Partial liquid ventilation ventilates better than gas ventilation

Partial liquid ventilation (PLV) improves oxygenation in several models of lung injury. However, PLV has only been compared with conventional gas vent ilation (GV) with low PEEP. Both PLV and GV can markedly improve oxygenatio n when PEEP is set above the lower corner pressure (Plc) on the inspiratory pressure-volume (P-V) curve of the total respiratory system. We questioned if the use of PEEP set above the Pie during PLV and CV would result in sim ilar gas exchange. Lung injury was induced in 12 sheep by saline lavage bef ore randomization to PLV (n = 6) or CV (n = 6). Animals in the PLV group we re filled with perflubron (22 ml/kg) until a meniscus at the teeth was obse rved. Both groups were then ventilated with pressure control (Fl(O2), 1.0; rate, 20/min; I:E, 1:1) and PEEP (1 cm H2O above the Plc on the inspiratory P-V curve). Peak inspiratory pressure (PIP) was limited to 35 cm H2O. Anim als were ventilated for 5 h and then killed for histologic examinations. Al l 12 animals survived the 5-h ventilation period. After increasing PEEP abo ve Plc, PaO2 increased significantly (p < 0.01) in both the GV and the PLV groups, but it did not differ significantly between groups (p = 0.86) at an y time during the experiment. Pa-CO2 and V-D/V-T in CV increased markedly t hroughout the experiment after increasing PEEP (p < 0.001), but there was n o significant change in Pa-CO2 in PLV (p = 0.13). Mean arterial blood press ure, mean pulmonary artery pressure, pulmonary artery occlusion pressure, a nd central venous pressure, increased and SVR decreased in GV (p < 0.05). T he extent and the severity of lung injury in the dependent regions was grea ter in the GV group (p < 0.05). Both PLV and GV improved oxygenation, but P LV resulted in better ventilation than GV while preserving lung structure w hen PEEP was set 1 cm H2O above the Plc and PIP limited to 35 cm H2O.