Time of day affects the frequency and duration of breathing events and the critical closing pressure during NREM sleep in participants with sleep apnea

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.

Obstructive Sleep Apnea in Women

“…[32][33][34][35][36] This can contribute to breathing instability during sleep and indeed supports the findings that apnea severity increases from the beginning to end of the night in individuals with sleep apnea. [37][38][39][40][41] These ventilatory responses to CO2 after episodic hypoxia are seen to be worse in men compared with women. 26…”

<p>Increased Oxidative Stress, Loop Gain And The Arousal Threshold Are Clinical Predictors Of Increased Apnea Severity Following Exposure To Intermittent Hypoxia</p>

“…In a group of ten males with obstructive sleep apnea, we measured the arousal threshold during a baseline sleep study using the model employed in the present investigation. In a subsequent sleep study, we measured the critical closing pressure of the upper airway using a standard method that we have employed previously 35. Our results revealed a positive correlation between measures of the arousal threshold and the critical closing pressure (AT: r = 0.74, p = 0.02).…”

Modulation of Motoneuronal Activity With Sleep-Wake States and Motoneuronal Gene Expression Vary With Circadian Rest-Activity Cycle

“…With the regard to upper airway control in OSA, which is an almost uniquely human disorder, data suggest that the frequency and duration of breathing events and the critical closing pressure during SWS vary with ToD (El-Chami et al, 2015 ). An important background for the interpretation of these findings may be that, in contrast to rats and human subjects with fully patent upper airway, lingual EMG in OSA patients is not atonic during SWS (Katz and White, 2003 ).…”

“…Additional day-night differences in the control of lingual EMG may occur during rapid eye movement sleep (REMS; Rukhadze et al, 2012 ). Other reports indicate that the propensity for central apneic episodes varies in rats with the phase of circadian cycle (Fink et al, 2014 ), and that time of the day (ToD) affects respiratory chemosensitivity, the frequency and duration of respiratory events, and propensity for upper airway collapse during slow-wave sleep (SWS) in human OSA subjects (El-Chami et al, 2014 , 2015 ). Accordingly, there are compelling reasons to investigate whether the effects of sleep-wake states on muscle tone vary with the phase of the rest-activity cycle.…”