title: Gas exchange responses during 6-min walk test in patients with pulmonary arterial hypertension.
abstract: The 6-min walk test (6MWT) is the most widely utilized method of assessing exercise capacity in pulmonary arterial hypertension (PAH). Cardiopulmonary exercise testing has the advantage of providing additional physiological information over 6MWT. The goals of our study were to describe the addition of gas exchange measurements to 6MWT and to determine how these parameters were related to the severity of PAH in three major subgroups of PAH (idiopathic (IPAH), connective tissue disease-related (CTPAH) and congenital heart disease-related (CHPAH)).
  
  
  
  Seventy-six PAH patients (IPAH, n = 28; CTPAH, n = 24; CHPAH, n = 24) completed the 6MWT with simultaneous gas exchange measurements. The 6-min walk distance (6MWD), oxygen uptake ( V ˙ O2), carbon dioxide production ( V ˙ CO2), oxygen saturation, minute ventilation to carbon dioxide output ( V ˙E/ V ˙ CO2) and end-tidal partial pressure for carbon dioxide (PETCO2) were compared between subgroups, different functional classes (FCs) and pharmacotherapy.
  
  
  
  Whilst no significant difference in 6MWT was observed, absolute V ˙ O2and V ˙ CO2were higher for IPAH (P < 0.05). Differences were removed when V ˙ O2and V ˙ CO2were expressed relative to body mass (i.e. mL/kg/min). CHPAH had the most significant desaturation during 6MWT (CPAH: 73 ± 15%; CTPAH: 90 ± 8%, IPAH: 92 ± 8%, P < 0.01). There was no difference in V ˙E/ V ˙ CO2and PETCO2between groups; however, New York Health Association (NYHA) FC II performed better than FC III subjects in 6MWT with lower V ˙E/ V ˙ CO2and higher end-exercise PETCO2. Similarly, individuals on more advanced pharmacotherapy (triple therapy vs monotherapy) had poorer gas exchange during exercise.
  
  
  
  Whilst 6MWT and gas exchange did not differentiate between PAH groups, individuals with more severe disease and on more advanced pharmacotherapy had poorer gas exchange during exercise.
authors.affiliation: School of Allied Health Sciences, Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia.|Queensland Lung Transplant Service, The Prince Charles Hospital, Brisbane, Queensland, Australia.
authors.forename: Norman R
authors.initials: NR
authors.lastname: Morris
authors.affiliation: Queensland Lung Transplant Service, The Prince Charles Hospital, Brisbane, Queensland, Australia.
authors.forename: Helen
authors.initials: H
authors.lastname: Seale
authors.affiliation: Queensland Lung Transplant Service, The Prince Charles Hospital, Brisbane, Queensland, Australia.
authors.forename: Julie
authors.initials: J
authors.lastname: Harris
authors.affiliation: Queensland Lung Transplant Service, The Prince Charles Hospital, Brisbane, Queensland, Australia.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Hall
authors.affiliation: School of Allied Health Sciences, Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia.
authors.forename: Aaron C W
authors.initials: AC
authors.lastname: Lin
authors.affiliation: Queensland Lung Transplant Service, The Prince Charles Hospital, Brisbane, Queensland, Australia.
authors.forename: Fiona
authors.initials: F
authors.lastname: Kermeen
mesh_terms: D000328:Adult; D000368:Aged; D003240:Connective Tissue Diseases / Q000150:complications*; D017079:Exercise Tolerance; D065627:Familial Primary Pulmonary Hypertension / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D005260:Female; D006330:Heart Defects, Congenital / Q000150:complications*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011652:Pulmonary Circulation; D011659:Pulmonary Gas Exchange; D012129:Respiratory Function Tests / Q000379:methods; D012720:Severity of Illness Index; D013223:Statistics as Topic; D000070857:Walk Test / Q000379:methods*
keywords: 6-min walk test; disease severity; exercise and pulmonary rehabilitation; gas exchange; pulmonary circulation