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Collapsibility of the relaxed pharynx and risk of sleep apnoea

¹ Depts of Medicine and ² Anesthesiology, Bnai Zion Medical Center, Technion, Haifa, Israel.

CORRESPONDENCE: A. Oliven, Dept of Internal Medicine, Bnai Zion Medical Center, 47 Golomb Str., Haifa, Israel. Fax: 972 48359770. E-mail: oliven{at}tx.technion.ac.il

Keywords: Anaesthesia, collapsibility, critical pressure, obstructive sleep apnoea, pharynx, propofol

Received: October 23, 2007
Accepted May 23, 2008

The present study measured hypotonic pharyngeal collapsibility in subjects not known to have obstructive sleep apnoea (OSA), and assessed the variables that affect collapsibility and the relationship with OSA.

The critical value of positive end-expiratory pressure (P_crit) was measured under the hypotonic condition of anaesthesia in 227 subjects who underwent elective surgery. The risk of OSA in this population was estimated using the Berlin questionnaire.

The mean P_crit for all subjects was positive (above atmospheric), ranging from 0.69 (95% confidence interval (CI) -7.39–8.77) to 4.0 (CI -4.82–12.82) cmH₂O for subjects with low and high prevalence of OSA, respectively. P_crit -5 cmH₂O was only found in 3.1% of the study subjects. In the general population, P_crit was similar in males and females and correlated positively with increasing age, while a correlation with neck circumference was found only in males. P_crit accounted for only 12.25% of the variability in OSA risk score.

In conclusion, subjects with high critical value of positive end-expiratory pressure are at an increased risk for developing obstructive sleep apnoea. However, the human pharynx is prone to collapse and occludes in most people in the absence of neuromuscular support. Therefore, in most subjects, the level of neuromuscular activity may ultimately determine the occurrence of sleep apnoea.

This article has been cited by other articles:

				R. Oliven, N. Tov, M. Odeh, L. Gaitini, U. Steinfeld, A. R. Schwartz, and A. Oliven Interacting effects of genioglossus stimulation and mandibular advancement in sleep apnea J Appl Physiol, May 1, 2009; 106(5): 1668 - 1673. [Abstract] [Full Text] [PDF]