Effects of Vaporized Perfluorocarbon on Pulmonary Blood Flow and Ventilation/Perfusion Distribution in a Model of Acute Respiratory Distress Syndrome

Background: Perfluorocarbon (PFC) liquids are known to improve gas exchange and pulmonary function in various models of acute respiratory failure. Vaporization has been recently reported as a new method of delivering PFC to the lung. Our aim was to study the effect of PFC vapor on the ventilation/perfusion (V A /Q) matching and relative pulmonary blood flow (Q rel ) distribution. Methods: In nine sheep, lung injury was induced using oleic acid. Four sheep were treated with vaporized perfluorohexane (PFX) for 30 min, whereas the remaining sheep served as control animals. Vaporization was achieved using a modified isoflurane vaporizer. The animals were studied for 90 min after vaporization. V A /Q distributions were estimated using the multiple inert gas elimination technique. Change in Q rel distribution was assessed using fluorescent-labeled microspheres. Results: Treatment with PFX vapor improved oxygenation significantly and led to significantly lower shunt values (P < 0.05, repeated-measures analysis of covariance). Analysis of the multiple inert gas elimination technique data showed that animals treated with PFX vapor demonstrated a higher V A /Q heterogeneity than the control animals (P < 0.05, repeated-measures analysis of covariance). Microsphere data showed a redistribution of Q rel attributable to oleic acid injury. Q rel shifted from areas that were initially high-flow to areas that were initially low-flow, with no difference in redistribution between the groups. After established injury, Q rel was redistributed to the nondependent lung areas in control animals, whereas Q rel distribution did not change in treatment animals. Conclusion: In oleic acid lung injury, treatment with PFX vapor improves gas exchange by increasing V A /Q heterogeneity in the whole lung without a significant change in gravitational gradient.