EFFECTS OF POSITIVE END-EXPIRATORY PRESSURE ON RIGHT-VENTRICULAR FUNCTION IN COPD PATIENTS DURING ACUTE VENTILATORY FAILURE

Objective: To examine the effects of external positive end-expiratory pressure (PEEP) on right ventricular function in chronic obstructive p ulmonary disease (COPD) patients with intrinsic PEEP (PEEPi). Design: Prospective study. Setting: General intensive care unit in a universit y teaching hospital. Patients: Seven mechanically ventilated flow-limi ted COPD patients (PEEPi = 9.7 +/- 1.3 cmH(2)O, mean+/-SD) with acute respiratory failure. Intervention: Hemodynamic and respiratory mechani c data were collected at four different levels of PEEP (0 - 5 - 10 - 1 5 cmH(2)O). Measurements and results: Hemodynamic parameters were obta ined by a Swan-Ganz catheter with a fast response thermistor. Cardiac index (CI) and end-expiratory lung volume (EELV) reductions started si multaneously when the applied PEEP was approximately 90% of PEEPi meas ured on 0 cmH(2)O (ZEEP). Changes in transmural intrathoracic pressure (PEEPi,cw) started only at a PEEP value much higher (120%) than PEEPi . The reduction in CI was related to a decrease in the right end-diast olic ventricular volume index (RVEDVI) (r = 0.61; p < 0.001). No corre lation between CI and transmural right atrial pressure was observed. T he RVEDVI was inversely correlated with PEEP-induced changes in EELV ( r = -55; p<0.001), but no with PEEPi,cw (r = -0.08; NS). The relations hip between RVEDVI and right ventricular stroke work index, considered an index of contractility, was significant in three patients, i.e., P EEP did not change contractility. In the other patients, an increase i n contractility seemed to occur. Conclusions: In COPD patients an exte rnal PEEP exceeding 90% Of PEEPi causes lung hyperinflation and reduce s the CI due to a preload effect. The reduction in RVEDVI seems relate d to changes in EELV, rather than to changes in transmural pressures, suggesting a lung/heart volume interaction in the cardiac fossa. Thus, in COPD patients, application of an external PEEP level lower than PE EPi may affect right ventricular function.