated, which increases the chances that sleep-disordered breathing will occur. Sleep-disordered breathing is characterized by a reduction in the size of upper airways, although the degree of the reduction varies. This reduction has multifactorial causes, which include anatomical abnormalities in the upper airway, alterations in the neuromuscular response and impairment of receptors in the upper airway. Upper airway functional and anatomical changes are likely to have genetic components, and, therefore, individuals exposed to certain environmental factors, such as allergies, have a greater chance of developing sleep-disordered breathing.
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89
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Kinkead R, Gulemetova R. Neonatal maternal separation and neuroendocrine programming of the respiratory control system in rats. Biol Psychol 2010; 84:26-38. [DOI: 10.1016/j.biopsycho.2009.09.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Revised: 08/28/2009] [Accepted: 09/02/2009] [Indexed: 10/20/2022]
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90
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Poetsch M, Nottebaum BJ, Wingenfeld L, Frede S, Vennemann M, Bajanowski T. Impact of sodium/proton exchanger 3 gene variants on sudden infant death syndrome. J Pediatr 2010; 156:44-48.e1. [PMID: 19772970 DOI: 10.1016/j.jpeds.2009.07.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Revised: 05/21/2009] [Accepted: 07/07/2009] [Indexed: 10/20/2022]
Abstract
OBJECTIVE To determine the contribution of variations in the sodium/proton exchanger 3 (NHE3) gene in sudden infant death syndrome (SIDS). STUDY DESIGN Variations in the exons and promoter of the NHE3 gene were analyzed with direct sequencing analysis and mini sequencing (SNaPshot analysis) in 251 cases of SIDS, plus 50 infant control subjects who had died of other causes, and 170 healthy adults. RESULTS The C2405T variant (exon 16) and 2 polymorphisms in the promoter (G1131A and C1197T) were encountered significantly more frequently in cases of SIDS than in control subjects. At least 1 of these 3 variants was detected in 49% of SIDS cases, but only in 30% of control subjects. CONCLUSIONS Our findings suggest the involvement of polymorphisms in the NHE3 gene and promoter in cases of SIDS, which may result in an overexpression of NHE3 in the medulla oblongata and which possibly leads to a disturbance in breathing control. Furthermore, our results underline the heterogeneous character of SIDS.
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Affiliation(s)
- Micaela Poetsch
- Institute of Forensic Medicine, University Hospital Essen, Essen, Germany.
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91
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Abstract
Sleep-induced apnea and disordered breathing refers to intermittent, cyclical cessations or reductions of airflow, with or without obstructions of the upper airway (OSA). In the presence of an anatomically compromised, collapsible airway, the sleep-induced loss of compensatory tonic input to the upper airway dilator muscle motor neurons leads to collapse of the pharyngeal airway. In turn, the ability of the sleeping subject to compensate for this airway obstruction will determine the degree of cycling of these events. Several of the classic neurotransmitters and a growing list of neuromodulators have now been identified that contribute to neurochemical regulation of pharyngeal motor neuron activity and airway patency. Limited progress has been made in developing pharmacotherapies with acceptable specificity for the treatment of sleep-induced airway obstruction. We review three types of major long-term sequelae to severe OSA that have been assessed in humans through use of continuous positive airway pressure (CPAP) treatment and in animal models via long-term intermittent hypoxemia (IH): 1) cardiovascular. The evidence is strongest to support daytime systemic hypertension as a consequence of severe OSA, with less conclusive effects on pulmonary hypertension, stroke, coronary artery disease, and cardiac arrhythmias. The underlying mechanisms mediating hypertension include enhanced chemoreceptor sensitivity causing excessive daytime sympathetic vasoconstrictor activity, combined with overproduction of superoxide ion and inflammatory effects on resistance vessels. 2) Insulin sensitivity and homeostasis of glucose regulation are negatively impacted by both intermittent hypoxemia and sleep disruption, but whether these influences of OSA are sufficient, independent of obesity, to contribute significantly to the "metabolic syndrome" remains unsettled. 3) Neurocognitive effects include daytime sleepiness and impaired memory and concentration. These effects reflect hypoxic-induced "neural injury." We discuss future research into understanding the pathophysiology of sleep apnea as a basis for uncovering newer forms of treatment of both the ventilatory disorder and its multiple sequelae.
