Variability of human upper airway collapsibility during sleep and the influence of body posture and sleep stage

Abstract

Summary The critical pressure at which the pharynx collapses (Pcrit) is an objective measurement of upper airway collapsibility, an important pathogenetic factor in obstructive sleep apnoea. This study examined the inherent variability of passive Pcrit measurement during sleep and evaluated the effects of sleep stage and body posture on Pcrit. Repeated measurements of Pcrit were assessed in 23 individuals (15 male) with diagnosed obstructive sleep apnoea throughout a single overnight sleep study. Body posture and sleep stage were unrestricted. Applied upper airway pressure was repetitively reduced to obtain multiple measurements of Pcrit. In 20 subjects multiple measurements of Pcrit were obtained. The overall coefficient of repeatability for Pcrit measurement was 4.1 cm H2O. Considering only the lateral posture, the coefficient was 4.8 cm H2O. It was 3.3 cm H2O in the supine posture. Pcrit decreased from the supine to lateral posture [supine mean 2.5 cm H2O, 95% confidence interval (CI) 1.4–3.6; lateral mean 0.3 cm H2O, 95% CI −0.8–1.4, P = 0.007] but did not vary with sleep stage (P = 0.91). This study has shown that the overall coefficient of repeatability was 4.1 cm H2O, implying that the minimum detectable difference, with 95% probability, between two repeated Pcrit measurements in an individual is 4.1 cm H2O. Such variability in overnight measures of Pcrit indicates that a single unqualified value of Pcrit cannot be used to characterize an individual’s overall collapsibility during sleep. When within‐subject variability is accounted for, change in body posture from supine to lateral significantly decreases passive pharyngeal collapsibility.

Defining Phenotypic Causes of Obstructive Sleep Apnea. Identification of Novel Therapeutic Targets

“…These include but are not limited to surface tension forces (50), lung volume effects (51), fluid shifts (52,53), body-head position (46,54), hormonal effects (55,56), and ventilatory responses to transient stimuli (57). Although many of these mechanisms may be mediated through one or more of the four traits defined in this study, these and other currently unknown factors must be important in either protecting against or perpetuating OSA for certain individuals.…”

Effects on upper airway collapsibility of presence of a pharyngeal catheter

“…Thus, any observed changes in upper airway collapsibility as a consequence of the presence or absence of an oesophageal catheter can confidently be attributed to the effects of the catheter alone. Of note was that the observed difference in Pcrit between the two conditions of 0.7 cmH 2 O was not statistically significant, is less than the reported variability of the measurement (Ong et al ., ), and would not be considered clinically significant (Gleadhill et al ., ). These findings suggest that, in traversing the pharynx, the oesophageal catheter does not splint the pharyngeal walls longitudinally or otherwise influence its propensity to collapse.…”

“…Despite there being no change in upper airway collapsibility between the conditions for the group overall, some individuals demonstrated variability with a change in Pcrit greater than that which would be considered clinically significant (3.4 cmH 2 O) (Kirkness et al ., ; Ong et al ., ) and/or a change in Rus of >10 cmH 2 O mL −1 s −1 . The direction of these changes was not related systematically to whether the catheter was in or out (Figs and ).…”

Efeitos da terapia miofuncional orofacial em pacientes com ronco primário e apneia obstrutiva do sono na anatomia e função da via aérea

“…[67] Porém não demonstra sofrer modificações de acordo com os estágios do sono. [68] Em estudo prévio randomizado com 31 pacientes com apneia obstrutiva do sono (AOS) moderada realizaram exercícios para musculatura orofaríngea, também denominada terapia miofuncional orofacial (TMO) [22] . Nesse trabalho inicial o número de pacientes foi relativamente pequeno, restringiu-se a pacientes com AOS moderada e a quantidade de exercícios que precisavam ser realizados 3 vezes ao dia foi muito grande (n=10) [22] .…”