Breath Test in Lung Cancer Patients

The Breath Test is based on the analysis of the exhaled breath which is largely composed of nitrogen, oxygen, carbon dioxide, water and inert gases. Trace components, volatile substances that are generated in the body or absorbed by the environment, present in the nmol/l-pmol/l range, make up the rest of the breath. The volatile compounds can be exogenous, originate from many solvents and petroleum based products; and endogenous, generated by the cellular biochemical processes of the body. There is a growing literature on the analysis of volatile organic compounds (VOCs) in the exhaled breath for the diagnosis of lung cancer. Recently, gaseous chemical sensing and identification devices have been developed that are able to detect a single or patterns of odorant molecules such as VOCs. These devices have used a variety of sensor arrays including conductive/nonconductive polymers, quartz microbalance sensors coated with metallo-porphirins, polymer coated surface acoustic wave devices. The premise with most of these systems is that absorption of gases onto the sensor system causes a change in the conductivity,mass,vibration, or color of the sensor, thus altering its’ output. The systems generally consist of an array of sensors, which can be tuned to their task. The composite output of the array requires multivariate statistical tecniques to analyze the patterns of output produced (a “smellprint”). The sensitivities of these devices to various chemical groups and concentrations vary with the particular sensing technology.