title: Is the elevated slope relating ventilation to carbon dioxide production in chronic heart failure a consequence of slow metabolic gas kinetics?
abstract: OBJECTIVE
  Patients with heart failure have slow metabolic gas exchange kinetics, which may contribute to the elevated slope of the relationship between ventilation and carbon dioxide production (Ve/Vco(2) slope).
  
  
  METHODS
  A tertiary referral centre for cardiology.
  
  
  METHODS
  Eleven patients with stable chronic heart failure and 11 age-matched controls.
  
  
  METHODS
  Each subject underwent maximal bicycle-based peak exercise testing with metabolic gas exchange analysis and three further repeated tests at 15%, 25% and 50% of the load achieved at peak exercise. The ventilation and carbon dioxide production from each of these steady-state tests was used to re-calculate the Ve/Vco(2) slope and compared with the Ve/Vco(2) slope derived from the maximal test.
  
  
  RESULTS
  Peak oxygen consumption [mean (S.D.)] was lower in heart failure patients [18.2 (4.0) vs. 31.2 (6.3) ml/kg per min; P<0.001] than in controls. The Ve/Vco(2) slope was steeper in patients than controls [32.7 (8.3) vs. 27.1 (1.6); P<0.05]. There was no difference between the Ve/Vco(2) slope reconstructed from the three steady state tests and resting data and that gained from the maximal test [35.3 (7.8) vs. 25.9 (3.2); P=0.43].
  
  
  CONCLUSIONS
  The elevated slope of the relationship between ventilation and carbon dioxide production is not a consequence of the short stages of a standard incremental exercise test combined with delayed metabolic gas kinetics in heart failure patients.
authors.affiliation: Academic Cardiology, Castle Hill Hospital, Castle Road, Cottingham, Hull HU16 5JQ, UK. klauswitte@hotmail.com
authors.forename: Klaus K A
authors.initials: KK
authors.lastname: Witte
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Clark
mesh_terms: D000368:Aged; D002245:Carbon Dioxide / Q000097:blood*; D002908:Chronic Disease; D004417:Dyspnea / Q000503:physiopathology; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D011379:Prognosis; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D014692:Ventilation-Perfusion Ratio / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen