Inhibitory effect of meconium on pulmonary surfactant function tested in vitro using the stable microbubble test

Meconium aspiration syndrome is related to mechanical obstruction of the airways and subsequent chemical pneumonitis. It has also been suggested that meconium causes inhibition of surfactant function. To assess its inhibitory effect on surfactant function in vitro, we used a stable microbubble (SM) test that was thought to reflect the adequacy of pulmonary surfactant. The mixtures were prepared by adding serial dilutions of human meconium to various concentrations of Surfactant-TA (SurfactenTM). The SM count at each concentration of surfactant significantly increased with the increasing concentration of surfactant. This shows that the SM test closely reflects the quantified function of surfactant. When various concentrations of meconium were added to the surfactant concentration of 0.05 mg/ml and 0.25 mg/ml, the SM test results were decreased even at low concentrations of meconium. Also the increase in the meconium concentration caused a decrease in the SM test result, which was dependent on the surfactant and the meconium concentration, accordingly. These results suggest that meconium inhibits surfactant function. Conclusion The stable microbubble test is an effective indirect method that tests the changes in surfactant quantity. In the in vitro experiment, we observed an inhibitory effect of meconium on the surfactant activity using the stable microbubble test.