Airway responsiveness in asthma: bronchial challenge with histamine and 4.5% sodium chloride before and after...

Inhalation of histamine is commonly used to assess the severity of and to monitor treatment of asthma. Histamine causes airways to narrow by acting directly on specific receptors. Hyperosmolar saline causes airways of asthmatics to narrow indirectly by endogenously mediated events that are potentially modified by drugs used to treat asthma. We wished to determine if hyperosmolar saline (S) is a useful challenge for assessing the airway responsiveness of asthmatic subjects being treated with steroids and to compare changes in airway responses to those changes observed with histamine (H). The airway responses to S and H were assessed by the dose of aerosol provoking a 20% fall in FEV1 and the percent fall in FEV1 per unit dose of aerosol inhaled-the dose response slope (DRS). We studied asthmatic subjects before and during treatment with budesonide-1000 micrograms per day. There was a significant correlation (Spearman's) between PD20 to H and S and DRS to H and S after budesonide (P < 0.05). After 2 months of treatment; the mean PD20 (95% CI) was increased 4.6 (2.5, 8.6) fold to H, and 9.7 (4.2, 22) fold to S, (P = NS) the DRS reduced 7.0 (4.3, 11.5) fold to H and 16.6 (8.4, 33) fold to S (P = NS). Responsiveness to H, measured by PD20 remained throughout the treatment, whereas five subjects did not record a 20% fall after S and the DRS decreased to values close to those we measured in healthy subjects. In conclusion, challenge with 4.5% sodium chloride can be used to assess the early benefits of treatment with aerosol steroids.