Figure 1.

Schematic representation of the pressure-time diagram at the end of each epoch in a single patient. Data at both PEEP levels studied are presented. P_atm, atmospheric pressure; EELV, end-expiratory lung volume measured by using the nitrogen technique; PEEP-volume, volume trapped by PEEP above the functional residual capacity, measured by using a long exhalation to atmospheric pressure (zero end-expiratory pressure); V_t, tidal volume; ΔEELV, EELV_{high PEEP} - EELV_{low PEEP} ; ΔPEEP-volume, PEEP-volume_{high PEEP} - PEEP-volume_{low PEEP}.