UV photoacoustic sensor for breath analysis: Pilot study of Asthma and COPD

Nidheesh V R 1, Aswini Kumar Mohapatra 2, Unnikrishnan V K 1, Vasudevan Baskaran Kartha 1, and Santhosh Chidangil 1

1. Centre for Biophotonics, Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal

2. Department of Respiratory Medicine , Kasturba Medical College, Manipal Academy of Higher Education, Manipal

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Abstract: 

Photoacoustic spectroscopy (PAS) is getting immense potential for biomedical applications by detecting volatile organic compounds (VOCs) present in exhaled breath. UV photoacoustic sensor is designed and assembled with source of excitation as 266 nm pulsed laser. The system is calibrated using standard VOCs and the limit of detection obtained as PPB. The assembled PAS sensor was used to record photoacoustic signals from a cohort of healthy volunteers, patients with asthma and chronic obstructive pulmonary disease (COPD). The photoacoustic signals were Fourier-transformed to frequency domain and subjected to Principal Component Analysis (PCA) for classification. It was shown that the three sets of photoacoustic signals were discriminated from each other by distinct cluster formation in a plot of principal components-1 (PC1) and principal components-2 (PC2).  A Match/No Match analysis using Mahalanobis-Distance and Sum of Squared Differences of simulated and actual signals (Spectral Residual) using a calibration set of normal samples have given sensitivity of 88% and specificity of 89%.  A comparison of results obtained from present data with the E-nose based VOC screening of the same volunteers confirmed the validity of the PAS technique for the diagnosis of Asthma and COPD.