Comparison of three commercial ultrasonic nebulizers

Background: The clinical acceptance of the initial ultrasonic nebulizers wa s impeded by their production of significant quantities of droplets larger than the respirable range that could have resulted in poor pulmonary deposi tion of nebulized medications. Subsequent modifications in the design of ul trasonic nebulizers have occurred. Overall nebulizer performance characteri stics of the newer ultrasonic devices have not been evaluated. Objective: Three commercially available ultrasonic nebulizers (DeVilbiss-Pu lmosonic, Omron-Microair, Rhone Poulenc-Rorer-Fisoneb) were studied to comp are the aerosol output characteristics. Methods: The parameters studied were total volume output (TVO), time to neb ulize total output (TTO), percent of droplets with volume diameters in the respirable range (PDVRR, 1 to 5 mu m), albuterol concentration during nebul ization, and the total drug delivered. All nebulizers were filled with 2.5 mL of saline and 0.5 mt of albuterol nebulizer solution. Three units from e ach manufacturer, each from a different lot, were evaluated in duplicate. Results: The nebulizer with the largest volume output was the Omron (mean 2 .94 mt), which also demonstrated the longest nebulization time (mean 10.3 m in). The DeVilbiss and Rhone Poulenc-Rorer units delivered smaller volumes (mean 2.5 mt, 2.4 mL, respectively) but nebulized more rapidly (mean 2.21 m in, 3.54 min, respectively). The Omron nebulizer generated the highest PDVR R with a mean of 38%. The DeVilbiss had a mean PDVRR of 16% and the Rhone P oulenc-Rorer a mean PDVRR of 21%. The majority of droplets from all three m achines had a volume diameter smaller than the respirable range, ie, in the 0.5 to 1.0 mu m range (Omron-60%, DeVilbiss-83%, Rhone Poulenc-Rorer-79%). For all three nebulizers there appeared to be no concentrating or diluting effect during nebulization implying that equal quantities of albuterol and diluent were delivered. The Rhone Poulenc-Rorer units demonstrated the gre atest unit-to-unit variability with respect to TVO while the Omron units de monstrated the greatest unit to unit variability with respect to TTO. Conclusion: We conclude that several improvements in the design of ultrason ic nebulizers have resulted in the reduction of the size of the droplets ge nerated. Our evaluation of the three commercially available ultrasonic nebu lizers revealed that the majority of droplets generated were within or belo w the respirable range. There was no concentrating or diluting effect durin g nebulization for all three nebulizers. The output characteristics of the three devices differ and this will effect the delivery time as well as amou nt of dug delivered to the lungs.