title: Oxygen uptake is more efficient in idiopathic pulmonary arterial hypertension than in chronic thromboembolic pulmonary hypertension.
abstract: OBJECTIVE
  The responses of oxygen uptake efficiency (OUE) during cardiopulmonary exercise training (CPET) have not been reported in patients with pulmonary hypertension. We aimed to investigate the differences in OUE between patients with idiopathic pulmonary arterial hypertension (IPAH) and chronic thromboembolic pulmonary hypertension (CTEPH).
  
  
  METHODS
  Forty-four patients with IPAH and 29 patients with CTEPH were retrospectively enrolled into our study. All patients underwent right-heart catheterization, pulmonary function test and performed the 6-min walk test and CPET.
  
  
  RESULTS
  We found that oxygen uptake efficiency plateau (OUEP) and oxygen uptake efficiency at anaerobic threshold (OUE@AT) was significantly higher in IPAH than that in CTEPH (both P = 0.002). However, patients with CTEPH had lower mean pulmonary artery pressure, pulmonary vascular resistance and transpulmonary gradient (all P < 0.05). The correlation between OUEP and heart rate at anaerobic threshold (HR_AT) was significant (r = 0.376, P < 0.05); however, no statistically significant correlation was found with ventilation at anaerobic threshold (VE_AT) (r = -0.074, P > 0.05) in patients with IPAH. In patients with CTEPH, both anaerobic threshold (r = 0.307, P > 0.05) and VE_AT (r = -0.709, P < 0.0001) were reduced. OUEP were higher in WHO functional class I/II patients than in WHO functional class III/IV patients (all P < 0.05).
  
  
  CONCLUSIONS
  OUEP and OUE@AT are higher in IPAH than that in CTEPH not in proportion to haemodynamics, probably due to differences in cardiac function and pulmonary vascular occlusion. OUEP correlates well with the exercise capacity and the severity of the disease.
authors.affiliation: Department of Pulmonary Circulation, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Shi
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 Circulation, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.
authors.forename: Sugang
authors.initials: S
authors.lastname: Gong
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 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 Circulation, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Pulmonary Circulation, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.
authors.forename: Wenjing
authors.initials: W
authors.lastname: Xiang
authors.affiliation: Department of Pulmonary Circulation, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.
authors.forename: Lan
authors.initials: L
authors.lastname: Wang
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 Circulation, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.|Department of Pulmonary Function Test, Shanghai Pulmonary Hospital Affiliated to Tongji University, Shanghai, China.
authors.forename: Jinming
authors.initials: J
authors.lastname: Liu
mesh_terms: D000328:Adult; D000368:Aged; D015308:Anaerobic Threshold; D015444:Exercise / Q000502:physiology; D005080:Exercise Test / Q000379:methods; D017079:Exercise Tolerance; D065627:Familial Primary Pulmonary Hypertension / Q000175:diagnosis / Q000378:metabolism / Q000503:physiopathology; D005260:Female; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D006976:Hypertension, Pulmonary / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D008168:Lung / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010100:Oxygen; D010101:Oxygen Consumption; D011655:Pulmonary Embolism / Q000150:complications / Q000503:physiopathology; D012129:Respiratory Function Tests / Q000379:methods; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013223:Statistics as Topic; D014655:Vascular Resistance
chemical_list: D010100:Oxygen
keywords: cardiopulmonary exercise testing; oxygen uptake efficiency; pulmonary arterial hypertension; right heart catheterization; submaximal exercise