Pulmonary function in obstructive sleep apnea. Relationships to pharyngeal resistance and cross-sectional area

Reduction in the size of the pharynx and increased pharyngeal airflow resistance have been demonstrated in patients with obstructive sleep apnea (OSA). We evaluated 15 men with severe OSA and 10 nonapneic control subjects matched for age and weight in order to determine if PCSA, inspiratory pharyngeal airflow resistance, and abnormal breathing events during sleep were associated with alterations in the flow-volume relationship and other awake PFTs. Pharyngeal cross-sectional area was determined by CT, and pharyngeal resistance between choanae and epiglottis was measured during quiet awake breathing. In patients with OSA, there was an inverse relationship between the mean cross-sectional area of the oropharynx and the ratio of FEF50%/FIF50% (rs = -0.54; p = 0.03). In all subjects, pharyngeal resistance was inversely related to percentage of predicted values for FEF25-75% (rs = -0.56; p = 0.01). The frequency of apneas during sleep was significantly (p less than 0.05) related to the percentage of predicted values for MVV, TLC, FVC, and PIF. Obesity appears to account for the strength of these relationships. Flow-volume loops and other PFTs did not distinguish patients with OSA from controls.