In vitro characteristics of tobramycin aerosol from ultrasonic and jet nebulizers

Study Objective. To compare the in vitro performance of an ultrasonic nebul izer and a jet nebulizer in producing a respirable aerosol of tobramycin so lution for injection. Design. In vitro observational study. Devices. Ultrasonic and jet nebulizers. Intervention. Output was determined by measuring the difference in nebulize r weight before and after nebulizing 3 ml Of tobramycin injection solution. Mass median aerodynamic diameter (MMAD) and respirable mass were determine d by sampling tobramycin aerosol into a cascade impactor. Measurements and Main Results. Mean (SD) output was 1.14 (0.09) ml/minute f or the ultrasonic nebulizer and 0.64 (0.08) ml/minute (p <0.001) for the je t nebulizer. Mean MMAD for the jet nebulizer (2.31 [0.10] mum) was less tha n that of the ultrasonic nebulizer (2.81 [0.17] mum, p <0.001). The majorit y of tobramycin aerosol produced was in the respirable range for both the u ltrasonic (65.1% [4.10%]) and jet (60.6% [0.73%], p=0.008) nebulizers. Conclusion. Despite small, clinically unimportant differences in aerosol si ze and respirable fraction, either device would be acceptable to administer tobramycin injection solution.