MITRAL AND PULMONARY VENOUS FLOW UNDER INFLUENCE OF POSITIVE END-EXPIRATORY PRESSURE VENTILATION ANALYZED BY TRANSESOPHAGEAL PULSED DOPPLER ECHOCARDIOGRAPHY

It has been known since 19481 that positive end-expiratory pressure (PEEP) ventilation causes a decrease in cardiac output. Since then, the effects of PEEP on the heart have been studied in detail. There are mainly 2 mechanisms discussed for the decrease in cardiac output with PEEP. The first hypothesis is that cardiac output is diminished by reduction of systemic venous return. This concept1,2 was questioned later by investigators3,4 who studied transmural pressures and found increased filling pressures with PEEP. They concluded that left ventricular compliance decreases with PEEP owing to interventricular septal shift from right ventricular overload4 or to compression of the heart by the expanded lungs. Subsequently, more precise measurements of filling pressure5 provided no evidence of decreased diastolic compliance. Left ventricular function impairment could not be detected using either equilibrium-gated blood pool scintigraphy or transesophageal 2-dimensional echocardiography.6 Most examinations have relied on hemodynamic measurements that are dependent on intricate pressure recordings that are not always reliable.4,5 This study attempts to gain insight into changes in hemodynamics after induction of PEEP by measuring flow patterns with Doppler echocardiography. To examine the mechanism of reduction in cardiac output produced by high levels of PEEP ventilation, left atrial and left ventricular filling patterns were recorded with pulsed Doppler for 0- and 15-cm H2O PEEP. © 1991.