title: Developing a reference of normal lung sounds in healthy Peruvian children.
abstract: OBJECTIVE
  Lung auscultation has long been a standard of care for the diagnosis of respiratory diseases. Recent advances in electronic auscultation and signal processing have yet to find clinical acceptance; however, computerized lung sound analysis may be ideal for pediatric populations in settings, where skilled healthcare providers are commonly unavailable. We described features of normal lung sounds in young children using a novel signal processing approach to lay a foundation for identifying pathologic respiratory sounds.
  
  
  METHODS
  186 healthy children with normal pulmonary exams and without respiratory complaints were enrolled at a tertiary care hospital in Lima, Peru. Lung sounds were recorded at eight thoracic sites using a digital stethoscope. 151 (81%) of the recordings were eligible for further analysis. Heavy-crying segments were automatically rejected and features extracted from spectral and temporal signal representations contributed to profiling of lung sounds.
  
  
  RESULTS
  Mean age, height, and weight among study participants were 2.2 years (SD 1.4), 84.7 cm (SD 13.2), and 12.0 kg (SD 3.6), respectively; and, 47% were boys. We identified ten distinct spectral and spectro-temporal signal parameters and most demonstrated linear relationships with age, height, and weight, while no differences with genders were noted. Older children had a faster decaying spectrum than younger ones. Features like spectral peak width, lower-frequency Mel-frequency cepstral coefficients, and spectro-temporal modulations also showed variations with recording site.
  
  
  CONCLUSIONS
  Lung sound extracted features varied significantly with child characteristics and lung site. A comparison with adult studies revealed differences in the extracted features for children. While sound-reduction techniques will improve analysis, we offer a novel, reproducible tool for sound analysis in real-world environments.
authors.affiliation: Division of Pulmonary and Critical Care, School of Medicine, Johns Hopkins University, 1800 Orleans Ave, Suite 9121, Baltimore, MD, 21205, USA.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Ellington
authors.forename: Dimitra
authors.initials: D
authors.lastname: Emmanouilidou
authors.forename: Mounya
authors.initials: M
authors.lastname: Elhilali
authors.forename: Robert H
authors.initials: RH
authors.lastname: Gilman
authors.forename: James M
authors.initials: JM
authors.lastname: Tielsch
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Chavez
authors.forename: Julio
authors.initials: J
authors.lastname: Marin-Concha
authors.forename: Dante
authors.initials: D
authors.lastname: Figueroa
authors.forename: James
authors.initials: J
authors.lastname: West
authors.forename: William
authors.initials: W
authors.lastname: Checkley
mesh_terms: D000367:Age Factors; D001314:Auscultation / Q000295:instrumentation / Q000592:standards*; D001827:Body Height; D001835:Body Weight; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008168:Lung / Q000502:physiology*; D008297:Male; D010568:Peru; D011237:Predictive Value of Tests; D012016:Reference Values; D012135:Respiratory Sounds; D012737:Sex Factors; D012815:Signal Processing, Computer-Assisted; D013018:Sound Spectrography; D019023:Stethoscopes / Q000592:standards; D013997:Time Factors