title: The relationship between resting lung-to-lung circulation time and peak exercise capacity in chronic heart failure patients.
abstract: BACKGROUND
  Peak exercise capacity (VO2peak) is a measure of the severity of chronic heart failure (CHF); however, few indices of resting cardiopulmonary function have been shown to predict VO2peak. A prolonged circulation time has been suggested as an index of increased severity of CHF. The aim of this study was to investigate the relationship between resting lung-to-lung circulation time (LLCT) and VO2peak in CHF.
  
  
  RESULTS
  Thirty CHF patients (59 +/- 13 years, New York Heart Association: 1.9 +/- 1.0) undertook the study. Each subject completed resting pulmonary and echocardiography measures and an incremental exercise test. LLCT was measured using the reappearance of end-tidal acetylene (P(ET),C2H2) after a single inhalation. Univariate and multivariate stepwise linear regression was used to determine the predictors of VO2peak. Univariate correlates of VO2peak (group mean 1.53 +/- 0.44 L/min(-1)) included LLCT (r = -0.75), inspiratory capacity (r = 0.41), ejection fraction (r = 0.33), peak early flow velocity (r = -0.39), and the ratio of early to late flow velocity (r = -0.31). LLCT was the only independent predictor where VO(2peak) = 3.923-0.045 (LLCT); r2 = 54%.
  
  
  CONCLUSIONS
  These results suggest that resting LLCT determined using the soluble inert gas technique represents a simple, noninvasive method that provides additional information regarding exercise capacity in CHF.
authors.affiliation: School of Physiotherapy and Exercise Science, Gold Coast Campus, Griffith University, Queensland, Australia.
authors.forename: Norman R
authors.initials: NR
authors.lastname: Morris
authors.forename: Eric M
authors.initials: EM
authors.lastname: Snyder
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Beck
authors.forename: Luke J
authors.initials: LJ
authors.lastname: Haseler
authors.forename: Lyle J
authors.initials: LJ
authors.lastname: Olson
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Johnson
mesh_terms: D000114:Acetylene / Q000493:pharmacokinetics; D000368:Aged; D002302:Cardiac Output / Q000502:physiology; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010101:Oxygen Consumption / Q000502:physiology*; D011652:Pulmonary Circulation / Q000502:physiology*; D012720:Severity of Illness Index
chemical_list: D000114:Acetylene