Although blood flow to peripheral tissues is difficult to measure, tissue oxygen supply may be approximated using the DO2I.
To measure tissue oxygen saturation near-infrared light (680 800 nm) is emitted into the thenar tissue with a depth of about 15 mm.
Regional differences in brain perfusion, metabolism and oxygenation could be large among different brain areas in TBI patients, and PtiO2 monitoring as a regional technique only measures tissue oxygen pressure in a very small tissue volume.
An alternative approach employed by several laboratories is to measure tissue oxygen as a proxy for BOLD, using the rationale that changes are driven by the same physiological mechanisms as changes in the BOLD signal (Thompson et al., 2003; Offenhauser et al., 2005; Masamoto et al., 2008; Lowry et al., 2010).
For these studies, a prototype clinic-compatible system (v100, Modulated Imaging Inc., Irvine, CA) was used to measure tissue oxygenated hemoglobin, deoxygenated hemoglobin, and tissue oxygen saturation (stO2).
As StO2 measures tissue oxygen saturation within 15 mm of depth that included skin and muscle, it could be an argument for abnormal skin perfusion in mottling area but the respective part of both tissues (skin and muscle) in the final result of stO2 is unknown.
In addition, it is demonstrated that this technique can be used to noninvasively measure tissue oxygen consumption.
Near-infrared spectroscopy (NIRS) measures tissue oxygen saturation (StO2) and has been proposed as a noninvasive system for monitoring regional circulation.
In particular, we have developed a portable optical instrument using visible-near-infrared light to evaluate the local microcirculation of periodontal tissues by measuring tissue hemoglobin concentrations and oxygen saturation in a non-invasive and real-time manner [ 13, 16, 17, 23].
