ORCID Profile
0000-0001-8561-9766
Current Organisation
University of Melbourne
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Biological Psychology (Neuropsychology, Psychopharmacology, Physiological Psychology) | Psychology | Motor Control | Physiology not elsewhere classified | Systems Physiology | Respiratory Diseases | Cardiorespiratory Medicine and Haematology | Cardiology (incl. Cardiovascular Diseases)
Respiratory System and Diseases (incl. Asthma) | Expanding Knowledge in Psychology and Cognitive Sciences | Expanding Knowledge in the Medical and Health Sciences | Cardiovascular System and Diseases |
Publisher: Oxford University Press (OUP)
Date: 04-2021
Abstract: Genioglossus (GG) after-discharge is thought to protect against pharyngeal collapse by minimizing periods of low upper airway muscle activity. How GG after-discharge occurs and which single motor units (SMUs) are responsible for the phenomenon are unknown. The aim of this study was to investigate genioglossal after-discharge. During wakefulness, after-discharge was elicited 8–12 times in healthy in iduals with brief isocapnic hypoxia (45–60 s of 10% O2 in N2) terminated by a single breath of 100% O2. GG SMUs were designated as firing solely, or at increased rate, during inspiration (Inspiratory phasic [IP] and inspiratory tonic [IT], respectively) solely, or at increased rate, during expiration (Expiratory phasic [EP] or expiratory tonic [ET], respectively) or firing constantly without respiratory modulation (Tonic). SMUs were quantified at baseline, the end of hypoxia, the hyperoxic breath, and the following eight normoxic breaths. A total of 210 SMUs were identified in 17 participants. GG muscle activity was elevated above baseline for seven breaths after hyperoxia (p & 0.001), indicating a strong after-discharge effect. After-discharge occurred due to persistent firing of IP and IT units that were recruited during hypoxia, with minimal changes in ET, EP, or Tonic SMUs. The firing frequency of units that were already active changed minimally during hypoxia or the afterdischarge period (p & 0.05). That genioglossal after-discharge is almost entirely due to persistent firing of previously silent inspiratory SMUs provides insight into the mechanisms responsible for the phenomenon and supports the hypothesis that the inspiratory and expiratory/tonic motor units within the muscle have idiosyncratic functions.
Publisher: Elsevier BV
Date: 10-2021
Publisher: American Thoracic Society
Date: 02-2012
Publisher: Oxford University Press (OUP)
Date: 03-2014
DOI: 10.5665/SLEEP.3498
Publisher: BMJ
Date: 06-2002
Abstract: Intrinsic positive end expiratory pressure (PEEPi) constitutes an inspiratory threshold load on the respiratory muscles, increasing work of breathing. The role of continuous positive airway pressure (CPAP) in alleviating PEEPi in patients with severe stable chronic obstructive pulmonary disease is uncertain. This study examined the effect of CPAP on the inspiratory threshold load, muscle effort, and lung volume in this patient group. Nine patients were studied at baseline and with CPAP increasing in increments of 1 cm H(2)O to a maximum of 10 cm H(2)O. Breathing pattern and minute ventilation (I), dynamic PEEPi, expiratory muscle activity, diaphragmatic (PTPdi/min) and oesophageal (PTPoes/min) pressure-time product per minute, integrated diaphragmatic (EMGdi) and intercostal EMG (EMGic) and end expiratory lung volume (EELV) were measured. Expiratory muscle activity was present at baseline in one subject. In the remaining eight, PEEPi was reduced from a mean (SE) of 2.9 (0.6) cm H(2)O to 0.9 (0.1) cm H(2)O (p<0.05). In two subjects expiratory muscle activity contributed to PEEPi at higher pressures. There were no changes in respiratory pattern but I increased from 9.2 (0.6) l/min to 10.7 (1.1) l/min (p<0.05). EMGdi remained stable while EMGic increased significantly. PTPoes/min decreased, although this did not reach statistical significance. PTPdi/min decreased significantly from 242.1 (32.1) cm H(2)O.s/min to 112.9 (21.7) cm H(2)O.s/min). EELV increased by 1.1 (0.3) l (p<0.01). High levels of CPAP reduce PEEPi and indices of muscle effort in patients with severe stable COPD, but only at the expense of substantial increases in lung volume.
Publisher: Elsevier BV
Date: 11-2017
DOI: 10.1016/J.JPEDS.2017.07.012
Abstract: To determine whether different modes of infant feeding are associated with childhood asthma, including differentiating between direct breastfeeding and expressed breast milk. We studied 3296 children in the Canadian Healthy Infant Longitudinal Development birth cohort. The primary exposure was infant feeding mode at 3 months, reported by mothers and categorized as direct breastfeeding only, breastfeeding with some expressed breast milk, breast milk and formula, or formula only. The primary outcome was asthma at 3 years of age, diagnosed by trained healthcare professionals. At 3 months of age, the distribution of feeding modes was 27% direct breastfeeding, 32% breastfeeding with some expressed breast milk, 26% breast milk and formula, and 15% formula only. At 3 years of age, 12% of children were diagnosed with possible or probable asthma. Compared with direct breastfeeding, any other mode of infant feeding was associated with an increased risk of asthma. These associations persisted after adjusting for maternal asthma, ethnicity, method of birth, infant sex, gestational age, and daycare attendance (some expressed breast milk: aOR, 1.64, 95% CI, 1.12-2.39 breast milk and formula, aOR, 1.73, 95% CI, 1.17-2.57 formula only: aOR, 2.14, 95% CI, 1.37-3.35). Results were similar after further adjustment for total breastfeeding duration and respiratory infections. Modes of infant feeding are associated with asthma development. Direct breastfeeding is most protective compared with formula feeding indirect breast milk confers intermediate protection. Policies that facilitate and promote direct breastfeeding could have impact on the primary prevention of asthma.
Publisher: American Physiological Society
Date: 07-2000
DOI: 10.1152/JAPPL.2000.89.1.47
Abstract: The sensation of increased respiratory resistance or effort is likely to be important for the initiation of alerting or arousal responses, particularly in sleep. Hypoxia, through its central nervous system-depressant effects, may decrease the perceived magnitude of respiratory loads. To examine this, we measured the effect of isocapnic hypoxia on the ability of 10 normal, awake males (mean age = 24.0 ± 1.8 yr) to magnitude-scale five externally applied inspiratory resistive loads (mean values from 7.5 to 54.4 cmH 2 O · l −1 · s). Each subject scaled the loads during 37 min of isocapnic hypoxia (inspired O 2 fraction = 0.09, arterial O 2 saturation of ∼80%) and during 37 min of normoxia, using the method of open magnitude numerical scaling. Results were normalized by modulus equalization to allow between-subject comparisons. With the use of peak inspiratory pressure (PIP) as the measure of load stimulus magnitude, the perception of load magnitude (Ψ) increased linearly with load and, averaged for all loaded breaths, was significantly lower during hypoxia than during normoxia (20.1 ± 0.9 and 23.9 ± 1.3 arbitrary units, respectively P = 0.048). Ψ declined with time during hypoxia ( P = 0.007) but not during normoxia ( P= 0.361). Our result is remarkable because PIP was higher at all times during hypoxia than during normoxia, and previous studies have shown that an elevation in PIP results in increased Ψ. We conclude that sustained isocapnic hypoxia causes a progressive suppression of the perception of the magnitude of inspiratory resistive loads in normal subjects and could, therefore, impair alerting or arousal responses to respiratory loading.
Publisher: Springer Science and Business Media LLC
Date: 07-2014
DOI: 10.1111/SBR.12084
Publisher: Oxford University Press (OUP)
Date: 03-2010
Publisher: Elsevier BV
Date: 10-2003
Abstract: Sleep apnea syndromes are a common cause of sleepiness and neurocognitive impairment and have been implicated as an independent risk factor for cardiovascular disease. While both epidemiological and sleep clinic-based studies indicate that sleep apnea syndromes are more common in men than in women, the gender difference in prevalence is more marked within the sleep clinic. Reasons for the relative failure of women to attend sleep clinics and the pathophysiologic differences that give rise to the male predominance of sleep apnea syndromes are unknown. The purpose of this review was to examine the literature with regard to these aspects, to provide clinical guidance to improve the reduced attendance of women to sleep laboratories and to stimulate research interest into the causes of these differences.
