An accurate recording system and its use in breath sounds spectral analysis

Abstract

An accurate recording system was set up and used for analyzing normal and asthmatic breath-sound features. Breath sounds are recorded at the trachea simultaneously with the airflow signal at 0.5- and 1-l/s levels. The study was carried out in the frequency domain using a fast-fourier transform (FFT). FFT are taken on 1024-sample blocks (1 block = 200 ms) over a duration of about 20 s. Different characteristics of the spectra are calculated in the range 60-1260 Hz for 11 normal and 10 asthmatic [human] subjects. This allows the computation of an index that discriminates (P < 0.0005) asthma cases from normal cases. Spectral features strongly depend on the flow rate both for normal and asthmatic subjects. Increasing the flow rate raises the high-frequency components of the spectra.