such as water, that are commonly present in the body. Figure 1 shows the NIR spectra (normalized to unit concentration) of alcohol and water acquired from the device which demonstrates the effect of molecular structure on NIR absorption. In addition, Beer’s Law states that the
Table 1—Study Demographics
the company obtains an independent, at arm’s length report. Tese new sensors can be networked across multiple sites and safety managers can analyze the impact of the testing program across their organiza- tions by looking at data by date, location, shiſt, gender, or age group. With this new information, the organization’s educational and support efforts can be appropriately aligned to those locations that will derive the greatest positive impact on productivity and safety. Te new infrared measurement is per-
formed by transmiting light into the skin via contact with an optical touch pad, and collecting a portion of the light reflected back by the skin. Te collected light is analyzed to determine the tissue alcohol concentration and for biometric verifica- tion of the user’s identity. Te light used is in the near-infrared spectral region and is safe for human skin exposure. Te light levels are less than the limits established by the FDA for non-ionizing radia- tion—orders of magnitude less that that required to cause skin heating or damage
46 datia focus
such as sunburn. Te devices measure the 4000-8000 cm-1
(1.25-2.5 μm) spectral
region, which is of prime interest for making noninvasive alcohol measure- ments. It offers specificity for a number of analytes, including alcohol and other organic molecules present in tissue, while allowing optical path lengths of several millimeters with acceptable absorbance characteristics. In addition this completely non-invasive approach to alcohol testing fully integrates biometric identity verifica- tion thus offering a number of significant improvements over existing methods. Tis unique combination makes routine, self –administered workplace testing a realistic and easy to deploy deterrence solution. From first touch to test results, the entire process can take less than 20 seconds. An advantage of NIR spectroscopy is
that the structure of a molecule dictates the specific manner in which it absorbs NIR light. Tus, the absorbance spectrum of each molecular species is unique, which allows the spectrum of alcohol to be dis- criminated from those of other molecules,
magnitude of the absorbance signal for a given substance (e.g. alcohol) is propor- tional to its concentration. Consequently, NIR spectroscopy provides noninvasive measurements that are both sensitive and selective for alcohol. Tis noninvasive alcohol measurement technology has been tested in multiple clinical studies involving over 400 participants and 10,000 alcohol measurements. Te study participants spanned a wide range of demographics (e.g. age, gender, ethnicity, and body type) and environmental conditions. All studies were been performed following a strict protocol approved by a hospital Institutional Review Board (IRB) to ensure the safety of the subjects and the safe use of the device. In one such peer-reviewed study3
, 26
volunteer subjects (demographics in Table 1) were measured to assess the accuracy of Tru- Touch and breath alcohol relative to venous blood alcohol. Subjects were consented ac- cording to an IRB-approved protocol. Alco- hol doses were administered to achieve peak blood alcohol (BAC) values of 120 mg/dL (0.12 percent). Blood alcohol measurements were acquired in approximately 15-min- ute intervals in order to monitor alcohol concentration. Once alcohol absorption was completed (15-40 minutes from ingestion, depending on the subject) and BAC began to decline, repeated cycles of blood, breath and noninvasive alcohol measurements were acquired (~15minutes per cycle) until the subject was below 20 mg/dL (0.02%). Tree hundred and sixty sets of noninvasive, blood and breath alcohol measurements were acquired from the 26 subjects. Te results (Figure 2) show a strong TruTouch-blood correlation (r>0.95) to blood chemistry (head space gas chromatography).
spring 2013
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