Total Liquid Ventilation Improves Oxygenation in an Experimental Model of Acute Respiratory Distress Syndrome

Overview

Objective:
To assess gas exchange during total liquid ventilation (TLV) in an experimental model of acute respiratory distress syndrome (ARDS).Type of study: Laboratory experiment on animal model.Setting: The laboratory of experimental pathophysiology, Medical Faculty, Masaryk University, Brno.Subjects: 12 laboratory animals – rabbits.Method: After premedication, tracheostomy was performed in all animals. EKG, central venous pressure and arterial pressure were monitored.After conventional mechanical ventilation rabbits were randomly allocated into two groups: 1 st group with intact lungs and 2nd group with experimentalARDS. The animals in the 1st group were ventilated with total liquid ventilation, followed by conventional mechanical ventilation. ARDS was inducedby wash-out of lungs with normal saline in the animals in the 2nd group. After period of total liquid ventilation, conventional mechanical ventilationfollowed. All phases of the experiment lasted 60 minutes. We monitored heart rate, acid-base balance, blood gases, central venous pressure and bloodpressure in 5 minutes interval; the values were compared at the end of each period.Results: Group 1: the decrease in pH during liquid ventilation (LV) persisted after the period of LV (statistically significant), the rise of paCO2during LV and the decrease after LV were statistically significant. The decrease of paO2/FiO2 during LV and its increase after LV was also statisticallysignificant. Group 2: pH decreased during lung lavage and subsequently during LV (all statistically significant), paCO2 increased during lavage andsubsequently during LV (statistically significant) with the decrease after LV. paO2/FiO2 after the decrease during lavage rised during LV andsubsequently decreased after LV period (all statistically significant).Conclusion: TLV can improve oxygenation after experimentally induced ARDS; hypercapnia and acidosis persist. In healthy lungs, however,oxygenation and ventilation are compromised; the changes are reversible.

Key words:
total liquid ventilation - acid-base balance - blood gases - ARDS - experiment