Comparison of Aerosol Particle Size Measured by Two Methods Using Three Brands of Mesh Nebulizer

L. Slator, Y. Degtyareva, L. Hardaker, D. von Hollen, J. Pritchard

We compared the particle size and fine particle fraction (FPF, % ≤5 μm) of 3 mesh nebulizers using cascade impaction with a Next Generation Impactor (NGI) and a modified laser diffraction method with a Spraytec particle sizer. Three of each nebulizer brand (InnoSpire Go [production equivalent], Aeroneb Go, and MicroAir U22) were tested with 1 mL of 5 mg/2.5 mL salbutamol sulphate in triplicate with a 15 L/min constant flow rate. NGI tests: the nebulizer was connected to the NGI and run until treatment completion; samples from the NGI were analyzed via high performance liquid chromatography. Spraytec tests: the Spraytec was set up with the inhalation cell fitted with the sheath flow collar with ports open, the flow straightener component fitted and connected to a vacuum pump such that there was 15 L/min flow at the inlet adapter ferrule. The nebulizer was connected to the inlet adapter ferrule; the nebulizer was run and stopped after 60 seconds of data measurements following a 10-second prime. The differences between the results of the NGI and Spraytec particle sizer were within 0.5 μm for particle size and 5% for FPF. The InnoSpire Go produced aerosols with the smallest particle sizes (mean ± standard deviation; 3.99 ± 0.26 μm MMAD and 4.17 ± 0.22 μm VMD) and largest FPFs (64.4 ± 4.42% and 63.4 ± 3.74%, respectively); the MicroAir U22 produced the largest particle sizes and smallest FPFs (5.83 ± 0.43 μm MMAD and 6.30 ± 0.19 μm VMD, and 41.3 ± 3.83% and 36.7 ± 1.62%, respectively). Span and geometric standard deviation were lowest for the InnoSpire Go. The modified Spraytec method has potential for use as a routine method in the future.

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