Abstract
In this preliminary study, we examined in human volunteers the performance of the developed prototype device for non-invasive quantification of blood alcohol concentration (BAC) by near-infrared light which is highly transparent to the body. We aimed at applying the results to the final goal of developing a novel alcohol-based vehicle ignition-interlock device. Accumulating evidence shows that one of the ethyl alcohol absorption peaks in the near-infrared region is present at 1,185 nm. We combined this with our recent development of a non-invasive optical method for blood glucose measurement, which we call pulse glucometry, using blood volume pulsations in a finger within a cardiac cycle. Thus, we developed a novel method, pulse alcometry, for non-invasive measurement of BAC. We calculated second derivative values of optical density (ODλ”) to remove baseline over a band including three wavelengths, 1,150 nm, 1,185 nm, and 1,220 nm. Then, a simple linear regression analysis was performed with the measured ODλ” to predict BAC levels. In 3 healthy male volunteers, during alcohol intake and washout, periodic optical measurements using the present device were made simultaneously with collection of blood samples for in vitro BAC analysis. In leave-one-out cross validations within an individual, the measured BAC and the predicted BAC correlated well (r = 0.773∼0.846, mean absolute error = 0.134∼0.333mg/ml). We conclude that, from the results of this preliminary study, the new method appears to be able to estimate BAC levels non-invasively. However, further investigations in a larger group of subjects will be needed in order to determine fully the operational performance of this new measurement system.
