Role of nose breathing in genioglossus muscle response to hypoxia in older and younger subjects.

Several studies showed that nasal airway is an active component of the respiratory system. Clinical data suggest that nasal obstruction causes episodes of obstructive apnea or hypopnea. In the present study, a possible influence of breathing through the nose on genioglossus muscle (GG, dilator of upper airway) reactivity to hypoxic activation was studied. Two groups of 20-30 years and 41-55 years old, 35 healthy subjects each, were investigated. The GG-EMG-activity was recorded and analyzed during progressive normocapnic hypoxia. The subjects breathed through the nose (N) or mouth (M) alone and through the nose and mouth (N&M). Significantly smaller increases in the GG-EMG-activity in response to hypoxia were observed during M breathing, as compared with N and M&N breathing, in both groups. The older subjects also showed a reduced response of GG-muscle to hypoxia, which was most pronounced during M breathing. We suggest that breathing through the nose activates the dilator muscle of upper airways, preventing apnea events.