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Assessment of tissue oxygen saturation during a vascular occlusion test using near-infrared spectroscopy: role of the probe spacing and measurement site studied in healthy volunteers

Introduction

To assess potential metabolic and microcirculatory alterations in critically ill patients, near-infrared spectroscopy (NIRS) has been used, in combination with a vascular occlusion test (VOT), for the noninvasive measurement of tissue oxygen saturation (StO2), oxygen consumption, and microvascular reperfusion and reactivity. However, the methodologies for assessing StO2 are very inconsistent in the literature and results vary from study to study. In this study we investigated the effects of the probe spacing and measurement site, using both a 15 mm and a 25 mm probe spacing on the thenar and the forearm, in healthy volunteers.

Methods

StO2 was noninvasively measured in eight healthy volunteers during 3-minute VOTs using two InSpectra Tissue Spectrometers equipped with either a 15 mm or a 25 mm probe. VOT-derived StO2 traces were analyzed for baseline, ischemic, reperfusion, and hyperemic parameters.

Results

Although not apparent at baseline, the probe spacing and measurement site significantly influenced VOT-derived StO2 parameters (Figures 1 and 2). StO2 parameters in the hyperemic phase of the VOT were shown to significantly correlate to the minimum StO2 value after 3 minutes of ischemia.

Figure 1
figure1

Mean ± SD StO 2 values in the thenar during a 3-minute VOT. BSLN, baseline.

Figure 2
figure2

Mean ± SD StO 2 values in the forearm during a 3-minute VOT. BSLN, baseline.

Conclusion

The present study showed that NIRS measurements in combination with a VOT are measurement site and probe dependent. Additionally, this study indicated that reactive hyperemia depends on the extent of ischemic hit and supports the use of a target StO2 over the use of a fixed time of occlusion.

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Bezemer, R., Lima, A., Klijn, E. et al. Assessment of tissue oxygen saturation during a vascular occlusion test using near-infrared spectroscopy: role of the probe spacing and measurement site studied in healthy volunteers. Crit Care 13, P244 (2009). https://doi.org/10.1186/cc7408

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Keywords

  • Healthy Volunteer
  • Probe Spacing
  • Fixed Time
  • Measurement Site
  • Reactive Hyperemia