[The flow-limiting segment (FS) of the nasal airway]

A modified anterior rhinomanometry and electromyography of the alar muscle were introduced to investigate the site and function of the FS. It was determined that the FS was confined to the area of nasal pathway 2.5 cm in length from the nostril. The location and limitation of this region, which accounted for 78.8% of overall nasal airway resistance, could not be altered by topical vasoactive agents. The most resistive site in the FS averaged 1.75cm distant from the nostril. In normal subjects, alar muscles constricted isometrically during respiration so as to keep the vestibular airway stable. On the contrary, the deformities and abnormalities of the FS could obliterate the nasal airway easily, leading to the symptom of nasal obstruction. Clinically, it is imperative to pay much attention to lesions in the FS in the diagnosis and treatment of nasal stuffiness. Furthermore, it is essential to protect the structural integrity of the FS in the daily rhinosurgery.