The Evaluation of Changes in the Breath Sound Spectrum with Bronchoconstriction and Bronchodilatation in Asthmatic Children.

OBJECTIVE: Focusing on the relative-middle sound area of the breath sound spectrum, the relationship between airway changes and breath sounds in asthmatic children was investigated. METHODS: In Study 1, 77 children (6-16 years old) were included. The breath sound parameters, the ratio of the second area to the third area of the power spectrum (A2/A3) and the ratio of the third area to the fourth area (B3/B4) were evaluated 3 times, before and just after methacholine inhalation and after beta2 agonist inhalation. Other breath sound parameters, the frequency limiting 99% of the power spectrum (F99), the rolloff from 600-1200 Hz (Slope) and the ratio of the third and fourth area to the total area under the curve (A3/AT and B4/AT), and the ratio of power and frequency at 50% and 75% of the highest frequency of the power spectrum (RPF75 and RPF50), were also evaluated. In Study 2, 91 children (6-16 years old) were included, with evaluations performed twice: before and after beta2 a gonist inhalation. Spirography a nd forced o scillation technique were also performed. RESULTS: In Study 1, A2/A3 and B3/B4 were significantly increased after methacholine inhalation and decreased after beta2 agonist inhalation (p < 0.001, P < 0.001, respectively). In Study 2, A2/A3 and B3/B4 were significantly decreased after beta2 agonist inhalation. These changes in A3/AT and B4/AT were the inverse of those in other spectrum curve indices. CONCLUSIONS: A2/A3 and B3/B4, indicate the breath sound changes after bronchoconstriction and bronchodilatation. These parameters may be useful for assessing bronchial reversibility in asthmatic children.