title: Hydrogen peroxide in exhaled air: a source of error, a paradox and its resolution.
abstract: The concentration of hydrogen peroxide (H2O2) in exhaled air has been reported to be elevated in asthma and chronic obstructive pulmonary disease (COPD), but results are inconsistent and difficult to reproduce. As H2O2occurs in ambient air, we examined its association with exhaled H2O2in human subjects. Exhaled breath condensate (EBC) of 12 COPD patients and nine healthy control subjects was collected either with an inhalation filter (efficiency 81%) or without. Ambient air condensate (AAC) was collected in parallel and samples were analysed for H2O2. Additionally, ambient H2O2was recorded by an atmospheric measuring device (online fluorometric measurement). H2O2concentration in AAC was significantly higher (p<0.001) than in EBC. AAC variations were concordant with the data from the atmospheric measuring instrument. In both subjects' groups, the inhalation filter reduced H2O2values (p<0.01). Despite generally low levels in exhaled air, analysis by a mathematical model revealed a contribution from endogenous H2O2production. The low H2O2levels in exhaled air are explained by the reconditioning of H2O2-containing inhaled air in the airways. Inhaled H2O2may be one factor in the heterogeneity and limited reproducibility of study results. A valid determination of endogenous H2O2production requires inhalation filters.
authors.affiliation: Institute and Outpatient Clinic for Occupational, Social and Environmental Medicine, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Peters
authors.affiliation: Institute and Outpatient Clinic for Occupational, Social and Environmental Medicine, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Angelika
authors.initials: A
authors.lastname: Kronseder
authors.affiliation: Institute and Outpatient Clinic for Occupational, Social and Environmental Medicine, Ludwig-Maximilians-University, Munich, Germany; Institute of Epidemiology I, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Karrasch
authors.affiliation: Robert Bosch GmbH, Stuttgart, Germany.
authors.forename: Petra A
authors.initials: PA
authors.lastname: Neff
authors.affiliation: Aero-Laser GmbH, Garmisch-Partenkirchen, Germany.
authors.forename: Matz
authors.initials: M
authors.lastname: Haaks
authors.affiliation: Department of Internal Medicine, Division for Pulmonary Diseases, Philipps-University, Marburg, Germany.
authors.forename: Andreas R
authors.initials: AR
authors.lastname: Koczulla
authors.affiliation: Institute of Molecular Pathogenesis at the Friedrich-Loeffler-Institute, Jena, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Reinhold
authors.affiliation: Institute and Outpatient Clinic for Occupational, Social and Environmental Medicine, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Dennis
authors.initials: D
authors.lastname: Nowak
authors.affiliation: Institute and Outpatient Clinic for Occupational, Social and Environmental Medicine, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Rudolf A
authors.initials: RA
authors.lastname: Jörres