The nasal valves: changes in anatomy and physiology in normal subjects.

There is confusion in the literature concerning the physiology and pathology of the nasal valve, and some debate as to whether there is one valve or two. In an attempt to clarify these uncertainties we have measured nasal function by assessing nasal minimum cross-sectional area, inspiratory resistance and peak inspiratory flow under baseline conditions and after the application of a topical vasoconstrictor. These measurements were then repeated following the application of external and internal nasal splints. Whatever test was employed the results showed that vasoconstriction tended to be the most potent stimulus which changed nasal function producing significant expansion of the minimum cross-sectional area, a decrease in inspiratory resistance and an increase in peak inspiratory flow. External splints also increased the minimal cross sectional area but they had no effect on inspiratory resistance or on the tendency of the vestibular rim to collapse at high inspiratory flow rates. The tendency for lower lateral cartilage collapse was, however, prevented by internal splintage using alar dilators. The results of this study suggest that there is an internal valve at the nasal isthmus where the principal alterations in airway patency follow changes in mucosal congestion, and a mobile external valve where airflow is limited by the tendency of the alar cartilages to collapse. These should be considered as separate entities with differing pathophysiology and these differences should be taken into account when treating patients with airway obstruction due to pathology at these sites.