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Affiliation(s)
- Jerome A Dempsey
- The John Rankin Laboratory of Pulmonary Medicine, Departments of Population Health Sciences and of Orthopedics and Rehabilitation, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706, USA.
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92
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Teppema LJ, van Dorp ELA, Dahan A. Arterial [H+] and the ventilatory response to hypoxia in humans: influence of acetazolamide-induced metabolic acidosis. Am J Physiol Lung Cell Mol Physiol 2009; 298:L89-95. [PMID: 19880504 DOI: 10.1152/ajplung.00255.2009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In this study, we investigated possible separate effects of H+ ions and CO2 on hypoxic sensitivity in humans. We also examined whether hypoxic sensitivity, conventionally defined as the ratio of (hypoxic - normoxic) ventilation over (hypoxic - normoxic) Hb oxygen saturation can also be estimated by taking the ratio (hypoxic - normoxic) ventilation over (logPa(O2) hypoxia - logPa(O2) normoxia), enabling one to measure the hypoxic response independently from potential confounding influences of changes in position of the Hb oxygen saturation curve. We used acetazolamide to induce a metabolic acidosis. To determine the acute hypoxic response (AHR), we performed step decreases in end-tidal Po2 to approximately 50 Torr lasting 5 min each at three different constant end-tidal Pco2 levels. Nine subjects ingested 250 mg of acetazolamide or placebo every 8 h for 3 days in a randomized double-blind crossover design. The metabolic acidosis was accompanied by a rise in ventilation, a substantial fall in Pa(CO2), and a parallel leftward shift of the ventilatory CO2 response curve. In placebo, CO2 induced equal relative increases in hypoxic sensitivity (O2-CO2 interaction) regardless of the way it was defined. Acetazolamide shifted the response line representing the relationship between hypoxic sensitivity and arterial [H+] ([H+](a)) to higher values of [H+](a) without altering its slope, indicating that it did not affect the O2-CO2 interaction. So, in contrast to an earlier belief, CO2 and H+ have separate effects on hypoxic sensitivity. This was also supported by the finding that infusion of bicarbonate caused a leftward shift of the hypoxic sensitivity-[H+](a) response lines in placebo and acetazolamide. A specific inhibitory effect of acetazolamide on hypoxic sensitivity was not demonstrated.
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Affiliation(s)
- Luc J Teppema
- Department of Anesthesiology, Leiden University Medical Center, PO Box 9600 2300 RC, Leiden, The Netherlands.
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93
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Abstract
To understand normal sleep pattern and physiological changes during sleep, sleep and breathing interaction, nomenclature and scales used in sleep study, discuss the effect of rapid eye movements and non-rapid eye movements while sleep and to review the effects of obstructive and restrictive lung disease on gas exchange during sleep and sleep architecture.
