Nasal dilator strips increase maximum inspiratory flow via nasal wall stabilization

Objective: Inspiratory flow limitation associated with collapse of the nasal vestibular walls is a feature of nasal breathing at high ventilatory levels. We examined whether an external nasal dilator strip (ENDS) device (Breathe Right, CNS Inc., Chanhassen, MN) influences maximum inspiratory and expiratory flow rates. Study Design: Prospective, randomized. Methods: We studied 20 Caucasian subjects (13 female, 7 male; age range, 16–49 y) performing maximum‐effort nasal flow‐volume loop studies with (ENDS) and without ENDS (control) and following topical nasal decongestant (oxymetazoline hydrochloride, 0.2 mg per nostril). Results: ENDS increased peak inspiratory flow from 2.55 ± 0.24 L/s (mean ± standard error [SE]) to 2.86 ± 0.25 L/s and forced inspiratory flow at 50% of vital capacity from 2.23 ± 0.24 L/s to 2.53 ± 0.24 L/s (both, P < .0001), but had no effect on maximum expiratory flows. Nasal decongestant increased the forced expiratory volume in 1 second from 3.39 ± 0.22 L/s to 3.59 ± 0.22 L/s and the average forced expiratory flow over 25% to 75% of vital capacity from 3.31 ± 0.31 L/s to 3.61 ± 0.28 L/s (both, P ⩽ .008), but had no effect on maximum inspiratory flows. The combination of decongestant and ENDS increased both inspiratory and expiratory maximum flows. Conclusion: Since ENDS selectively increases maximum nasal inspiratory flow rates, we conclude that ENDS increases inspiratory nasal patency during maximum inspiratory efforts through the nose by supporting the lateral nasal vestibular walls and making them more resistant to collapse.