Publisher: Aerospace Medical Association
Date: 2022
Abstract: OBJECTIVES: Airline cabin crew experience high levels of fatigue and sleepiness. Whether these are solely related to their work schedules/jetlag or are in part related to in idual factors is unknown. The COVID-19 pandemic has significantly disrupted the aviation industry and many cabin crew have been grounded. This provides a unique opportunity to assess the causes of fatigue and sleepiness in this population. METHODS: An online anonymous survey was distributed in April–June 2020 to cabin crew who were 1) flying, 2) grounded but doing alternative work, and 3) grounded, not working, or unemployed. The survey measured fatigue, sleepiness, and mental health. It also screened their risk for insomnia, depression, and shift work disorder and assessed drug and caffeine use. RESULTS: Collected were 409 valid responses: 45 currently flying 35 grounded but doing alternate work and 329 not working. On average, all three groups experienced normal levels of fatigue and sleepiness. The risk for major depressive disorder was 27.4%, with 59.5% of in iduals reporting abnormal levels of anxiety. Caffeine intake and the use of drugs and alcohol to facilitate sleep were common, although not different between those currently flying vs. grounded. CONCLUSIONS: With reduced workloads or not flying, cabin crew reported lowered fatigue and sleepiness compared to prepandemic findings, along with reduced risk for major depressive disorder. However, a high occurrence of negative emotional states were reported, potentially related to the uncertainty surrounding the pandemic. This study suggests fatigue and sleepiness is primarily related to airline operational rather than personal variables. Wen CC-Y, Nicholas CL, Howard ME, Trinder J, Jordan AS. Understanding sleepiness and fatigue in cabin crew using COVID-19 to dissociate causative factors . Aerosp Med Hum Perform. 2022 93(1):50–53.
Publisher: American Physiological Society
Date: 03-2007
DOI: 10.1152/AJPREGU.00642.2006
Abstract: Our aim was to evaluate cardiac changes evoked by spontaneous and sound-induced arousals from sleep. Cardiac responses to spontaneous and auditory-induced arousals were recorded during overnight sleep studies in 28 young healthy subjects (14 males, 14 females) during non-rapid eye movement sleep. Computerized analysis was applied to assess beat-to-beat changes in heart rate, atrio-ventricular conductance, and ventricular repolarization from 30 s before to 60 s after the auditory tone. During both types of arousals, the most consistent change was the increase in the heart rate (in 62% of spontaneous and in 89% of sound-induced arousals). This was accompanied by an increase or no change in PR interval and by a decrease or no change in QT interval. The magnitude of all cardiac changes was significantly higher for tone-induced vs. spontaneous arousals (mean ± SD for heart rate: +9 ± 8 vs. +13 ± 9 beats per min for PR prolongation: 14 ± 16 vs. 24 ± 22 ms for QT shortening: −12 ± 6 vs. −20 ± 9 ms). The prevalence of transient tachycardia and PR prolongation was also significantly higher for tone-induced vs. spontaneous arousals (tachycardia: 85% vs. 57% of arousals, P 0.001 PR prolongation: 51% vs. 25% of arousals, P 0.001). All cardiac responses were short-lasting (10–15 s). We conclude that cardiac pacemaker region, conducting system, and ventricular myocardium may be under independent neural control. Prolongation of atrio-ventricular delay may serve to increase ventricular filling during arousal from sleep. Whether prolonged atrio-ventricular conductance associated with increased sympathetic outflow to the ventricular myocardium contributes to arrhythmogenesis during sudden arousal from sleep remains to be evaluated.
Publisher: Elsevier BV
Date: 12-2022
DOI: 10.1016/J.BRAT.2022.104222
Abstract: Sleep has been found to play a key role in fear conditioning, extinction learning and extinction recall, and sleep disturbances are linked to many mental disorders including post-traumatic stress disorder (PTSD). Previous studies examining associations between sleep and fear or extinction processes primarily focused on objectively measured sleep architecture. Little research has so far focused on subjective sleep measures and particularly in clinical populations, which often experience subjectively poor sleep, including PTSD. Here we investigated whether subjective sleep disturbance, sleep onset latency, wake after sleep onset or sleep efficiency were related to fear conditioning, extinction learning or extinction recall in a large s le of in iduals with a range of PTSD symptom severity (n = 248). Overall, we did not find that subjective sleep was associated with fear conditioning or extinction processes. However, exploratory analyses examining the moderating effect of sex found that shorter sleep onset latency and greater sleep efficiency were associated with improved extinction recall in women with higher PTSD symptom severity. This suggests that less time falling asleep and longer time asleep while in bed may be protective in highly symptomatic women against the commonly observed impaired extinction recall in PTSD. More studies are needed to explore sex-specific effects further.
Publisher: American Physiological Society
Date: 12-2010
DOI: 10.1152/JAPPLPHYSIOL.00812.2010
Abstract: Single motor unit (SMU) analysis provides a means to examine the motor control of a muscle. SMUs in the genioglossus show considerable complexity, with several different firing patterns. Two of the primary stimuli that contribute to genioglossal activation are carbon dioxide (CO 2 ) and negative pressure, which act through chemoreceptor and mechanoreceptor activation, respectively. We sought to determine how these stimuli affect the behavior of genioglossus SMUs. We quantified genioglossus SMU discharge activity during periods of quiet breathing, elevated CO 2 (facilitation), and continuous positive airway pressure (CPAP) administration (inhibition). CPAP was applied in 2-cmH 2 O increments until 10 cmH 2 O during hypercapnia. Five hundred ninety-one periods (each ∼3 breaths) of genioglossus SMU data were recorded using wire electrodes( n = 96 units) from 15 awake, supine subjects. Overall hypercapnic stimulation increased the discharge rate of genioglossus units (20.9 ± 1.0 vs. 22.7 ± 0.9 Hz). Inspiratory units were activated ∼13% earlier in the inspiratory cycle, and the units fired for a longer duration (80.6 ± 5.1 vs. 105.3 ± 4.2% inspiratory time P 0.05). Compared with baseline, an additional 32% of distinguishable SMUs within the selective electrode recording area were recruited with hypercapnia. CPAP led to progressive SMU inhibition at ∼6 cmH 2 O, there were similar numbers of SMUs active compared with baseline, with peak frequencies of inspiratory units close to baseline, despite elevated CO 2 levels. At 10 cmH 2 O, the number of units was 36% less than baseline. Genioglossus inspiratory phasic SMUs respond to hypercapnic stimulation with changes in recruitment and rate coding. The SMUs respond to CPAP with derecruitment as a homogeneous population, and inspiratory phasic units show slower discharge rates. Understanding upper airway muscle recruitment/derecruitment may yield therapeutic targets for maintenance of pharyngeal patency.
Publisher: Oxford University Press (OUP)
Date: 06-2013
DOI: 10.5665/SLEEP.2698
Publisher: Elsevier BV
Date: 02-2007
Publisher: Oxford University Press (OUP)
Date: 06-2015
DOI: 10.5665/SLEEP.4750
Publisher: Elsevier BV
Date: 2008
Publisher: American Physiological Society
Date: 2002
DOI: 10.1152/JAPPLPHYSIOL.00461.2001
Abstract: 10.1152/japplphysiol.00461.2001.—Obstructive sleep apnea (OSA) is more common in men than in women for reasons that are not clearly understood. An underlying difference between men and women in the respiratory-related neural control of upper airway dilator muscles has been suggested as a possible reason for the gender difference. We have compared three aspects of upper airway dilator muscle function in healthy men and women: 1) resting inspiratory genioglossus electromyogram (EMGgg) activity, 2) the respiratory EMGgg “afterdischarge” after a brief hypoxic stimulus, and 3) the relationship between the EMGgg and pharyngeal airway pressure. Inspired minute ventilation (V˙i), epiglottic pressure (P epi ), and EMGgg and diaphragm EMG (EMGdi) activity were measured in 24 subjects (12 men, 12 women in the luteal menstrual phase) and were compared between genders while lying supine awake. Every 7–8 min over 2 h, subjects were exposed to 45-s periods of isocapnic hypoxia (9% O 2 in N 2 ) that were abruptly terminated with one breath of 100% O 2 . The relationship between P epi and EMGgg activity was also compared between genders. The results of 117 trials with satisfactory end-tidal Pco 2 control and no sighs or swallows are reported. There was no gender difference in the resting level of peak inspiratory EMGgg [3.7 ± 0.8 (women) vs. 3.2 ± 0.6% maximal activity (men)]. Repeated-measures ANOVA showed no gender or gender-by-time interaction effect between men and women inV˙i or EMGgg or EMGdi activity during or after the hypoxic stimulus. The relationship between P epi and EMGgg was not different between men (slope −0.63 ± 0.20) and women (slope −0.69 ± 0.33). These results do not support the hypothesis that the higher prevalence of OSA in men is related to an underlying gender difference in respiratory neural control of upper airway dilator muscles.
