Effects of partial liquid ventilation with perfluorocarbons on pressure-flow relationships, vascular compliance, and filtration coefficients of isolated blood-perfused rabbit lungs

Objectives: The density of perfluorocarbons is almost twice that of blood. Therefore, we hypothesized that partial liquid ventilation with these fluids markedly affects pulmonary hemodynamics and filtration coefficients. To test these hypotheses we studied pressure-flow relationships, vascular compliances, capillary pressures, and filtration coefficients in normal and perfluorocarbon-ventilated rabbit lungs. Design: Controlled animal study with an ex-vivo isolated lung preparation. Setting: Research laboratory for experimental anesthesiology at the Heinrich-Heine-University of Dusseldorf. Subjects: Fourteen New Zealand White rabbits. Interventions: The lungs were perfused under zone 3 flow conditions with autologous blood at various flow rates (50 to 250 mL/min, closed circuit, roller pump, 37 degrees C) and ventilated with 5% CO2 in air (positive end-expiratory pressure: 2 cm H2O, tidal volume: 10 mL/kg, respiratory rate: 30 breaths/min) without (control group, n = 7) and with (n = 7) perfluorocarbon administered intratracheally (15 mL/kg). Measurements and Main Results: Pulmonary arterial, left atrial, and airway pressures, as well as blood reservoir volume (reflecting changes in pulmonary blood volume) and lung weight, were measured continuously. Inconsistent with our hypothesis, we found no significant differences between both groups in the slopes and intercepts of the pressure-flow relationships. There were no significant differences in capillary pressures determined by double occlusion (6.7 +/- 1.2 vs. 6.3 +/- 1.3 cm H2O for control group, p = .53), vascular compliances (0.51 +/- 0.10 vs. 0.47 +/- 0.09 mL/cm H2O for control group, p = .38), and filtration coefficients (0.33 +/- 0.06 vs. 0.37 +/- 0.07 mL/min/mm Hg/100 g wet weight for control group, p = .80, Mann-Whitney). Conclusions: Partial liquid ventilation with perfluorocarbons has no relevant effects on pulmonary filtration coefficients and global hemodynamic variables of isolated zone 3 lungs. These findings suggest that right ventricular afterload is not changed with partial liquid ventilation. It is likely, however, that intrapulmonary blood flow is redistributed toward less dependent regions, although relevant global hemodynamic changes are absent during partial liquid ventilation.