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Affiliation(s)
- Sumer S. Choudhary
- Department of Pulmonary Medicine, Sleep Medicine, Critical Care, Shree Ramjevan Choudhary Memorial Hospital and Research Centre, Nagpur - 02, India
| | - Sanjiw R. Choudhary
- Department of Pulmonary Medicine, Sleep Medicine, Critical Care, Shree Ramjevan Choudhary Memorial Hospital and Research Centre, Nagpur - 02, India
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94
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Salloum A, Rowley JA, Mateika JH, Chowdhuri S, Omran Q, Badr MS. Increased propensity for central apnea in patients with obstructive sleep apnea: effect of nasal continuous positive airway pressure. Am J Respir Crit Care Med 2009; 181:189-93. [PMID: 19762565 DOI: 10.1164/rccm.200810-1658oc] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE There is increasing evidence of increased ventilatory instability in patients with obstructive sleep apnea (OSA), but previous investigations have not studied whether the hypocapnic apneic threshold is altered in this group. OBJECTIVES To compare the apneic threshold, CO2 reserve, and controller gain between subjects with and without OSA matched for age, sex, and body mass index. METHODS Hypocapnia was induced via nasal mechanical ventilation for 3 minutes. Cessation of mechanical ventilation resulted in hypocapnic central hypopnea or apnea depending upon the magnitude of the hypocapnia. The apnea threshold (Pet(CO2)-AT) was defined as the measured Pet(CO2) at which the apnea closest to the last hypopnea occurred. The CO2 reserve was defined as the change in Pet(CO2) between eupneic Pet(CO2) and Pet(CO2)-AT. Controller gain was defined as the ratio of change in Ve between control and hypopnea or apnea to the DeltaPet(CO2). MEASUREMENTS AND MAIN RESULTS Eleven pairs of subjects were studied. There was no difference in the Pet(CO2)-AT between the two groups. However, the CO2 reserve was smaller in the subjects with OSA (2.2 +/- 0.6 mm Hg) compared with the control subjects (4.5 +/- 1.4 mm Hg; P < 0.001). The controller gain was increased in the subjects with OSA (3.7 +/- 1.3 L/min/mm Hg) compared with the control subjects (1.6 +/- 0.5 L/min/mm Hg; P < 0.001). Controller gain decreased and CO2 reserve increased in seven subjects restudied after using continuous positive airway pressure for 1 month. CONCLUSIONS Ventilatory instability is increased in subjects with OSA and is reversible with the use of continuous positive airway pressure.
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Affiliation(s)
- Anan Salloum
- Wayne State University School of Medicine, Division of Pulmonary, Allergy, Critical Care & Sleep, Harper University Hospital, 3 Hudson 3990 John R, Detroit, MI 48201, USA
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95
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Bell HJ, Haouzi P. Acetazolamide suppresses the prevalence of augmented breaths during exposure to hypoxia. Am J Physiol Regul Integr Comp Physiol 2009; 297:R370-81. [DOI: 10.1152/ajpregu.00126.2009] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Augmented breaths, or “sighs,” commonly destabilize respiratory rhythm, precipitating apneas and variability in the depth and rate of breathing, which may then exacerbate sleep-disordered breathing in vulnerable individuals. We previously demonstrated that hypocapnia is a unique condition associated with a high prevalence of augmented breaths during exposure to hypoxia; the prevalence of augmented breaths during hypoxia can be returned to normal simply by the addition of CO2to the inspired air. We hypothesized that counteracting the effect of respiratory alkalosis during hypocapnic hypoxia by blocking carbonic anhydrase would yield a similar effect. We, therefore, investigated the effect of acetazolamide on the prevalence of augmented breaths in the resting breathing cycle in five awake, adult male rats. We found a 475% increase in the prevalence of augmented breaths in animals exposed to hypocapnic hypoxia compared with room air. Acetazolamide treatment (100 mg/kg ip bid) for 3 days resulted in a rapid and potent suppression of the generation of augmented breaths during hypoxia. Within 90 min of the first dose of acetazolamide, the prevalence of augmented breaths in hypoxia fell to levels that were no greater than those observed in room air. On cessation of treatment, exposure to hypocapnic hypoxia once again caused a large increase in the prevalence of augmented breaths. These results reveal a novel means by which acetazolamide acts to stabilize breathing and may help explain the beneficial effects of the drug on breathing stability at altitude and in patients with central forms of sleep-disordered breathing.
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96
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Boutin I, Saint-Raymond C, Borel JC, Tamisier R, Lévy P, Pépin JL. [Management of central sleep apnea]. REVUE DE PNEUMOLOGIE CLINIQUE 2009; 65:261-272. [PMID: 19789053 DOI: 10.1016/j.pneumo.2009.07.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Central sleep apnea is highly prevalent in association with heart failure, some neurological diseases and chronic opioids use. There are two main categories of central sleep apnea respectively related with different underlying conditions. Some hypocapnic patients exhibit respiratory control system instability and central apnea occurs when PaCO(2) falls below the threshold for apnea during sleep. The other group are patients with chronic hypercapnia mainly in the context of neuromuscular disorders or obesity hypoventilation syndrome. All these patients should be assessed by recording blood gases, polysomnography and ventilatory responses to CO(2). Cardiologic assessment should include pro-brain natriuretic factor (pro-BNP) and cardiac echography whereas neurological examination requires brain imaging and/or electromyography. Ventilatory supports used for treating central sleep apnea are non-invasive ventilation and servo-assisted ventilation in hypercapnic and hypocapnic patients respectively.
