Collapsibility of the relaxed pharynx and risk of sleep apnoea

¹ Dept of Medicine, Bnai Zion Medical Center, Technion, Haifa, Israel
² Dept of anesthesiology, Bnai Zion Medical Center, Technion, Haifa, Israel

^* To whom correspondence should be addressed. E-mail: oliven{at}tx.technion.ac.il.

	Abstract

In this study we measured hypotonic pharyngeal collapsibility in subjects not known to have obstructive sleep apnoea (OSA), and assessed variables that affect collapsibility and its relationship to OSA.

The critical closing pressure of the pharynx (Pcrit) was measured under the hypotonic condition of anesthesia in 227 subjects that underwent elective surgery. The risk of OSA in this population was estimated using the Berlin questionnaire.

The mean Pcrit for all subjects was positive (above-atmospheric), ranging from 0.69 (CI -7.39 to 8.77) to 4.0 (CI -4.82 to 12.82) cmH₂O for subjects with low and high prevalence of OSA, respectively. Pcrit -5 cmH₂O was found only in 3.1% of our subjects. In this general population, Pcrit was similar in men and women, and correlated positively with increasing age, while a correlation with neck circumference was found only in men. Pcrit accounted only for 12.25% of the variability in OSA risk score.

We conclude that subjects with high Pcrit are at increased risk to develop OSA. However, the human pharynx is prone to collapse, and occludes in most people in the absence of neuromuscular support. Therefore, the level of neuromuscular activity may ultimately determine, in most subjects, the occurrence of sleep apnea.

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