title: Impaired pulmonary diffusion during exercise in patients with chronic heart failure.
abstract: BACKGROUND
  Pulmonary diffusion is impaired at rest in patients with chronic heart failure (CHF) and has been implicated in the generation of symptoms and exercise intolerance. The aim of this study was to determine whether pulmonary diffusion is impaired during exercise in CHF, to examine its relationship to pulmonary blood flow, and to consider its functional significance in relation to metabolic gas exchange.
  
  
  RESULTS
  Carbon monoxide transfer factor (TLCO) and pulmonary blood flow (Q(C)) were measured by a rebreathe technique at rest and during steady-state cycling at 30 W in 24 CHF patients and 10 control subjects. Both patients and control subjects were able to raise TLCO and Q(C) during exercise. However, the patient group had a lower diffusion for a given blood flow (TLCO/Q(C)) both at rest (3.6+/-0.16 and 4.8+/-0.23 mL x L(-1) x mm Hg(-1); P<0.001) and during exercise (2.8+/-0.16 and 3.4+/-0.13 mL x L(-1) x mm Hg(-1) for CHF patients and control subjects, respectively; P<0.05). TLCO/Q(C) was related to the ventilatory equivalent for carbon dioxide (VEVCO(2)) production at 30 W (TLCO/Q(c) versus VEVCO(2), r = -0.58, P<0.01) and to peak exercise oxygen consumption measured during a progressive test (TLCO/Qc versus VO(2peak), r = 0.57, P<0.01) in these patients.
  
  
  CONCLUSIONS
  Patients with CHF are able to recruit reserves of TLCO and Q(C) during exercise. However, the TLCO/Q(C) ratio is consistently impaired in these patients and relates to both exercise hyperpnea and peak exercise oxygen consumption. Whether this impairment in alveolar gas exchange is reversible in CHF and therefore is a potential target for therapy has yet to be determined.
authors.affiliation: Clinical Research Initiative in Heart Failure, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, UK.
authors.forename: A A
authors.initials: AA
authors.lastname: Smith
authors.forename: P J
authors.initials: PJ
authors.lastname: Cowburn
authors.forename: M E
authors.initials: ME
authors.lastname: Parker
authors.forename: M
authors.initials: M
authors.lastname: Denvir
authors.forename: S
authors.initials: S
authors.lastname: Puri
authors.forename: K R
authors.initials: KR
authors.lastname: Patel
authors.forename: J G
authors.initials: JG
authors.lastname: Cleland
mesh_terms: D002303:Cardiac Output, Low / Q000503:physiopathology*; D002908:Chronic Disease; D015444:Exercise; D005080:Exercise Test; D006706:Homeostasis; D006801:Humans; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011652:Pulmonary Circulation; D011653:Pulmonary Diffusing Capacity; D012146:Rest