ABSTRACT
Exhaled human breath (EB) contains a variety of volatile disease biomarkers, which could either be endogenously produced or administered and subsequently metabolized within the human body. The ancient Greek physicians knew that the specific odor of EB could be associated with certain diseases or health conditions. One of the major advantageous characteristics of exhaled breath analysis methods is the noninvasive nature of the procedure. Infrared spectroscopy is an optical measurement technique that provides direct access to the fundamental vibrational and vibro-rotational signatures of molecular constituents. Direct absorption spectroscopy is probably the most robust optical detection method in gas analysis, and may detect and discriminate a wide variety of molecular species at trace levels. Cavity-enhanced spectroscopic techniques are based on high-finesse optical cavities for increasing the interaction of the period of light with the analytes of interest. Using cavities, extended effective absorption path lengths of up to 10 km have been achieved.
