Bronchoconstriction induced by distilled water. Sensitivity in asthmatics and relationship to exercise-induced bronchospasm.

We studied the ability of bronchial challenge with an ultrasonically produced, distilled water aerosol to detect airways hyperreactivity in asthmatics and also evaluated its relationship to exercise-induced bronchoconstriction. Fifteen asthmatics and 10 normal subjects inhaled, at room temperature, distilled water aerosol in increasing concentrations. On a separate day, each subject performed a standard methacholine challenge. On the third day, all asthmatics exercised on a treadmill for 6 min at 90% maximal heart rate while breathing room-temperature, dry air. Pulmonary mechanics (FEV1 and SGaw) were measured before and after each challenge. Seven of the asthmatics and all of the normal subjects did not react to challenge with distilled water. Distilled-water challenge caused a 20% decrease in FEV1 in only 53% (8 of the 15) asthmatics, whereas all of the asthmatics reacted to methacholine challenge with a 20% fall in FEV1. Thus, distilled water was not a sensitive challenge procedure for the detection of airways hyperreactivity in asthma and it cannot be used as a routine screening test. However, in the asthmatics, the response to distilled water challenge correlated significantly with the response to exercise (r = 0.81, p less than 0.001). Seven asthmatics were reactive to both exercise and water, 7 were reactive to neither exercise nor water, and 1 reacted to water but not to exercise. Cromolyn completely or partially blocked both distilled-water- and exercise-induced bronchospasm in the reactive asthmatics.(ABSTRACT TRUNCATED AT 250 WORDS)