No abstract

We investigated the sensitivity and reproducibility of a test procedure for measuring hydrogen peroxide (H202) in exhaled breath condensate and the effect of storage of the condensate on the H2O2 concentration, and compared the results to previous studies. Twenty stable COPD patients breathed into our collecting device twice for a period of 10 min. The total exhaled air volume (EAV) and condensate volume were measured both times and the H2O2 concentration of the condensate was determined fluorimetrically. The concentration was measured again after freezing the reaction product at -70 degrees C for a period of 10, 20 and 40 days. We collected 2-5 ml condensate in 10 min. The EAV and condensate volumes were strongly correlated. There was no significant difference between the mean H2O2 concentration of the first and second test. We obtained a detect on limit for the H2O2 concentration of 0.02 micromoll(-1). The H2O2 concentration appeared to remain stable for a period up to 40 days of freezing. Compared to previous studies we developed a more efficient breath condensate collecting device and obtained a lower H2O2 detection limit. The measurement of exhaled H2O2 was reproducible. In addition, storage of the samples up to 40 days showed no changes in H2O2 concentration.

Background: Because inflammation induces oxidative stress, exhaled hydrogen peroxide (H₂O₂), 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 H₂O₂ in COPD patients. Objective: The aim of this study was to investigate the variability of the H₂O₂ 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 ∼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 H₂O₂ 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 H₂O₂ 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 H₂O₂ concentration increased significantly during the day in both stable COPD patients and controls. Over a period of 3 weeks, the mean H₂O₂ concentration did not change and the variability within the subjects was similar in both groups.

Background: The effects of inhaled corticosteroids (ICS) on markers of oxidative stress in patients with stable COPD are unclear. Objectives: The aim was to investigate the effect of ICS on exhaled H₂O₂ in stable COPD patients and to compare ICS with different lung deposition. Methods: Forty-one stable patients with moderate COPD (FEV₁ ∼60% predicted) were randomized to sequence 1; first HFA-134a beclomethasone dipropionate (HFA-BDP, an ICS with more peripheral deposition) 400 µg b.i.d., then fluticasone propionate (FP, an ICS with more central deposition) 375 µg b.i.d. (n = 20) or sequence 2 ; first FP, then HFA-BDP (n = 21). Both 4-week treatment periods were preceded by a 4-week washout period. After each period, the concentration of H₂O₂ in exhaled breath condensate was measured. Results: The H₂O₂ concentration decreased significantly after the first treatment period in both sequence 1 and 2 (p < 0.05, p = 0.01, respectively). In neither sequence was there a return to baseline values after the second washout, indicating a carry-over effect. The concentrations remained low in both sequences during the second treatment period. Conclusions: Both ICS appeared to reduce exhaled H₂O₂ in stable COPD patients. However, this study showed no difference between ICS with different deposition patterns, which in part may be due to the carry-over effect.

We evaluated the analytical performance of the Hitachi 704 automatic analyzer. The spectrophotometer showed a linearity of response at 340 nm up to 2.8 A. Photometric imprecision measured bichromatically at 340 and 376 nm was 0.49% at 0.16 A, 0.14% at 0.46 A, and 0.17% at 0.76 A. Imprecision of the sample probe was 0.4% for 5, 10, and 20 microL, and the volume delivered deviated -2.4%, -4.4%, and -4.2% from these preset volumes, respectively. Imprecision of the reagent probe over the range 50 to 500 microL ranged from 0.14% to 0.29%; volume delivered deviated from +1.7% to +4.4%). At equilibrium, the temperature in the cuvets was 29.8 (SD 0.05) degree C as measured by cresol red spectrophotometry. No sample carryover was detected. Reagent carryover was detected when a bilirubin assay was preceded by a total protein assay and when lactate dehydrogenase was measured after alanine aminotransferase. Imprecision for nine tests at three concentrations ranged from 1.1% to 4.4%. Comparison of methods with the SMAC II as reference method showed good results. Precision was better than reported for the Hitachi 705 automatic analyzer.