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Affiliation(s)
- I Boutin
- Laboratoire du sommeil et EFCR, pôle rééducation et physiologie , CHU de Grenoble, BP 217, 38043 Grenoble cedex 09, France
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97
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Continuous positive airway pressure reduces loop gain and resolves periodic central apneas in the lamb. Respir Physiol Neurobiol 2009; 168:239-49. [PMID: 19616133 DOI: 10.1016/j.resp.2009.07.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Revised: 07/09/2009] [Accepted: 07/09/2009] [Indexed: 11/24/2022]
Abstract
Continous positive airway pressure (CPAP) is used to treat infant respiratory distress syndrome and apnea of prematurity, but its mode of action is not fully understood. We hypothesised that CPAP increases lung volume and stabilises respiratory control by decreasing loop gain (LG). Experimentally induced periodic breathing (PB) in the lamb was terminated early by CPAP in a dose-dependent manner, with a control epoch of 45.4+/-5.1s at zero CPAP falling to 32.9+/-5.4, 13.2+/-4.2 and 9.8+/-3.1s at 2.5, 5 and 10 cmH(2)O, respectively (p<0.001); corresponding duty ratios (duration of the ventilatory phase of PB divided by its cycle duration) increased from 0.50+/-0.02 to 0.62+/-0.05, 0.76+/-0.06 and 0.68+/-0.08, respectively (p<0.001). Since epoch duration and duty ratio are surrogate measures of LG, we conclude that CPAP ameliorates the effects of recurrent central apneas, and perhaps mixed and obstructive apneas, by decreasing LG via increases in lung volume.
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98
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Atalaia A, De Carvalho M, Evangelista T, Pinto A. Sleep characteristics of amyotrophic lateral sclerosis in patients with preserved diaphragmatic function. ACTA ACUST UNITED AC 2009; 8:101-5. [PMID: 17453638 DOI: 10.1080/17482960601029883] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
There are a number of sleep studies in amyotrophic lateral sclerosis (ALS), in general including a heterogeneous population of patients. We aimed to study sleep in a population of selected ALS patients by investigating nocturnal polysomnography (PSG) characteristics in ALS patients with normal respiratory function tests and preserved diaphragmatic innervation. Ninety-two ALS patients were screened by percutaneous nocturnal oximetry (PNO). Eleven ALS patients with normal respiratory function tests, phrenic motor responses and preserved motor units on needle electromyography of the diaphragm, but abnormal PNO, were selected for PSG. REM was present in eight patients, but normal in only three. Three patients had mixed apnoea-hypopnoea, severe in one. Seven showed a pattern of periodic mild O(2) desaturation, which occurred in REM 3, REM and NREM 3 and in NREM sleep 1. One patient studied six months later had more severe changes in the second evaluation. In conclusion, the most common sleep disordered breathing was periodic mild O(2) desaturation independent of the sleep stage (REM, NREM). This might represent central drive dysfunction or respiratory muscle fatigue in ALS.
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Affiliation(s)
- António Atalaia
- Laboratory of Clinical Neurophysiology, British Hospital--Lisbon XXI, Lisbon. Portugal.
