System improvements for exhaled breath measurement system

As many as 200 kinds of volatile organic compounds (VOCs) are included in human exhaled breath. Many papers using VOCs as a biomarker of respiratory diseases have been reported. However, it is very difficult to measure very low concentration of VOCs in exhaled breath with high precision. Moreover, it is also difficult to distinguish VOCs in exhaled breath and VOCs in atmosphere. Therefore, measurement of VOCs is rarely used in a clinical field because complicated and large-sized system is required for measure VOCs in exhaled breath. We are developing exhaled breath measurement system which overcame these problems. Our system analyzes exhaled breath discharged from living body by inhaling atmosphere from which VOCs were removed. In this paper, results of system improvements are reported. At first, we adopted a cold trap method with dry ice as a method of purifying atmosphere (method A). Method A needs complicated device and long processing time. Next, we changed the method into solid absorbent from method A (method B). We verified purity of purified air. Concentration of 10 kinds of VOCs contained in both exhaled breath and atmosphere were measured. Selected VOCs are as follows: benzene, cyclohexane, ethylbenzene, heptanes, hexane, isoprene, nonane, octane, toluene and xylene. Atmosphere was purified by the method A and B. Concentrations of VOCs contained in the purified air were measured by gas chromatography. As a result of measurement, almost VOCs were not detected in the purified air made by both methods. Furthermore, time to make purified air was reduced from 70 minutes to 10 minutes. Simplification of the system and shorter processing time than method A were realized by method B while keeping purity.