Publisher: Informa UK Limited
Date: 06-2018
DOI: 10.2147/NSS.S143296
Publisher: American Thoracic Society
Date: 12-2004
Publisher: American Thoracic Society
Date: 05-2011
Publisher: American Thoracic Society
Date: 07-2005
Publisher: Informa UK Limited
Date: 06-2020
DOI: 10.2147/NSS.S254473
Publisher: American Thoracic Society
Date: 15-10-2014
Publisher: BMJ
Date: 10-2007
Publisher: Oxford University Press (OUP)
Date: 12-2016
DOI: 10.5665/SLEEP.6304
Publisher: American Physiological Society
Date: 06-2011
DOI: 10.1152/JAPPLPHYSIOL.00972.2010
Abstract: There is not a clinically available technique for measuring the physiological traits causing obstructive sleep apnea (OSA). Therefore, it is often difficult to determine why an in idual has OSA or to what extent the various traits contribute to the development of OSA. In this study, we present a noninvasive method for measuring four important physiological traits causing OSA: 1) pharyngeal anatomy/collapsibility, 2) ventilatory control system gain (loop gain), 3) the ability of the upper airway to dilate/stiffen in response to an increase in ventilatory drive, and 4) arousal threshold. These variables are measured using a single maneuver in which continuous positive airway pressure (CPAP) is dropped from an optimum to various suboptimum pressures for 3- to 5-min intervals during sleep. Each in idual's set of traits is entered into a physiological model of OSA that graphically illustrates the relative importance of each trait in that in idual. Results from 14 subjects (10 with OSA) are described. Repeatability measurements from separate nights are also presented for four subjects. The measurements and model illustrate the multifactorial nature of OSA pathogenesis and how, in some in iduals, small adjustments of one or another trait (which might be achievable with non-CPAP agents) could potentially treat OSA. This technique could conceivably be used clinically to define a patient's physiology and guide therapy based on the traits.
Publisher: Oxford University Press (OUP)
Date: 04-2006
Publisher: MDPI AG
Date: 02-2023
Abstract: Airline cabin crew operate in dynamic work environments that are continuously changing, from unpredictable shift work hours to travelling through multiple time zones. These likely impact cabin crews’ overall health and may affect their performance on safety-related tasks. Research on this population has been limited therefore, the aim was to summarise the relevant literature regarding fatigue, sleepiness and mental health of cabin crew. This review followed the PRISMA-ScR guidelines and conducted a systematic search utilising five databases. The initial search identified 1223 studies, and through vigorous screening processes, 27 studies were selected for this review. Over half of the selected studies focused on international or long-haul flights, and a large proportion of the s le participants were women. Findings suggested a high prevalence of fatigue and sleepiness as well as unsatisfactory sleep quality with elevated susceptibility to sleep disorders. Factors identified with health outcomes were associated with flight operations (e.g., rosters) and in idual differences (e.g., age and coping strategies). Regarding mental health, cabin crews are potentially at a greater risk for depression and anxiety compared to the general public. This review draws attention to the importance of using a standardised approach, such as validated measures for fair and consistent inferences.
Publisher: Oxford University Press (OUP)
Date: 28-07-2023
Abstract: Transient arousal from sleep has been shown to elicit a prolonged increase in genioglossus muscle activity that persists following the return to sleep and which may protect against subsequent airway collapse. We hypothesized that this increased genioglossal activity following return to sleep after an arousal is due to persistent firing of inspiratory-modulated motor units (MUs) that are recruited during the arousal. Thirty-four healthy participants were studied overnight while wearing a nasal mask with pneumotachograph to measure ventilation and with 4 intramuscular genioglossus EMG electrodes. During stable N2 and N3 sleep, auditory tones were played to induce brief (3-15s) AASM arousals. Ventilation and genioglossus MUs were quantified before the tone, during the arousal and for 10 breaths after the return to sleep. A total of 1089 auditory tones were played and gave rise to 239 MUs recorded across arousal and the return to sleep in 20 participants (aged 23 ± 4.2 years and BMI 22.5 ± 2.2 kg/m2). Ventilation was elevated above baseline during arousal and the first post-arousal breath (p & .001). Genioglossal activity was elevated for five breaths following the return to sleep, due to increased firing rate and recruitment of inspiratory modulated MUs, as well as a small increase in tonic MU firing frequency. The sustained increase in genioglossal activity that occurs on return to sleep after arousal is primarily a result of persistent activity of inspiratory-modulated MUs, with a slight contribution from tonic units. Harnessing genioglossal activation following arousal may potentially be useful for preventing obstructive respiratory events.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2007
DOI: 10.1097/01.ANES.0000281928.88997.95
Abstract: It is standard practice to administer a cholinesterase inhibitor (e.g., neostigmine) at the end of a surgical case to reverse suspected effects of neuromuscular blocking agents regardless of whether such residual effects are present. The authors hypothesized that cholinesterase inhibition when given the in absence of neuromuscular blockade (NB) would decrease upper airway dilatory muscle activity and consequently upper airway volume. The authors measured genioglossus and diaphragm electromyograms during spontaneous ventilation in anesthetized, tracheostomized rats before and after administration of neostigmine (0.03, 0.06, or 0.12 mg/kg), after recovery of the train-of-four ratio (quadriceps femoris muscle) to unity after NB (n = 18). For comparison, the authors made the same measurements in rats that had no previous NB (n = 27). In intact anesthetized rats, the authors measured upper airway volume and end-expiratory lung volume by magnetic resonance imaging before and after 0.12 mg/kg neostigmine (n = 9). Neostigmine treatment in rats that had fully recovered from NB based on the train-of-four ratio caused dose-dependent decreases in genioglossus electromyogram (to 70.3 +/- 7.6, 49.2 +/- 3.2, and 39.7 +/- 2.3% of control, respectively), decreases in diaphragm electromyogram (to 103.1 +/- 6.5, 83.1 +/- 4.7, and 68.7 +/- 7.3% of control), and decreases in minute ventilation to a nadir value of 79.6 +/- 6% of preneostigmine baseline. Genioglossus electromyogram effects were the same when neostigmine was given with no previous NB. Neostigmine caused a decrease in upper airway volume to 83 +/- 3% of control, whereas end-expiratory lung volume remained constant. The cholinesterase inhibitor neostigmine markedly impairs upper airway dilator volume, genioglossus muscle function, diaphragmatic function, and breathing when given after recovery from vecuronium-induced neuromuscular block.
Publisher: Elsevier BV
Date: 06-2007
Publisher: American Physiological Society
Date: 06-2015
Abstract: Muscle fibers of the genioglossus (GG) form the bulk of the muscle mass at the base of the tongue. The motor control of the tongue is critical for vocalization, feeding, and breathing. Our goal was to assess the patterns of motor innervation of GG single motor units (SMUs) in humans. Simultaneous monopolar recordings were obtained from four sites in the base of the tongue bilaterally at two antero-posterior levels from 16 resting, awake, healthy adult males, who wore a face mask with airway pressure and airflow sensors. We analyzed 69 data segments in which at least one lead contained large action potentials generated by an SMU. Such potentials served as triggers for spike-triggered averaging (STA) of signals recorded from the other three sites. Spontaneous activity of the SMUs was classified as inspiratory modulated, expiratory modulated, or tonic. Consistent with the antero-posterior orientation of GG fibers, 44 STAs (77%) recorded ipsilateral to the trigger yielded sharp action potentials with a median litude of 52 μV [interquartile range (IQR): 25–190] that were time shifted relative to the trigger by about 1 ms. Notably, 48% of recordings on the side opposite to the trigger also yielded sharp action potentials. Of those, 17 (29%) had a median litude of 63 μV (IQR: 39–96), and most were generated by tonic SMUs. Thus a considerable proportion of GG muscle fibers receive a crossed motor innervation. Crossed innervation may help ensure symmetry and stability of tongue position and movements under normal conditions and following injury or degenerative changes affecting the tongue.
Publisher: Oxford University Press (OUP)
Date: 22-08-2018
DOI: 10.1093/SLEEP/ZSY160
Publisher: Springer Science and Business Media LLC
Date: 26-10-2011
DOI: 10.1007/S00424-011-1041-3
Abstract: Normal sleep has a profound effect on the cardiovascular system, reducing cardiovascular activity throughout non-rapid eye movement sleep changes that are modified and augmented by circadian system influence. There is also evidence that sleep-initiated changes in autonomic balance may in turn modify the development of sleep within a night, particularly the development of slow wave sleep. It is assumed that the cardiovascular changes that accompany sleep reflect a functional aspect of sleep, although the precise functional role has not been agreed upon. Nevertheless, there is good evidence that the cardiovascular changes that occur during normal sleep are beneficial for the cardiovascular system. Arousals from sleep, which are common even in normal sleep, are associated with a surge in activity in cardiorespiratory systems, with marked effects on the sleep-related pattern of cardiovascular activity when they occur frequently. Despite the importance of this aspect of sleep, controversy remains as to both the nature of the activation response and the circumstances under which it is elicited. The concept that sleep-related changes in cardiovascular activity are beneficial leads to the corollary that sleep disturbance would result in adverse cardiovascular consequences. While there is strong empirical evidence for such a relationship, it remains unclear whether this is a direct effect or, as has been suggested recently, the effect of disturbed sleep is mediated via stress-related modification of neuroendocrine systems.
Publisher: Informa UK Limited
Date: 19-06-2020
Publisher: American Physiological Society
Date: 2000
DOI: 10.1152/JAPPL.2000.88.1.3
Abstract: The gradual decay in ventilation after removal of a respiratory stimulus has been proposed to protect against cyclic breathing disorders such as obstructive sleep apnea (OSA). The male predominance of OSA, and the increased incidence of OSA in women after menopause, indicates that the respiratory-stimulating effect of progesterone may provide protection against OSA by altering the rate of poststimulus ventilatory decline (PSVD). It was therefore hypothesized that PSVD is longer in premenopausal women than in men and is longer in the luteal menstrual phase compared with the follicular phase. PSVD was measured in 12 men and in 11 women at both their luteal and follicular phases, after cessation of isocapnic hypoxia and normoxic hypercapnia. PSVD was compared between genders and between women in the luteal and follicular phases by repeated-measures ANOVA. There were no significant differences in PSVD between any of the groups after either respiratory stimulus. This suggests that the higher occurrence of OSA in men does not reflect an underlying gender difference in PSVD and implies the increased prevalence of OSA in women after menopause is not representative of an effect of progesterone on PSVD.