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Thomas RJ, Weiss MD, Mietus JE, Peng CK, Goldberger AL, Gottlieb DJ. Prevalent hypertension and stroke in the Sleep Heart Health Study: association with an ECG-derived spectrographic marker of cardiopulmonary coupling. Sleep 2009; 32:897-904. [PMID: 19639752 PMCID: PMC2706909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023] Open
Abstract
STUDY OBJECTIVES The electrocardiogram (ECG)-based sleep spectrogram generates a map of cardiopulmonary coupling based on heart rate variability and respiration derived from QRS amplitude variations. A distinct spectrographic phenotype, designated as narrow-band elevated low frequency coupling (e-LFC(NB)), has been associated with central apneas and periodic breathing and predicts sleep laboratory failure of continuous positive airway pressure therapy. This study assesses, at a population level, the associations of this spectrographic biomarker with prevalent cardiovascular disease using the Sleep Heart Health Study (SHHS)-I dataset. DESIGN Retrospective analysis of the Sleep Heart Health Study-I dataset. SETTING Laboratory for complex physiologic signals analysis. MEASUREMENTS AND RESULTS The fully-automated ECG-derived sleep spectrogram technique was applied to 5247 (of the original 6441) polysomnograms from the SHHS-I. Associations were estimated with use of various drugs and pathologies including prevalent hypertension and cardiovascular and cerebrovascular disease. Increasing with age and more common in males, e-LFC(NB) is also associated with greater severity of sleep apnea and fragmented sleep. After adjustment for potential confounders, an independent association with prevalent hypertension and stroke was found. CONCLUSIONS An ECG-derived spectrographic marker related to low frequency cardiopulmonary coupling is associated with greater sleep apnea severity. Whether this biomarker is solely a sign of more severe disease or whether it reflects primary alterations in sleep apnea pathophysiology (which may either cause or result from sleep apnea) is unknown. This ECG-based spectral marker is associated with a higher prevalence of hypertension and stroke.
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Affiliation(s)
- Robert Joseph Thomas
- Division of Pulmonary, Critical Care and Sleep Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
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Cummings KJ, Frappell PB. Breath-to-breath hypercapnic response in neonatal rats: temperature dependency of the chemoreflexes and potential implications for breathing stability. Am J Physiol Regul Integr Comp Physiol 2009; 297:R124-34. [PMID: 19420287 DOI: 10.1152/ajpregu.91011.2008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The breathing of newborns is destabilized by warm temperatures. We hypothesized that in unanesthetized, intact newborn rats, body temperature (T(B)) influences the peripheral chemoreflex response (PCR response) to hypercapnia. To test this, we delivered square-wave challenges of 8% CO(2) in air to postnatal day 4-5 (P4-P5) rats held at a T(B) of 30 degrees C (Cold group, n = 11), 33 degrees C (Cool group, n = 10), and 35 degrees C thermoneutral zone group [thermoneutral zone (TNZ) group, n = 11], while measuring ventilation (Ve) directly with a pneumotach and mask. Cool animals were challenged with 8% CO(2) balanced in either air or hyperoxia (n = 10) to identify the PCR response. Breath-to-breath analysis was performed on 30 room air breaths and every breath of the 1-min CO(2) challenge. As expected, warmer T(B) was associated with an unstable breathing pattern in room air: TNZ animals had a coefficient of variation in Ve (Ve CV%) that was double that of animals held at cooler T(B) (P < 0.001). Hyperoxia markedly suppressed the hypercapnic ventilatory response over the first 10 breaths (or approximately 4 s), suggesting that this domain is dominated by the PCR response. The PCR response (P = 0.03) and total response (P = 0.04) were significantly greater in TNZ animals compared with hypothermic animals. The total response had a significant, negative relationship with Vco(2) (R(2) = 0.53; P < 0.001). Breathing stability was positively related to the total response (R(2) = 0.36; P < 0.001) and to a lesser extent, the PCR response (R(2) = 0.19; P = 0.01) and was negatively related to Vco(2) (R(2) = 0.34; P < 0.001). ANCOVA confirmed a significant effect of T(B) alone on breathing stability (P < 0.01), with no independent effects of Vco(2) (P = 0.41), the PCR response (P = 0.82), or the total Ve response (P = 0.08). Our data suggest that in early postnatal life, the chemoreflex responses to CO(2) are highly influenced by T(B), and while related to breathing stability, are not predictors of stability after accounting for the independent effect of T(B).
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Affiliation(s)
- Kevin J Cummings
- Department of Zoology, La Trobe University, Melbourne, Victoria, Australia.
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