Differing responses in right and left ventricular filling, loading and volumes during positive end-expiratory pressure

Using a combined hemodynamic and radionuclide technique, 20 patients with varied ventricular function were evaluated during positive endexpiratory pressure (PEEP) application. Left ventricular (LV) and right ventricular (RV) ejection fractions and cardiac output were measured, and ventricular volumes were derived. Seven patients (group 1) who had an increase in LV end-diastolic volume with PEEP and 13 patients (group 2) who had the more typical response, a decrease in LV end-diastolic volume with PEEP, were identified. Compared with group 2, group 1 patients had a higher incidence of coronary artery disease (5 of 7 vs 1 of 13, p < 0.0005) and lower cardiac output (3.9 ±1.6 vs 9.1 ±3.2 liters/min, p < 0.005), LV ejection fraction (27 ±13 vs 51 ±21%, p < 0.05), RV ejection fraction (15 ±6 vs 32 ±8%, p < 0.005) and peak filling rate (1.32 ±0.43 vs 3.51 ±1.70 end-diastolic volumes/s, p < 0.005). LV and RV volumes increased and peak filling rate decreased with PEEP in group 1, whereas in group 2 LV volume decreased and RV volume and peak filling rate remained unchanged. Using stepwise regression analysis, the change in LV volume with PEEP was related directly to baseline systemic vascular resistance and inversely to baseline blood pressure. Similarly, the change in peak filling rate with PEEP was inversely related to the change in RV end-diastolic volume. Thus, the hemodynamic response to PEEP is heterogenous and may be related to LV ischemia. In patients with coronary artery disease and severely depressed biventricular function, LV volume may increase, LV ejection fraction may decrease and filling may worsen with PEEP.