Publisher: Elsevier BV
Date: 02-2016
DOI: 10.1016/J.RESP.2016.10.014
Abstract: Respiratory related evoked potentials (RREPs) were used to investigate whether sensory detection of small mid-inspiratory resistive loads (≈1.2-6.2 cmH
Publisher: Wiley
Date: 27-07-2004
Publisher: American Physiological Society
Date: 08-2010
DOI: 10.1152/JAPPLPHYSIOL.00373.2010
Abstract: Increasing either genioglossus muscle activity (GG) or end-expiratory lung volume (EELV) improves airway patency but not sufficiently for adequate treatment of obstructive sleep apnea (OSA) in most patients. The mechanisms by which these variables alter airway collapsibility likely differ, with increased GG causing airway dilation, whereas increased EELV may stiffen the airway walls through caudal traction. We sought to determine whether the airway stabilizing effect of GG activation is enhanced when EELV is increased. To investigate this aim, 15 continuous positive airway pressure (CPAP)-treated OSA patients were instrumented with an epiglottic catheter, intramuscular GG-EMG electrodes, magnetometers, and a nasal mask neumotachograph. Subjects slept supine in a sealed, head-out plastic chamber in which the extra-thoracic pressure could be lowered (to raise EELV) while on nasal CPAP with a variable deadspace to allow CO 2 stimulation (and GG activation). The pharyngeal critical closing pressure (P CRIT ) was measured by sudden reduction of CPAP for three to five breaths each minute during non-rapid eye movement (NREM) sleep in 4 conditions: a) baseline, b) 500 ml increased EELV, c) 50% increased GG, and d) conditions b and c combined. P CRIT was found to be reduced from 2.2 ± 0.7 cmH 2 O at baseline to −1.0 ± 0.5 with increased EELV, 0.6 ± 0.7 with increased GG and −1.6 ± 0.7 when both variables were raised ( P 0.001). The slope of the P CRIT curves remained unchanged in all conditions ( P = 0.05). However, the CPAP level at which flow limitation developed was lower in both increased EELV conditions ( P = 0.001). These findings indicate that while both increased GG and EELV improve airway collapsibility, the combination of both variables has little additional effect over increasing EELV alone.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 05-2008
DOI: 10.1097/ALN.0B013E31816C8A60
Abstract: Anesthesia impairs upper airway integrity, but recent data suggest that low doses of some anesthetics increase upper airway dilator muscle activity, an apparent paradox. The authors sought to understand which anesthetics increase or decrease upper airway dilator muscle activity and to study the mechanisms mediating the effect. The authors recorded genioglossus electromyogram, breathing, arterial blood pressure, and expiratory carbon dioxide in 58 spontaneously breathing rats at an estimated ED50 (median effective dose) of isoflurane or propofol. The authors further evaluated the dose-response relations of isoflurane under different study conditions: (1) normalization of mean arterial pressure, or end-expiratory carbon dioxide (2) bilateral lesion of the Kölliker-Fuse nucleus and (3) vagotomy. To evaluate whether the markedly lower inspiratory genioglossus activity during propofol could be recovered by increasing flow rate, a measure of respiratory drive, the authors performed an additional set of experiments during hypoxia or hypercapnia. In vagally intact rats, tonic and phasic genioglossus activity were markedly higher with isoflurane compared with propofol. Both anesthetics abolished the genioglossus negative pressure reflex. Inspiratory flow rate and anesthetic agent predicted independently phasic genioglossus activity. Isoflurane dose-dependently decreased tonic and increased phasic genioglossus activity, and increased flow rate, and its increasing effects were abolished after vagotomy. Impairment of phasic genioglossus activity during propofol anesthesia was reversed during evoked increase in respiratory drive. Isoflurane compared with propofol anesthesia yields higher tonic and phasic genioglossus muscle activity. The level of respiratory depression rather than the level of effective anesthesia correlates closely with the airway dilator muscle function during anesthesia.
Publisher: American Physiological Society
Date: 02-2010
DOI: 10.1152/JAPPLPHYSIOL.00755.2009
Abstract: Changes in end-expiratory lung volume (EELV) affect upper airway stability. The passive pharyngeal critical pressure (Pcrit), a measure of upper airway collapsibility, is determined using airway pressure drops. The EELV change during these drops has not been quantified and may differ between obese obstructive sleep apnea (OSA) patients and controls. Continuous positive airway pressure (CPAP)-treated OSA patients and controls were instrumented with an epiglottic catheter, magnetometers (to measure change in EELV), and a nasal mask neumotachograph. Subjects slept supine in a head-out plastic chamber in which the extrathoracic pressure could be lowered (to raise EELV) while on nasal CPAP. The magnitude of EELV change during Pcrit measurement (sudden reductions of CPAP for 3–5 breaths each minute) was assessed at baseline and with EELV increased ∼500 ml. Fifteen OSA patients and 7 controls were studied. EELV change during Pcrit measurement was rapid and pressure dependent, but similar in OSA and control subjects (74 ± 36 and 59 ± 24 ml/cmH 2 O respectively, P = 0.33). Increased lung volume (mean +521 ml) decreased Pcrit by a similar amount in OSA and control subjects (−3.1 ± 1.7 vs. −3.9 ± 1.9 cmH 2 O, P = 0.31). Important lung volume changes occur during passive Pcrit measurement. However, on average, there is no difference in lung volume change for a given CPAP change between obese OSA subjects and controls. Changes in lung volume alter Pcrit substantially. This work supports a role for lung volume in the pathogenesis of OSA, and lung volume changes should be a consideration during assessment of pharyngeal mechanics.
Publisher: Elsevier BV
Date: 09-2008
DOI: 10.1093/BJA/AEN176
Publisher: American Physiological Society
Date: 11-2015
Abstract: Common drive is thought to constitute a central mechanism by which the efficiency of a motor neuron pool is increased. This study tested the hypothesis that common drive to the upper airway muscle genioglossus (GG) would increase with increased respiratory drive in response to an inspiratory load. Respiration, GG electromyographic (EMG) activity, single-motor unit activity, and coherence in the 0–5 Hz range between pairs of GG motor units were assessed for the 30 s before an inspiratory load, the first and second 30 s of the load, and the 30 s after the load. Twelve of twenty young, healthy male subjects provided usable data, yielding 77 pairs of motor units: 2 Inspiratory Phasic, 39 Inspiratory Tonic, 15 Expiratory Tonic, and 21 Tonic. Respiratory and GG inspiratory activity significantly increased during the loads and returned to preload levels during the postload periods (all showed significant quadratic functions over load trials, P 0.05). As hypothesized, common drive increased during the load in inspiratory modulated motor units to a greater extent than in expiratory/tonic motor units (significant load × discharge pattern interaction, P 0.05). Furthermore, this effect persisted during the postload period. In conclusion, common drive to inspiratory modulated motor units was elevated in response to increased respiratory drive. The postload elevation in common drive was suggestive of a poststimulus activation effect.
Publisher: Oxford University Press (OUP)
Date: 19-07-2019
DOI: 10.1093/SLEEP/ZSZ141
Abstract: Low lung volumes are thought to contribute to obstructive sleep apnea (OSA). OSA is worse in the supine versus lateral body position, men versus women, obese versus normal-weight (NW) in iduals and REM versus NREM sleep. All of these conditions may be associated with low lung volumes. The aim was to measure FRC during wake, NREM, and REM in NW and overweight (OW) men and women while in the supine and lateral body positions. Eighty-one healthy adults were instrumented for polysomnography, but with nasal pressure replaced with a sealed, non-vented mask connected to an N2 washout system. During wakefulness and sleep, repeated measurements of FRC were made in both supine and right lateral positions. Two hundred eighty-five FRC measures were obtained during sleep in 29 NW (body mass index [BMI] = 22 ± 0.3 kg/m2) and 29 OW (BMI = 29 ± 0.7 kg/m2) in iduals. During wakefulness, FRC differed between BMI groups and positions (supine: OW = 58 ± 3 and NW = 68 ± 3% predicted lateral OW = 71 ± 3, NW = 81 ± 3% predicted). FRC fell from wake to NREM sleep in all participants and in both positions by a similar amount. As a result, during NREM sleep FRC was lower in OW than NW in iduals (supine 46 ± 3 and 56 ± 3% predicted, respectively). FRC during REM was similar to NREM and no sex differences were observed in any position or sleep stage. Reductions in FRC while supine and with increased body weight may contribute to worsened OSA in these conditions, but low lung volumes appear unlikely to explain the worsening of OSA in REM and in men versus women.
