Oxygenation is not improved by partial liquid high frequency ventilation using a high lung volume strategy. An experimental study.

Abstract

OBJECTIVE: To investigate the effect on oxygenation and lung damage of partial perfluorocarbon liquid high frequency oscillatory ventilation (PL-HFOV) versus high frequency oscillatory ventilation (HFOV) alone, in rabbits with acute lung injury, using high lung volume strategy HFOV. METHODS: Twelve adult New Zealand white rabbits were initially ventilated with HFOV after anaesthesia, sedation and paralysis. After induction of lung injury with saline lavage, all animals received a single sigh breath of 30 cmH(2)O for 30 seconds. They were then allocated to receive either HFOV alone (n = 6) or PL-HFOV (n = 6). Arterial blood gases were taken pre- and post-lavage and then hourly for 5 hours. The oxygenation index (OI, in cmH(2)O/mmHg) was calculated using the formula: OI = (MAP x F(I)O(2) x 100) / PaO(2). The lungs were then removed for histological examination to score lung injury. RESULTS: Two rabbits died in the PL-HFOV group and none in the HFOV group, p = 0.45 (Fisher's exact test). At one hour the oxygenation index (OI) was 4.5 in the HFOV group and 6.6 in the PL-HFOV group, p = 0.49 and the PaO(2) was 374 mmHg in the HFOV group and 311 mmHg in the PL-HFOV group, p = 0.39. Average OI over the first three hours was 3.6 in the HFOV group and 5.0 in the PL-HFOV group, p = 0.27 and the PaO(2) was 404 mmHg in the HFOV group and 337 mmHg in the PL-HFOV group, p = 0.12. The lung histology damage score was 2.33 in the HFOV group and 2.50 in the PL-HFOV group, p = 0.83. CONCLUSIONS: In this model of acute lung injury, using a high volume HFOV strategy to optimise lung recruitment, PL-HFOV did not result in any further improvement in oxygenation when compared with HFOV alone. The question of safety with PL-HFOV remains.