| As developing of modern medical technology and interdisciplinarity, early diagnosis, a leading research area in medicine, has been making breakthroughs and innovations. Breath analysis, offering potential for nonintrusive disease diagnosis and metabolic status monitoring via testing exhaled breath components, has become an emerging research field in medicine, human healthcare, and medical instrumentation. But Current breath gas analysis with human subjects faces two challenges:1) limited number of human subjects or samples are used partially due to high costs of using the conventional analytical methods such as GC-MS and long testing time resulting from the sophisticated sample preparation such as sample pre-concentration.2) Due to the same limitation of using the conventional time-consuming analytical techniques that have low data throughput, advance in breath analysis study is often hindered by "a long study period" in the case a large number of subjects or samples have to be used. To this end, a real-time online breath analyzer with high data throughput (analyzing a large number of subjects in a short experimental period) would be desired in the field. Compared to the conventional MS-based method and electronic nose, CRDS technique has the advantages of fast response, relatively low costs, and relatively small instrument geometry. These unique properties make CRDS be a suitable technique for developing a portable instrument for real-time, online breath analysis with high data throughput for solving the two problems.In the theory, we analysis the using acetone the fingerprint spectra of acetone and demonstrates the parameters of the key components in the experiment of principles of CRDS, providing the basis for the design of instrument and component selection.In the design and development of instrument, we realized the CRDs breath acetone analyzer development by the design idea of module. We report the tests of instruments in detail. The performance of the instrument for quantitative measurements of breath acetone was investigated and validated using the certificated GC-MS. The results show this portable analyzer is ready for reliable near-real time (1 s), online (online introduction of breath sample without pre-treatment) breath acetone analysis with high sensitivity (>57 ppb), high selectivity, high accuracy, and high data throughput.In the application of breath analyzer, the breath analysis of rats and human subjects was carried out by the validated CRDS breath acetone analyzer. In rat experiment,18 non-diabetic healthy rats and 20 lab-developed type 1 diabetic (T1D) rats were used as two subject groups. A significant negative relationship (R=0.678, P< 0.05) between breath acetone and BG was found in the T1D rats. The validated portable breath analyzer was demonstrated via measuring hundreds of breath acetone samples in a clinic. The mean breath acetone concentrations were determined to be 4.9 ± 1.6 ppm (T1D), and 1.5 ±1.5 ppm (T2D), which are about 4.5 and 1.4 times of the one in the 52 non-diabetic healthy subjects,1.0 ± 0.6 ppm respectively. A preliminary quantitative correlation (R=0.56, P<0.05) between the mean individual breath acetone concentration and the mean individual BG levels does exist in 20 T1D subjects with no ketoacidosis. The results from a relatively large number of subjects tested indicate that an elevated mean breath acetone concentration exists in diabetic patients in general. Although many physiological parameters affect breath acetone, under a specifically controlled condition fast (<1 min) and portable breath acetone measurement can be used for screening abnormal metabolic status including diabetes, for point-of-care monitoring status of ketone bodies which have the signature smell of breath acetone, and for a breath acetone related clinical studies requiring a large number of tests. At same time, The current CRDS instrument platform can be extended for the development of a line of breath gas instruments using corresponding laser sources and ringdown mirrors. |
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