The site and function of the nasal valve.

Previous observers have suggested that the main site of respiratory airflow resistance is localized to the vestibular region of the nose. This resistive segment of the airway was investigated using a "head-out" body plethysmograph in subjects with anatomically normal noses (a) untreated, (b) congested and (c) decongested. In all three conditions, 2/3 of the total nasal airflow resistance was found within the bony cavum in the vicinity of the pyriform aperture and about 1/3 in the cartilaginous vestibule. As might be expected, caval resistance changed proportionately with the degree of mucosal congestion; but, more surprisingly, vestibular resistance changed similarly. This was due in part to the observed forward expansion of the anterior ends of the inferior turbinates with congestion. EMG recordings in subjects breathing through both nostrils demonstrated a gradation of inspiratory alar dilator muscle activity with increased minute ventilation and with mucosal congestion, and there was no evidence of inspiratory alar collapse. But with elevated ventilation through one nostril only, or when the alar muscles were paralyzed by lidocaine block of the VIIth nerve, alar collapse occurred. These findings are of importance in the management of the congested but anatomically normal nose and in surgery of the nasal tip.