Changes in the breath sound spectrum with bronchodilation in children with asthma.

BACKGROUND

Breath sound parameters have been suggested to be new biomarkers of airway function in patients with asthma.

METHODS

We investigated the effect of bronchodilation on breath sound parameters in sixty-four children (mean age, 8.9 years; range, 6-16 years) using a breath sound analyzer. The breath sound parameters included frequency limiting 50% and 99% of the power spectrum (F50 and F99), roll-off from 600-1200 Hz (slope), and spectrum curve indices such as the ratios of the third and fourth power area to the total area of the power spectrum (P3/PT and P4/PT), 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). Lung function was assessed using spirometry and the forced oscillation technique (FOT). All variables were assessed before and after inhalation of a β2-agonist.

RESULTS

The spectrum curve indices, A3/AT, B4/AT, RPF75, and RPF50, showed statistically significant increase following β2-agonist inhalation. The increase in RPF50 was correlated with the decrease in the difference between resistance at 5 Hz and 20 Hz, R5-R20, measured by FOT. In the multiple regression analysis adjusted for the effect of ΔRPF75, the changes in A3/AT and B4/AT were positively correlated with that in the forced expiratory volume in one second.

CONCLUSIONS

The spectrum curve indices indicated bronchodilation, and may be useful for the assessment of bronchial reversibility in children with asthma.