Errors arising in cross-sectional area estimation by acoustic rhinometry produced by breathing during measurement.

Standardization of acoustic rhinometry is becoming increasingly important as the use of this technique becomes more widespread. The effects of breathing through the nose during acoustic rhinometry were investigated to determine if this affected the measurements of minimal cross-sectional area. During inspiration, and inspiration with the contralateral nasal airway obstructed, the minimal cross-sectional area decreased by 12.48% (p < 0.05) and 56.68% (p < 0.01), respectively, from the measurement made during a breathing pause. During expiration the reverse was observed, with increases in the minimal cross-sectional area of 13.95% (p > 0.05) and 40.20% (p < 0.05), respectively. In all but quiet expiration, the minimum cross-sectional area recorded during respiratory manoevres, differed significantly from those measured during a breathing pause. We recommend that in order to avoid changes in nasal measurements during breathing, acoustic rhinometry should be performed during a brief breathing pause.