Distilled water challenges in asthmatic children. Comparison of different protocols

Inhalation of ultrasonically nebulized distilled water (UNDW) appears a promising candidate for routine challenge testing in bronchial asthma. We have compared two different methods of application of UNDW in 12 asthmatic children with a positive response to methacholine provocation (MCh), in an attempt to increase UNDW sensitivity and to establish standard testing protocols. In addition, results from UNDW challenges were compared to responses to inhalation of jet-nebulized distilled water (JNDW) and cold air (CACh). Compared to MCh, the sensitivity of continuously or intermittently (iUNDW) inhaled UNDW was 67 percent or 75 percent, respectively, when a positive response was defined by a greater than or equal to 20 percent fall in FEV1, but was higher when definition of a positive response was based on results from flow volume curves. Sensitivity of continuous or intermittent inhalation of JNDW was lower than for UNDW. The UNDW inhalations were better tolerated than CACh. Following stepwise iUNDW challenge, there was a clear reaction plateau for all variables measured. Results indicate that testing protocols with iUNDW inhalations over 6 to 10 min (corresponding to 7 to 11 ml water inhalation) yield the maximum sensitivity attainable with UNDW challenges, and require a minimum of patient and investigator effort.