AVERAGED AND TIME-GATED SPECTRAL-ANALYSIS OF RESPIRATORY SOUNDS - REPEATABILITY OF SPECTRAL PARAMETERS IN HEALTHY-MEN AND IN PATIENTS WITH FIBROSING ALVEOLITIS

Study objective: To obtain a basis for assessment of changes in breath sound spectra in patients with pulmonary diseases, short-term and day -to-day repeatability of spectral parameters was studied. Design: Brea th sounds were recorded simultaneously from the trachea and from the c hest twice at an interval of 15 min (short-term repeatability) and of 1 to 3 days (day-to-day repeatability), During recordings, air flow at the mouth was controlled, the target inspiratory and expiratory peak flow being 1.25 L/s. Inspiratory and expiratory breath sound spectra w ere averaged over 7 to 10 successive respiratory cycles, The repeatabi lity of sound intensity (RMS), frequency of maximum intensity (Fmax), and median frequency (F50) was analyzed with analysis of variance. Par ticipants: Short-term repeatability was studied in 10 healthy nonsmoki ng men (age 25 to 44 years), and day-to-clay repeatability was studied in 10 healthy nonsmoking men (age 23 to 41 years) and in 12 patients with clinically stable fibrosing alveolitis (age 35 to 82 years). Resu lts: Short-term coefficient of variation (CoV) of Fmax and F50 was 2.6 to 6.7% when recorded from the chest, and 6.2 to 8.7% when recorded f rom the trachea. Day-to-day CoV of Fmax and F50 in healthy subjects wa s 4.7 to 8.5% and 5.0 to 8.7% recorded from the chest or from the trac hea, respectively. Inspiratory day-to-day variation in those parameter s was higher in patients with fibrosing alveolitis, CoV of RMS was hig h, ranging from 18 to 47% in different subject groups and sampling sit uations. Conclusions: Repeatability of F50 of averaged flow-controlled lung sound spectra is good both in healthy subjects and in patients w ith fibrosing alveolitis. Thus, F50 of respiratory sound spectra may b e useful in monitoring of changes induced by respiratory diseases and interventions. These results emphasize the importance of standardizati on of recording conditions and of analyzing techniques.