TIME-COURSE OF STEPWISE CPAP TITRATION - BEHAVIOR OF RESPIRATORY AND NEUROLOGICAL VARIABLES

Because successful medical treatment of obstructive sleep apnea/hypopn ea syndrome (SAHS) depends on adequate CPAP treatment, we have analyze d in nine SAHS patients the behavior of respiratory and neurological p arameters during a stepwise, polysomnography-controlled CPAP titration to achieve an optimal CPAP. Particularly, we have focused on which si mple variable could predict the optimal CPAP pressure and could better define a distinctive optimal-suboptimal pattern. Main parameters anal yzed through the CPAP titration procedure were respiratory events (apn ea, hypopnea), the contour of inspiratory flow, the pleural pressure b ehavior, the thoraco-abdominal motion, oximetry, arousals, and sleep s tage. During the CPAP titration we observed: (1) a rounded shape in th e inspiratory flow contour was associated with the lowest esophageal p ressure; (2) during stepwise increases in CPAP, almost all apnea event s changed to hypopnea periods, followed by prolonged periods of limite d inspiratory flow with still high esophageal pressure but without aro usals (probably suboptimal CPAP); and (3) as CPAP reached suboptimal l evels, sleep stage moved to deeper stages without arousals. We conclud e that if during CPAP titration the end point is the disappearance of arousals, most patients with SAHS will still exhibit periods of high i ntrathoracic pressures with limited inspiratory flow. Alternatively, i f the end point to be reached is the lowest esophageal pressure, highe r CPAP levels will be needed. The contour of inspiratory flow appears as the simplest variable that best correlates with lowest esophageal p ressure during CPAP titration.