Abstract 172: Ultra-Fast Cooling Through Total Liquid Ventilation is Safe and Feasible in Non-Human Primates

Abstract

Introduction: Total liquid ventilation (TLV) with temperature-controlled perfluorocarbons (PFC) provides ultra-rapid and protective cooling in animal models of cardiac arrest. However, the ideal ventilatory parameters still need to be determined for a perfectly safe translation of the procedure in humans, especially regarding expiratory residual volume (RV) and tidal volume of PFC (TV) during TLV. Hypothesis: We hypothetised that TLV with low RV and TV of PFC is safe and efficient for ultra-fast cooling induction in non-human primates. Method: We enrolled two 13-years monkeys ( Macaca Fascicularis ) weighting 10.6 and 11.7 kg, respectively. Lung functional residual capacity (FRC) was measured by CT-scan and 3D-reconstruction of the lung. Two weeks later, animals were anesthetised and submitted to 20 min of TLV with end-expiratory volume of ≈50% of the FRC and TV = 8 ml/kg. The respiratory rate was set to 8/min and the target temperature was 33°C. After the TLV procedure, animals were weaned by prolonged exhalation followed by 6 hours under conventional mechanical ventilation (PEEP = 5 mmHg) before awakening. Three weeks later, they were ansthestized again for blood gases measurement and CT-scan examination for evaluation of the lung parenchyma integrity. Result: The initial CT-scan revealed a FRC of 26 and 32 ml/kg in the two animals, respectively. RV was then set at 15 ml/kg for TLV in both animals. During TLV, gas exchanges were normal (arterial partial pressure of CO 2 was 34 and 43 mmHg, respectively). Pulse oxymetry also remained above 97% throughout TLV. The target temperature of 33°C was achieved in the entire body within 15 min for both animals. Additionally, lung static compliance was not altered during or after TLV. After animal weaning, no any sign of respiratory discomfort was evidenced despite careful clinical monitoring. After three weeks, CT-scan examination revealed no structural abnormality of the lung parenchym and arterial partial pressure of CO 2 was normal (35 and 46 mmHg). Based on their excellent health status, animals were transferred to a rehabilitation center. Conclusion: Total liquid ventilation below FRC is feasible and safe, without any impairement of the cooling performance in a clinically relevant non-human primate model.