Cardiac output during liquid (perfluorocarbon) breathing in newborn piglets

Background and Methods: Liquid ventilation using perfluorocarbons is a new technique for ventilation of infants with restrictive lung disease. However, this method of ventilation has been shown to impair cardiac output (Qt) in several animal species, casting doubt as to its feasibility. This study tested whether Qt could be maintained during liquid breathing by intravascular volume expansion. Seven piglets were carefully hydrated, instrumented for continuous Qt measurement, and subjected to 2 hr of liquid breathing. PaCo₂ was maintained at 40 to 50 torr (5.3 to 6.7 kPa), and PaO₂ >80 torr (>10.7 kPa). Additional colloid was given during liquid breathing if Qt decreased to <90% of preliquid breathing values. Results: Four piglets maintained Q̇t throughout the liquid breathing trial with maintenance fluids only. Three piglets each required one 10 mL/kg fluid bolus for Q̇t 82% to 89% of the baseline value, after which Q̇t rapidly increased to >90% of baseline. Oxygen consumption and serum lactate levels remained normal throughout liquid breathing. Conclusion: Q̇t is readily maintained during liquid breathing in properly hydrated animals.