Dynamic components of nasal resistance.

This investigation was undertaken to demonstrate the contributions of dynamic vestibular and mucosal components to nasal air-flow resistance in healthy human adults. The studies were made by video recording of alar movement, electromyography of alar muscle activity, and by computer-assisted plethysmographic measurement of nasal air-flow resistance. Inspiratory approximation of the alae toward the septum from their expiratory position averaged only 0.6 mm at the high nasal ventilation of 35 L/min; it was less at lower ventilation and absent during voluntary mouth breathing. Inspiratory electromyographic activity also was directly related to the extent of nasal ventilation and was absent during voluntary mouth breathing. The activity was consistent with phasic muscular restraint of vestibular compliance with inspiratory transnasal pressures. Physiologic nasal air-flow resistance changes associated with posture, the nasal cycle, exercise, and hyperventilation persisted despite immobilization of the alae by splinting the vestibule widely open. These changes were abolished by topical decongestant, even in the unsplinted nose, and are therefore vascular.