NEBULIZER CALIBRATION USING LITHIUM-CHLORIDE - AN ACCURATE, REPRODUCIBLE AND USER-FRIENDLY METHOD

Conventional gravimetric (weight loss) calibration of jet nebulizers o verestimates their aerosol output by up to 80% due to unaccounted evap orative loss. We examined two methods of measuring true aerosol output from jet nebulizers. A new adaptation of a widely available clinical assay for lithium (determined by flame photometry, LiCl method) was co mpared to an existing electrochemical method based on fluoride detecti on (NaF method). The agreement between the two methods and the repeata bility of each method were examined. Ten Mefar jet nebulizers mere stu died using a Mefar MK3 inhalation dosimeter, There was no significant difference between the two methods (p=0.76) with mean aerosol output o f the 10 nebulizers being 7.40 mg.s(-1) (sD 1.06; range 5.86-9.36 mg.s (-1)) for the NaF method and 7.27 mg.s(-1) (SD 0.82; range 5.52-8.26 m g.s(-1)) for the LiCl method. The LiCl method had a coefficient of rep eatability of 1.3 mg.s(-1) compared with 3.7 mg.s(-1) for the NaF meth od. The LiCl method accurately measured true aerosol output and was co nsiderably easier to use. It was also more repeatable, and hence more precise, than the NaF method, Because the LiCl method uses an assay th at is routinely available from hospital biochemistry laboratories, it is easy to use and, thus, can readily be adopted by busy respiratory f unction departments.