Effect of nasal obstruction on upper airway muscle activation in normal subjects.

It is not known whether nasal occlusion produces obstructive sleep apnea (OSA) by decreasing upper airway muscle activation via nasal reflexes or by increasing upper airway resistance and hence lowering the pressure in the pharnyx. The purpose of this study was to determine the effect of nasal occlusion on upper airway muscle activation. We studied seven men and measured alae nasi (AN) and genioglossal (GG) electromyograms (EMGs) during two nights of sleep, one with their nose open and the other with their nose occluded. Nasal occlusion produced OSA in all subjects and also increased the percentage of time during sleep in which phasic AN and GG EMG activity was present. Apneas tended to occur at the nadirs of EMG activity. This suggests that nasal occlusion generally increases respiratory drive to upper airway muscles during sleep and that it does not cause OSA by merely decreasing respiratory drive to these muscles.