Inspiratory and expiratory effects of nasal breathing.

The purpose of the present study was to assess quantitatively the nasal valve area during normal inspiratory and expiratory maneuvers. The pressure-flow technique of Warren was used to estimate nasal size in 15 adult subjects who had no previous history of nasal surgery or abnormality. Cross-sectional size of the nasal airway was also assessed (1) after insertion of tubing to eliminate alar effects, (2) after administration of 0.1% Otrivin decongestant to eliminate mucosal effects, and (3) by blocking each nostril individually. Mean areas of 0.63 cm2 +/- 0.17 during inspiration and 0.56 cm2 +/- 0.14 during expiration. This difference is statistically significant (less than 0.01) and the effect was maintained under conditions of occlusion of either nostril, insertion of tubing, and administration of Otrivin. These findings suggest that the nasal valve acts as a respiratory brake during expiration possibly to allow adequate time for gas exchange at the alveoli.