CHANGES IN THORACOPULMONARY COMPLIANCE AND HEMODYNAMIC-EFFECTS OF POSITIVE END-EXPIRATORY PRESSURE IN PATIENTS WITH OR WITHOUT HEART-FAILURE

Purpose: The purpose of this study was to confirm that positive end-ex piratory pressure (PEEP) has a different effect on cardiac index (CI) in patients with or without heart failure, even after controlling for differences in thoracopulmonary compliance (Ctp) and minimizing the se condary effects of PEEP related changes in oxygenation and breathing e ffort. Materials and Methods: The hemodynamic effects of PEEP were eva luated in two groups of sedated and paralyzed patients with a low Ctp at 0 PEEP: 12 patients with normal pulmonary artery occlusion pressure (Ppao) and a CI > 2.5 L/min and 12 patients with a CI < 2.5 L/min and increased oxygen extractio ratio, despite a Ppao > 15 mm Hg. Results: In patients with low CI and high Ppao, PEEP had no hemodynamic effect and Ctp remained low at all PEEP levels. However, PEEP-induced CI red uction in patients with normal cardiovascular function was associated with an increase in Ctp with incremental PEEP. Concerning PEEP-related hemodynamic effects, the significance between group differences persi sted when data were analyzed after controlling for C-tp changes. Howev er, Ctp changes with PEEP were the most significant correlators and di scriminators of the magnitude and direction of PEEP-induced CI change. Conclusions: We conclude that (1) the observed different effect of PE EP on CI in patients with and without heart failure persists after the elimination of secondary effects due to underlying differences in Ctp , oxygenation, and breathing effort; and (2) PEEP-related changes in C tp should be taken into consideration when dealing with the cardiovasc ular effects of PEEP. Our data support the hypothesis that, in additio n to the transmission of PEEP to the pleural space, changes in lung vo lume are a significant determinant of PEEP-induced CI changes. Copyrig ht (C) 1997 by W.B. Saunders Company.