LEFT-VENTRICULAR DIASTOLIC FUNCTION DURING SHORT-TERM POSITIVE END-EXPIRATORY PRESSURE VENTILATION IN DOGS

Simultaneous recordings of left ventricular (LV) pressure and volume (sonomicrometry) were made in acutely instrumented dogs anaesthetized with pentobarbital during intermittent positive pressure ventilation with zero and positive end-expiratory pressure at 10 and 20 cmH2O (PEEP10 and PEEP20). Pericardial pressure was measured continuously in order to obtain transmural LV pressure. PEEP reduced LV endiastolic volume and transmural pressure significantly. This was accompanied by significantly reduced stroke volume. LV peak diastolic filling rate, calculated as dV/dt(max), was significantly reduced when PEEP was applied, independent of LV volume alterations. LV diastolic compliance, assessed by the slope of LV pressure-volume relationship during LV filling, decreased significantly with increasing PEEP levels. A positive correlation was observed between reductions in peak diastolic filling rate and reductions in end-diastolic volume. The reduced peak diastolic filling rate, on the other hand, was closely correlated to reduced LV diastolic compliance. Isovolumetric relaxation rate (T) increased slightly at the highest PEEP level. This could, however, not be related to a reduced LV diastolic filling rate. The close association between reduced LV diastolic compliance and reduced diastolic filling rate may indicate that a tamponade-like effect is involved in the reduction of LV preload observed during PEEP ventilation.