Objective: To evaluate the effect of combination of partial liquid ventilation (PLV) and high frequency oscillatory ventilation (HFO) on blood gases exchange in acute respiratory distress syndrome (ARDS) model. Type of study: Laboratory experiment on animal model. Setting: The laboratory of experimental pathophysiology, Medical Faculty, Masaryk University, Brno. Subjects: 18 laboratory animals – rabbits. Method: After premedication, tracheostomy was performed in all animals. ECG, central venous pressure and arterial pressure were monitored. After initial conventional mechanical ventilation, rabbits were randomly allocated into two groups: 1st group with intact lungs and 2nd group with experimental ARDS. The animals in the 1st group were ventilated with HFO, followed by PLV with HFO. Subsequently, perfluorocarbon (PFC) was removed b y suction and rabbits were ventilated in HFO. ARDS was induced by repeated wash-out of lungs with normal saline in the animals in the 2nd group; PLV with HFO followed, after PFC removal replaced with HFO. All phases of the experiment lasted 60 minutes. We monitored acid-base balance, blood gases and mean airway pressure in 5 minutes interval; the values were compared at the end of each period. Results: Group 1: Decrease in pH during PLV and gradual return to normal values is not statistically significant, as well as paCO2 rise during PLV and decrease during HFO. paO2/FiO2 during the initial phase of PLV decreases, in the late phase increases and is even higher compared to initial HFO. Nevertheless, after PLV termination, during HFO, decrease can be observed. Almost no changes can be detected in mean airway pressure (Paw). Group 2: decrease in pH during lung lavage is statistically significant, during PLV gradually increases and returns to normal values. paCO2 increases during lavage and initial phase of PLV, but during PLV and during HFO decreases to original levels. paO2/FiO2 steeply decreases after lavage and even in the initial phase of PLV increases, peaking at the end of PLV. In the following period of HFO decreases again. Paw during experiment does not change significantly. Conclusion: Using combination of PLV and HFO in experimental ARDS model, significant improvement of oxygenation could be achieved; this improvement is restricted to the PLV and HFO period only, not extending beyond PLV termination. Ventilation is kept within normal limits, transitory acidosis is controlled with PLV and HFO. In intact lungs, PLV and HFO combination also leads to improvement in oxygenation which is not possible without PLV. Changes in pH and ventilation are not statistically significant. Blood gases could be maintained within normal limits during PLV and HFO with minimal Paw.

        Key words: partial liquid ventilation – high frequency oscillatory ventilation - acute respiratory distress syndrome - experiment - acid-base balance - ventilation - oxygenation