Comparison of a Nebulizer Using a Novel Aerosol Generator with a Standard Ultrasonic Nebulizer Designed for Use during Mechanical Ventilation

Figure 1: Diagram of SUN 145 (from product instruction manual) Ultrasonic nebulizers (USNs) generate aerosols without changing ventilator volumes or alarms. However, USN output varies with gas flow, is position dependent and generates heat. We wanted to determine whether the AeronebTM Professional Nebulizer System (Aeroneb Pro; Aerogen, Inc., Sunnyvale, CA)* has similar limitations. METHODS: We compared performance of the SUN 145 (Siemens-Elema AB, Solna, Sweden) and the Aeroneb Pro operated with 0.083% albuterol sulfate, in both upright and inverted orientation. Mass mean aerodynamic diameter (MMAD) was determined by cascade impaction. Emitted aerosol output and residual volume were determined at flows of 6, 30 and 60 L/min through each nebulizer (n=3). A digital thermistor placed in the medication reservoir monitored changes in temperature. RESULTS: Output from the SUN 145 varied between 0.18 ± 0.02 (mean ± SE), 0.40 ± 0.05, and 0.56 ± 0.1 mL/min at 6, 30 and 60 L/min, respectively (p < 0.01; ANOVA) in the upright position, with no aerosol generated in the inverted position. In contrast, the Aeroneb Pro had a mean output of 0.35 ± 0.03 mL/min in the plume up (AG up) position at 6, 30 and 60 L/min , increasing to a mean of 0.41 ± 0.05 mL/min (p < 0.05) when plume down. The MMAD (4.1 μm) and residual volume (0.8 mL) were greater with the SUN 145 than the Aeroneb Pro (3.5 μm and 0.2 mL, respectively; p < 0.05 for both). A greater increase (or fluctuation) in temperature from baseline was observed with the SUN 145 (24 ± 3oC) than the Aeroneb Pro (2 ± 1oC; p < 0.01). SUMMARY: Unlike the standard ultrasonic nebulizer, the Aeroneb Pro operated in both plume up and plume down orientation did not exhibit flow dependent output and did not significantly heat the medication. CONCLUSION: The Aeroneb Pro provided more consistent aerosol output than the ultrasonic nebulizer.