The relationship between nasal cross-sectional area and nasal air volume in normal and nasally impaired adults.

The controversy concerning the effects of nasal airway impairment on facial growth has stimulated renewed interest in upper airway respiratory function. The subjective manner in which airway impairment and mouth breathing have been assessed is, in our opinion, responsible for the differences observed among investigators and for their conclusions. We have been involved in a series of studies dealing with airway impairment and have report modifications of two techniques for objectively assessing respiration. The purpose of the present study was to examine a large population of adults, with and without nasal airway impairment, and assess the relationship between nasal cross-sectional area and nasal air volume to determine at what point airway size controls the passage of air during breathing. Statistical analysis of the data demonstrates that airway size alters air volume when nasal cross-sectional area is less than 0.4 cm2. The relationship between area and volume is very linear below 0.4 cm2, with air volume decreasing with decreased size. Although the data do indicate some influence over volume at sizes greater than 0.4 cm2, the effect is very slight. These findings support the prediction that upper airway impairment is present at nasal airways less than 0.4 cm2 in adults.