Changes in nasal airway dimensions in infancy

Thirty-nine infants, previously examined as neonates, were re-examined at I year of age with continuous wide-band noise acoustic rhinometry using a sp ecific probe optimized for infants, to determine the dimensional growth and maturation of nasal airway geometry in otherwise healthy infants. During t he first year of life, the acoustically determined dimensions of the nasal airways increased significantly. The total minimal cross-sectional area inc reased by 67% (0.21 cm(2)-->0.35 cm(2)), the volume of the anterior 4 cm of the nasal airway by 36% (1.80 cm(3)-->2.43 cm(3)) and the distance to the minimum cross-sectional area by 19% (0.78 cm-->0.93 cm). The rhinometric va lues of male infants were significantly larger than those of females. Howev er, after adjusting for the significantly larger anthropometric values of m ales, the difference disappeared, indicating that it was mainly due to body size and not directly to gender. A highly significant correlation (r = 0.4 4, p < 0.006) was observed between the minimum cross-sectional area and hea d circumference, which anatomically are the most closely related rhinometri c and anthropometric values. Furthermore, when differentiating between infa nts with or without signs of nasal congestion during the fortnight precedin g the rhinometric evaluation, a reduction in the total volume of the anteri or 4 cm (17%, p < 0.02) and minimum cross-sectional area (17%, ns) was obse rved after adjustment. We conclude that the optimized acoustic rhinometric probe is a useful investigative modality, permitting studies of upper airwa y physiology of healthy and diseased infants.