Development And Clinical Application Of Breath Acetone Analyzer Based On CRDS

Diabetes is a serious metabolic disorder syndrome, The population prevalence of China is as high as10.5%, the world’s largest numbers of diabetic population. At present, both diagnostics and treatment are relie on blood glucose measurement with invasive blood glucose meters. While breath analysis determines the concentration of volatile organic compounds (VOCs) therefore diagnose disease or monitor metabolic state non-invasively. To date, over30biomarkers are recognized to be related to certain disease of human, and acetone is considered to be a potential biomarker for diabetes, which can be applied to the diagnostics and monitoring of diabetes.The golden standard of breath VOCs detection is gas chromatography mass spectrometry (GC-MS), which has extremely high accuracy, high selectivity, and ablity to profile unknown breath constitution. However, it’s a time-consuming, expernsive method, and moreover, it requires complicated sample pre-concentration, therefore it’s confined to laboratory research currently. Cavity ring down spectroscopy (CRDS) is an ultrasensitive absorption spectrometry method. Because of its real-time response, high accuracy, direct sample introduction and ability of point-of-care (POC), etc., CRDS is expected to become preferred breath analysis techniques in the future.Objective:To develop a breath acetone analyzer based on CRDS, and provide instruments for large amount of clinical breath analysis, then study the correlation betwwen acetone and diabetes, and to promote application of breath analysis in the disease diagnostics and metabolic monitoring.Methods:Firstly, construct a movable CRDS breath acetone analyzer with compact266nm pulsed laser as light source, photomultiplier tube (PMT) as the detector, and the newly designed software as the control and measurement part. And then a series of instruments performance is tested and discussed, including stability, linear response to standard acetone sample with various concentration, validation of gold standard GC-MS, performance of real breath sample analysis and reproducibility during long-term clinical breath analysis. Using Matlab simulation and experimental verification, a series factors may influence system performance are discussed, including breath sampling bags, bandwidth of circuit and detection, amplitude perturbation of ring-down signal, data processing and sample intrduction methods, and waveform fitting algorithm for a detailed discussion. Finally, the breath acetone analyzer is applied to clinical breath analysis.19healthy volunteers and14diabetic patients (3with type1diabetes,11with type2diabetes) participated in the experiment under various states (fasting and2hours after meals).75breath samples were measured in total and six healthy volunteers participated in the oral glucose tolerance test (OGTT), which conducted dynamic monitoring of blood glucose and breath acetone.Results:According to the performance of this breath analyzer, the mirrors’reflectivity are estimated to be greater than99.94%, and the typical ring-down time of the baseline is2.6831μs with stability of0.18%, which leads to the detection limit of55.63ppbv (3-σ criterion). Response of standard acetone with various concentration has good linerity(R=0.99). The ration between the results of GC-MS and CRDS is1.01, indicating the reliability of this analyzer. Good repeatability and stability of long-term clinical breath analysis, and mean acetone concentration of healthy subjects, type1and type2diabetic subjects are1.19ppmv,2.41ppmv and2.17ppmv, respectively. Breath acetone mean concentration of healthy subjects under fasting state (1.34ppmv) is higher than that under post meal2hours (1.04ppmv). No significant correlation between breath acetone and blood glucose are observed among healthy in type2diabetic subjects, while in group with type1diabetes, correlation of blood glucose and breath acetone is linear (R=0.98). in the OGTT, breath acetone concetraton of healthy subjects kept decreasing from the fasting state to2hours after digestion of oral glucose, which is accord to metabolic pathway of acetone and previous literatures’reports.Conclusion:The breath acetone analyzer has high sensitivity comparable to GC-MS and good long-term stability, and is able to apply to a large amount of clinical breath analysis.