Nasal cavity area in term infants determined by acoustic rhinometry.

The present study was undertaken to determine whether a modification to commercially available acoustic rhinometry (AR) instrumentation might allow equipment designed for use in adults to determine accurately the nasal cavity configuration of infants and children. The standard wave tube was replaced with a version having a narrow (0.312-cm2) internal diameter (ID). Before use with neonates, the accuracy of this instrument was evaluated using the nasal cavity of a full-term infant cadaver. Acoustic nasal area curves were compared to area measurements of polyvinylsiloxane nasal casts and direct volume measurements of the specimen. AR correlated well with nasal cast data (r = .88) for total nasal cavity area. The acoustic method underestimated the total area at the nasal valve by only 1.8 mm2 (22.1 mm2 vs. 23.9 mm2) and overestimated choanal area by 10 mm2 (56.9 mm2 vs. 46.9 mm2). In addition, AR measured total nasal volume to within 5.2% of the value obtained by direct measurement. In a cohort of 10 normal, term infants, the mean acoustic value for total nasal valve area was 19.2 +/- 0.05 mm2 and for total nasal volume was 1.76 +/- 0.53 cm3. This, the first report of nasal area and volume information in live infants, suggests that the modified AR device has utility both in airway research and as a nasal patency screening tool in the pediatric population.