UV laser-based photoacoustic breath analysis for the diagnosis of respiratory diseases: Detection of Asthma

Photoacoustic spectroscopy (PAS) can detect volatile organic compounds (VOCs) present in exhaled breath with very high sensitivity. A PAS setup using laser excitation at 266 nm and calibrated with Acetone, was used to record photoacoustic signals from a cohort of 20 normal healthy volunteers and 15 Asthma patients. The photoacoustic wave-form signals were Fourier-transformed to frequency domain and subjected to Principal Component Analysis (PCA) for classification. It was shown that the two sets of photoacoustic signal data, could be discriminated from each other by distinct cluster formation in a plot of Factors PC1 and PC2. A Match/No Match analysis, using Mahalanobis Distance and Sum of Squared Differences of simulated and actual signal (Spectral Residual) using a Calibration set of Asthma samples, gave a sensitivity of 89% and specificity of 93%. 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.