966 CLINICAL CHEMISTRY Vol 20 No R 1n74 Breath Analysis as a Technique in Clinical Chemistry

Breath possesses unique advantages as a specimen for clinical chemical analyses, including the continuous equilibrium of gases and volatile substances between expired alveolar air and the pulmonary blood circulation. Substances amenable to analysis in breath include 02, C02, CO,and other gases, volatile organic compounds, and many drugs with sufficiently high vapor pressures at physiological temperatures. Practical aspects of breath sampling and breath analysis are discussed, exemplified by breath-alcohol analysis. The requirements for ob-taining breath samples in equilibrium with the pulmonary blood circulation are delineated, and experimental data are presented for the significant breath-sample charac-teristics bearing on design of breath collection and stor-age systems (end-expiratory temperature, breath vol