Comparison between refractoriness after distilled water-induced asthma and exercise-induced asthma

Inhalation of distilled water (DW) frequently induces bronchoconstriction in asthmatic patients. We compared the degree of refractoriness to repeated inhalation of DW to that of repeated exercise challenge in 14 asthmatics. Refractoriness was seen following inhalation of DW. The maximum drop in FEV1 (% of predicted) following the first challenge was 31 +/- 13% and the maximal drop following the second challenge was 18 +/- 9% (P less than .01). The pattern of the airway response seen during 45 minutes following repeated inhalation of DW and exercise was similar. Cross refractoriness was also seen when inhalation of DW followed exercise challenge. It was concluded that both stimuli probably share a common mechanism of action on the airway.