Respiratory mechanics and timing during sleep in occlusive sleep apnea

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Abstract
Human obese subject [6] with the sleep apnea hypersomnolence syndrome associated with upper airway occlusion (UAO) were studied during sleep to characterize respiration. Measurements included the timing components of ventilation, pulmonary resistance, flow and esophageal and gastric pressures before and during UAO. During the period between UAO, the resistance progressively increased (9.4-18.1 cm H2O/1-1.cntdot.s, P < 0.05) as the ventilation decreased (1.82-0.77 1/s, P < 0.05), but without changes in esophageal pressure swings. During this period inspiratory time-to-total cycle time decreased (0.42-0.25 s, P < 0.05) due to expiratory phase prolongation. The apnea began after expiration and terminated on inspiration with the maximal swings in esophageal and gastric pressure near the termination. During the UAO the respiratory cycle time decreased slightly, but the expiratory pause time was significantly shortened immediately before ventilation. The UAO is but one aspect of this syndrome. A decrease in CNS activity diminishes the respiratory drive before the onset of the UAO.