Publisher: Oxford University Press (OUP)
Date: 11-2011
DOI: 10.5665/SLEEP.1380
Publisher: Oxford University Press (OUP)
Date: 08-04-2020
Abstract: Quantification of upper airway collapsibility in obstructive sleep apnea (OSA) could help inform targeted therapy decisions. However, current techniques are clinically impractical. The primary aim of this study was to assess if a simple, novel technique could be implemented as part of a continuous positive airway pressure (CPAP) titration study to assess pharyngeal collapsibility. A total of 35 participants (15 female) with OSA (mean ± SD apnea–hypopnea index = 35 ± 19 events/h) were studied. Participants first completed a simple clinical intervention during a routine CPAP titration, where CPAP was transiently turned off from the therapeutic pressure for ≤5 breaths/efforts on ≥5 occasions during stable non-rapid eye movement (non-REM) sleep for quantitative assessment of airflow responses (%peak inspiratory flow [PIF] from preceding 5 breaths). Participants then underwent an overnight physiology study to determine the pharyngeal critical closing pressure (Pcrit) and repeat transient drops to zero CPAP to assess airflow response reproducibility. Mean PIF of breaths 3–5 during zero CPAP on the simple clinical intervention versus the physiology night were similar (34 ± 29% vs. 28 ± 30% on therapeutic CPAP, p = 0.2 range 0%–90% vs. 0%–95%). Pcrit was −1.0 ± 2.5 cmH2O (range −6 to 5 cmH2O). Mean PIF during zero CPAP on the simple clinical intervention and the physiology night correlated with Pcrit (r = −0.7 and −0.9, respectively, p & 0.0001). Receiver operating characteristic curve analysis indicated significant diagnostic utility for the simple intervention to predict Pcrit & −2 and & 0 cmH2O (AUC = 0.81 and 0.92), respectively. A simple CPAP intervention can successfully discriminate between patients with and without mild to moderately collapsible pharyngeal airways. This scalable approach may help select in iduals most likely to respond to non-CPAP therapies.
Publisher: Oxford University Press (OUP)
Date: 08-2011
DOI: 10.5665/SLEEP.1144
Publisher: Elsevier BV
Date: 04-2009
Publisher: Oxford University Press (OUP)
Date: 11-2010
Publisher: Springer Science and Business Media LLC
Date: 13-02-2019
DOI: 10.1038/S41393-019-0256-6
Abstract: Prospective, double-blind, randomised, placebo-controlled, cross-over trial of nasal decongestion in tetraplegia. Tetraplegia is complicated by severe, predominantly obstructive, sleep apnoea. First-line therapy for obstructive sleep apnoea is nasal continuous positive airway pressure, but this is poorly tolerated. High nasal resistance associated with unopposed parasympathetic activation of the upper airway contributes to poor adherence. This preliminary study tested whether reducing nasal decongestion improved sleep. Participants' homes in Melbourne and Sydney, Australia. Two sleep studies were performed in participants' homes separated by 1 week. Participants were given a nasal spray (0.5 mL of 5% phenylephrine or placebo) in random order and posterior nasal resistance measured immediately. Outcomes included sleep apnoea severity, perceived nasal congestion, sleep quality and oxygenation during sleep. Twelve middle-aged (average (SD) 52 (12) years) overweight (body mass index 25.3 (6.7) kg/m These preliminary data found that phenylephrine acutely reduced nasal resistance but did not significantly change sleep-disordered breathing severity.
Publisher: Elsevier BV
Date: 04-2022
DOI: 10.1016/J.BBR.2022.113802
Abstract: Disrupted sleep through sleep deprivation or sleep fragmentation has previously been shown to impair cognitive processing. Nevertheless, limited studies have examined the impact of disrupted sleep on the processing of emotional information. The current study aimed to use an experimental approach to generate sleep disruption and examine whether SD and SF in otherwise healthy in iduals would impair emotional facial processing. Thirty-five healthy in iduals participated in three-day/two-night laboratory study which consisted of two consecutive overnight polysomnograms and cognitive testing during the day. The first night was an adaptation night of normal sleep while the second was an experimental night where participants underwent either a night of 1) normal sleep, 2) no sleep (SD) or 3) fragmented sleep (SF). The emotional Go/No-Go task was completed in the morning following each night. Data from 33 participants (14 females, mean age = 24.6 years) were included in the final analysis. Following a night of SD or SF, participants performed significantly poorer with emotional (fearful and happy) targets, while no significant changes occurred after a night of normal sleep. Further, sleep deprived in iduals experienced additional impairments with notably poorer performance with neutral targets and slower reaction time for all targets, suggesting an overall slowing of cognitive processing speed. These findings suggest that facial recognition in socio-emotional contexts may be impaired in in iduals who experience disrupted sleep.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2009
DOI: 10.1097/ALN.0B013E3181A16337
Abstract: Anesthetics depress both ventilatory and upper airway dilator muscle activity and thus put the upper airway at risk for collapse. However, these effects are agent-dependent and may involve upper airway and diaphragm muscles to varying degrees. The authors assessed the effects of pentobarbital on upper airway dilator and respiratory pump muscle function in rats and compared these results with the effects of normal sleep. Tracheostomized rats were given increasing doses of pentobarbital to produce deep sedation then light and deep anesthesia, and negative pressure airway stimuli were applied (n = 11). To compare the effects of pentobarbital with those of natural sleep, the authors chronically instrumented rats (n = 10) with genioglossus and neck electromyogram and electroencephalogram electrodes and compared genioglossus activity during wakefulness, sleep (rapid eye movement and non-rapid eye movement), and pentobarbital anesthesia. Pentobarbital caused a dose-dependent decrease in ventilation and in phasic diaphragmatic electromyogram by 11 +/- 0.1%, but it increased phasic genioglossus electromyogram by 23 +/- 0.2%. Natural non-rapid eye movement sleep and pentobarbital anesthesia (10 mg/kg intraperitoneally) decreased respiratory genioglossus electromyogram by 61 +/- 29% and 45 +/- 35%, respectively, and natural rapid eye movement sleep caused the greatest decrease in phasic genioglossus electromyogram (95 +/- 0.3%). Pentobarbital in rats impairs respiratory genioglossus activity compared to the awake state, but the decrease is no greater than seen during natural sleep. During anesthesia, in the absence of pharyngeal airflow, phasic genioglossus activity is increased in a dose-dependent fashion.
Publisher: Elsevier BV
Date: 03-2021
Publisher: American Thoracic Society
Date: 15-01-2022
Publisher: Georg Thieme Verlag KG
Date: 10-2010
Publisher: Oxford University Press (OUP)
Date: 03-2016
DOI: 10.5665/SLEEP.5516
Publisher: Oxford University Press (OUP)
Date: 05-2012
DOI: 10.5665/SLEEP.1834
Publisher: American Physiological Society
Date: 12-2002
DOI: 10.1152/JAPPLPHYSIOL.00135.2002
Abstract: Obstructive sleep apnea (OSA) is more common in men than in women for reasons that are unclear. The stability of the respiratory controller has been proposed to be important in OSA pathogenesis and may be involved in the gender difference in prevalence. Repetitive hypoxia elicits a progressive rise in ventilation in animals [long-term facilitation (LTF)]. There is uncertainty whether LTF occurs in humans, but if present it may stabilize respiration and possibly also the upper airway. This study was conducted to determine 1) whether LTF exists during wakefulness in healthy human subjects and, if so, whether it is more pronounced in women than men and 2) whether inspiratory pump and upper airway dilator muscle activities are affected differently by repetitive hypoxia. Twelve healthy young men and ten women in the luteal menstrual phase were fitted with a nasal mask and intramuscular genioglossal EMG (EMGgg) recording electrodes. After 5 min of rest, subjects were exposed to ten 2-min isocapnic hypoxic periods (∼9% O 2 in N 2 , arterial O 2 saturation ∼80%) separated by 2 min of room air. Inspired minute ventilation (V˙i) and peak inspiratory EMGgg activity were averaged over 30-s intervals, and respiratory data were compared between genders during and after repetitive hypoxia by using ANOVA for repeated measures. V˙i during recovery from repetitive hypoxia was not different from the resting level and not different between genders. There was no facilitation of EMGgg activity during or after repetitive hypoxia. EMGgg activity was reduced below baseline during recovery from repetitive hypoxia in women. In conclusion, we have found no evidence of LTF of ventilation or upper airway dilator muscle activity in healthy subjects during wakefulness.
