title: Averaged and time-gated spectral analysis of respiratory sounds. Repeatability of spectral parameters in healthy men and in patients with fibrosing alveolitis.
abstract: 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.
  
  
  METHODS
  Breath sounds were recorded simultaneously from the trachea and from the chest 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 were averaged over 7 to 10 successive respiratory cycles. The repeatability of sound intensity (RMS), frequency of maximum intensity (Fmax), and median frequency (F50) was analyzed with analysis of variance.
  
  
  METHODS
  Short-term repeatability was studied in 10 healthy nonsmoking men (age 25 to 44 years), and day-to-day 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).
  
  
  RESULTS
  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 from the trachea. Day-to-day CoV of Fmax and F50 in healthy subjects was 4.7 to 8.5% and 5.0 to 8.7% recorded from the chest or from the trachea, respectively. Inspiratory day-to-day variation in those parameters was higher in patients with fibrosing alveolitis. CoV of RMS was high, ranging from 18 to 47% in different subject groups and sampling situations.
  
  
  CONCLUSIONS
  Repeatability of F50 of averaged flow-controlled lung sound spectra is good both in healthy subjects and in patients with fibrosing alveolitis. Thus, F50 of respiratory sound spectra may be useful in monitoring of changes induced by respiratory diseases and interventions. These results emphasize the importance of standardization of recording conditions and of analyzing techniques.
authors.affiliation: Department of Medicine, Helsinki University Central Hospital, Finland.
authors.forename: A R
authors.initials: AR
authors.lastname: Sovijärvi
authors.forename: L P
authors.initials: LP
authors.lastname: Malmberg
authors.forename: E
authors.initials: E
authors.lastname: Paajanen
authors.forename: P
authors.initials: P
authors.lastname: Piirilä
authors.forename: K
authors.initials: K
authors.lastname: Kallio
authors.forename: T
authors.initials: T
authors.lastname: Katila
mesh_terms: D000328:Adult; D006801:Humans; D008297:Male; D011658:Pulmonary Fibrosis / Q000503:physiopathology*; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D012135:Respiratory Sounds; D013018:Sound Spectrography; D013997:Time Factors