Effect of surfactant deficiency and surfactant replacement on airway patency in the piglet lung

We investigated the effect of surfactant deficiency on airway patency and the effectiveness of surfactant replacement as either an instilled liquid bolus, a non-hygroscopic aerosol or a hygroscopic aerosol. Small airway patency was assessed in isolated piglet lungs by passing a continuous flow of gas though a cannulated airway. Occlusion was assessed by measuring increases in pressure in the cannula that resulted from airway obstruction. In surfactant-deficient conditions the amount of airway closure increased approximately three-fold. However, administration of exogenous surfactant as an instilled liquid bolus, non-hygroscopic aerosol or a hygroscopic aerosol decreased airway closure such that it was statistically similar to that recorded prior to induction of surfactant deficiency, although the instilled and hygroscopic aerosol surfactant both appeared superior to the non-hygroscopic aerosol. These experiments showed that pulmonary surfactant does have a role in maintaining airway patency and that airway closure induced by surfactant deficiency could be reduced by administration of surfactant in any of the aforementioned forms.