The efficacy of exogenous
surfactant administration is influenced by numerous factors, which has resulted in variable outcomes of clinical trials evaluating this treatment for the
acute respiratory distress syndrome (ARDS). We investigated several of these factors in an animal model of
acid aspiration including different
surfactant preparations, and different delivery methods. In addition, high-frequency oscillation (HFO), a mode of
mechanical ventilation known to recruit severely damaged lungs, was utilized.
Lung injury was induced in adult rabbits via intratracheal instillation of 0.2 N HCl followed by conventional
mechanical ventilation (CMV) until Pa(O2)/FI(O2) values ranged from 220 to 270 mm Hg. Subsequently, animals were given one of three
surfactants administered via three different methods and physiological responses were assessed over a 1-h period. Regardless of the
surfactant treatment strategy utilized, oxygenation responses were not sustained. In contrast, HFO resulted in a superior response compared with all
surfactant treatment strategies involving CMV. The deterioration in physiological parameters after
surfactant treatment was likely due to overwhelming
protein inhibition of the
surfactant. In conclusion, various
surfactant treatment strategies were not effective in this model of
lung injury, although the lungs of these animals were recruitable with HFO, as reflected by the acute and sustained oxygenation improvements.