Effects of PEEP and tolazoline infusion on respiratory and inert gas exchange in experimental meconium aspiration.

Meconium aspiration syndrome often produces respiratory failure in the neonate. We utilized the multiple inert gas elimination technique to study the effects on respiratory and inert gas exchange of the application of positive end expiratory pressure or continuous infusion of tolazoline HCl. The application of PEEP, with the optimal level of PEEP defined for each animal, produced a decrease in AaDO2 and pulmonary shunt, without an increase in blood flow to low VA/Q areas, or an increase in dead space. Tolazoline infusion, at 2 mg/kg/hour, had no apparent effect on AaDO2 or shunt, or magnitude of low VA/Q regions. Tolazoline therapy was associated with an increase in heart rate and a decrease in systemic blood pressure. We conclude that immediate postaspiration application of PEEP, but not of tolazoline, will diminish pulmonary shunt without creating low VA/Q areas, and therefore will improve gas exchange in MAS.