The respiratory sound features of COVID-19 patients fill gaps between clinical data and screening methods

Ying hui Huang; Si jun Meng; Yi Zhang; Shui sheng Wu; Yu Zhang; Ya wei Zhang; Yi xiang Ye; Qi feng Wei; Nian gui Zhao; Jian ping Jiang; Xiao ying Ji; Chun xia Zhou; Chao Zheng; Wen Zhang; Li zhong Xie; Yong chao Hu; Jian quan He; Jian Chen; Wang yue Wang; Chang hua Zhang; Liming Cao; Wen Xu; Yunhong Lei; Zheng hua Jian; Wei ping Hu; Wen juan Qin; Wan yu Wang; Yu long He; Hang Xiao; Xiao fang Zheng; Yi Qun Hu; Wen Sheng Pan; Jian feng Cai

A. Ratio of inhalation to exhalation time. Yellow is for breathing in and blue is for breathing out. B. The vesicular breath sounds of the above respiratory cycle. The two white arrows indicate the location of the cackles. C. Extract and amplify the breath sound including cackles to make waveform and time -frequency diagrams respectively. The waveform shows a sharp peak in high intensity range, and the interval time are about 50ms. The main frequencies are between 150 and 600. Cackles: Crackles are short, explosive, nonmusical sounds heard on inspiration and sometimes during expiration. The feature is duration<100ms, frequency range is about 350Hz (Fine cackles) , or 650Hz (Coarse cackles) 6 , other studies have reported the rang is 100-1000 Hz 8 . The likey mechanism of crackles is the sudden inspiratory opening of small airways held closed by surface forces during the previous expiration, which can be correlated to COPD, pneumonia, fibrosis or bronchiectasis 18 .