Publisher: Oxford University Press (OUP)
Date: 03-2009
Publisher: American Thoracic Society
Date: 10-2017
Publisher: Elsevier BV
Date: 02-2014
Publisher: American Physiological Society
Date: 12-2011
DOI: 10.1152/JAPPLPHYSIOL.00653.2011
Abstract: Numerous studies have demonstrated upper-airway neuromuscular abnormalities during wakefulness in snorers and obstructive sleep apnea (OSA) patients. However, the functional role of sensorimotor impairment in OSA pathogenesis/disease progression and its potential effects on protective upper-airway reflexes, measures of respiratory sensory processing, and force characteristics remain unclear. This study aimed to gain physiological insight into the potential role of sensorimotor impairment in OSA pathogenesis/disease progression by comparing sensory processing properties (respiratory-related evoked potentials RREP), functionally important protective reflexes (genioglossus and tensor palatini) across a range of negative pressures (brief pulses and entrained iron lung ventilation), and tongue force and time to task failure characteristics between 12 untreated OSA patients and 13 controls. We hypothesized that abnormalities in these measures would be present in OSA patients. Upper-airway reflexes (e.g., genioglossus onset latency, 20 ± 1 vs. 19 ± 2 ms, P = 0.82), early RREP components (e.g., P1 latency 25 ± 2 vs. 25 ± 1 ms, P = 0.78), and the slope of epiglottic pressure vs. genioglossus activity during iron lung ventilation (−0.68 ± 1.0 vs. −0.80 ± 2.0 cmH 2 O/%max, P = 0.59) were not different between patients and controls. Maximal tongue protrusion force was greater in OSA patients vs. controls (35 ± 2 vs. 27 ± 2 N, P 0.01), but task failure occurred more rapidly (149 ± 24 vs. 254 ± 23 s, P 0.01). Upper-airway protective reflexes across a range of negative pressures as measured by electromyography and the early P1 component of the RREP are preserved in OSA patients during wakefulness. Consistent with an adaptive training effect, tongue protrusion force is increased, not decreased, in untreated OSA patients. However, OSA patients may be vulnerable to fatigue of upper-airway dilator muscles, which could contribute to disease progression.
Publisher: American Academy of Sleep Medicine (AASM)
Date: 15-05-2018
DOI: 10.5664/JCSM.7090
Publisher: Oxford University Press (OUP)
Date: 09-2010
Publisher: Oxford University Press (OUP)
Date: 13-04-2017
DOI: 10.1093/SLEEP/ZSX056
Publisher: Oxford University Press (OUP)
Date: 18-04-2017
DOI: 10.1093/SLEEP/ZSX057
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.RESP.2013.06.011
Abstract: Common oscillatory inputs to genioglossus (GG) and tensor palatini (TP) motoneurons were assessed using coherence analysis. Oscillations in the ranges 0-5 Hz (common drive) and 10-30 Hz (short term synchrony) were analyzed. GG and TP electromyograms were recorded via intramuscular fine wire electrodes in 32 subjects during wakefulness. Coherence analysis was conducted on 201 pairs of motor units paired according to their discharge patterns. Results were similar for the two muscles. Common drive was significantly higher for unilateral than bilateral pairs of units (p<.001), and was highest in Inspiratory Tonic pairs and lowest in Tonic pairs (p<.001). Pairs constructed from one muscle had higher common drive than pairs from two muscles (p<.001), the difference being greater for tonic pairs (interaction effect, p=.003). Short term synchrony was weak. The results indicate strong common drive to GG and TP phasic motoneurons, while common drive to Tonic motoneurons was weaker and idiosyncratic to each muscle.
Publisher: AME Publishing Company
Date: 07-2016
Publisher: American Physiological Society
Date: 11-2016
DOI: 10.1152/JAPPLPHYSIOL.00571.2016
Abstract: Respiratory magnetometers are increasingly being used in sleep studies to measure changes in end-expiratory lung volume (EELV), including in obese obstructive sleep apnea patients. Despite this, the accuracy of magnetometers has not been confirmed in obese patients nor compared between sexes. Thus we compared spirometer-measured and magnetometer-estimated lung volume and tidal volume changes during voluntary end-expiratory lung volume changes of 1.5, 1, and 0.5 l above and 0.5 l below functional respiratory capacity in supine normal-weight [body mass index (BMI) 25 kg/m] and healthy obese (BMI 30 kg/m) men and women. Two different magnetometer calibration techniques proposed by Banzett et al. [Banzett RB, Mahan ST, Garner DM, Brughera A, Loring SH. J Appl Physiol (1985) 79: 2169–2176, 1995] and Sackner et al. [Sackner MA, Watson H, Belsito AS, Feinerman D, Suarez M, Gonzalez G, Bizousky F, Krieger B. J Appl Physiol (1985) 66: 410–420, 1989] were assessed. Across all groups and target volumes, magnetometers overestimated spirometer-measured EELV by ~65 ml ( .001) with no difference between techniques (0.07). The Banzett method overestimated the spirometer EELV change in normal-weight women for all target volumes except +0.5 l, whereas no differences between mass or sex groups were observed for the Sackner technique. The variability of breath-to-breath measures of EELV was significantly higher for obese compared with nonobese subjects and was higher for the Sackner than Banzett technique. On the other hand, for tidal volume, both calibration techniques underestimated spirometer measurements ( .001), with the underestimation being more marked for the Banzett than Sackner technique (0.03), in obese than normal weight ( .001) and in men than in women (0.003). These results indicate that both body mass and sex affect the accuracy of respiratory magnetometers in measuring EELV and tidal volume.
Publisher: American Thoracic Society
Date: 15-11-2011
Publisher: Wiley
Date: 04-10-2016
DOI: 10.1111/RESP.12913
Abstract: Obstructive sleep apnoea (OSA) is a common disorder caused by not only an impaired upper airway anatomy (i.e. anatomically narrow/collapsible airway), but also by several non-anatomical factors. In this review, we summarise what is known about how each of the pathological factors that cause OSA vary according to disease severity as measured by the apnoea-hypopnoea index. Our synthesis of the available literature indicates that most of the key factors that cause OSA vary with disease severity. However, there is substantial heterogeneity such that the relative contribution of each of these traits varies both between patients and within different severities of disease. These differences likely contribute to variable efficacy of many non-continuous positive airway pressure treatments and inconsistencies in responses with regard to different OSA severities at baseline.
Publisher: Oxford University Press (OUP)
Date: 03-2016
DOI: 10.5665/SLEEP.5522
Publisher: Oxford University Press (OUP)
Date: 03-2008
Publisher: Elsevier BV
Date: 10-2023
Publisher: American Academy of Sleep Medicine (AASM)
Date: 15-11-2016
DOI: 10.5664/JCSM.6272
Publisher: MDPI AG
Date: 22-12-2020
Abstract: Background: Aviation pilots and cabin crew regularly undertake shift work, and may experience circadian disruption, restricted sleep, sleepiness and impaired health. Research on aviation fatigue and sleepiness has focused on pilots, with less being known about cabin crew. This study aimed to identify likely predictors of fatigue, sleepiness, shift work disorder (SWD) and depression in cabin crew. Methods: An online anonymous survey was distributed to active cabin crew around the world. It measured sleepiness, fatigue, and screened for insomnia, depression and SWD. Information on in iduals’ habits and work schedules were collected. Results: 930 valid responses were analysed. 63.5% of the s le had abnormal levels of fatigue and 46.9% experienced excessive daytime sleepiness. 68.0% were at risk for SWD, 57.7% screened positive for insomnia, and 40.0% for depression. Caffeine and use of alcohol and drugs for sleep were independently associated with insomnia and SWD (p 0.05), whereas, type of route (international, domestic, both) and number of duty days per week predicted fatigue (p 0.05). Conclusions: Cabin crew had a high prevalence of fatigue, sleepiness and elevated risk for SWD, insomnia and depression. Many cabin crew engaged in behaviours detrimental to good sleep hygiene, highlighting targets for future interventional studies.
Publisher: Wiley
Date: 25-04-2018
DOI: 10.1113/JP275222
Publisher: American Thoracic Society
Date: 04-2021
Publisher: Oxford University Press (OUP)
Date: 04-2013
DOI: 10.5665/SLEEP.2544
Publisher: Informa UK Limited
Date: 25-04-2023
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2003
DOI: 10.1097/00063198-200311000-00002
Abstract: The pathogenesis of obstructive sleep apnea (OSA) is incompletely understood. Historically it was believed that patients with OSA have a small upper airway (often due to obesity) that is kept patent during wakefulness by the activity of upper airway dilating muscles. With the reduction in muscle tone at sleep onset, the airway collapses and causes apnea. While this appears to be the case for many patients with OSA, other patients show no major airway anatomic defects or minimal obesity. This has led to the concept that other factors such as unstable ventilatory control and changes in lung volume during sleep may be involved in the pathogenesis of OSA. Recently there have been several advances in our understanding of how these mechanisms are involved in OSA pathogenesis. A more complete understanding of apnea pathogenesis may improve therapeutic techniques and reduce the consequences of OSA.
