Droplet size distributions of nebulised aerosols for inhalation therapy.

Jet nebulisers are used commonly for aerosol therapy in patients with asthma and bronchitis, but the manufacturers' information regarding aerosol droplet size is often inadequate. In this study, mass median diameter, geometric standard deviation and the percentage of the aerosol mass contained within 'respirable' (less than 5 micron diameter) droplets have been measured for 11 brands of jet nebuliser with a solution of hypertonic (7%) saline at compressed gas flow rates between 6 and 121 min-1 using a laser light scattering device (Malvern Instruments 2600 HSD analyser). There was a considerable variation in droplet size between the nebuliser brands and among nebulisers of the same brand. Droplet size decreased with increasing compressed gas flow rate. These findings suggest that the quantity of drug available to the patient depends on the individual nebuliser used, and upon the pressure and flow of the compressed gas.