Lung sound analysis for continuous evaluation of airflow obstruction in asthma.
We developed a system for monitoring airflow obstruction noninvasively, based on the principle that the proportion of the breath cycle occupied by wheezing (Tw/Ttot) in any one subject corresponds to the severity of airways obstruction. Lung sounds were recorded continuously from the chest wall. Fifty 250 ms sound segments were randomly chosen from five-minute periods and analyzed for the presence or absence of wheezes. The proportion with wheezes was used as an estimate of Tw/Ttot (Est Tw/Ttot). For 12 wheezy patients, there was a good correlation between the Est Tw/Ttot and the forced expiratory volume in one second (r = 0.893, p less than 0.001). The system was used to evaluate nocturnal asthma. Five subjects were studied over eight nights. It was found that there was more wheezing from 4:00 to 4:30 AM than from midnight to 12:30 AM (p less than 0.05). This technique may prove useful in continuous, noninvasive monitoring of wheezy patients.
D000328:Adult; D001249:Asthma / Q000503:physiopathology*; D005541:Forced Expiratory Volume; D005583:Fourier Analysis; D006801:Humans; D008875:Middle Aged; D012135:Respiratory Sounds / Q000503:physiopathology*; D012890:Sleep / Q000502:physiology; D013997:Time Factors