BREATHING ROUTE DEPENDENCE OF UPPER AIRWAY MUSCLE-ACTIVITY DURING HYPERPNEA

Exercise (Ex) and hypercapnia (HC) both lead to increases in ventilati on and upper airway muscle (UAM) activity. To determine whether differ ent breathing routes (nasal vs, oral) or stimuli produced differential UAM activation, electromyographic (EMG) activity of the alae nasi (AN ) and genioglossus (GG) were measured in seven normal subjects seated on a bicycle ergometer. Subjects performed paired runs during both pro gressive Ex and HC while breathing through the nose alone (N) or the m outh alone (O). During hyperpnea, AN EMG was greater when the subjects were breathing via N [81 +/- 6% maximum (HC) and 69 +/- 7% maximum (E x)] than when they were breathing via O [30 +/- 5% maximum (HC) and 27 +/- 5% maximum (Ex); both P < 0.01], whereas the GG EMG did not diffe r between N and O. Both AN and GG EMG were similar for Ex and HC when the subjects were breathing via the same route. We conclude that UAM a ctivation was independent of the nature of the stimulus. However, the AN muscle but not the GG muscle demonstrated breathing-route dependenc e of activity.