Influence of nasal airflow and resistance on nasal dilator muscle activities during exercise.

Our purpose was to assess the separate effects of nasal airflow and resistance on the activity of the nasal dilator [alae nasi (AN)] muscles. Nasal airflow and the AN electromyogram were recorded at rest and during progressive-intensity exercise at 60, 120, and 150-180 W in 10 healthy subjects who breathed nasally under all conditions. The activity of the AN muscles increased linearly as a function of the increase in nasal minute ventilation evoked by progressive-intensity exercise (r = 0.99, P < 0.002). Reciprocal changes in nasal airflow and resistance were produced by surreptitious substitution of 12-15 breaths of 79% He-21% O2 for air at rest and during exercise. The switch to He-O2 decreased airway resistance (anterior rhinomanometry) by approximately 30% at rest and 40-60% during exercise. He-O2 did not change nasal flow or AN activities significantly under resting conditions. In contrast, He-O2 increased nasal flow and decreased the AN electromyogram by 25-50% during exercise (P < 0.05). The results suggest that AN muscle activities during nasal breathing are regulated by mechanisms that track airway resistance or the level of flow turbulence. The increase in AN activities during exercise probably helps ensure nasal airway patency in the face of the considerable collapsing pressures that prevail under these conditions.