OBJECTIVE: Partial liquid ventilation (PLV) is a novel means for improving gas exchange during which a perfluorocarbon liquid (PFC) is instilled into the lung and tidal gas ventilation is maintained with a conventional ventilator. We examined regional pulmonary blood flow pattern evolution during PLV in a healthy infant animal model.

METHODS: Eight healthy lambs (mean weight 11 kg) were anesthetized, instrumented, and ventilated supine for three hours with conventional mechanical ventilation (CMV) at standard settings. They then received 10 cc/kg of either air or PFC (Liquivent®, perflubron, Alliance Pharmaceutical Corp., San Diego, CA) instilled into the trachea at hours 3, 4, and 5. Radiolabelled microspheres (15 μm) were injected into the right atrium over a four hour study period at hours 3, 4, 5, 6, and 7. The animals were sacrificed and after lung sectioning, regional pulmonary blood flow was quantitated with a multichannel scintillation counter. For comparisons between subjects, each subject's regional flows were standardized relative to their mean baseline flow. Comparisons were performed with analysis of variance.

RESULTS: During CMV, we found regional pulmonary blood flow to be stable over the four hour study period and to favor dependent (1.9 ± 0.6) over non-dependent (0.2 ± 0.2) lung regions (p < 0.01) without a significant apical/caudal flow gradient (p = 0.55). During PLV, we found an initial overall reduction in flow to the most dependent segment from 1.8± 0.06 to 0.16 ± 0.2 (p < 0.001) and a redistribution of flow favoring non-dependent (p = 0.05) regions in hilar segments; however, additional PFC did not significantly magnify this effect, although there was a trend toward redistribution of flow to more apical segments with further dosing. This pattern remained stable over a two hour period following the last dose of PFC.

CONCLUSION: PLV led to a reversal of the pulmonary blood flow gradient we found during conventional ventilation, from dependent favored flow during CMV to a gradient favoring non-dependent flow during PLV. We did not find a significant dose dependent effect. Redistribution of blood flow in this manner, if matched with preferential ventilation in the same region, may be one means for the improved gas exchange observed during PLV in the injured lung.

Supported in part by Alliance Pharmaceutical Corp. San Diego, CA.