title: Usefulness of decrease in oxygen uptake efficiency to identify gas exchange abnormality in patients with idiopathic pulmonary arterial hypertension.
abstract: BACKGROUND
  Decline in oxygen uptake efficiency (OUE), especially during exercise, is found in patients with chronic heart failure. In this study we aimed to test the validity and usefulness of OUE in evaluating gas exchange abnormality of patients with idiopathic pulmonary arterial hypertension (IPAH).
  
  
  METHODS
  We retrospectively investigated the cardiopulmonary exercise test (CPET) with gas exchange measurements in 32 patients with confirmed IPAH. All patients also had resting hemodynamic measurements and pulmonary function test (PFT). Sixteen healthy subjects, matched by age, sex, and body size were used as controls, also had CPET and PFT measurements.
  
  
  RESULTS
  In IPAH patients, the magnitude of absolute and percentage of predicted (%pred) oxygen uptake efficiency slope (OUES) and oxygen uptake efficiency plateau (OUEP), as well as several other CPET parameters, were strikingly worse than healthy subjects (P<0.0001). Pattern of changes in OUE in patients is similar to that in controls, In IPAH patients, OUE values at rest, warming up, anaerobic threshold and peak exercise were all significantly lower than in normal (P<0.0001). OUEP%pred, better than OUES%pred, correlated significantly with New York Heart Association (NYHA) functional Class (r = -0.724, P<0.005), Total Pulmonary Vascular Resistance (TPVR) (r = -0.694, P<0.005), diffusing capacity for carbon monoxide (DLCO) (r = 0.577, P<0.05), and the lowest ventilation versus CO2 output ratio during exercise (LowestV˙E/V˙CO2) (r = -0.902, P<0.0001). In addition, the coefficient of variation (COV) of OUEP was lower (20.9%) markedly than OUES (34.3%) (P<0.0001).
  
  
  CONCLUSIONS
  In patients with IPAH, OUES and OUEP are both significantly lower than the healthy subjects. OUEP is a better physiological parameter than OUES in evaluating the gas exchange abnormality of patients with IPAH.
authors.affiliation: Department of Pulmonary Function Test, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China; State Key Laboratory of Cardiovascular Disease, Heart-Lung Function Testing Center, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
authors.forename: Xiaoyue
authors.initials: X
authors.lastname: Tan
authors.affiliation: Department of Pulmonary Function Test, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.
authors.forename: Wenlan
authors.initials: W
authors.lastname: Yang
authors.affiliation: Department of Pulmonary Function Test, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Guo
authors.affiliation: Department of Pulmonary Function Test, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China; Respiratory Division, Hangzhou, Zhejiang Provincial Hospital of traditional Chinese Medicine, The First Affiliated Hospital of Zhejiang Chinese Medicine University, Hangzhou, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Pulmonary Function Test, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.
authors.forename: Changwei
authors.initials: C
authors.lastname: Wu
authors.affiliation: Department of Pulmonary Circulation, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.
authors.forename: Rikesh
authors.initials: R
authors.lastname: Sapkota
authors.affiliation: Department of Pulmonary Circulation, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.
authors.forename: Shailendra Prasad
authors.initials: SP
authors.lastname: Kushwaha
authors.affiliation: Department of Pulmonary Circulation, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.
authors.forename: Sugang
authors.initials: S
authors.lastname: Gong
authors.affiliation: State Key Laboratory of Cardiovascular Disease, Heart-Lung Function Testing Center, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
authors.forename: Xingguo
authors.initials: X
authors.lastname: Sun
authors.affiliation: Department of Pulmonary Function Test, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China; Department of Pulmonary Circulation, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.
authors.forename: Jinming
authors.initials: J
authors.lastname: Liu
mesh_terms: D000328:Adult; D002302:Cardiac Output; D016022:Case-Control Studies; D015444:Exercise / Q000502:physiology; D065627:Familial Primary Pulmonary Hypertension / Q000378:metabolism* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation; D012146:Rest / Q000502:physiology; D012189:Retrospective Studies