Elevated exhalation of hydrogen peroxide and thiobarbituric acid reactive substances in patients with community acquired pneumonia

Abstract

Background: Bacterial pneumonia involves influx of activated phagocytes into distal airways. These cells release oxidants including H 2O 2, that may be exhaled or induce peroxidative damage to lung tissues with formation of thiobarbituric reactive substances (TBARs). Study objectives: To determine whether concentrations of H 2O 2 and TBARs in exhaled breath condensate (EBC) is elevated and correlate with systemic response to pneumonia during 10 days of hospital treatment. Design: The concentration of H 2O 2 and TBARs was measured in EBC of 43 inpatients with community acquired pneumonia (CAP) and 20 healthy never smoked subjects over 10 days and were accompanied by monitoring of WBC count, serum concentration of C-reactive protein (CRP) and peroxyl radical-trapping capacity. Results: Patients with CAP exhaled 4.6-, 3.7-, 3.9-, 3.3-times more H 2O 2 than healthy controls at 1st, 3rd, 5th and 10th day of treatment ( P<0.05), respectively. EBC concentrations of TBARs were elevated at 1st and 3rd day. H 2O 2 and TBARs levels decreased along with treatment course. Correlation ( P<0.05) was found between H 2O 2 levels and CRP and WBC count ( r=0.31) at 1st day and between TBARs and CRP at 5th ( r=0.34) and 10th day ( r=0.46). The mean H 2O 2 exhalation estimated over ten days of treatment correlated with pneumonic chest X-ray score ( r=0.42), CRP levels ( r=0.46) and WBC count ( r=0.33) at admission ( P<0.05). Conclusions: Pneumonia is accompanied by oxidative stress in airways that moderately correlates with intensity of systemic inflammatory response. Determination of H 2O 2 in EBC may be helpful for non-invasive monitoring of oxidants production during lower respiratory tract infection.