In this paper, Guo et al. test the ability of their WM-DPTR to detect ethanol over a range of blood alcohol concentrations (inclusive of the legal limits for driving in Europe, the United States and Canada) in an ethanol and water solution phantom, as well as an ethanol and blood serum solution that was diffused into human skin. The WM-DPTR technique uses two out-of-phase modulated quantum cascade lasers operating at wavelengths corresponding to the peak of the ethanol absorption band and its adjacent minimum to noninvasively measure ethanol in the blood. By selectively tuning the amplitude ratio and optical phase shift of the signals generated by the two lasers, the authors are able to optimize their alcohol detection abilities to achieve high sensitivity and resolution. The authors found that the WM-DPTR technique was superior to standard single-PTR techniques that were not able to resolve ethanol concentrations over the range of blood alcohol concentrations that were tested and detected using WM-DPTR. Moreover, by capitalizing on the technique’s photothermal properties and tuning capabilities, the authors are able to use WM-DPTR to differentiate ethanol concentration from glucose concentration (which share the same fundamental absorption peak) and account for variations in blood glucose that might otherwise confound the accuracy of measuring ethanol concentration in diabetic individuals.
In conclusion, Guo et al. provide preliminary evidence that WM-DPTR can be used to noninvasively and reliably measure ethanol over relevant ranges of blood alcohol concentrations. While the technique has shown exciting results in phantoms, it still needs to be tested in vivo to better assess its repeatability and reproducibility. Nevertheless, it will be exciting to follow the testing of WM-DPTR in living systems to better understand whether the technique can be translated and developed into an alcohol ignition interlock with universal application to the general public in hopes of improving public safety.
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