Artificial ventilation with positive end-expiratory pressure (PEEP) reduces venous return by raising intrathoracic pressure. To determine whether PEEP decreases cardiac output further by depressing myocardial function, we constructed Starling curves, using rapid dextran infusion in 7 anesthetized dogs ventilated with zero (ZEEP) and 20 cm PEEP. The changes in stroke volume and in left ventricular stroke work (LVSW) when PEEP was added or removed were significantly greater than could be attributed to the corresponding change in transmural left ventricular end-diastolic pressure (LVEDPTM) on these Starling curves. To the extent that PEEP did not alter left ventricular diastolic volume-pressure characteristics, these data indicated PEEP depressed ventricular function. Identical changes with PEEP in cardiac output (-30%), esophageal pressure (+10 cmH2O), and left ventricular function were observed after pulmonary edema was induced with oleic acid. These results confirm and extend recent suggestions that high levels of PEEP depress left ventricular function in dogs, accounting for about half of the reduction in cardiac output before and during acute pulmonary edema.
