[en] The development of new techniques for breath analysis searching for objective biomarkers of oxidative stress showed promise in non-invasive disclosing health information of the well-being of a person. Although numerous biomarkers have been identified so far using breath analysis, very little is known about their origin if they are metabolic or providing from mouth contamination. For the introduction of breath tests into clinical practice, standardization of sample collection needs to be taken into account. Breath analysis has been performed using laser photoacoustic spectroscopy to evaluate exhaled breath by mouth and nose before and after brushing with toothpaste/baking soda in order to identify the important endogenous biomarkers without contaminant sources. As a known biomarker of oxidative stress in the human body, it is important to accurately assess ethylene from exhaled air. Differences in the concentrations of exhaled ethylene are observed after using toothpaste and baking soda. The levels of ethylene are lower for nose breathing compared with mouth breathing. However, the differences are not significant proving that ethylene is generally endogenous but may still exist some contamination, depending of the oral hygiene of each person. These results may lead to a procedure, whereby subjects should be instructed to use toothpaste before each breath test sampling, to avoid the possibility of contamination of endogenous biomarkers.

[en] In recent years there has been a large increase in the areas related to developments in the prevention of diseases, especially in explaining the role of oxidative stress. Lipid peroxidation and oxidative stress contributes to morbidity in hemodialysis (HD) patients. It is therefore relevant to analyze the impact of oxidative stress and its related species (ethylene) immediately after dialysis treatment in order to prevent trauma in the renal failure of elderly patients. In this paper we describe recent progress in laser photoacoustic spectroscopy detection of ethylene in renal failure patients. We have found that HD treatment increases ethylene concentration in the exhaled breath of elderly patients and may intensify oxidative stress. (paper)