Effect of hyperoxia on bronchial response to inhaled methacholine

Abstract
Bronchial reactivity in a double‐blind controlled study in 10 normal subject and nine asthmatic patients. The normal volunteers were challenged while breathing dry. 21% and 100% O2 and the maximal percent talls in forced expired volume in 1s (FEV1) following inhalation of the highest concentration of MCH (64 mg/ml) were 8±5% and 9±8% respectively. P−‐ NS. The asthmatic patients had their MCH challenge breathing the same gas composition and the provocative concentrations that caused a 20% fall in FEV1 (PC.) were 0.18 mg/ml (range 0.06–5.73) and 0.25 mg/ml (range 0.07–8.49) respectively which were statistically not significantly different. We conclude that in humans. 100% O2 does not affect bronchial reactivity to MCH.