Alae nasi activation decreases nasal resistance during hyperoxic hypercapnia

It has been proposed that decreases in nasal resistance (Rn) during hypercapnia are entirely due to vasoconstriction in the nasal cavity. We hypothesized that alae nasi (AN) muscle activity dilates the nasal vestibule and contributes to the decrease in Rn during hypercapnia. Nine normal subjects were studied during hyperoxic hypercapnia (HH). Rn and vestibular resistance (Rvest) for one nasal passage were measured simultaneously with the AN electromyogram before and after nasal decongestion. HH decreased Rvest from 1.6 +/- 0.6 to 0.8 +/- 0.9 cmH2O . l-1 . s (predecongestant) and from 1.3 +/- 0.8 to 0.6 +/- 0.7 cmH2O . l-1 . s (postdecongestant; both P < 0. 01). Nasal decongestant decreased Rn but not Rvest. Significant inverse linear relationships between Rvest and AN electromyogram were demonstrated for all subjects. We conclude that in normal subjects during HH 1) decreases in Rvest are predominantly due to increases in AN activity; and 2) decreases in Rn are due to a combination of mucosal vasoconstriction and AN activation.