Static mechanics of the velopharynx of patients with obstructive sleep apnea

TLDR

Nine OSA patients were endoscopically examined to assess the static mechanics of their hypotonic velopharynx, which was the sole site of narrowing. The velopharynx closed at a mean pressure of 0.18 cmH₂O, with a steep, curvilinear pressure–area relationship that fits an exponential model (R² ≈ 0.98 per patient, 0.85 for the group), and flow limitation occurred when mask pressure exceeded closing pressure by 0.5–3.0 cmH₂O, indicating a high compliance range of 0–3 cmH₂O above closing pressure.

Abstract

The static mechanics of the hypotonic pharynx were endoscopically evaluated in nine sleeping patients with obstructive sleep apnea, having a primary narrowing only at the velopharynx. The velopharynx closed completely at a mean pressure of 0.18 +/- 1.21 cmH2O, and the mean half-dilation pressure was 1.93 cmH2O above closing pressure. The dependence of area on pressure was distinctly curvilinear, being steep near closing pressure and asymptotically approaching maximum area (mean = 1.32 cm2). The data for each patient were satisfactorily fitted by an exponential function (mean R2 = 0.98), and a single exponential relationship usefully represented the dependence of relative area on pressure above closing pressure for the population (R2 = 0.85). During the test inspiration, flow limitation was consistently observed when mask pressure exceeded closing pressure by 0.5–3.0 cmH2O. In summary, the static mechanics of the hypotonic velopharynx of patients with obstructive sleep apnea can be described by an exponential pressure-area relationship, with a closing pressure near atmospheric pressure and a high compliance in the range of airway pressure 0–3 cmH2O above closing pressure.