Effect of Increasing Perfluorocarbon Dose on ˙Va/˙Q Distribution during Partial Liquid Ventilation in Acute Lung Injury

Background: Although gas exchange during partial liquid ventilation (PLV) depends on perfluorocarbon liquid, the effect of perfluorocarbon dose on the ventilation-perfusion ([spacing dot above]Va/[spacing dot above]Q) distribution is not known. This study investigated how [spacing dot above]Va/[spacing dot above]Q distribution of an acutely injured lung is affected during PLV at increasing perfluorocarbon dose.

Methods: In eight rabbits (3.2 +/- 0.1 kg), acute lung injury (ALI) was created by repeated saline lavage (arterial oxygen partial pressure/fraction of inspired oxygen, 37 +/- 11 mm Hg). Three different doses of perfluorodecalin (9 ml/kg = low dose; 13.5 ml/kg = medium dose; 18 ml/kg = functional residual capacity [FRC] dose) were applied in random order during PLV. [spacing dot above]Va/[spacing dot above]Q distribution at different doses was evaluated by multiple inert gas elimination technique.

Results: Inert gas shunt (63 +/- 21% at ALI) decreased with increasing perfluorocarbon dose (43 +/- 21% at low dose, 29 +/- 10% at medium dose, 11 +/- 9% at FRC dose;P = 0.022). Compared with ALI (0%), the proportion of low [spacing dot above]Va/[spacing dot above]Q units was higher at all tested doses (19 +/- 10, 25 +/- 12, and 34 +/- 18%, respectively; all P < 0.05). Compared with ALI (27 +/- 14%), the proportion of normal [spacing dot above]Va/[spacing dot above]Q units was not increased at low or medium doses but was increased only at the FRC dose (45 +/- 13% ;P = 0.027).