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 β2 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 β2 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 β2 agonist inhalation. These parameters may be useful for the assessment of bronchial reversibility in asthmatic children.