Publisher: Oxford University Press (OUP)
Date: 2015
DOI: 10.5665/SLEEP.4324
Publisher: American Physiological Society
Date: 15-09-2012
DOI: 10.1152/JAPPLPHYSIOL.00608.2012
Abstract: Arousals from sleep are thought to predispose to obstructive sleep apnea by causing hyperventilation and hypocapnia, which reduce airway dilator muscle activity on the return to sleep. However, prior studies of auditory arousals have not resulted in reduced genioglossus muscle activity [GG-electromyogram (EMG)], potentially because airway resistance prior to arousal was low, leading to a small ventilatory response to arousal and minimal hypocapnia. Thus we aimed to increase the ventilatory response to arousal by resistive loading prior to auditory arousal and determine whether reduced GG-EMG occurred on the return to sleep. Eighteen healthy young men and women were recruited. Subjects were instrumented with a nasal mask with a pneumotachograph, an epiglottic pressure catheter, and intramuscular GG-EMG electrodes. Mask CO 2 levels were monitored. Three- to 15-s arousals from sleep were induced with auditory tones after resting breathing (No-Load) or inspiratory-resistive loading (Load average 8.4 cmH 2 O·l −1 ·s −1 ). Peak minute ventilation following arousal was greater after Load than No-Load (mean ± SE 8.0 ± 0.6 vs. 7.4 ± 0.6 l/min, respectively). However, the nadir end tidal partial pressure of CO 2 did not differ between Load conditions (43.1 ± 0.6 and 42.8 ± 0.5 mmHg, respectively), and no period of reduced GG activity occurred following the return to sleep (GG-EMG baseline, minimum after Load and No-Load = 2.9 ± 1.2%, 3.1 ± 1.3%, and 3.0 ± 1.3% max, respectively). These findings indicate that the hyperventilation, which occurs following tone-induced arousal, is appropriate for the prevailing level of respiratory drive, because loading did not induce marked hypocapnia or lower GG muscle activity on the return to sleep. Whether similar findings occur following obstructive events in patients remains to be determined.
Publisher: American Thoracic Society
Date: 15-10-2013
Publisher: Informa UK Limited
Date: 16-07-2020
DOI: 10.1080/14767058.2020.1789583
Abstract: An association between the increased risk of late stillbirth and the maternal supine sleeping position has been recently established. The risk of stillbirth following supine sleep has been suspected to occur as a result of aortocaval compression by the gravid uterus. A number of studies conducted during wakefulness have reported compromised cardiovascular function during supine rest, as demonstrated by reductions in cardiac output, blood pressure and utero-placental blood flow. It remains unclear whether similar effects are also present during sleep, due to the presence of key sleep-specific changes in cardiovascular function. To investigate the changes in maternal cardiovascular function between the supine and left-lateral positions during wakefulness and non-rapid eye movement (NREM) sleep in late pregnancy. Twenty-nine women with a singleton pregnancy between 24.7 and 36.7 weeks' gestation participated in a single overnight sleep study. Physiological measures (blood pressure, heart rate, heart rate variability - HRV, and pulse arrival time - PAT) were measured and recorded throughout the night using standard polysomnography equipment and the Portapres Model-2 device. As the present study evaluated cardiovascular changes during natural rest and sleep in pregnancy, participants were not given explicit instructions on which position to adopt. Body position was continuously recorded using a position monitor and verified with video recording. No changes in systolic, diastolic or mean arterial blood pressure were observed between the left-lateral and supine positions during wakefulness or sleep. However, heart rate was significantly higher in the supine position compared to the left during wakefulness ( Blood pressure did not appear to differ significantly between the left-lateral and supine positions during wakefulness and sleep. The lack of blood pressure differences may reflect elevated sympathetic activity during rest and sleep in the supine position (compared to the left), suggesting that some degree of compensation for aortocaval compression may still be possible during sleep.
Publisher: American Thoracic Society
Date: 02-2014
Publisher: American Physiological Society
Date: 05-2017
DOI: 10.1152/JAPPLPHYSIOL.00872.2016
Abstract: Upper airway muscle activity is reportedly elevated during slow-wave sleep (SWS) when compared with lighter sleep stages. To uncover the possible mechanisms underlying this elevation, we explored the correlation between different indices of central and reflex inspiratory drive, such as the changes in airway pressure and end-expiratory CO 2 and the changes in the genioglossus (GG) and tensor palatini (TP) muscle activity accompanying transitions from the lighter N2 to the deeper N3 stage of non-rapid eye movement (NREM) sleep in healthy young adult men. Forty-six GG and 38 TP continuous electromyographic recordings were obtained from 16 men [age: 20 ± 2.5 (SD) yr body mass index: 22.5 ± 1.8 kg/m 2 ] during 32 transitions from NREM stages N2 to N3. GG but not TP activity increased following transition into N3 sleep, and the increase was positively correlated with more negative airway pressure, increased end-tidal CO 2 , increased peak inspiratory flow, and increased minute ventilation. None of these correlations was statistically significant for TP. Complementary GG and TP single motor unit analysis revealed a mild recruitment of GG units and derecruitment of TP units during the N2 to N3 transitions. These findings suggest that, in healthy in iduals, the increased GG activity during SWS is driven primarily by reflex stimulation of airway mechanoreceptors and central chemoreceptors. NEW & NOTEWORTHY The characteristic increase in the activity of the upper airway dilator muscle genioglossus during slow-wave sleep (SWS) in young healthy in iduals was found to be related to increased stimulation of airway mechanoreceptors and central chemoreceptors. No evidence was found for the presence of a central SWS-specific drive stimulating genioglossus activity in young healthy in iduals. However, it remains to be determined whether a central drive exists in obstructive sleep apnea patients.
Publisher: Oxford University Press (OUP)
Date: 04-2006
Abstract: This study compares the heart rate responses to the termination of respiratory events, both with and without associated leg movements. Heart rate was measured for 15 R-R intervals before (T-15 to T-1) and after (T+1 to T+15) the termination of respiratory events as a change from the baseline rate, defined as the average of 10 R-R intervals occurring before the termination of each respiratory event (T-15 to T-6). In idual heart rate changes of the 21 patients were then averaged separately for 10 respiratory events with and 10 without associated leg movements. N/A. Twenty-one patients with obstructive sleep apnea who had respiratory events both with and without associated leg movements. N/A. Maximal heart rate rise for respiratory events with leg movements (7.9 beats per minute) was significantly greater than for respiratory events without leg movements (5.1 beats per minute) (p < .0001). The area under the curve for heart rate increase from T-5 to T+9 was 50.1% higher for respiratory events with leg movements than without leg movements. When respiratory events with and without accompanying leg movements were compared, there were no significant differences in mean duration of respiratory events, mean oxygen desaturation after respiratory events, mean duration of electroencephalogram arousal following respiratory events, or mean heart rate during the baseline period. Heart rate rise did correlate with duration of the leg movements (p < .001) in those respiratory events with leg movements. Cardiac activation is significantly greater when the termination of respiratory events is associated with leg movements compared to those without leg movements. This exaggerated heart rate response may be an independent consequence of the leg movements themselves, as other features of the respiratory events and associated arousal were not different in the two conditions.
Publisher: Wiley
Date: 04-05-2007
Publisher: American Physiological Society
Date: 11-2005
DOI: 10.1152/JAPPLPHYSIOL.00410.2004
Abstract: Obstructive sleep apnea (OSA) is two to three times more common in men as in women. The mechanisms leading to this difference are currently unclear but could include gender differences in respiratory stability [loop gain (LG)] or upper airway collapsibility [pharyngeal critical closing pressure (Pcrit)]. The aim of this study was to compare LG and Pcrit between men and women with OSA to determine whether the factors contributing to apnea are similar between genders. The first group of 11 men and 11 women were matched for OSA severity (mean ± SE apnea-hypopnea index = 43.8 ± 6.1 and 44.1 ± 6.6 events/h). The second group of 12 men and 12 women were matched for body mass index (BMI 31.6 ± 1.9 and 31.3 ± 1.8 kg/m 2 , respectively). All measurements were made during stable supine non-rapid eye movement sleep. LG was determined using a proportional assist ventilator. Pcrit was measured by progressively dropping the continuous positive airway pressure level for three to five breaths until airway collapse. Apnea-hypopnea index-matched women had a higher BMI than men (38.0 ± 2.4 vs. 30.0 ± 1.9 kg/m 2 P = 0.03), but LG and Pcrit were similar between men and women (LG: 0.37 ± 0.02 and 0.37 ± 0.02, respectively, P = 0.92 Pcrit: 0.35 ± 0.62 and −0.18 ± 0.87, respectively, P = 0.63). In the BMI-matched subgroup, women had less severe OSA during non-rapid eye movement sleep (30.9 ± 7.4 vs. 52.5 ± 8.1 events/h P = 0.04) and lower Pcrit (−2.01 ± 0.62 vs. 1.16 ± 0.83 cmH 2 O P = 0.005). However, LG was not significantly different between genders (0.38 ± 0.02 vs. 0.33 ± 0.03 P = 0.14). These results suggest that women may be protected from developing OSA by having a less collapsible upper airway for any given degree of obesity.
