Bronchoconstriction: upper airway dilating muscle and diaphragm activity

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Abstract
The effect of bronchoconstriction on the activity of the diaphragm and the upper dilating airway muscles were studied by administering graded doses of methacholine to anesthetized dogs spontaneously breathing O2. The electrical activity of the genioglossus, posterior cricoarytenoid and alae nasi was compared with that of the diaphragm at different levels of pulmonary resistance. Induced bronchoconstriction was associated with increases in the electrical activity of all muscles examined. Bilateral cervical vagotomy diminished but did not prevent the bronchoconstrictor effects of methacholine. When greater concentrations of methacholine were administered to produce bronchoconstriction comparable with that produced prevagotomy, both genioglossus and diaphragm activity increased. Evidently, the upper airway muscles and the diaphragm respond to bronchoconstriction. The activation of the upper airway muscles with bronchoconstriction may decrease upper airway resistance serving to partially offset increases in pulmonary resistance and to modulate airflow patterns during bronchoconstriction.