We tested the hypothesis that administration of perfluorohexane (PFH) vapor does not significantly affect the relative pulmonary blood flow (Qrel) distribution in isolated rabbit lungs. Fourteen isolated rabbit lungs were perfused with a Krebs-Henseleit buffer solution (flow 150 mL/min). Pulmonary afterload was set to 3 mm Hg. The lungs were ventilated with 4% CO(2) in room air using a small animal ventilator (respiratory rate, 30 breaths/min; tidal volume, 12 mL/kg body weight; positive end-expiratory pressure, 2 cm H(2)O). After a steady-state period, 18 vol. % of PFH vapor was administered to 9 lungs for 30 min. In a second set of experiments five lungs served as controls. Change in (Qrel) distribution was assessed using fluorescent-labeled microspheres. The unpaired Student's t-test was used to compare variables between groups. The paired Student's t-test, the one-sample Student's t-test, the Anderson-Hauck test of equivalence, and Pearson correlation were used to analyze changes within groups. The mean correlation coefficients of (Qrel) were 0.564 +/- 0.182 for the PFH group and 0.502 +/- 0.295 for the control group, respectively. No significant changes in (rel) distribution over time and between groups were found. However, in the PFH group a tendency towards redistribution of (Qrel) to more ventral lung areas was noted. Our results suggest that PFH vapor has no significant effects on redistribution of (Qrel) in isolated rabbit lungs.