Liquid ventilator for ultrafast hypothermia induction in juvenile lambs: Preliminary results

Total liquid ventilation (TLV) is an emerging mechanical ventilation technique. In this technique, the lungs are filled with liquid perfluorocarbons (PFC) and a liquid ventilator assures ventilation by periodically renewing a volume of oxygenated, CO
₂
freed and temperature controlled PFC. A huge difference between conventional mechanical ventilation and TLV relates to the fact that PFCs are about 1500 times denser than air. Thus, the PFCs filled lungs turn into an efficient heat exchanger with the circulating blood. One of the most appealing utilization of the lungs as a heat exchanger in TLV is for ultrafast induction of mild therapeutic hypothermia (MTH) for neuroprotection and cardioprotection after ischemia-reperfusion injuries. This study aimed to perform ultrafast MTH induction by TLV in animals up to 25 kg, then perform a fast post-hypothermic rewarming while maintaining proper ventilation. A thermal model of the lamb and liquid ventilator was developed to predict the dynamic and the control strategy to adopt for MTH induction. Two juvenile lambs were instrumented with temperature sensors in the femoral artery, pulmonary artery, oesophagus, right eardrum and rectum. After stabilization in conventional mechanical ventilation, TLV was initiated with ultrafast MTH induction, followed by posthypothermic rewarming. Preliminary results in the two juvenile lambs reveal that the liquid ventilator Inolivent-6.0 can induce MTH by TLV in less than 2.5 min for systemic arterial blood and in less than 10 min for venous return, esophagus and eardrum. Rectal temperature reached MTH in respectively 19.4 and 17.0 min for both lambs. Experimental results were consistent with the model predictions. Moreover, blood gas analysis exhibited that the gas exchange in the lungs was maintained adequately for the entire experiments.