EFFECT OF POSITIVE END-EXPIRATORY PRESSURE ON LEFT AND RIGHT VENTRICULAR DIASTORIC FUNCTION ASSESSED BY TRANSESOPHAGEAL PULSED-DOPPLER ECHOCARDIOGRAPHY

Abstract

S118 Although effects of positive end-expiratory pressure (PEEP) on ventricular diastolic function have been studied, most of investigations have focused primarily on ventricular compliance [1,2]. Diastolic function depends on active (ventricular relaxation) and passive (ventricular compliance) components and profoundly influences ventricular filling. Transesophageal pulsed-Doppler echocardiography is a suitable method for assessing ventricular diastolic function by measuring ventricular filling pattern. In the present study, Doppler parameters were used to evaluate the effect of increasing levels of PEEP during mechanical ventilation on both left and right ventricular diastolic function with regard to active and passive components. METHODS: After receiving approval of institutional committee and informed consent, 14 ASA physical status I patients (38-57 yr) were included in the study. Under general anesthesia (isoflurane and nitrous oxide in oxygen) using mechanical ventilation, PEEP level was increased stepwise (0, 5, 10, 15, 20 cmH2 O). At each PEEP level, with transesophageal pulsed-Doppler echocardiography, transmitral and transtricuspid blood flow was obtained and the following variables were assessed: peak velocity of early filling (peak E velocity (cm/s)); peak velocity of atrial contraction (peak A velocity (cm/s)); the ratio of the peak velocity of early filling to atrial contraction (E/A ratio); acceleration half time (AHT (ms)); and deceleration half time (DHT (ms)) of early filling. Care was taken that the Doppler beam was directed as parallel as possible to the long axis of the left and right ventricular inflow tracts, and the data in which the angle between the ultrasound beam and the presumed flow direction exceeded 30 degrees were excluded from the result. Echocardiographic examination was performed at the end-expiration and calculations were averaged over three consecutive cardiac cycles. Differences between 0 cmH2 O PEEP and different PEEP levels were evaluated by ANOVA with repeated measures followed by Bonferroni-Dunn test (p<0.05). RESULTS: Although a measurement of left ventricular Doppler variables was completed in all cases, an adequate measurement of right ventricular Doppler variables was possible only in 8 out of the 14 patients (57%). Peak E velocity of left and right ventricles decreased significantly during PEEP ventilation, while there was no change in the peak A velocity. Consequently, a significant decrease in peak E/A velocity ratio of both ventricles was observed with PEEP. There was no change in AHTs, but DHTs of both ventricles increased significantly with PEEP. (Table 1)Table 1: Doppler echocardiographic data at different levels of PEEPCONCLUSION: Changes in flow patterns indicate left and right ventricular diastolic function abnormalities. Acceleration and deceleration of early filling are theoretically related to ventricular relaxation and compliance, respectively [3]. It is suggested that PEEP is associated with a decrease in compliance of both ventricles, whereas PEEP does not alter ventricular relaxation.