title: Lung sound analysis helps localize airway inflammation in patients with bronchial asthma.
abstract: OBJECTIVE
  Airway inflammation can be detected by lung sound analysis (LSA) at a single point in the posterior lower lung field. We performed LSA at 7 points to examine whether the technique could identify the location of airway inflammation in patients with asthma.
  
  
  METHODS
  Breath sounds were recorded at 7 points on the body surface of 22 asthmatic subjects. Inspiration sound pressure level (ISPL), expiration sound pressure level (ESPL), and the expiration-to-inspiration sound pressure ratio (E/I) were calculated in 6 frequency bands. The data were analyzed for potential correlation with spirometry, airway hyperresponsiveness (PC20), and fractional exhaled nitric oxide (FeNO).
  
  
  RESULTS
  TheE/Idata in the frequency range of 100-400 Hz (E/Ilow frequency [LF],E/Imid frequency [MF]) were better correlated with the spirometry, PC20, and FeNO values than were theISPLorESPLdata. The left anterior chest and left posterior lower recording positions were associated with the best correlations (forced expiratory volume in 1 second/forced vital capacity:r=-0.55 andr=-0.58; logPC20:r=-0.46 andr=-0.45; and FeNO:r=0.42 andr=0.46, respectively). The majority of asthmatic subjects with FeNO ≥70 ppb exhibited highE/IMF levels in all lung fields (excluding the trachea) andV50%pred <80%, suggesting inflammation throughout the airway. Asthmatic subjects with FeNO <70 ppb showed high or lowE/IMF levels depending on the recording position, indicating uneven airway inflammation.
  
  
  CONCLUSIONS
  E/ILF andE/IMF are more useful LSA parameters for evaluating airway inflammation in bronchial asthma; 7-point lung sound recordings could be used to identify sites of local airway inflammation.
authors.affiliation: Clinical Research Center, Fukuoka National Hospital, Fukuoka.
authors.forename: Terufumi
authors.initials: T
authors.lastname: Shimoda
authors.affiliation: Second Department of Internal Medicine, School of Medicine, Nagasaki University, Nagasaki.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Obase
authors.affiliation: Kyoto Respiratory Center, Otowa Hospital, Kyoto, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Nagasaka
authors.affiliation: Clinical Research Center, Fukuoka National Hospital, Fukuoka.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakano
authors.affiliation: Clinical Research Center, Fukuoka National Hospital, Fukuoka.
authors.forename: Akiko
authors.initials: A
authors.lastname: Ishimatsu
authors.affiliation: Clinical Research Center, Fukuoka National Hospital, Fukuoka.
authors.forename: Reiko
authors.initials: R
authors.lastname: Kishikawa
authors.affiliation: Clinical Research Center, Fukuoka National Hospital, Fukuoka.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Iwanaga
keywords: 7-point analysis; airway obstruction; expiration sound pressure level; expiration-to-inspiration sound pressure ratio; inspiration sound pressure level