title: Are oxygen uptake kinetics in chronic heart failure limited by oxygen delivery or oxygen utilization?
abstract: BACKGROUND
  The delay in O(2) uptake kinetics during and after submaximal physical activity (O(2) onset and recovery kinetics, respectively) correlates well with the functional capacity of patients with chronic heart failure (CHF). This study examined the physiological background of this delay in moderately impaired CHF patients by comparing kinetics of cardiac output (Q) and O(2) uptake (V(O(2))).
  
  
  METHODS
  Fourteen stable CHF patients (New York Heart Association class II-III) and 8 healthy subjects, matched for age and body mass index, were included. All subjects performed a submaximal constant-load exercise test to assess O(2) uptake kinetics. Furthermore, in 10 CHF patients Q was measured by a radial artery pulse contour analysis method, which enabled the simultaneous modelling of exercise-related kinetics of Q and V(O(2)).
  
  
  RESULTS
  Both O(2) onset and recovery kinetics were delayed in the patient group. There were no significant differences between the time constants of Q and V(O(2)) during exercise-onset (62+/-25 s versus 59+/-28 s, p=0.51) or recovery (61+/-25 s versus 57+/-20 s, p=0.38) in the patient group, indicating that O(2) delivery was not in excess of the metabolic demands in these patients.
  
  
  CONCLUSIONS
  The delay in O(2) onset and recovery kinetics in moderately impaired CHF patients is suggested to be due to limitations in O(2) delivery. Therefore, strategies aimed at improving exercise performance of these patients should focus more on improvements of O(2) delivery than on O(2) utilization.
authors.affiliation: Department of Cardiology, Máxima Medical Centre, Veldhoven, The Netherlands. H.Kemps@wxs.nl
authors.forename: Hareld M
authors.initials: HM
authors.lastname: Kemps
authors.forename: Goof
authors.initials: G
authors.lastname: Schep
authors.forename: Maria L
authors.initials: ML
authors.lastname: Zonderland
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Thijssen
authors.forename: Wouter R
authors.initials: WR
authors.lastname: De Vries
authors.forename: Bart
authors.initials: B
authors.lastname: Wessels
authors.forename: Pieter A
authors.initials: PA
authors.lastname: Doevendans
authors.forename: Pieter F
authors.initials: PF
authors.lastname: Wijn
mesh_terms: D000368:Aged; D002302:Cardiac Output / Q000502:physiology; D002908:Chronic Disease; D005080:Exercise Test / Q000379:methods; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000493:pharmacokinetics*; D010101:Oxygen Consumption / Q000502:physiology*
chemical_list: D010100:Oxygen