title: Technical considerations related to the minute ventilation/carbon dioxide output slope in patients with heart failure.
abstract: BACKGROUND
  The minute ventilation (VE)-carbon dioxide output (VCO(2)) relationship has recently been demonstrated to have prognostic significance in the heart failure (HF) population. However, the method by which the VE/VCO(2) slope is expressed has been inconsistent.
  
  
  METHODS
  One hundred eighty-eight subjects, who had received diagnoses of HF, underwent exercise testing. Two VE/VCO(2) slope calculations were made, one using exercise data prior to the ventilatory threshold (VT), and one using all data points from rest to peak exercise. Four separate peak exercise VE/VCO(2) slope calculations also were derived with unaveraged, 10-s, 30-s, and 60-s ventilatory expired gas sampling intervals.
  
  
  RESULTS
  Although univariate Cox regression analysis demonstrated pre-VT and peak VE/VCO(2) slope calculations to both be significant predictors of cardiac-related mortality and hospitalization (p < 0.001), the peak classification scheme was significantly better (p < 0.01). The ventilatory expired gas-sampling interval that was used did not impact the predictive ability of the peak VE/VCO(2) slope.
  
  
  CONCLUSIONS
  Although both the pre-VT and peak VE/VCO(2) slope calculations were prognostically significant, the peak expression was superior. The sampling interval did not appear to have a significant impact on prognostic utility. We hope that the results of the present study will contribute to the standardization of the VE/VCO(2) slope and will enhance its clinical application.
authors.affiliation: Department of Physical Therapy, Virginia Commonwealth University, Medical College of Virginia, Health Sciences Campus, Richmond, 23298-0224, USA. raarena@mail2.vcu.edu
authors.forename: Ross
authors.initials: R
authors.lastname: Arena
authors.forename: Jonathan
authors.initials: J
authors.lastname: Myers
authors.forename: Syed Salman
authors.initials: SS
authors.lastname: Aslam
authors.forename: Elsa B
authors.initials: EB
authors.lastname: Varughese
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Peberdy
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002245:Carbon Dioxide / Q000378:metabolism*; D002303:Cardiac Output, Low / Q000145:classification / Q000378:metabolism / Q000401:mortality; D005080:Exercise Test; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D011379:Prognosis; D012372:ROC Curve
chemical_list: D002245:Carbon Dioxide