New Technique to Analyze the Breath Sound Spectrum in Children with Asthma.

OBJECTIVE: Breath sound parameters have been reported as useful biomarkers for evaluating the airway condition. METHODS: The reliability of breath sound analysis using an improved method was investigated. Eighty-three asthmatic children were included in the present study. After adjusting the 0 level based on the background noises of the breath sound spectrum, the total area under the curve of the dBm (AT), the roll-off from 600-1200 Hz (Slope), the ratio of the third and fourth area to the AT (A3/AT and B4/AT), and the ratio of power and frequency at 50% and 75% of the highest frequency (RPF75 and RPF50), were evaluated before and after ß2 agonist inhalation. Spirography and the forced oscillation technique were also used to evaluate all subjects. RESULTS: Using the new method, A3/AT, B4/AT, RPF75 and RPF50, were significantly increased after ß2 agonist inhalation. The increase in A3/AT and B4/AT were significantly correlated with the increase in FEV1 and FEE25-75, and the increase in RPF75 was reversibly correlated with that in R5-R20. CONCLUSIONS: The spectrum curve indices using the adjusted 0 level can indicate bronchial dilation with ß2 agonist inhalation. These parameters may be useful for the assessment of bronchial reversibility in asthmatic children.