The use of water as a diluent for bronchodilator nebuliser solutions

Inhalation of nebulised water can provoke bronchoconstriction in asthmatic patients. In the first part of this study, a community survey identified that about 20% of patients with home nebulisers currently use water as a diluent. In the second part of this study, the airways effect of the use of water as a diluent for nebulised beta agonist was investigated. Nineteen asthmatic subjects were administered nebulised 2.5 mg salbutamol, diluted with either 2 mL water or physiological saline, and forced expiratory volume in one second (FEV1) was measured at baseline and at regular intervals for 45 minutes after nebulisation. Although there was a trend towards a reduced bronchodilator response with water as diluent, the differences between the two diluents were not significantly different. Paradoxical bronchoconstriction was not observed when salbutamol was diluted with water. We conclude that the common practice of diluting bronchodilator nebuliser solution with water does not result in a significant reduction in the overall bronchodilator response.