Fig. 1.

Illustration of simplified decremental positive end-expiratory pressure (PEEP) maneuver for estimating derecruited lung volume. In this example, respiratory frequency was transiently reduced to 10 breaths per minute to allow a prolonged expiration. Afterward, PEEP was reduced from 15 to 5 cmH₂O. The difference in expiratory tidal volumes (i.e., integral of flow) between the breath while decreasing PEEP (blue area) and the one before changing PEEP (red area) was referred to as the total change in lung volume. Derecruited volume was the difference between the total changes in measured vs. predicted lung volumes (see text for details). Paw Airway pressure