A large number of variables exist in the performance of this maneuver, however, yielding apparently conflicting results selleck Regorafenib and uncertainty as to the significance of the various VOT-derived StO2 parameters [11]. The analysis, interpretation, and understanding of VOT-derived StO2 traces, although being widely employed in septic and trauma patients, is limited, especially for the post-occlusion phase of the VOT. Consequently, identification of which StO2 parameters are most appropriate for scoring (micro)vascular reperfusion and reactivity remains to be determined. Proper characterization of VOT-derived StO2 parameters in health is hence needed to allow translation of results obtained in patients to pathophysiological phenomena.

The main problem with the interpretation of StO2 data in the literature is the diversity of methodologies used for assessing StO2 during a VOT. Results vary from study to study, making data comparison and interpretation difficult and possibly inadequate. Two major aspects regarding the inconsistent methodology are the measurement site and probe spacing (that is, the spatial separation between the illumination and detection fibers of the NIRS probe). The measurement site is important because differences may exist in the sensitivity of muscle groups and/or other anatomical structures to the VOT during health and/or pathophysiological conditions. Probe spacing, on the other hand, will determine the depth of measurement within the respective muscle group. To study the roles of both variables, we performed 3-minute VOTs in healthy volunteers and measured using 15 mm and StO2 25 mm probe spacings on the thenar and the forearm.

VOT-derived StO2 traces were quantified for baseline, ischemic, reperfusion, and hyperemic StO2 parameters. We expect these results to provide an essential frame of reference for conducting StO2 measurements in future clinical studies.Materials and methodsSubjectsThe study protocol was approved by the Medical Ethics Committee of the Erasmus Medical Center Rotterdam. Eight healthy volunteers (Table (Table1)1) who were not receiving any vaso-active medication were requested to refrain from consuming caffeine-containing beverages prior to the experiments. The subjects were comfortably seated in the experimental room (mean �� standard deviation room temperature was 21 �� 1��C) 1 hour before measurements and were requested not to perform any physical labor (for example, lifting and writing).

Table 1Demographic characteristics of the studied subjectsNear-infrared spectroscopyStO2 was continuously and non-invasively measured using two InSpectra tissue spectrometers (Model 325; Hutchinson Technology, Hutchinson, MN, USA). The spectrometers use reflectance mode probes that have a 1.5 mm optical fiber to illuminate the tissue and Cilengitide a 0.4 mm optical fiber to collect the backscattered light from the tissue.