title: Increased Dead Space Ventilation Mediates Reduced Exercise Capacity in Systolic Heart Failure.
abstract: Patients with chronic heart failure have limited exercise capacity, which cannot be completely explained by markers of cardiac dysfunction. Reduced pulmonary diffusing capacity at rest and excessively high ventilation during exercise are common in heart failure. We hypothesized that the reduced pulmonary diffusing capacity in patients with heart failure would predict greater dead space ventilation during exercise and that this would lead to impairment in exercise capacity.
  
  
  
  To determine the relationship between pulmonary diffusing capacity at rest and dead space ventilation during exercise, and to examine the influence of dead space ventilation on exercise in heart failure.
  
  
  
  We analyzed detailed cardiac and pulmonary data at rest and during maximal incremental cardiopulmonary exercise testing from 87 consecutive heart transplant assessment patients and 18 healthy control subjects. Dead space ventilation was calculated using the Bohr equation.
  
  
  
  Pulmonary diffusing capacity at rest was a significant predictor of dead space ventilation at maximal exercise (r = -0.524, P < 0.001) in heart failure but not in control subjects. Dead space at maximal exercise also correlated inversely with peak oxygen consumption (r = -0.598, P < 0.001), peak oxygen consumption per kilogram (r = -0.474, P < 0.001), and 6-minute-walk distance (r = -0.317, P = 0.021) in the heart failure group but not in control subjects.
  
  
  
  Low resting pulmonary diffusing capacity in heart failure is indicative of high dead space ventilation during exercise, leading to excessive and inefficient ventilation. These findings would support the concept of pulmonary vasculopathy leading to altered ventilation perfusion matching (increased dead space) and resultant dyspnea, independent of markers of cardiac function.
authors.affiliation: 1 Department of Allergy, Immunology and Respiratory Medicine, The Alfred, Prahran, Victoria, Australia; and.|2 Department of Medicine, Monash University, Melbourne, Victoria, Australia.
authors.forename: Kirk
authors.identifier: 0000-0002-7180-6357
authors.initials: K
authors.lastname: Kee
authors.affiliation: 2 Department of Medicine, Monash University, Melbourne, Victoria, Australia.
authors.forename: Christopher
authors.initials: C
authors.lastname: Stuart-Andrews
authors.affiliation: 2 Department of Medicine, Monash University, Melbourne, Victoria, Australia.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Ellis
authors.affiliation: 1 Department of Allergy, Immunology and Respiratory Medicine, The Alfred, Prahran, Victoria, Australia; and.|2 Department of Medicine, Monash University, Melbourne, Victoria, Australia.
authors.forename: Jeremy P
authors.initials: JP
authors.lastname: Wrobel
authors.affiliation: 2 Department of Medicine, Monash University, Melbourne, Victoria, Australia.
authors.forename: Kris
authors.initials: K
authors.lastname: Nilsen
authors.affiliation: 2 Department of Medicine, Monash University, Melbourne, Victoria, Australia.
authors.forename: Meenal
authors.initials: M
authors.lastname: Sharma
authors.affiliation: 1 Department of Allergy, Immunology and Respiratory Medicine, The Alfred, Prahran, Victoria, Australia; and.|2 Department of Medicine, Monash University, Melbourne, Victoria, Australia.
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Thompson
authors.affiliation: 1 Department of Allergy, Immunology and Respiratory Medicine, The Alfred, Prahran, Victoria, Australia; and.|2 Department of Medicine, Monash University, Melbourne, Victoria, Australia.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Naughton
mesh_terms: D000328:Adult; D005080:Exercise Test / Q000706:statistics & numerical data*; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D054143:Heart Failure, Systolic / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D012126:Respiratory Dead Space / Q000502:physiology*
keywords: exercise; heart failure; lung; perfusion; ventilation