title: Oxygen Uptake Efficiency Slope and Breathing Reserve, Not Anaerobic Threshold, Discriminate Between Patients With Cardiovascular Disease Over Chronic Obstructive Pulmonary Disease.
abstract: OBJECTIVE
  The study sought to compare the relative discrimination of various cardiopulmonary exercise testing (CPX) variables between cardiac and respiratory disease.
  
  
  BACKGROUND
  CPX testing is used in many cardiorespiratory diseases. However, discrimination of cardiac and respiratory dysfunction can be problematic. Anaerobic threshold (AT) and oxygen-uptake to work-rate relationship (VO2/WR slope) have been proposed as diagnostic of cardiac dysfunction, but multiple variables have not been compared.
  
  
  METHODS
  A total of 73 patients with chronic obstructive pulmonary disease (COPD) (n = 25), heart failure with reduced ejection fraction (HFrEF) (n = 40), or combined COPD and HFrEF (n = 8) were recruited and underwent CPX testing on a bicycle ergometer. Following a familiarization test, each patient underwent a personalized second test aiming for maximal exercise after ∼10 min. Measurements from this test were used to calculate area under the receiver-operator characteristic curve (AUC).
  
  
  RESULTS
  Peak VO2 was similar between the 2 principal groups (COPD 17.1 ± 4.6 ml/min/kg; HFrEF 16.4 ± 3.6 ml/min/kg). Breathing reserve (AUC: 0.91) and percent predicted oxygen uptake efficiency slope (OUES) (AUC: 0.87) had the greatest ability to discriminate between COPD and HFrEF. VO2/WR slope performed significantly worse (AUC: 0.68). VO2 at the AT did not discriminate (AUC for AT as percent predicted peak VO2: 0.56). OUES and breathing reserve remained strong discriminators when compared with an external cohort of healthy matched controls, and were comparable to B-type natriuretic peptide.
  
  
  CONCLUSIONS
  Breathing reserve and OUES discriminate heart failure from COPD. Despite it being considered an important determinant of cardiac dysfunction, the AT could not discriminate these typical clinical populations while the VO2/WR slope showed poor to moderate discriminant ability. (Identifying an Ideal Cardiopulmonary Exercise Test Parameter [PVA]; NCT01162083).
authors.affiliation: International Centre for Circulatory Health, Imperial College London and Imperial College NHS Trust, London, England. Electronic address: anthonybarron@hotmail.co.uk.
authors.forename: Anthony
authors.initials: A
authors.lastname: Barron
authors.affiliation: International Centre for Circulatory Health, Imperial College London and Imperial College NHS Trust, London, England.
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
authors.affiliation: International Centre for Circulatory Health, Imperial College London and Imperial College NHS Trust, London, England; St Mary's Hospital, Imperial College Healthcare NHS Trust, London, England.
authors.forename: Jamil
authors.initials: J
authors.lastname: Mayet
authors.affiliation: Department of Internal Medicine B-Cardiology, Intensive Care, Pulmonary Medicine and Infectious Diseases, University of Greifswald, Greifswald, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Ewert
authors.affiliation: Department of Internal Medicine B-Cardiology, Intensive Care, Pulmonary Medicine and Infectious Diseases, University of Greifswald, Greifswald, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Obst
authors.affiliation: Harefield Hospital, Royal Brompton and Harefield NHS Foundation Trust, London, England.
authors.forename: Mark
authors.initials: M
authors.lastname: Mason
authors.affiliation: St Mary's Hospital, Imperial College Healthcare NHS Trust, London, England.
authors.forename: Sarah
authors.initials: S
authors.lastname: Elkin
authors.affiliation: Institute of Cardiovascular Sciences, University College London, London, England.
authors.forename: Alun D
authors.initials: AD
authors.lastname: Hughes
authors.affiliation: International Centre for Circulatory Health, Imperial College London and Imperial College NHS Trust, London, England; Watford General Hospital, West Herts NHS Trust, Hertfordshire, England.
authors.forename: Roland
authors.initials: R
authors.lastname: Wensel
mesh_terms: D000368:Aged; D015308:Anaerobic Threshold / Q000502:physiology*; D002318:Cardiovascular Diseases / Q000175:diagnosis / Q000378:metabolism* / Q000503:physiopathology; D003937:Diagnosis, Differential; D004452:Echocardiography; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000378:metabolism* / Q000503:physiopathology
chemical_list: D010100:Oxygen
keywords: cardiopulmonary exercise testing; chronic heart failure; exercise physiology; obstructive pulmonary disease