Pharyngeal and glottic changes following methacholine challenge in normal subjects.

Recent evidence indicates that some normal subjects exhibit glottic narrowing following experimentally induced bronchospasm. Similar findings have been observed during episodes of bronchospasm in asthmatics. The exact mechanism of this effect is unknown but it is thought to occur as part of a generalized reflex response associated with constriction of intrapulmonary airways. We tested the hypothesis that in addition to the glottic changes, coincident with intrapulmonary airway constriction which occurred after inhalation of methacholine, the pharynx would show similar changes. Pharyngeal and glottic cross-sectional areas were measured using the acoustic reflection technique in seven healthy subjects before and after inhalation of metacholine. Before methacholine, pharyngeal and glottic areas (mean +/- SE) were 5.0 +/- 0.2 cm2 and 2.4 +/- 0.3 cm2 respectively. After inhalation of methacholine, these areas were reduced to 4.6 +/- 0.3 cm2 and 1.9 +/- 0.3 cm2 respectively (p less than 0.05). We conclude that inhalation of methacholine induces similar reductions in glottic and pharyngeal areas. The role of local or reflex mechanisms accounting for this reduction remains unclear.