Jet nebulisers show an unreasonable variation in drug output and nebulisation rates that leads to clinical and regulatory problems. Current evaluation methods appear inadequate for the purpose. Our objective was to evaluate Technetium-99m radiometry to study nebuliser parameters and the factors influencing it quantitatively. Drug output, rate and residue, and the effect of surface tension, excipient, temperature, air-jet speed, and equipment brand & aging were studied. Though nebulisation of radiolabeled drugs followed first-order kinetics, the rates were significantly different; the heaviest drug (Tc99m colloid) and Tc-99m salbutamol had the least nebulisation. Nebulisation rate for the first minute was invariably higher than the mean rate signifying the concentration effect of the solute. Drug residue was 35–75%. Drug output of different nebuliser chamber and air compressor brands was different to the extent of 270% and 180% respectively. ‘Aging’ of fluid chamber, cold drug fluid and obstruction in air-jet resulted in significant reduction in output while addition of 2% saline as excipient did not change the output rate. Addition of ethyl alcohol resulted in a maximum of 260% enhancement (with Tc99m Salbutamol), while further reduction in surface tension was counterproductive irrespective of the drug used. We conclude that radiometry provides valuable parametric information on the performance of jet nebulisers.
Technetium-99m, Radiometry, Jet nebuliser performance
