title: Impaired carbon monoxide diffusing capacity is the strongest predictor of exercise intolerance in COPD.
abstract: BACKGROUND
  Exercise intolerance is a hallmark of chronic obstructive pulmonary disease (COPD) and forced expiratory volume in one second (FEV1) is the traditional metric used to define the severity of COPD. However, there is dissociation between FEV1 and exercise capacity in a large proportion of subjects with COPD. The aim of this study was to investigate whether other lung function parameters have an additive, predictive value for exercise capacity and whether this differs according to the COPD stage.
  
  
  METHODS
  Spirometry, body plethysmography and diffusing capacity for carbon monoxide (DLCO) were performed on 88 patients with COPD GOLD stages II-IV. Exercise capacity (EC) was determined in all subjects by symptom-limited, incremental cycle ergometer testing.
  
  
  RESULTS
  Significant relationships were found between EC and the majority of lung function parameters. DLCO, FEV1 and inspiratory capacity (IC) were found to be the best predictors of EC in a stepwise regression analysis explaining 72% of EC. These lung function parameters explained 76% of EC in GOLD II, 72% in GOLD III and 40% in GOLD IV. DLCO alone was the best predictor of exercise capacity in all GOLD stages.
  
  
  CONCLUSIONS
  Diffusing capacity was the strongest predictor of exercise capacity in all subjects. In addition to FEV1, DLCO and IC provided a significantly higher predictive value regarding exercise capacity in COPD patients. This suggests that it is beneficial to add measurements of diffusing capacity and inspiratory capacity when clinically monitoring COPD patients.
authors.affiliation: Department of Medical Sciences: Clinical Physiology, Uppsala University, Uppsala, Sweden. amir.farkhooy@medsci.uu.se
authors.forename: Amir
authors.initials: A
authors.lastname: Farkhooy
authors.forename: Christer
authors.initials: C
authors.lastname: Janson
authors.forename: Rangheidur Harpa
authors.initials: RH
authors.lastname: Arnardóttir
authors.forename: Andrei
authors.initials: A
authors.lastname: Malinovschi
authors.forename: Margareta
authors.initials: M
authors.lastname: Emtner
authors.forename: Hans
authors.initials: H
authors.lastname: Hedenström
mesh_terms: D000368:Aged; D002248:Carbon Monoxide; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007320:Inspiratory Capacity; D008297:Male; D008875:Middle Aged; D010993:Plethysmography, Whole Body; D011237:Predictive Value of Tests; D011653:Pulmonary Diffusing Capacity; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012720:Severity of Illness Index; D013147:Spirometry
chemical_list: D002248:Carbon Monoxide