A POTENTIAL CLINICAL METHOD FOR CALCULATING TRANSMURAL LEFT-VENTRICULAR FILLING PRESSURE DURING POSITIVE END-EXPIRATORY PRESSURE VENTILATION - AN INTRAOPERATIVE STUDY IN HUMANS

Objectives. This study sought to investigate whether right atrial pres sure could be used to estimate pericardial pressure during positive en d-expiratory pressure (PEEP), Background. Because of elevated intratho racic pressure during PEEP, pulmonary capillary wedge pressure may not accurately reflect left ventricular preload, An estimate of pericardi al pressure during PEEP would allow assessment of transmural filling p ressure, Methods. In eight patients, at the start of cardiac surgery, pericardial and pleural pressures were recorded by balloon transducers placed over the anterolateral left ventricular wall. We also recorded intravascular pressures and left ventricular short-asis area by trans esophageal echocardiography, Results. A stepwise increase in PEEP from 0 to 15 cm H2O caused a linear increase in pleural pressure from 0.3 +/- 0.6 (mean +/- SEM) to 6.1 +/- 0.8 mm Hg (p < 0.01), Pericardial pr essure increased from 2.3 +/- 0.5 to 5.9 +/- 0.6 mm Hg (p < 0.01), The correlation between right atrial (P-ra) and pericardial sure (P-peric ) was good: P-ra = 0.85 x P-peric + 1.8, r = 0.77, The correlation bet ween changes in right atrial pressure and in pericardial pressure was better: Delta P-ra = 0.96 x Delta P-peric -0.2, r = 0.97, Pulmonary ca pillary wedge pressure increased with PEEP (p < 0.05), whereas left ve ntricular area decreased (p < 0.05), However, there was a progressive reduction in transmural pressure, calculated as wedge pressure minus p ericardial pressure (p < 0.05), and in transmural pressure, estimated as wedge pressure minus right atrial pressure (p < 0.05), The estimate d transmural filling pressure correlated (r = 0.86) with end-diastolic area. Conclusions. The present observations suggest that right atrial pressure may be used to estimate changes in pericardial pressure with PEEP and that pulmonary capillary wedge pressure minus right atrial p ressure is a potentially clinically useful approximation of transmural filling pressure.