Lateral position decreases collapsibility of the passive pharynx in patients with obstructive sleep apnea.

BACKGROUND Reduction of nocturnal obstructive events during lateral position in patients with obstructive sleep apnea was previously reported. However, little information is available regarding mechanisms of the improvement and the precise pharyngeal site influenced by the lateral position. The authors tested the hypothesis that structural properties of the passive pharynx change by changing the body position from supine to lateral. METHOD Total muscle paralysis was induced with general anesthesia in eight patients with obstructive sleep apnea, eliminating neuromuscular factors contributing to pharyngeal patency. The cross-sectional area of the pharynx was measured endoscopically at different static airway pressures. Comparison of static pressure-area plot between the positions allowed assessment of the influence of the position change on the mechanical properties of the pharynx. RESULTS The static pressure-area curves of the lateral position were above those of the supine position, with increasing maximum cross-sectional area and decreasing the closing pressure at both retropalatal and retroglossal airways. CONCLUSIONS Lateral position structurally improves maintenance of the passive pharyngeal airway in patients with obstructive sleep apnea.