How mild is mild asthma?

Abstract

Asthmatic volunteers (19) underwent methacholine-induced asthma to the point when tightness in the chest was just sensed (threshold symptom). Changes in the following indices of lung function were measured; static lung volumes, forced expiratory volume in 1 s and airways conductance. Increase in airways resistance necessary for threshold detection was at least double that previously reported in experiments using external resistive loads. Despite the symptom''s mildness, increases in lung volumes to levels previously described during acute and severe asthma were occasionally found. There may be little leeway in respiratory reserve between development of minor and severe symptoms in some asthmatic patients.