Mechanical properties of the lung and upper airways in patients with sleep-disordered breathing.

We studied the changes in lung and upper airway mechanics in adult human subjects with obstructive sleep apnea/hypopnea syndrome (OSAHS) during wakefulness, sleep, and at arousal from sleep. We used two numerical methods that we have previously developed specifically for dealing with inspiratory flow limitation during sleep: the modified Mead-Whittenberger method, and information-weighted histograms obtained using recursive least squares. Full polysomnography including esophageal pressure and airflow measurements was performed in seven men with OSAHS (respiratory disturbance index: 55.8 +/- 23.2 events/h). Pharyngeal pressure was recorded in four of the subjects to partition lung mechanics into its upper airway and lower lung components. Both techniques showed that total lung resistance and elastance increased significantly (p < 0.05) during obstructed breathing and that this increase was reversed at the end of the obstruction. The partitioning of mechanics showed that upper airway collapse was primarily responsible for the increase in lung resistance. Our results suggest that OSAHS may lead to transient abnormalities in the recruitment of lung units and the gas exchanging capacity of the lungs.