The effects of osmotic challenge on bronchial responsiveness to methacholine in non-asthmatic subjects

We have measured the airway responses to methacholine on three days in sixteen non-asthmatic subjects. On the first day the methacholine challenge alone was performed. The other two days were randomized between pretreatment with distilled water or hypertonic saline administered by ultrasonic nebulizer. Distilled water and hypertonic saline did not affect baseline specific conductance (sGaw). Provocative dose producing a 35% fall in sGaw (PD35sGaw) was slightly reduced by both distilled water and hypertonic saline (15.83 to 8.55 mumol with distilled water and to 11.80 mumol with hypertonic saline). Six out of 16 subjects reached a plateau of maximal response with methacholine. The level of this plateau was not affected by pretreatment with distilled water or hypertonic saline. These results show that distilled water and 3.6% saline produced small increases in non-specific reactivity in normal subjects and confirm that substantial osmotic challenge does not change airway calibre in non-asthmatic subjects.