Fig. 2.

Sample CFD model results for a subject with severe OSAS. Pharynx anatomy with pressure contours at peak inspiration phase (phase = 3, top left) and peak expiration phase (phase = 8, top right); note larger cross-sectional area during inspiration in nasopharynx (NP), velopharynx (VP), and hypopharynx (HP). Only retrolingual oropharynx (OP) cross section is smaller during inspiration. Bottom left: cross-sectional areas and flow rate vs. phase increment. Bottom right: area-pressure curves for each subject. Effective compliance is defined as the pressure-area slope of the section, between maximum inspiratory and maximum expiratory flow (lines). Sections NP, VP, and HP have negative effective compliance; the airway expands the airway during inspiration, while OP has positive slope, indicating net passive response to airway pressure loads.