RELATION OF THE HYPERTONIC SALINE RESPONSIVENESS OF THE AIRWAYS TO EXERCISE INDUCED ASTHMA SYMPTOM SEVERITY AND TO HISTAMINE OR METHACHOLINE REACTIVITY

Background Conflicting views exist over whether responsiveness of the airways to hypertonic saline relates to nonspecific bronchial hyperresponsiveness measured by histamine or methacholine challenge. The bronchoconstrictor responses to exercise and hypertonic saline are reported to be closely related, but the relationship between the symptoms of exercise induced asthma and airway responsiveness to hypertonic saline is not known. Methods In 29 asthmatic patients with a history of exercise induced asthma, the response to an ultrasonically nebulised hypertonic saline (3.6% sodium chloride) aerosol, measured as the volume of hypertonic saline laden air required to produce a fall in forced expiratory volume in one second (FEV1) of greater-than-or-equal-to 20% (PD20)), was compared with the concentration of histamine (PC20; group 1) and methacholine (PC20; group 2) producing a 20% fall in baseline FEV, and exercise induced asthma symptom severity score (groups 1 and 2). The hypertonic responsiveness was determined in a dose-response manner to a maximum dose of 310 1 and the exercise induced asthma symptom severity was scored on a scale of 0-5. Results Of the 29 patients, 23 (79%) were responsive to the hypertonic saline, with PD20 values ranging from 9 to 310 1. A significant correlation was found between the PD20 hypertonic saline and the exercise induced asthma symptom score. There was no significant correlation between the PD20 response to hypertonic saline and the histamine PC20 or methacholine PC20. The exclusion of those subjects who failed to respond to hypertonic saline improved the relationship between hypertonic saline and methacholine PC20. No significant correlation was found between the exercise induced asthma symptom score and histamine PC20 or methacholine PC20. Conclusion These findings suggest that hypertonic saline responsiveness bears a closer relationship to the severity of exercise induced asthma symptoms than to the non-specific bronchial hyperresponsiveness measured by histamine or methacholine reactivity.