An optimal dose of perfluorocarbon for respiratory mechanics in partial liquid ventilation for dependent lung-dominant acute lung injury.

BACKGROUND Despite increasing knowledge about partial liquid ventilation (PLV), the optimal dose of perfluorocarbon (PFC) is not yet established. Because there exist normal regions in the lung with ARDS and because PLV in the normal lung results in worsened gas exchange, we postulated that the optimal dose of PFC for PLV may be less than the functional residual capacity (FRC) dose in the lung with limited disease. DESIGN AND SETTING Animal study at the Asan Institute for Life Sciences, Seoul, Korea. SUBJECTS Twelve rabbits in which dependent lung-dominant lung injury was created by a modified saline solution lavage. INTERVENTIONS PLV performed at six different doses of perfluorodecalin in sequence (3, 6, 9, 12, 15, and 18 mL/kg every 15 min). MEASUREMENTS AND RESULTS Our modified saline solution lavage induced atelectasis and hemorrhage confined to the dependent lung with severe hypoxia (PaO(2)/fraction of inspired oxygen = 37 +/- 6 mm Hg). Peak airway pressure (Ppeak) and inspiratory pause pressure (Ppause) with PLV were lower at doses of 3 to 15 mL/kg (all p < 0.05), but not different at a dose of 18 mL/kg, when compared with gas ventilation. Ppeak increased at doses of 12, 15, and 18 mL/kg, when each was compared with the preceding PFC dose. At increasing PFC doses, the change in the elastic component of airway pressure (Ppause after minus Ppause before) was negative until the dose of 9 mL/kg, but was positive at doses of 12 mL/kg and above. The change in the resistive component ([Ppeak minus Ppause] after minus [Ppeak minus Ppause] before) was negative until the dose of 6 mL/kg, but was positive at the dose > or = 9 mL/kg. CONCLUSION Respiratory mechanics during PLV for dependent lung-dominant lung injury were optimal at a PFC dose less than the FRC.