Pulmonary function and sleep apnea.

The purpose of this study was to determine whether there is a relationship between pulmonary function measured during wakefulness and sleep apnea. We prospectively studied 1296 patients, who were free of any lung disease, referred to our sleep clinic for evaluation of possible sleep apnea. All patients had in-hospital nocturnal polysomnography and pulmonary function measurements, which included flow-volume curve, body plethysmography, and single-breath diffusing capacity for carbon monoxide. The results were analyzed by comparing pulmonary function data between four groups of patients, grouped according to apnea severity as reflected by their apnea/hypopnea index: nonapneics (apnea-hypopnea index </= 10), mild apnea (10 < apnea-hypopnea index </= 30), moderate apnea (30 < apnea-hypopnea index </= 50), and severe apnea (apnea-hypopnea index > 50). Analysis of covariance demonstrated no difference in any of the pulmonary function parameters between the four groups, after adjusting for age, body mass index, or weight as the covariate. We conclude that in nonsmoking patients without lung disease, sleep apnea is unrelated to pulmonary function measured during wakefulness.