Fig. 1. Continuous recordings of changes in arterial oxygen tension (Pao2; left ) and arterial carbon dioxide tension (Paco2; right ) from the beginning (time 0) to 15 min after endotracheal suctioning in nine patients undergoing at random open and closed-circuit endotracheal suctioning. Pao2and Paco2were sampled every second in each individual patient, and the mean curves are represented. Black lines represent open suctioning, whereas gray lines represent closed-circuit suctioning followed by a recruitment maneuver. Gray arrows indicate the beginning of the recruitment maneuver.