Surfactant nebulisation: safety, efficiency and influence on surface lowering properties and biochemical composition.

Objective: The objectives of this study were, to select a nebuliser first, that operates safely in a neonatal ventilator setting and, second, that is most efficient. Thirdly, we studied the particle sizes of the surfactant aerosol. Fourthly, we studied where the nebulised surfactant is deposited in the tubing system of the ventilator. Finally, we studied whether nebulisation influences the composition and biophysical properties of surfactant.

Measurements And Results: Safety was assessed by measuring "mean airway pressures" in a test lung before, during and after surfactant nebulisation, for three jet nebulisers. The MiniNEB did not alter these pressures, and is thus safe, whereas the other two nebulisers (Intersurgical and Flo-Thru) increased these pressures. The efficiency of nebulisation was assessed by measuring the amount of phospholipid deposited in the test lung. The MiniNEB showed the highest efficiency: 10% versus 1-3% of the other two nebulisers. The particle sizes of surfactant aerosol were assessed by the laser diffraction method. Seventy percent of the particles were 1-5 microns. The deposition of surfactant aerosol in the tubing system was assessed by nebulising surfactant that was labelled with 99mTc Nanocoll. Afterwards the tubing system was imaged using a gamma camera. The majority of surfactant was deposited in the expiratory hose (28%), nebuliser (20%), Y-piece (16%) and expiratory filter (12%). Finally the phospholipid composition, spreading velocity, static and dynamic surface tensions were assessed for the nebulised surfactant and compared to the stock surfactant. In addition, nebulised surfactant was instilled in premature rabbits and tidal volumes were measured to assess the dose-response relation. We found that neither the composition nor biophysical properties had been altered by nebulisation.

Conclusions: The MiniNEB nebulised surfactant safely in a neonatal ventilator setting with respect to airway pressures. The efficiency of nebulisation is low: the majority of the surfactant aerosol is deposited in the expiratory tubing. The surfactant composition and function is not altered by nebulisation. Therefore the nebulisation of surfactant is feasible, but efforts should be made to improve the efficiency of this procedure.