An Evaluation of Three Styles of Jet Nebulizers: Standard Jet,Breath Enhanced,and Breath Actuated/Breath Enhanced

Abstract

Background:

Inhaled medications delivered via nebulizer are less dependent upon patient effort and technique when compared to pressurized metered dose inhalers (pMDI) and are often used in acute care settings for this reason. Because pMDIs can deliver medications so quickly, design improvements of standard jet nebulizers have been made to create high efficiency nebulizers that include the breath enhancement (BE), which utilizes entrained flow to make more drug available for inhalation, and the breath actuated (BA) feature which only emits medication upon inhalation.

Methods:

Three different nebulizers were evaluated (no. = 5); one BA/BE (AeroEclipse II), one BE only (TurboMist), and one constant output SJN (Misty Max10). Each nebulizer was loaded with 3 mL of 2.5 mg albuterol sulfate solution with the gas flow set to deliver 8 L/min. The nebulizer was connected to a spontaneous breathing servo lung model (ASL 5000) with the following settings: V_T 500 mL, frequency 10, and I:E ratio of 1:2. A filter was placed between the mouthpiece of the nebulizer and the test lung to capture inspired aerosol. Gas flow was stopped every minute and the filter exchanged for a fresh one. Nebulizer output was determined by rinsing the filter medium in methanol and then placing the filtrate into HPLC. Parallel measurements of fine droplet fraction (FDF < 4.7 μm) were made using a Spraytec laser diffractometer. Fine droplet mass was determined as the product of recovered mass and FDF < 4.7 μm.

Results:

The run length was determined by the nebulizer with the shortest run time, TurboMist approximately 4 min. All Fine Droplet Mass (FDM) or dosing in the respirable range of 1-5 µm was reported at the 4-min mark though some nebulizers had more medication left in the cup. Post hoc analysis was performed using Tukey’s honest significant difference; AeroEclipse II FDM 305.2 ± 73.3 differed from the FDM of both the TurboMist (202.5 ± 11.9) and Misty Max (180.3 ± 16.8), P < .01. The difference in FDM between the TurboMist and the Misty Max was P < .01 (Fig 1).

Conclusions:

Being able to provide adequate medication delivery over a shorter period is desirable, first to elicit relief for the patient, but also to promote efficiency in workflow. Even though the AeroEclipse II still had medication left to nebulize, performing a 4 min timed dose still allowed for a 33% increase in respirable dose over TurboMist and a 41% increase over Misty Max 10 allowing the user to get more medication into the distal airways in a short period of time.

Table 1: Fine droplet mass by nebulizer over four minutes

Figure 1: Fraction of delivered output mass with particles < 4.7 μm.