Fig. 2. After cross-clamp application, stroke volume decreases in both positive end-expiratory pressure (PEEP) groups but not with zero end-expiratory pressure (ZEEP). Subsequent volume administration tended to maintain stroke volume during cross-clamp. However, after cross-clamp release, stroke volume increased in both PEEP groups and was highest in the PEEP + volume group. During reperfusion, stroke volume remained similar in PEEP and ZEEP + volume groups. (A  indicates P < 0.005 compared with previous adjacent value within the group;B  indicates P < 0.005 compared with baseline value within the group;C  indicates P < 0.005 compared with ZEEP animals;D  indicates P < 0.005 compared with ZEEP + volume animals;E  indicates P < 0.005 compared with PEEP animals).