Publisher: American Thoracic Society
Date: 15-12-2003
Publisher: BMJ
Date: 09-2007
Publisher: Elsevier
Date: 2014
Publisher: European Respiratory Society (ERS)
Date: 23-12-2010
Publisher: American Physiological Society
Date: 12-2019
DOI: 10.1152/JAPPLPHYSIOL.00186.2019
Abstract: This study aimed to determine whether there is impairment of genioglossus neuromuscular responses to small negative pressure respiratory stimuli, close to the conscious detection threshold, in obstructive sleep apnea (OSA). We compared genioglossus electromyogram (EMGgg) responses to midinspiratory resistive loads of varying intensity (≈1.2–6.2 cmH 2 O·L −1 ·s), delivered via a nasal mask, between 16 severe OSA and 17 control participants while the subjects were awake and in a seated upright position. We examined the relationship between stimulus intensity and peak EMGgg litude in a 200-ms poststimulus window and hypothesized that OSA patients would have an increased activation threshold and reduced sensitivity in the relationship between EMGgg activation and stimulus intensity. There was no significant difference between control and OSA participants in the threshold ( P = 0.545) or the sensitivity ( P = 0.482) of the EMGgg litude vs. stimulus intensity relationship, where change in epiglottic pressure relative to background epiglottic pressure represented stimulus intensity. These results do not support the hypothesis that deficits in neuromuscular response to negative upper airway pressure exist in OSA during wakefulness however, the results are likely influenced by a counterintuitive and novel genioglossus muscle suppression response observed in a significant proportion of both OSA and healthy control participants. This suppression response may relate to the inhibition seen in inspiratory muscles such as the diaphragm in response to sudden-onset negative pressure, and its presence provides new insight into the upper airway neuromuscular response to the collapsing force of negative pressure. NEW & NOTEWORTHY Our study used a novel midinspiratory resistive load stimulus to study upper airway neuromuscular responses to negative pressure during wakefulness in obstructive sleep apnea (OSA). Although no differences were found between OSA and healthy groups, the study uncovered a novel and unexpected suppression of neuromuscular activity in a large proportion of both OSA and healthy participants. The unusual response provides new insight into the upper airway neuromuscular response to the collapsing force of negative pressure.
Publisher: European Respiratory Society (ERS)
Date: 05-03-2008
Publisher: Elsevier BV
Date: 07-2008
Publisher: Oxford University Press (OUP)
Date: 06-10-2017
DOI: 10.1093/SLEEP/ZSX160
Abstract: Ventilatory after-discharge (sustained elevation of ventilation following stimulus removal) occurs during sleep but not when hypocapnia is present. Genioglossus after-discharge also occurs during sleep, but CO2 effects have not been assessed. The relevance is that postarousal after-discharge may protect against upper airway collapse. This study aimed to determine whether arousal elicits genioglossus after-discharge that persists into sleep, and whether it is influenced by CO2. Twenty-four healthy in iduals (6 female) slept with a nasal mask and ventilator. Sleep (EEG, EOG, EMG), ventilation (pneumotachograph), end-tidal CO2 (PETCO2), and intramuscular genioglossus EMG were monitored. NREM eucapnia was determined during 5 minutes on continuous positive airway pressure (4 cmH2O). Inspiratory pressure support was increased until PETCO2 was ≥2 mm Hg below NREM eucapnia. Supplemental CO2 was added to reproduce normocapnia, without changing ventilator settings. Arousals were induced by auditory tones and genioglossus EMG compared during steady-state hypocapnia and normocapnia. Eleven participants (4 female) provided data. Prearousal PETCO2 was less (p < .05) during hypocapnia (40.74 ± 2.37) than normocapnia (43.82 ± 2.89), with differences maintained postarousal. After-discharge, defined as an increase in genioglossus activity above prearousal levels, occurred following the return to sleep. For tonic activity, after-discharge lasted four breaths irrespective of CO2 condition. For peak activity, after-discharge lasted one breath during hypocapnia and 6 breaths during normocapnia. However, when peak activity following the return to sleep was compared between CO2 conditions no in idual breath differences were observed. Postarousal genioglossal after-discharge may protect against upper airway collapse during sleep. Steady-state CO2 levels minimally influence postarousal genioglossus after-discharge.
Publisher: BMJ
Date: 05-2006
Publisher: Wiley
Date: 19-12-2022
DOI: 10.1113/EP090580
Abstract: What is the central question of this study? How does alcohol intake, which worsens obstructive sleep apnoea, alter motor control of the genioglossus muscle, an upper airway dilator, in healthy awake human volunteers, and does alcohol alter genioglossus muscle afterdischarge? What is the main finding and its importance? Alcohol consumption had a very minor effect on the activity of the genioglossus in healthy young in iduals studied during wakefulness and did not alter afterdischarge, leaving open the possibility that alcohol worsens obstructive sleep apnoea via other mechanisms. Alcohol worsens obstructive sleep apnoea (OSA). This effect is thought to be due to alcohol's depressant effect on upper airway dilator muscles such as the genioglossus, but how alcohol reduces genioglossal activity is unknown. The aim of this study was to investigate the effect of alcohol consumption on genioglossus muscle single motor units (MUs). Sixteen healthy in iduals were studied on two occasions (alcohol: breath alcohol concentration ∼0.07% and placebo). They were instrumented with a nasal mask, four intramuscular genioglossal EMG electrodes, and an ear oximeter. They were exposed to 8–12 hypoxia trials (45–60 s of 10% O 2 followed by one breath of 100% O 2 ) while awake. MUs were sorted according to their firing patterns and quantified during baseline, hypoxia and recovery. For the alcohol and placebo conditions, global muscle activity (mean ± SD peak inspiratory EMG = 119.3 ± 44.1 and 126.5 ± 51.9 μV, respectively, P = 0.53) and total number of MUs recorded at baseline (68 and 67, respectively) were similar. Likewise, the peak discharge frequency did not differ between conditions (21.2 ± 4.28 vs. 22.4 ± 4.08 Hz, P = 0.09). There was no difference between conditions in the number (101 vs. 88, respectively) and distribution of MU classes during hypoxia, and afterdischarge duration was also similar. In this study, alcohol had a very minor effect on genioglossal activity and afterdischarge in these otherwise healthy young in iduals studied while awake. If similar effects are observed during sleep, it would suggest that the worsening of OSA following alcohol may be related to increased upper airway resistance/nasal congestion or arousal threshold changes.
Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.RESP.2016.09.014
Abstract: Obstructive sleep apnoea (OSA) is highly prevalent in people with tetraplegia. Nasal congestion, a risk factor for OSA, is common in people with tetraplegia. The purpose of this study was to quantify objective and perceived nasal resistance and its stability over four separate days in people with tetraplegia and OSA (n=8) compared to able-bodied controls (n=6). Awake nasal resistance was quantified using gold standard choanal pressure recordings (days 1 and 4) and anterior rhinomanometry (all visits). Nasal resistance (choanal pressure) was higher in people with tetraplegia versus controls (5.3[6.5] vs. 2.1[2.4] cmH
Publisher: Informa UK Limited
Date: 11-2021
Publisher: American Physiological Society
Date: 06-2010
DOI: 10.1152/JAPPLPHYSIOL.01437.2009
Abstract: On the basis of recent reports, the genioglossus (GG) negative-pressure reflex consists initially of excitation followed by a secondary state-dependent suppression phase. The mechanistic origin and functional role of GG suppression is unknown but has been hypothesized to arise from transient inhibition of respiratory active neurons as a protective reflex to prevent aspiration, as observed in other respiratory muscles (e.g., diaphragm) during airway occlusion. Unlike GG, tensor palatini (TP) is a tonic muscle with minimal respiratory phasic activation during relaxed breathing, although both muscles are important in preserving pharyngeal patency. This study aimed to compare GG vs. TP reflex responses to the same negative-pressure stimulus. We hypothesized that reflex suppression would be present in GG, but not TP. Intramuscular GG and TP EMGs were recorded in 12 awake, healthy subjects (6 female). Reflex responses were generated via 250-ms pulses of negative upper airway pressure (approximately −16 cmH 2 O mask pressure) delivered in early inspiration. GG and TP demonstrated reflex activation in response to negative pressure (peak latency 31 ± 4 vs. 31 ± 6 ms and peak litude 318 ± 55 vs. 314 ± 26% baseline, respectively). A secondary suppression phase was present in 8 of 12 subjects for GG (nadir latency 54 ± 7 ms, nadir litude 64 ± 6% baseline), but not in any subject for TP. These data provide further support for the presence of excitatory and inhibitory components of GG (phasic muscle) in response to brief upper airway negative-pressure pulses. Conversely, no reflex suppression below baseline was present in TP (tonic muscle) in response to the same stimuli. These differential responses support the hypothesis that GG reflex suppression may be mediated via inhibition of respiratory-related premotor input.
Publisher: Elsevier BV
Date: 2023
Publisher: Oxford University Press (OUP)
Date: 04-2008
Start Date: 2017
End Date: 2019
Funder: Australian Research Council
View Funded ActivityStart Date: 2014
End Date: 2016
Funder: National Health and Medical Research Council
View Funded ActivityStart Date: 06-2017
End Date: 12-2022
Amount: $361,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2012
End Date: 06-2015
Amount: $255,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 05-2011
End Date: 12-2018
Amount: $706,552.00
Funder: Australian Research Council
View Funded ActivityStart Date: 05-2016
End Date: 12-2019
Amount: $345,000.00
Funder: Australian Research Council
View Funded Activity