Partial Liquid Ventilation (PLV) combined with Proportional Assist Ventilation (PAV) in Spontaneously Breathing Animals: Follow-up of Gas Exchange and Survival over a Four Week Period in a Rabbit Model 1673

This study tests the hypothesis that animals can be returned safely to gas ventilation after assisted ventilation with PLV combined with PAV.Methods: Nine anesthetized and intubated adult rabbits were ventilated using PAV with an FiO₂ of 1.0 and a PEEP of 6 [4-6] cmH₂O. The degree of unloading was adjusted to compensate approximately for the resistance of the endotracheal tube and to maintain a PaCO₂ of 40-50 mmHg. An arterial femoral line was placed for blood gas measurements. Then a single dose of 30 ml/kg Perfluorocarbon (PFC), (Rimar 101) was instilled continuously into the endotracheal tube (rate 0.5ml/kg/min). The first two animals (early extubation group) were extubated after PaO₂ had returned to baseline (approximately after 1 1/2 h); in subsequent animals(late extubation group; n=7) FiO₂ was weaned after 3 h from 1.0 to 0.21 and animals were extubated after 5 h. Arterial blood gases were obtained in hourly intervals as well as 1 h, 12 h and 28 days after extubation. Weight gain was assessed in weekly intervals. Results: The two early extubated animals died within 48 h. Lung autopsy showed severe local emphysema in non-dependent regions, suggesting that evaporation had been incomplete, resulting in overdistension of non-dependent ventilated areas. 2/7 animals of the late extubation group died (one from a pneumothorax immediately after extubation and another for unknown reasons). Both did not show any evidence for pulmonary emphysema on autopsy. The other 5 animals were longterm survivors and showed progressive weight gain (106 ± 97 g/wk).Conclusion: Animals may be returned safely to gas ventilation after being supported with PLV combined with PAV if evaporation of PFC is complete. Table

Table 1 No caption available.