title: Variability of exhaled hydrogen peroxide in stable COPD patients and matched healthy controls.
abstract: BACKGROUND
  Because inflammation induces oxidative stress, exhaled hydrogen peroxide (H(2)O(2)), which is a marker of oxidative stress, may be used as a non-invasive marker of airway inflammation in chronic obstructive pulmonary disease (COPD). There are no data on the circadian variability of exhaled H(2)O(2) in COPD patients.
  
  
  OBJECTIVE
  The aim of this study was to investigate the variability of the H(2)O(2) concentration in breath condensate of stable COPD patients and of matched healthy control subjects.
  
  
  METHODS
  We included 20 patients with stable mild COPD (forced expiratory volume in 1 s approximately 70% of predicted) and 20 healthy subjects, matched for age, sex and pack-years, all smokers or ex-smokers. Breath condensate was collected and its H(2)O(2) concentration determined fluorometrically three times on day 0 (9 and 12 a.m., and 3 p.m.) and once on days 1, 2, 3, 8 and 21.
  
  
  RESULTS
  The mean H(2)O(2) concentration increased significantly during the day in both the patient and control groups (p = 0.02 and p < 0.01, respectively). Over a longer period up to 21 days, the mean concentration did not change in both groups. There was no significant difference between patients and controls. The mean coefficient of variation over 21 days was 45% in the patient group and 43% in the control group (p = 0.8).
  
  
  CONCLUSIONS
  The exhaled H(2)O(2) concentration increased significantly during the day in both stable COPD patients and controls. Over a period of 3 weeks, the mean H(2)O(2) concentration did not change and the variability within the subjects was similar in both groups.
authors.affiliation: Department of Pulmonology, Catharina Hospital Eindhoven, The Netherlands. w.beurden@researchlab-long.demon.nl
authors.forename: W J C
authors.initials: WJ
authors.lastname: van Beurden
authors.forename: P N R
authors.initials: PN
authors.lastname: Dekhuijzen
authors.forename: G A
authors.initials: GA
authors.lastname: Harff
authors.forename: F W J M
authors.initials: FW
authors.lastname: Smeenk
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001944:Breath Tests; D002940:Circadian Rhythm / Q000502:physiology*; D003367:Cotinine / Q000032:analysis; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress / Q000502:physiology; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000378:metabolism / Q000503:physiopathology*
chemical_list: D006861:Hydrogen Peroxide; D003367:Cotinine