SURFACTANT NEBULIZATION - LUNG-FUNCTION, SURFACTANT DISTRIBUTION AND PULMONARY BLOOD-FLOW DISTRIBUTION IN LUNG LAVAGED RABBITS

Objective: Surfactant nebulisation is a promising alternative to surfa ctant instillation in newborns with the respiratory distress syndrome. Although less surfactant is deposited in the lung, it improves gas ex change, probably due to a superior distribution. We hypothesize that a more uniform distribution of nebulised surfactant results in a more u niform pulmonary blood flow and consequently a more efficient gas exch ange. We asked whether the pulmonary blood flow changes after surfacta nt replacement, and to what extent pulmonary blood flow is influenced by the amount of surfactant deposition. Furthermore, we investigated w hether sufficient nebulised surfactant is deposited in the lungs to ac hieve a sustained improvement in lung function, Interventions: Surfact ant was nebulised or instilled, or saline was nebulised, in 18 lung-la vaged rabbits. After 2 h the rabbits were weaned from mechanical venti lation to continuous positive airway pressure: 40 % oxygen. We measure d blood gasses, dynamic lung compliance, surfactant distribution using 99m technetium nanocoll label, and the pulmonary blood flow distribut ion, using microspheres. Results: Partial pressure of oxygen in arteri al blood and lung compliance were significantly higher after surfacfan t nebulisation than after saline nebulisation. Surfactant instillation gave a superior effect with respect to these variables, Nebulised sur factant was distributed more uniformly over the lungs than instilled s urfactant. Although pulmonary blood flow changed over time, it remaine d uniformly distributed following both modes of surfactant treatment, Surfactant deposition was neither strongly related to pulmonary blood now nor strongly related to the change in blood flow. Conclusions: Alt hough nebulised surfactant is uniformly distributed, we can provide no evidence that: this results in a more uniform pulmonary blood flow di stribution, Therefore, other than a superior surfactant distribution, no additional reason tvas found for the efficient gas exchange after n ebulisation.