title: Colored 3-dimensional analyses of respiratory resistance and reactance in COPD and asthma.
abstract: BACKGROUND
  The forced oscillation technique (FOT) is a noninvasive method with which to measure respiratory system resistance (Rrs) and reactance (Xrs) at a wide range of frequencies during breathing at rest in a short time. The purpose of this study was to assess the differences in Rrs and Xrs between patients with chronic obstructive pulmonary disease (COPD) and asthma using a new method of FOT with colored 3-dimensional visualization.
  
  
  METHODS
  Fifty-one patients with stable COPD and 49 patients with controlled or partly controlled asthma were enrolled. Whole-breath or within-breath changes of Rrs and Xrs were measured and compared between the diseases.
  
  
  RESULTS
  The colored 3-dimensional images clarified the complex oscillatory properties of the respiratory system. Whole-breath resistance (the difference in Rrs at 5 and 20 Hz) and reactance (Xrs at 5 Hz and resonant frequency), and within-breath changes in reactance (Xrs at 5 Hz and resonant frequency) discriminated between patients with COPD and asthma. In multivariate regression analyses, inspiratory-expiratory differences in Xrs at 5 Hz contributed significantly to the differentiation between COPD and asthma, independent of age, gender, body weight, and pulmonary function.
  
  
  CONCLUSIONS
  This new method of FOT is useful in the differential diagnosis of COPD and asthma.
authors.affiliation: Department of Respiratory Medicine, Shizuoka General Hospital, 4-27-1 Kita-ando, Aoi, Shizuoka, Japan.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Mori
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Shirai
authors.forename: Masashi
authors.initials: M
authors.lastname: Mikamo
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Shishido
authors.forename: Takefumi
authors.initials: T
authors.lastname: Akita
authors.forename: Satoru
authors.initials: S
authors.lastname: Morita
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Asada
authors.forename: Masato
authors.initials: M
authors.lastname: Fujii
authors.forename: Takafumi
authors.initials: T
authors.lastname: Suda
authors.forename: Kingo
authors.initials: K
authors.lastname: Chida
mesh_terms: D000328:Adult; D000368:Aged; D000403:Airway Resistance / Q000502:physiology*; D001249:Asthma / Q000503:physiopathology*; D016022:Case-Control Studies; D003116:Color; D003198:Computer Simulation; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D009991:Oscillometry; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012044:Regression Analysis; D012129:Respiratory Function Tests / Q000379:methods*