Type of investigation: Laboratory experiment on animal model. Place: Laboratory of the Chair of Experimental Pathophysiology, Masaryk University Brno. Subjects: 18 laboratory animals - rabbits. Method: After premedication, tracheostomy was performed in the animals, ECG, central venous pressure and arterial pressure were monitored. After the initial conventional mechanical ventilation the rabbits were divided into two groups: group 1 with intact lungs and group 2 with experimental ARDS. In group 1 the initial HFO took place and subsequently PLV with HFO. Then perfluorocarbon (PFC) was drawn off and the rabbits were again connected to HFO. In group 2 after the initial HFO ARDS was induced by repeated lavage of the lungs with saline, followed by PLV with HFO and finally, after drawing off PFC, only HFO. Each stage lasted 60 minutes. After five-minute intervals the authors recorded the acid-base balance blood gases and mean airway pressure. The values were compared at the end of each stage. Results: Group 1: Drop of pH during PLV and gradual return to normal is not statistically significant, similarly as the rise of PaCO2 during PLV and the decline during HFO. PaO2/FiO2 at the beginning of PLV declines, but at the end of PLV it rose and is even higher than during the initial HFO. Nevertheless after termination of PLV, during HFO a decline is apparent. The mean airway pressure (Paw) remains almost unchanged throughout the experiment. Group 2: The decline of pH during the lavage of the lungs is statistically significant but during PLV it rises gradually and returns to normal. PaCO2 increases during lavage and at the onset of PLV, but during PLV and HFO it declines to original levels. PaO2/FiO2 declines briskly after lavage and increases already at the onset of PLV, the values being highest at the end of PLV. During the subsequent HFO it declines again. Paw does not undergo any significant changes during the experiment. Conclusion: By combination of PLV and HFO in experimental ARDS it is possible to achieve markedly improved oxygenation which does not proceed after termination of PLV. Ventilation is maintained within the limits of normal values, the transient acidosis is normalized by a combination of PLV and HFO. In intact lungs, by combination of PLV and HFO, improved oxygenation is achieved which is not possible without PLV. Changes of pH and ventilation are not statistically signifikant. During PLV with HFO it is possible to maintain blood gases at satisfactory levels with minimal Paw.

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