title: The ability of volumetric capnography to distinguish between chronic obstructive pulmonary disease patients and normal subjects.
abstract: OBJECTIVE
  The aim of our study was to evaluate volumetric capnography (VCap) in the differentiation between chronic obstructive pulmonary disease (COPD) patients and normal subjects.
  
  
  METHODS
  Thirty-nine healthy male volunteers and 60 male COPD patients were enrolled. Regression equations between VCap indices and age, weight, height, and tidal volume in healthy volunteers were established by stepwise regression analysis. Predicted normal values of VCap indices in COPD patients were calculated. A paired t test was used to compare the difference between observed and predicted values for VCap indices in COPD patients. Receiver operating characteristic (ROC) curve analysis was used to evaluate the power of each VCap index alone in differentiating COPD patients and normal subjects. The power of the combination of VCap indices was assessed by discriminant analysis.
  
  
  RESULTS
  All regression equations were significant (P < 0.01) as were the differences between the observed and predicted normal VCap indices in COPD patients (P < 0.001). ROC curve analysis showed that the volume between 25 and 50% of F CO2et (Vm25-50), slope of Phase II (dC2/dV), and slope of Phase III (dC3/dV) were valuable predictors. Nearly all (90.9%) subjects were correctly classified by discriminant analysis.
  
  
  CONCLUSIONS
  Vm25-50, dC2/dV, or dC3/dV alone are valuable for differentiating COPD patients and normal subjects, but more powerful are the combinations of Vm25-50, dC2/dV, and dC3/dV, the ratio of dC2/dV to dC3/dV (SR23), dead space according to the Bohr method (VDB), and dead space according to the Wolff and Brunner methods (PIE).
authors.affiliation: Department of Respiratory Medicine, Shanghai Pudong New Area People's Hospital, Shanghai, China.
authors.forename: Guang-Sheng
authors.initials: GS
authors.lastname: Qi
authors.forename: Wen-Chao
authors.initials: WC
authors.lastname: Gu
authors.forename: Wen-Lan
authors.initials: WL
authors.lastname: Yang
authors.forename: Feng
authors.initials: F
authors.lastname: Xi
authors.forename: Hao
authors.initials: H
authors.lastname: Wu
authors.forename: Jin-Ming
authors.initials: JM
authors.lastname: Liu
mesh_terms: D000328:Adult; D019540:Area Under Curve; D019296:Capnography / Q000379:methods*; D016022:Case-Control Studies; D016002:Discriminant Analysis; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology; D012372:ROC Curve