title: Assessment of reproducibility of exhaled hydrogen peroxide concentration and the effect of breathing pattern in healthy subjects.
abstract: BACKGROUND
  Hydrogen peroxide (H2O2) is detectable in exhaled breath condensate (EBC) and has been proposed to be a surrogate marker of oxidative stress in the airways. In this study we tested whether the breathing pattern during EBC collection influences the concentration of exhaled H2O2.
  
  
  METHODS
  EBC was collected during (1) tidal breathing and (2) breathing with increased tidal volume for 10 min from 16 healthy volunteers. On-line H2O2 measurement was performed by the EcoCheck™ biosensor system. Repeated measurements were also conducted to assess intrasubject reproducibility.
  
  
  RESULTS
  Minute ventilation, tidal volume, expiratory flow rate were all increased significantly when subjects were asked to perform breathing with increased tidal volume. In parallel, EBC volume increased (1413±59 vs. 1959±71 μL, p<0.001), whereas exhaled H2O2 levels decreased significantly (1400±170 vs. 840±130 nmol/L, p<0.001). H2O2 levels did not correlate with any individual breathing parameters (p>0.05). Assessment of intersubject variability of H2O2 measurements during the two types of breathing revealed a coefficient of variation of 49 and 54%, respectively. The EBC H2O2 measurement was highly reproducible (888±176 vs. 874±156 nmol/L) as tested during normal breathing.
  
  
  CONCLUSIONS
  These data demonstrate that the concentration of H2O2 in EBC depends on the ventilatory pattern during sample collection that has to be taken into consideration in all EBC H2O2 assays.
authors.affiliation: Department of Thoracic Medicine, NHLI, Imperial College London, London, United Kingdom.
authors.forename: Reka
authors.initials: R
authors.lastname: Gajdocsi
authors.forename: Andras
authors.initials: A
authors.lastname: Bikov
authors.forename: Balazs
authors.initials: B
authors.lastname: Antus
authors.forename: Ildiko
authors.initials: I
authors.lastname: Horvath
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Barnes
authors.forename: Sergei A
authors.initials: SA
authors.lastname: Kharitonov
mesh_terms: D000328:Adult; D001944:Breath Tests; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008297:Male; D015203:Reproducibility of Results; D012119:Respiration
chemical_list: D006861:Hydrogen Peroxide