Aerosolized surfactant reverses respiratory failure in lung–lavaged rats

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Abstract
The effects of surfactant replacement by aerosol inhalation and by bolus instillation were compared in rats with respiratory failure induced by repeated lung lavage. The rats were anesthetized with pentobarbital sodium and mechanically ventilated with 100% oxygen. The PaO2 of control rats not given surfactant (n = 9) remained below 13 kPa. A bolus instillation of a modified natural surfactant (75 mg.kg-1 b.w. in 1.5 ml.kg-1 b.w. saline) into the airways rapidly reversed the respiratory failure; the mean PaO2 value (n = 9) 15-180 min after instillation remained over 50 kPa (P < 0.05 vs. controls). Inhalation of the aerosolized surfactant for 60 min through an ultrasonic nebulizer delivering < or = 75 mg.kg-1 b.w. of the surfactant into the lungs gradually reversed the respiratory failure. The mean PaO2 value (n = 9) 15 min after initiation of inhalation was 19.6 kPa (NS vs. controls), but after 60 min it rose to above 43 kPa (P < 0.05 vs. controls; NS vs. bolus instillation). Treatment with surfactant either by continuous aerosol or by bolus led to significant increases of over 24% in the dynamic lung-thorax compliance. We conclude that aerosolized surfactant reverses respiratory failure induced by lung lavage, although the response is slower than after bolus instillation.