A clinical method for detecting bronchial reversibility using a breath sound spectrum analysis in infants  Mayumi Enseki, Mariko Nukaga, Hideyuki Tabata, Kota Hirai, Shinichi Matsuda, Hiroyuki Mochizuki  Respiratory Investigation  Volume 55, Issue 3, Pages 219-228 (May 2017) DOI: 10.1016/j.resinv.2016.11.005 Copyright © 2016 The Japanese Respiratory Society Terms and Conditions

Fig. 1 A sound spectrogram of an infant. The spectrogram of a 7-month-old healthy boy is shown after performing a Fourier analysis, with the vertical axis showing the frequency in Hz and the horizontal axis showing time. The sound intensity of the breath sounds is indicated using the color; high intensity was red, and low intensity was blue. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Respiratory Investigation 2017 55, 219-228DOI: (10.1016/j.resinv.2016.11.005) Copyright © 2016 The Japanese Respiratory Society Terms and Conditions

Fig. 2 Analysis by the sound spectrograph. (a) The sound intensity of the breath sounds is indicated using the color. The red vertical line indicates the highest frequency of the inspiratory breath sounds. (b) The horizontal axis shows the frequency in Hz and the vertical axis shows the power in dB at the point of the red vertical line in (a). (c) A five-point moving average was used for smoothing to determine the suitable values of dB to determine 0dB in the slope for each sound spectrum. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Respiratory Investigation 2017 55, 219-228DOI: (10.1016/j.resinv.2016.11.005) Copyright © 2016 The Japanese Respiratory Society Terms and Conditions

Fig. 3 Parameters of the sound spectrum. (a) The common parameters of the sound spectrum. F99: The frequency at 99% of the maximum frequency, Q25: the frequency at 25% of the power spectrum, Q50: the frequency at 50% of the power spectrum, Q75: the frequency at 75% of the power spectrum, HFI: the highest frequency of inspiratory breath sounds, dBmax: the power at the maximum point at that frequency. (b) The ratio-dependent parameters of the sound spectrum. AT: The total area of 100–2000Hz, A3/AT: the ratio of the third area to the total area. (c) The ratio-dependent parameters of the sound spectrum. AT: the total area of 100–2000Hz, B4/AT: the ratio of the forth area to the total area. (d) The ratio-dependent parameters of the sound spectrum. dBF50: the dB at F50, dBF75: the dB at F75, RPF50: the ratio of the power to (F99−F50) (=dBF50/(F99−F50)), RPF75: the ratio of the power to (F99−F75) (=dBF75/(F99−F75)). The RPF75 and RPF50 were calculated to evaluate the right angle of the spectrum triangle. Respiratory Investigation 2017 55, 219-228DOI: (10.1016/j.resinv.2016.11.005) Copyright © 2016 The Japanese Respiratory Society Terms and Conditions

Fig. 4 Sound spectra of infants. The results of patients No. 1, 2, 3, and 4. The raw data for the breath sound spectra were similar and reproducible in terms of the shape of results following repeated measures in the same patient. However, the shapes of the sound spectra were slightly different between the young subjects. The first, second, and third samples in each patient are indicated in red, blue, and green, respectively. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Respiratory Investigation 2017 55, 219-228DOI: (10.1016/j.resinv.2016.11.005) Copyright © 2016 The Japanese Respiratory Society Terms and Conditions

Fig. 5 A comparison of the A3/AT and RPF50 obtained by examiner A and examiner B (inter-observer) with Bland–Altman plots. Bland–Altman plots showed little inter-observer variation for the A3/AT and RPF50 values. (a) The A3/AT, (b) RPF50. Respiratory Investigation 2017 55, 219-228DOI: (10.1016/j.resinv.2016.11.005) Copyright © 2016 The Japanese Respiratory Society Terms and Conditions

Fig. 6 Change in the parameters before and after β2 agonist inhalation. (a) The A3/AT, (b) B4/AT, (c) RPF75, and (d) RPF50 before and after β2 agonist inhalation (n=20). Respiratory Investigation 2017 55, 219-228DOI: (10.1016/j.resinv.2016.11.005) Copyright © 2016 The Japanese Respiratory Society Terms and Conditions

Fig. 7 Estimated changes in the sound spectrum parameters. When bronchial dilatation is introduced, the high-pitched area in the sound spectrum is the most changed, showing a consequent decrease. (a) The A3/AT before and after β2 agonist inhalation. The ratio of high frequency area increased owing to bronchial dilatation. (b) RPF50 before and after β2 agonist inhalation. The angle of the high frequency area increased owing to bronchial dilatation. Respiratory Investigation 2017 55, 219-228DOI: (10.1016/j.resinv.2016.11.005) Copyright © 2016 The Japanese Respiratory Society Terms and Conditions