Effects of Positive EndExpiratory Pressure Ventilation on Right Atrial Size and Atrial Natriuretic Factor Release in Humans

Atrial natriuretic factor (ANF) release is augmented by atrial distention whereas positive end-expiratory pressure (PEEP) ventilation has the opposite effect. We tested the hypothesis that PEEP-induced decrease in ANF secretion is mediated by decrease in right atrial (RA) distention. Accordingly, eight hemodynamically stable mechanically ventilated patients (age: 22-49) in sinus rhthm and without kidney or cardiovascular disease were studied. central venous catheter (3Fr) and fluid-filled probe were inserted into the R and esophagus, respectively, in order to measure transmural R pressure (tP). radial artery catheter was placed to monitor blood pressure (BP) and withdraw blood samples for the measurement of plasm immunoreactive ANF (irANF). Blood pressure, diuresis, tP, endsystolic R are at the level of the foramen ovale (acquired using transesophageal echocardiography at end-expiration) and irANF were measured at the end of 3 consecutive 30 min periods of: (1) mechanical ventilation at zero end-expiratory pressure (ZEEP1); (2) application of PEEP + 15 cm of H2O; and (3) after withdrawal of the PEEP (ZEEP2). Results: Variations of irANF and R are were directly correlated (r = 0.82, p < 0.001)). Results are expressed as mean ± SEM; *: p < 0.05 versus ZEEP1 values. Conclusion: As expected, PEEP resulted in decrease in both R are and tP as well as ANF secretion. These dat support the hypothesis that PEEP-induced decreases in circulating ANF are related to decreased R distention, which may contribute to the antidiuresis noted in patients ventilated with positive end-expiratory pressure.