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.