Steady-state gas exchange in normothermic, anesthetized, liquid-ventilated dogs

Anesthetized, paralyzed, purebred beagle dogs were ventilated for 45 min (n = 5) and 60 min (n = 5) with oxygenated (PIO2 = 685 mmHg) FC-80 fluorocarbon liquid at 38 degrees C. The PaCO2 remained constant at approximately 43 mmHg during 60 min of liquid ventilation (mean tidal volume = 290 ml, mean respiratory frequency = 2.8 breaths/min). The end-tidal PCO2 was consistently higher than PaCO2 during liquid ventilation. Histological examination by light as well as scanning electron microscopy of the lungs of dogs killed 10, 30, or 180 days after liquid ventilation revealed no pathological changes except for a slight increase in the number of macrophages, especially around the alveolar ducts. It is concluded that a steady state of gas exchange at near normal arterial carbon dioxide partial pressures can be maintained in anesthetized, normothermic dogs ventilated with FC-80 at respiratory frequencies of approximately 3 breaths/min.