139395.fig.004a
(a)
139395.fig.004b
(b)
Figure 4: Comparison of sounds obtained from a control subject and a patient with COPD. Time amplitude plots of a single breath are displayed in stacked mode, center panel. The choice of colors is arbitrary and used here to aid in visual separation of channels. The thin green line under each channel waveform indicates the duration of inspiration at that channel as automatically identified by the STG software. Vertical lines mark the start and the end of inspiratory sound recorded at the trachea. Notice that in the control subject the inspiratory sound starts and ends at almost the same time at all the chest sites as well as the trachea. In COPD, inspiratory lung sounds at the chest sites lead the inspiratory sound at the trachea in the beginning of the inspiration. In addition, inspiratory lung sounds at the chest sites tend to lag the inspiratory sound at the trachea at the end of inspiration. The lead time at each chest wall site is displayed superimposed over the body plot, left panel. The circle diameter is proportional to the time delay. The lag time at each chest wall site is also displayed, right panel. The top right panel shows microphone location on the chest. In the control patient, the average lead was 15 ms or 1% and the average lag 199 ms or 17%. In the COPD patient, the average lead was 267 ms or 22% and the average lag 520 ms or 43%. In the control patient, the lead asynchrony was 2% and lag asynchrony was 18%. In the COPD patient, the lead asynchrony was 24% and lag asynchrony was 48%.