Chest
Volume 96, Issue 3, September 1989, Pages 505-508
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Clinical Investigations
Importance of Evaporative Water Losses During Standardized Nebulized Inhalation Provocation Tests

https://doi.org/10.1378/chest.96.3.505Get rights and content

Evaporative water losses from jet nebulizers produce temperature drop, reduction in total nebulizer output with increased nebulization time, and increasing concentration of solute remaining in the nebulizer. These were documented and quantitated for the Wright nebulizer which is used for one histamine/methacholine inhalation test method. Indirect determination of nebulizer aerosol output, made by estimation of total sodium lost from the nebulizer, was about 25 percent of total output as determined by weight change. A similar tendency was seen for a DeVilbiss 40 nebulizer for both reduction in total nebulizer output with increasing duration of nebulization, and increased solute concentration remaining in the nebulizer. These data must be taken into account when standardizing inhalation provocation tests. Nebulizers should be calibrated under the same conditions that they are used during the test. Histamine and methacholine solutions should be discarded after a single use in the 2-min tidal breathing Wright nebulizer method.

Section snippets

Nebulizers

Four Wright nebulizers and one DeVilbiss 40 nebulizer were employed in this investigation. Two Wright nebulizers were those routinely used in the laboratory for a histamine/methacholine inhalation test or for allergen inhalation tests, and two were “spares.” With exception of the hand-held squeeze bulb DeVilbiss 40 trials, the nebulizers (including the DeVilbiss) were run with compressed dry medical air at 50 psi with the flow rate set at 8 L/min.

Temperature Change

Temperature change was measured with three

RESULTS

Changes in temperature over 10 min are shown in Figure 1. The mean temperature fell from 24.5° to 13.5°C, the majority occurring in the first 2 min.

The weight loss for various periods of nebulization and volumes is shown for the Wright nebulizer 1 in Figure 2 and for all five nebulizers in Table 1. For all nebulizers, the mean weight loss per minute fell markedly with increasing nebulization time. The volume (3 vs 5 ml) did not alter the weight loss. For the Wright nebulizers, the mean output

DISCUSSION

These data document and quantitate evaporation-related events during the operation of Wright nebulizers in the fashion that they are used for inhalation provocation tests. A temperature drop of 12°C occurred chiefly in the first 2 min. This is due to the latent heat of vaporization, ie, the amount of energy (lost) in the form of heat required to convert water from liquid to vapor. A progressive reduction in the amount of weight loss produced by the nebulization occurred over time; again, this

ACKNOWLEDGMENTS:

The authors wish to thank Mr. J. Mink and Mrs. J. Bramley for their assistance in preparing the manuscript.

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Manuscript received November 2; revision accepted January 23.

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