Increased pulmonary vascular resistance during liquid ventilation

The effect of liquid ventilation on pulmonary vascular resistance was studied in an isolated cat lung preparation in situ. Lungs were perfused with whole blood from a donor cat at a constant flow of 100 ml . min-1 kg-1. Pulmonary arterial venous pressures were measured, and pulmonary vascular resistance calculated during gas ventilation (control) and ventilation with fluorocarbon, FC-80. During control ventilation at a mean tidal volume (VT) of 28 +/- 1 (SEM) ml and lung volume of 108 +/- 8 (SEM) ml, pulmonary vascular resistance was 0.07 +/- 0.01 (SEM) PRU. During liquid ventilation at similar lung volumes, pulmonary vascular resistance increased by 62% to 0.12 +/- 0.03 (SEM) PRU (P less than 0.05). At greater liquid lung volumes reflecting optimum CO2 elimination, pulmonary vascular resistance increased by 115% over control values to 0.15 +/- 0.01 (SEM) PRU (P less than 0.005). These data demonstrate significant alterations in pulmonary circulation during liquid ventilation, and suggest that further studies should be completed before hyperbaric applications in human can be considered.