INFLUENCE OF POSITIVE END-EXPIRATORY PRESSURE ON RIGHT AND LEFT-VENTRICULAR PERFORMANCE ASSESSED BY DOPPLER 2-DIMENSIONAL ECHOCARDIOGRAPHY

The advent of modern Doppler two-dimensional ultrasound technology has overcome the need of invasive measurements of several important cardi ac parameters. It allows estimation of preload, contractility, and aft erload. Positive end-expiratory pressure (PEEP) is associated with a r eduction in cardiac output. The responsible mechanisms are controversi al. To evaluate the cardiovascular responses to PEEP, we employed diff erent Doppler hemodynamic indices for the first time, combined with co nventional two-dimensional echocardiography. Twenty-one healthy, young , and unsedated volunteers were admitted to the study. Under spontaneo us respiration, PEEP level was increased stepwise (0, 5, 7.5, 10, 12.5 cm H2O). At each PEEP level, the following right and left ventricular parameters were assessed with Doppler two-dimensional echocardiograph y: two-dimensional variables: end-diastolic volume indices (EDVI), eje ction fraction (EF), and left ventricular afterload - LaPlace relation (combined with cuff systolic pressure); Doppler variables: cardiac in dex (CI) (combined with two-dimensional measure of valve area), maximu m velocity (Vmax), time velocity integral (TVI), acceleration time (AT ), deceleration time (DT), deceleration rate (DR), ratio of early to a trial peak (E/A), ratio isovolumic contraction time to ejection time ( IVCT/ET), and maximum blood acceleration (dv/dt) in aorta and main pul monary artery. Increasing PEEP resulted in a proportional decrease in biventricular EDVI. Moreover, PEEP application is also causing a drop of CI, which is determined from a decrease in Vmax and TVI, while EF, IVCT/ET, dv/dt, Doppler transatrioventricular parameters, and afterloa d stay in normal ranges. Employing Doppler hemodynamic indices for the first time in this study setting clearly supports data that the drop in EDVI and CI during PEEP is caused by reduction in ventricular filli ng due to decreased venous return. Using the Doppler parameters IVCT/E T and dv/dt, changes in myocardial contractility, as well as changes i n afterload (LaPlace relation) can be ruled out.