Alae nasi activation decreases nasal resistance during hyperoxic hypercapnia

It has beenproposed that decreases in nasal resistance (Rn) during hypercapnia areentirely due to vasoconstriction in the nasal cavity. We hypothesizedthat alae nasi (AN) muscle activity dilates the nasal vestibule andcontributes to the decrease in Rn during hypercapnia. Nine normalsubjects were studied during hyperoxic hypercapnia (HH). Rn andvestibular resistance (Rvest) for one nasal passage were measuredsimultaneously with the AN electromyogram before and after nasaldecongestion. HH decreased Rvest from 1.6 ± 0.6 to 0.8 ± 0.9 cmH₂O · l¹ · s(predecongestant) and from 1.3 ± 0.8 to 0.6 ± 0.7 cmH₂O · l¹ · s(postdecongestant; both P < 0.01).Nasal decongestant decreased Rn but not Rvest. Significant inverselinear relationships between Rvest and AN electromyogram weredemonstrated for all subjects. We conclude that in normal subjectsduring HH 1) decreases in Rvest arepredominantly due to increases in AN activity; and2) decreases in Rn are due to acombination of mucosal vasoconstriction and ANactivation.