Noninvasive NIR monitoring of interstitial ethanol concentration

Abstract

A practical limitation encountered in alcohol research is the relatively small number of body compartments (e.g. blood, liver, tissue) that can be directly interrogated. In this work, an NIR spectroscopic device was investigated that provided a direct measurement of alcohol concentration in skin tissue (interstitial fluid). This work is intended to characterize the relationship of forearm interstitial fluid alcohol concentration relative to capillary blood using a first order kinetic model. Concurrent blood and tissue alcohol concentrations were collected on 101 test subjects while consuming alcohol. Estimates of the first order kinetic rate constant were calculated for each of the subjects. It is hoped that this characterization will lead to further improvements in optical based alcohol monitors for impairment detection.

An absolute calibration method of an ethyl alcohol biosensor based on wavelength-modulated differential photothermal radiometry

“…6 An effort is underway to develop alcohol detection technologies that could be fitted in vehicles and should be non-invasive, reliable, durable, quick to use, seamless with the driving task and require little or no maintenance. 7 Alcohol detection technologies can be grouped into one of four technology types: (1) tissue spectrometry that estimates BAC from a near-infrared (NIR) beam diffusely reflected a) mandelis@mie.utoronto.ca from the interstitial fluid (ISF) in the dermis of the subject's skin; 8 (2) distant spectrometry that analyzes BAC by using measurements of exhaled carbon dioxide (CO 2 ) based on midinfrared (MIR) spectroscopy as an indication of the degree of dilution of the alcohol in exhaled air; (3) fuel-cell based electrochemical devices in which BAC is determined from the current produced by the oxidation of ethanol; and (4) a behavioral system that attempts to identify cues of typical drunk driving behavior related to lane position maintenance, speed control, judgment, and vigilance. 9 Out of these four technology categories, the Driver Alcohol Detection System for Safety (DADSS) has chosen only tissue-spectrometry-based TruTouch and distantspectrometry-based Autoliv technologies for prototype development.…”

Comparison of spectroscopically measured finger and forearm tissue ethanol concentration to blood and breath ethanol measurements

“…Similar methods for in vivo spectroscopy have been previously described. 1,2,24,30 Prior works have indicated that the pharmacokinetic differences between blood and tissue alcohol concentrations can be pronounced during the initial period following the ingestion of the alcohol dose (termed the absorption phase) relative to the descending portion of the alcohol experiment (termed the elimination phase).…”

“…Furthermore, in prior work the underlying distribution of each set of estimates was determined to be lognormal at 95% confidence. 2 Consequently, the parameterization in Table 3 reflects the lognormal distribution of the rate constant estimates. Table 3 also shows the rms concentration difference between compartments from the experimental data (rms exp ), the rms concentration difference between the experimental breath (arterial) concentrations and the estimated concentrations determined by integration of Eq.…”

“…The forearm device was identical in design to the device reported in previous works. 1,2 The only fundamental difference between the finger and forearm devices was the optical probe design (discussed in Sec. 2.5).…”

“…1,2 That work showed a first order kinetic model used by other researchers to explain alcohol pharmacokinetics between arterial and venous blood [3][4][5][6] also reasonably explained the pharmacokinetic differences between forearm tissue and blood alcohol concentrations. However, the kinetic constants associated with the forearm tissue measurement were smaller in magnitude (a larger pharmacokinetic difference) than those observed when comparing blood types to each other.…”