Background:We examined the effects of varying inspiratory to expiratory (I:E) ratio on gas exchange and hemodynamics during high frequency partial liquid ventilation (HFPLV), a combination of high frequency ventilation (HFV) and partial liquid ventilation (PLV), in a rabbit model of acute lung injury.Methods: Twelve rabbits treated with repeated saline lavage were divided into two groups. In the HFPL group (n = 6), 6 ml/kg of perfluorodecaline was administered through the endotracheal tube. Rabbits in this group and in the HFJ group (n = 6) were treated with high frequency jet ventilation (HFJV) at I:E ratios of 1:1, 1:2, and 1:3 for 15 minutes, and arterial blood gas, mixed venous blood gas and hemodynamic parameters were measured.Results: We observed no significant respiratory and hemodynamic differences between the two groups. At an I:E ratio of 1:1, the PaO2 was significantly higher, and the shunt rate and PaCO2 were significantly lower in both groups, compared with I:E ratios of 1:2 and 1:3. Cardiac output at the 1:3 I:E ratio was significantly higher than at 1:1.Conclusions: These findings indicate that, in this model, a 1:1 I:E ratio was superior for oxygenation and ventilation than I:E ratios of 1:2 or 1:3, while having no detrimental effects on hemodynamics.