MEASUREMENTS OF ETHYLENE CONCENTRATION BY LASER PHOTOACOUSTIC TECHNIQUES WITH APPLICATIONS AT BREATH ANALYSIS

Abstract

It has been known that the breath contains clues to many diseases. Laser photoacoustic spectroscopy offers a promising new effective technique for the quantitative analysis of trace gases in human breath. This technique enables sensitive, selective detection, quantification and monitoring in real time of gases present in breath. As a typical application, we present precise measurement of trace gases that can be found in the exhaled breath, some of them giving the possibility of a non invasive diagnosis. Exhaled ethylene from many patients was used as a biomarker for lipid peroxidation in lung epithelium following the inhalation of cigarette smoke and X-ray therapy. The breath contains valuable information because only a slender barrier separates the air in the alveoli of the lung from the blood capillaries. Specific physiological processes inside human body may be indicated by trace gases originating from the lungs. A physiological process in the body is generally based on many biochemical reactions chained each other and very well regulated by hormones and enzymes. Along a biochemical chained reaction many molecular end products and intermediate products, in excess or discarded, may accumulate in the blood and released trough the pulmonary function in the breath. It is possible to study the time evolution of specific substances found in the breath (markers) to get information about the corresponding physiological processes. The analysis of exhaled breath to detect or asses a given substance with the aim to perform a diagnosis or study a body function is called breath test. The photoacoustic technique applied to trace gas analysis exploits the infrared absorption characteristics of gases for detection and measurement. This