Perfluorocarbon-associated gas exchange in normal and acid-injured large sheep

Objectives: We hypothesized that: a) perfluorocarbon-associated gas exchange could be accomplished in normal large sheep; b) the determinants of gas exchange would be similar during perfluorocarbon-associated gas exchange and conventional gas ventilation; c) in large animals with lung injury, perfluorocarbon-associated gas exchange could be used to enhance gas exchange without adverse effects on hemodynamics; and d) the large animal with lung injury could be supported with an FiO₂ of <1.0 during perfluorocarbon-associated gas exchange. Design: Prospective, observational animal study and prospective randomized, controlled animal study. Setting: An animal laboratory in a university setting. Subjects: Thirty adult ewes. Measurements and Main Results: Five normal ewes (61.0 ± 4.0 kg) underwent perfluorocarbon-associated gas exchange to ascertain the effects of tidal volume, end-inspiratory pressure, and positive end-expiratory pressure (PEEP) on oxygenation. Respiratory rate, tidal volume, and minute ventilation were studied to determine their effects on CO₂ clearance. Sheep, weighing 58.9 ± 8.3 kg, had lung injury induced by instilling 2 mL/kg of 0.05 Normal hydrochloric acid into the trachea. Five minutes after injury, PEEP was increased to 10 cm H₂O. Ten minutes after injury, sheep with PaO₂ values of <100 torr (<13.3 kPa) were randomized to continue gas ventilation (control, n = 9) or to institute perfluorocarbon-associated gas exchange (n = 9) by instilling 1.6 L of unoxygenated perflubron into the trachea and resuming gas ventilation. Blood gas and hemodynamic measurements were obtained throughout the 4-hr study. Both tidal volume and end- inspiratory pressure influenced oxygenation in normal sheep during perfluorocarbon-associated gas exchange. Minute ventilation determined CO₂ clearance during perfluorocarbon-associated gas exchange in normal sheep. After acid aspiration lung injury, perfluorocarbon-associated gas exchange increased PaO₂ and reduced intrapulmonary shunt fraction. Hypoxia and intrapulmonary shunting were unabated after injury in control animals. Hemodynamics were not influenced by the institution of perfluorocarbon- associated gas exchange. Conclusions: Tidal volume and end-inspiratory pressure directly influence oxygenation during perfluorocarbon-associated gas exchange in large animals. Minute ventilation influences clearance of CO₂. In adult sheep with acid aspiration lung injury, perfluorocarbon- associated gas exchange at an FiO₂ of <1.0 supports oxygenation and improves intrapulmonary shunting, without adverse hemodynamic effects, when compared with conventional gas ventilation.