HYDROGEN PEROXIDE RELEASE AND ACID-BASE STATUS IN EXHALED BREATH CONDENSATE AT REST AND AFTER MAXIMAL EXERCISE IN YOUNG, HEALTHY SUBJECTS

Objective: Exhaled breath condensate (EBC) contains among a large number of mediators hydrogen peroxide (H2O2) as a marker of airway inflammation and oxidative stress. Similarly EBC pH also changes in respiratory diseases. It was the aim of our investigation to prove if hydrogen peroxide release and changes in pH of EBC changes with exercise. Methods: EBC was collected from 100 litres exhaled air along with samples of arterialized blood of 16 healthy subjects (9 males, 7 females, age 23 +/- 1 years). EBC hydrogen peroxide was analyzed with EcoCheck amperometer (FILT, Berlin). The rate of H2O2 release was calculated from the concentration and collection time. pH and PCO2 in blood and in EBC were measured with the Radiometer blood gas analyzer, EBC was equilibrated with a gas mixture (5% CO2 in O-2). The bicarbonate concentration was calculated according to the law of mass action for CO2 and HCO3-(pK = 6.1). Results: H2O2 concentration in EBC was 190 +/- 109 nmol/l, and H2O2 release at rest was 31.0 +/- 18.3 pmol/min. At maximal exercise, the H2O2 concentration in EBC increased to 250 +/- 120 nmol/l, and H2O2 release significantly increased at maximal exercise to 84.4 +/- 39.9 pmol/min (P<0.01). At rest pH of the CO2 equilibrated EBC was at 6.08 +/- 0.23 and the [HCO3-] was 1.03 +/- 0.40 mmol/l. At maximum exercise, pH 6.18 +/- 0.17 and [HCO3-] 1.23 +/- 0.30 mmol/l remained almost unaltered. Conclusions: The rate of H2O2 release in EBC increased during exhausting exercise (external load: 300 Watt) by a factor of 2, whereas the pH and the bicarbonate concentration of the EBC, equilibrated with 5% CO2 at 37 degrees C were not significantly altered. It has to be proven by further experiments whether there is a linear relationship between the rates of H2O2 release in EBC in graded submaximal exercise.