Comparison of Laser Diffraction Measurements by Mastersizer X and Spraytec to Characterize Droplet Size Distribution of Medical Liquid Aerosols

Abstract

Abstract

Background:

The Mastersizer X (Malvern Instruments) used to be the reference device for assessing droplet size distribution of aerosols by laser diffraction, but it has not been updated and has gradually been replaced by the Spraytec (Malvern Instruments), which is considered to provide greater accuracy and higher acquisition speed.

Methods:

The aim of this study was to compare the use of the two diffractometers to characterize medical liquid aerosols in a wide range of droplet sizes, using four nasal sprays to produce large droplets (10–180 μm) and 10 nebulizers to produce smaller droplets (0.5–20 μm). The influence of the inhalation cell provided with the Spraytec on the measurements was also determined.

Results:

Correlation between the devices was low for large droplets (R²=0.37) and high for smaller droplets (R²=0.97). The Spraytec overestimated the median diameter of small droplets by 14%, and Bland-Altman tests showed no equivalence (limits of agreement over 20%). An artifact peak in the large size range was observed with the Spraytec, which could be due to difficulty for the multiple scattering algorithm to process high-density aerosol clouds. The difference was reduced to 5% by using the inhalation cell provided by the Spraytec with a 15 L/min aspiration.

Conclusion:

The Mastersizer X and the Spraytec cannot be considered as equivalent laser diffraction devices, but the difference can be reduced with the Spraytec inhalation cell.