Abstract
Background:
Various improvements have been made to the basic jet nebulizer design with the intent of delivering more medication to the distal airways while still providing aerosol within the respirable range of 3 – 5 μm. The design changes can be one of three categories; breath enhanced, breath actuated, and breath enhanced and breath actuated. With breath enhancement, air is entrained into the nebulizer as the patient inspires providing greater inspiratory flow, breath-actuated nebulizers generate aerosol when inspiratory efforts are sensed by the nebulizer and cease upon expiration. Breath enhanced nebulizers entrain air to provide extra flow, while breath actuated only aerosolize when triggered by inspiration. The aim of the enhancements is to increase drug deposition within the lung, this can be done by increasing aerosol output and maintaining the majority of particles generated to be within the respirable range.
Methods:
Four different nebulizers were evaluated each representing a specific design; a breath-actuated (Aeromist) a breath-enhanced (Respironics Sidestream), a breath-actuated and breath-enhanced (Aeroeclipse II), as well as a standard jet nebulizer (Misty Max). Each nebulizer was loaded with 3 mL of 2.5 mg albuterol sulfate solution. The mouthpiece of the nebulizer was connected inline to a spontaneous breathing servo lung model (ASL 5000) using the following settings: VT 500 mL, breathing frequency 10 breaths/min, I:E 1:2. A filter was positioned between the test lung and the nebulizer to capture inspired aerosol. The filter was changed every minute and output was determined using HPLC. Parallel measurements of fine droplet fraction (FDF <4.7μm) were made with each nebulizer using a laser diffractometer. Fine droplet mass was determined as the product of recovered mass and FDF <4.7μm.
Results:
Five new nebulizers were tested for each design. All values were significant for both Aeromist and the AeroEclipse II (P < .01). The Sidestream and Misty Max performed similarly (P > .05). There was no significant difference in environmental medication loss with longer run time, (P > .99), but significant loss when compared with shorter run times (P < .01).
Conclusions:
Enhancements to jet nebulizers which allow for increased inspired flow and limiting the cycle for aerosol generation have a positive influence on both delivered medication and particle size fraction delivered to the patient. The devices which had the shortest run times experienced the greatest environmental loss of medication.
Table 1.
Nebulizer
Avg Run Time ± SD (sec)
Sputter ± SD (sec)
Rec Mass ± SD(μg)
Fine Droplet Mass < 4.7 (μm)
Aeromist
780 ± 0
693.2 ± 7.1
2095.1 ± 109.6
452.0 ± 35.5
AE II BAN
540 ± 60
458 ± 69.5
2369.4 ± 67.5
714.6 ± 80.6
Sidestream
360 ± 0
265 ± 3.65
1506.2 ± 45.8
216.9 ± 10.5
Misty Max
360 ± 0
287 ± 8.66
1886.9 ± 110.3
262.5 ± 20.3
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