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. Vap orization has been recently reported as a new method of delivering PFC to t he lung. Our aim was to study the effect of PFC vapor on the ventilation/pe rfusion ((V) over dot(A)/(Q) over dot) matching and relative pulmonary bloo d flow ((Q) over dot(rel)) distribution. Methods: In nine sheep, lung injury was induced using oleic acid. Four shee p 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) over dot(A)/(Q) over dot) distributions were estimated using the multiple Inert gas elimination technique. Change in (Q) over dot( rel) distribution was assessed using fluorescent-labeled microspheres. Results: Treatment with PFX vapor improved oxygenation significantly and le d to significantly lower shunt values (P < 0.05, repeated-measures analysis of covariance). Analysis of the multiple inert gas elimination technique d ata showed that animals treated with PFX vapor demonstrated a higher hetero geneity than the control animals (P < 0.05, repeated-measures analysis of c ovariance). Microsphere data showed a redistribution of (Q) over dot(rel) a ttributable to oleic acid injury. (Q) over dot(rel) shifted from areas that were initially high-flow to areas that were initially low-flow, with no di fference in redistribution between the groups. After established injury, (Q ) over dot(rel) was redistributed to the nondependent lung areas in control animals, whereas (Q) over dot(rel) distribution did not change in treatmen t animals. Conclusion: in oleic acid lung Injury, treatment with PFX vapor improves ga s exchange by increasing ((V) over dot(A)/(Q) over dot) heterogeneity in th e whole lung without a significant change in gravitational gradient.