Hemodynamic effects of positive end-expiratory pressure during high-frequency ventilation

We studied the intrapleural and hemodynamic effects of positive end-expiratory pressure (PEEP) during high-frequency ventilation (HFV) with a Venturi high-frequency ventilator (Bird). Ten healthy mongrel dogs were anesthetized with sodium pentobarbital, catheterized with intrapleural and thermodilution pulmonary artery lines, and subjected to oleic acid-induced pulmonary edema. A mean PEEP of 16 +/- 6 (SD) cm H2O restored venous admixture to baseline in nine animals. Both mean airway pressure (Paw) and mean intrapleural pressure (Ppl) increased significantly with each increment of PEEP during HFV. Approximately 50% of Paw was transmitted to the intrapleural space. Cardiac index (CI) decreased with increments of PEEP in spite of constant transmural central venous and pulmonary capillary wedge pressures, so that oxygen delivery decreased despite increased PaO2. Possible mechanisms of PEEP-induced depression of CI during HFV are discussed. We conclude that both hemodynamic and intrapleural effects of PEEP during HFV are similar to those during conventional mechanical ventilation.