Bimodal UV photoacoustic and fluorescence sensor for breath analysis

Breath analysis using spectroscopy techniques is coming up as one of the non-invasive methods for disease diagnosis. Among several spectroscopic methods, photoacoustic spectroscopy (PAS) and laser-induced fluores-cence (LIF) are used to obtain information on sample's absorption and emission characteristics, respectively. In the present work, we present breath analysis results using a bimodal sensor using 266 nm UV laser, which can be used for both PAS and LIF measurements of volatile organic compounds (VOCs). The system is optimized using standard VOC samples to show limits of detection of the order of ppb-s. Preliminary breath analysis has been carried out for breath samples from Asthma patients and healthy volunteers. Principal component analysis has shown that the two sets of PAS and LIF data of Asthma and normal breath samples are discriminated from each other as distinct clusters enabling clear discrimination. Match/no match study using M-distance and spectral residual gives a sensitivity of 90 % and specificity of 96 % for PAS, and 85 % sensitivity and 86 % specificity for LIF, using optimized M-distance cutoff values. The receiver operating curve (ROC) and the area under the curve (AUC)-ROC shows that the method is quite suitable for applying bimodal spectroscopy for breath analysis. A comparison of the breath study of the same volunteers has been carried out using an E-nose to confirm the validity of UV laser-based PAS-LIF bimodal sensor.

Automated summary

Breath analysis using spectroscopy techniques is a non-invasive method for disease diagnosis. In this study, a bimodal sensor using a 266 nm UV laser was used for breath analysis. Preliminary analysis of breath samples from Asthma patients and healthy volunteers showed distinct clusters for Asthma and normal breath samples. The method achieved high sensitivity and specificity for both photoacoustic spectroscopy (PAS) and laser-induced fluorescence (LIF). The comparison with an E-nose confirmed the validity of the UV laser-based PAS-LIF bimodal sensor for breath analysis.