Partial liquid ventilation (PLV) with perflubron (LiquiVent® Alliance Pharmaceutical Corp) improves lung function in animal models of surfactant deficiency or dysfunction, as well as in preliminary clinical trials. The mechanisms for this improvement are not fully elucidated. Replacement of the alveolar gas-liquid interface with a liquid-liquid interface during PLV reduces surface tension, recruits alveolar volume, and establishes a more uniform alveolar architecture. We hypothesized that PLV with perflubron may also directly or indirectly increase endogenous surfactant production. We examined the alveolar pool size of surfactant-associated phospholipid (PL) in preterm lambs with severe RDS supported by PLV as compared with conventional ventilation (CMV). Serial gas exchange and lung compliance were measured. Lung parenchyma and bronchoalveolar lavage (BAL) fluid were assayed for total protein and PL. In vivo labeling of phosphatidylcholine with 3H-choline quantitated newly synthesized and secreted surfactant in the BAL and parenchyma. Results: During PLV, PaO2, PaCO2, and compliance were improved as compared with CMV. PL was increased in the PLV group to 8.7 ± 3.4 mg/kg over the CMV group at 3.6± 1.6 mg/kg (P ≤ 0.05). The fraction of total PL as phosphatidyl choline was within normal range for endogenous surfactant (PLV: 67 ± 6%; CMV: 62 ± 3%). Alveolar protein was elevated in both groups (PLV: 360 ± 82 mg; CMV: 224 ± 17 mg). 3H-PC appeared to be increased in the parenchyma of the PLV group (3.7 × 103 ± 1.3 cpm/kg) as compared with the CMV group (2.5 × 103 ± 0.9 cpm/kg), as well as in the BAL (PLV: 4.9 × 103 ± 2.3 cpm/kg; CMV:2.6 × 103 ± 0.9 cpm/kg). We conclude that a brief period of PLV increased the alveolar pool of surfactant in the preterm lamb with RDS, despite significant parenchymal injury. This may represent, at least in part, upregulated synthesis and secretion of surfactant during PLV.
