Coronary flow limits right ventricular performance during positive end-expiratory pressure.

The effect of positive end-expiratory pressure (PEEP) on right ventricular performance and myocardial blood flow was determined in 16 dogs before and after right coronary artery (RCA) occlusion. Right ventricular ejection fraction (RVEF), end-diastolic volume (EDV) and end-ejection volume were measured by thermodilution. Right ventricular end-ejection pressure-volume relations (RVEEPVR) were determined at baseline and at 20 cm H2O PEEP, both before and after RCA occlusion. In four of the dogs, RVEEPVR were also determined at 10 cm H2O PEEP after RCA occlusion. With intact RCA flow, RVEF declined with PEEP (37 +/- 5 to 19 +/- 6%) with no significant change in EDV (50 +/- 11 to 42 +/- 11 ml) or end-ejection volume (31 +/- 7 to 36 +/- 9 ml). RVEEPVR and right ventricular myocardial blood flow were also unchanged with PEEP. After RCA occlusion, RVEF declined with PEEP (27 +/- 4 to 15 +/- 5%) in association with a significant increase in end-ejection volume (39 +/- 8 to 49 +/- 10 ml), but no change in EDV (53 to 55 ml). In addition, RVEEPVR and myocardial blood flow declined with RCA occlusion, and declined further with 20 cm H2O, but not with 10 cm H2O PEEP, after RCA occlusion. Therefore, in this experimental model, right ventricular performance was adversely affected during PEEP when right coronary blood flow was limited.