Importance of dosimeter calibration method on nebulizer output.
BACKGROUND
We have observed that dosimeter-run nebulizers have a much smaller output when manually activated than when breath activated; however, this has not been adequately investigated.


OBJECTIVE
To evaluate the effect of different calibration methods on nebulizer output.


METHODS
Six healthy subjects performed all calibrations. The nebulizers were operated by 2 different dosimeters and were calibrated to produce 9 microL per actuation by breath activation followed by exhalation to the room. The nebulizers were then operated at these identical settings, and the output determined in 3 ways: (1) breath activation followed by exhalation to the room, (2) breath activation with exhalation into the nebulizer, and (3) manual activation (with no subject using the nebulizer). These 3 methods were termed regular, rebreathe, and manual, respectively.


RESULTS
There was a large and statistically significant difference in nebulizer output among the 3 methods. The measured rebreathe outputs (5.6 and 5.7 microL per actuation) were approximately two thirds and the manual outputs (3.2 and 3.9 microL per actuation) were approximately one third of the regular calibration outputs (8.6 and 8.9 microL per actuation); the 2 values are for the 2 dosimeters. The results were highly statistically significant (P < .001).


CONCLUSIONS
The method by which a nebulizer-dosimeter system is calibrated results in different nebulizer outputs. This has a high likelihood of influencing the concentration of methacholine causing a 20% decrease in volume in the first second of forced expiration.
Todd
David C
DC
Division of Respiratory Medicine, Department of Medicine, University of Saskatchewan, Royal University Hospital, Saskatoon, Canada.
Davis
Beth E
BE
Smycniuk
Audrey J
AJ
Cockcroft
Donald W
DW
D000328:Adult; D001249:Asthma / Q000175:diagnosis*; D002138:Calibration; D006801:Humans; D016210:Methacholine Chloride / Q000008:administration & dosage*; D009330:Nebulizers and Vaporizers / Q000592:standards*; D011446:Prospective Studies; D012129:Respiratory Function Tests / Q000379:methods* / Q000592:standards
D016210:Methacholine Chloride