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

Abstract

Abstract. Previous works investigated a spectroscopic technique that offered a promising alternative to blood and breath assays for determining in vivo alcohol concentration. Although these prior works measured the dorsal forearm, we report the results of a 26-subject clinical study designed to evaluate the spectroscopic technique at a finger measurement site through comparison to contemporaneous forearm spectroscopic, venous blood, and breath measurements. Through both Monte Carlo simulation and experimental data, it is shown that tissue optical probe design has a substantial impact on the effective path-length of photons through the skin and the signal-to-noise ratio of the spectroscopic measurements. Comparison of the breath, blood, and tissue assays demonstrated significant differences in alcohol concentration that are attributable to both assay accuracy and alcohol pharmacokinetics. Similar to past works, a first order kinetic model is used to estimate the fraction of concentration variance explained by alcohol pharmacokinetics (72.6-86.7%). A significant outcome of this work was significantly improved pharmacokinetic agreement with breath (arterial) alcohol of the finger measurement (mean k Art-Fin = 0.111 min − 1 ) relative to the forearm measurement (mean k Art-For = 0.019 min − 1 ) that is likely due to the increased blood perfusion of the finger. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Robust Calibration Transfer in Noninvasive Ethanol Measurements, Part II: Modification of Instrument Measurements by Incorporation of Expert Knowledge (MIMIK)

“…Recent work has evaluated the two sources of reference error and a reasonable estimate of the cumulative root mean square reference error for the present work is 7–9 mg/dL. 5…”

“…21–23 The noninvasive measurement devices were identical in design to those reported in previous work. 1–5 The interferometer (see Fig. 1 in Part I) operated at 32 cm −1 spectral resolution with a 0.8 cm/s scan speed that yielded 8–9 double sided, 2048 point interferograms per s. The spectral acquisition time was 1 min for all measurements.…”

“…Several publications have discussed the underlying near-infrared spectroscopic method 1,2 and its clinical comparison to blood and breath alcohol assays. 3–5 The purpose of this work is to investigate an approach to calibration transfer that avoids methodologies that are commercially prohibitive due to the nature of noninvasive alcohol tests. For example, several commonly employed calibration transfer methodologies require a subset of the calibration samples to be measured on each device in order to determine a spectral transform that is applied to either the calibration data or to future validation data.…”

Robust Calibration Transfer in Noninvasive Ethanol Measurements, Part I: Mathematical Basis for Spectral Distortions in Fourier Transform Near-Infrared Spectroscopy (FT-NIR)

“…1–3 Several studies have discussed the underlying near-infrared (NIR) spectroscopic method 4,5 and its clinical comparison to blood and breath alcohol assays. 6–8 The purpose of this work is to investigate and evaluate an approach to calibration transfer that achieves acceptable performance while avoiding the use of methodologies that would be prohibitive due to the nature of noninvasive alcohol tests.…”

Transmission versus reflectance spectroscopy for quantitation

“…This region is important spectroscopically as it contains combinations of the fundamental vibrational modes of important functional groups such as C─H, O─H, and N─H. 21 As such, even minor analytes, such as ethanol 22 and glucose, 23 can be quantitated using this spectroscopic region. Water concentrations in the range 66.5% to 73.5%, typical of skin water content, 24 were chosen at random, and combined with random concentrations of other analytes, plus water temperature variation of AE0.5°C, to form the total absorption coefficient spectrum, μ a ¼ lnð10Þ P ε i c i .…”