Extreme variability in aerosol output of the DeVilbiss 646 jet nebulizer

Ten new jet nebulizers (DeVilbiss 646) were studied to determine their consistency of output. Each nebulizer, containing 2 ml of saline solution, was run for 1 min in triplicate at four different straw (capillary tube) positions, keeping all other variables constant. Total output in milliliters per minute and volume of aerosol in the respirable range (1.0 to 5.0 microns) were measured. There was significant variability in output and volume of output in the respirable range (VORR) for every nebulizer at each of the tested straw positions (p less than 0.0001). Irregularities in manufacture of the bowl and straw appear to be responsible for this significant variability. In summary, there is considerable intranebulizer and internebulizer variability that could influence both patient care and medical use for diagnostic purposes.