Perfluorocarbon (PFC) Improves Oxygenation in Severely Surfactant-Depleted Spontaneously Breathing Rabbits maintained on Proportional Assist Ventilation(PAV) 1760

Background: Partial liquid ventilation (PLV) has been shown to improve pulmonary mechanics and gas exchange in severe respiratory distress syndrome during controlled mechanical ventilation. PAV, also known as resistive and elastic unloading, compensates for high airway resistance and low alveolar compliance, and thereby facilitates spontaneous breathing. We hypothesized that PLV would improve oxygenation in non-paralyzed surfactant deficient rabbits breathing spontaneously while assisted by PAV.Methods: Nine anesthetized rabbits (median 2345g, range 2240-2630g) received an arterial femoral line for blood gas measurements and subsequently underwent pulmonary lavage until the PaO₂ was < 100 mmHg during mechanical ventilation using a PEEP of 6 cmH₂O and an FiO₂ of 1.0. Thereafter, the rabbits were switched to PAV (PEEP 8 cmH₂O), and the degree of unloading was adjusted to compensate approximately for the resistance of the endotracheal tube and to maintain PaCO₂ at 40-50 mmHg. They were randomized to PAV with or without PLV. For PLV, the rabbits received 25 ml/kg Rimar-101 by intratrachcal infusion (1 ml/kg/min). Evaporated PFC was replenished q 30 minutes. Mean airway pressure (MAP), expiratory minute ventilation (VE), respiratory rate (RR), heart rate (HR) and mean blood pressure (MBP) were recorded continuously for 5 hours. Every 30 minutes, a 15-minute average was obtained, and PaO₂ and PaCO₂ were measured. Results: PaO₂ was significantly higher in the PLV rabbits compared to controls (p<0.05, RM ANOVA). All other parameters were similar in both group (table, medians and 25th - 75th percentile). Conclusion: Partial Liquid Ventilation improves oxygenation in spontaneously breathing severely surfactant depleted rabbits maintained on Proportional Assist Ventilation.

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