[Importance and perspectives of breath analysis].

Quantitative chemical analysis of volatile constituents in exhaled gas can provide useful insights into biochemical processes in the body. Relations between the chemical composition of human exhaled air and inflammatory processes, states of high oxidative activity, inhalation or ingestion of various noxious substances as well as diseases like ARDS, pneumonia or sleep apnea have been described. Clinical interpretation of these findings, however, remains difficult because definite marker substances for certain diseases could not yet be identified, substance concentrations in the exhaled air change under various conditions, and results vary in a wide range. Because of very low substance concentrations in the exhaled air sophisticated analytical techniques are necessary. Analyses are hampered by high water content and numerous contaminants in the samples. A clear distinction has to be made between substances originating from within the patient and those coming from outside of the body. Despite all these limitations there is no doubt that relations exist between the chemical composition of human exhaled air and clinical parameters. Upcoming new analytical techniques will allow more efficient extraction and preconcentration of substances in minute concentrations. Fast track bedside analyses will shortly become possible with the introduction of miniature gas chromatographic and mass spectrometric equipment. This will open a new area for clinical and basic research.