Incorporation and analysis of ultrasonically nebulized distilled water challenges in an epidemiologic study of asthma and bronchial reactivity.

The usefulness of an ultrasonically nebulized distilled water (UNDW) challenge as a screening procedure was tested in an on-going epidemiologic study of asthma and bronchial reactivity. Sixty-six individuals underwent a methacholine challenge, an UNDW challenge, and were administered a standardized respiratory disease questionnaire. To perform the UNDW challenge, subjects inhaled increasing volumes of nebulized distilled water while breathing tidally. Thirty-eight asthmatics, two former asthmatics, 14 normal, and 12 allergic subjects, were included. Sixty-six percent of the asthmatics dropped 20% from their baseline FEV1 during the UNDW challenge. Only one allergic or normal subject had a similar drop. The Pearson's correlation coefficient between methacholine and UNDW challenges was 0.60. If positive, an UNDW seems to be highly specific in supporting a diagnosis of asthma, while methacholine challenges are more useful in verifying the presence of non-specific bronchial reactivity.