Influence of the right ventricle on canine left ventricular function with PEEP.

In anesthetized dogs we evaluated the influence of increased right ventricular (RV) pressures on left ventricular (LV) function by comparing the hemodynamic effects of increases in RV afterload (pulmonary arterial pressure) produced by positive end-expiratory pressure (PEEP) with those due to pulmonary arterial occlusion (PAO). Left atrial (Pla) and right atrial (Pra) pressures increased with PEEP and PAO [for Pla: 3.1 +/- 0.7 Torr (PEEP), 2.4 +/- 0.9 Torr (PAO); for Pra: 2.9 +/- 0.4 Torr (PEEP), 3.1 +/- 1.2 Torr (PAO)]. RV septal-free wall dimension (RVD) increased, and LV septal-posterolateral dimension (L2) decreased with both conditions [increases in RVD: 1.9 +/- 0.3 mm (PEEP), 2.2 +/- 0.5 mm (PAO); decrease in L2: 1.1 +/- 0.4 mm (PEEP), 0.9 +/- 0.3 mm (PAO)]. Extracorporeal bypass of the great veins did not alter these findings. LV function curves showed less stroke work at any Pla during PEEP, this being unaffected by vagotomy. When the RV was bypassed, there were no PEEP or PAO related changes in Pla or LV function. Thus diminished LV function with PEEP is probably due to the influence on the LV of a stressed RV in this situation.