SURFACTANT NEBULIZATION - SAFETY, EFFICIENCY AND INFLUENCE ON SURFACELOWERING PROPERTIES AND BIOCHEMICAL-COMPOSITION

Objective: The objectives of this study were, to select a nebuliser fi rst, that operates safely in a neonatal ventilator setting and, second , that is most efficient. Thirdly, we studied the particle sizes of th e surfactant aerosol. Fourthly, we studied where the nebulised surfact ant is deposited in the tubing system of the ventilator. Finally, we s tudied whether nebulisation influences the composition and biophysical properties of surfactant. Measurements and results: Safety was assess ed by measuring ''mean airway pressures'' in a test lung before, durin g and after surfactant nebulisation, for three jet nebulisers. The Min iNEB did not alter these pressures, and is thus safe, whereas the othe r two nebulisers (Intersurgical and Flo-Thru) increased these pressure s. The efficiency of nebulisation was assessed by measuring the amount of phospholipid deposited in the test lung. The MiniNEB showed the hi ghest efficiency: 10 % versus 1-3 % of the other two nebulisers. The p article sizes of surfactant aerosol were assessed by the laser diffrac tion method. Seventy percent of the particles were 1-5 mu m. The depos ition of surfactant aerosol in the tubing system was assessed by nebul ising surfactant that was labelled with Tc-99m Nanocoll. Afterwards th e tubing system was imaged using a gamma camera. The majority of surfa ctant was deposited in the expiratory hose (28 %), nebuliser (20 %), Y -piece (16 %) and expiratory filter (12 %). Finally the phospholipid c omposition, spreading velocity, static and dynamic surface tensions we re assessed for the nebulised surfactant and compared to the stock sur factant. In addition, nebulised surfactant was instilled in premature rabbits and tidal volumes were measured to assess the dose-response re lation. We found that neither the composition nor biophysical properti es had been altered by nebulisation. Conclusions: The MiniNEB nebulise d surfactant safely in a neonatal ventilator setting with respect to a irway pressures. The efficiency of nebulisation is low: the majority o f the surfactant aerosol is deposited in the expiratory tubing. The su rfactant composition and function is not altered by nebulisation. Ther efore the nebulisation of surfactant is feasible, but efforts should b e made to improve the efficiency of this procedure.