Hemodynamic effects of positive end-expiratory pressure during partial liquid ventilation in newborn lambs

Abstract

Background/Purpose: The aim of this study was to compare the effect of positive end-expiratory pressure (PEEP) application on hemodynamics, lung mechanics, and oxygenation in the intact newborn lung during conventional ventilation (CV) and partial liquid ventilation (PLV) at functional residual capacity (FRC). CV or PLV modes of ventilation do not affect hemodynamics nor the optimum PEEP for oxygenation. Methods: Seven newborn lambs (1 to 3 days old) were instrumented to measure pulmonary hemodynamics and airway mechanics. Each lamb was used as their own control to compare different modes of ventilation (CV followed by PLV) under graded variations of PEEP (4, 8, 12, and 16 cm H2O) on the influence on pulmonary blood flow and pulmonary vascular resistance. Results: There was a significant drop in pulmonary blood flow (PBF) from baseline (PEEP of 4 cm H2O on CV, 1,229 ± 377 mL/min) in both modes of ventilation on a PEEP of 16 cm H2O (CV, 750 ± 318 mL/min v PLV, 926 ± 396 mL/min, respectively; P <.05). Peak inspiratory pressure (PIP) was higher on PLV at PEEP states of 4 cm H2O (16.5 ± 1.3 cm H2O to 10.6 ± 2.1 cm H2O; P <.05) and 8 cm H2O (18.8 ± 2.2 cm H2O to 15.1 ± 2.6 cm H2O; P <.05) when compared with CV. Conversely, PIP required to maintain the pCO2 was lower on PLV at PEEP states of 12 (22.5 ± 3.6 cm H2O to 24.2 ± 3.8 cm H2O; P <.05) and 16 cm H2O (27.0 ± 1.6 cm H2O to 34.0 ± 5.9 cm H2O; P <.05). Conclusions: Hemodynamically, CO is impaired at a PEEP above 12 cm H2O in intact lungs. PFC at FRC does provide an advantage in lung mechanics more than 10 to 12 cm H2O of PEEP by decreasing the amount PIP needed to achieve the similar levels of gas exchange and minute ventilation, implying a reduced risk for barotrauma with chronic ventilation. Thus, selection of the appropriate level of PEEP appears to be important if PLV is to be utilized at FRC. The best strategy for PLV, including the selection of PEEP, remains to be determined. J Pediatr Surg 36:1327-1332. Copyright © 2001 by W.B. Saunders Company.