Can central-venous oxygen saturation be estimated from tissue oxygen saturation during a venous occlusion test?

Objective To test whether tissue oxygen saturation (StO2) after a venous occlusion test estimates central venous oxygen saturation (ScvO2). Methods Observational study in intensive care unit patients. Tissue oxygen saturation was monitored (InSpectra Tissue Spectrometer Model 650, Hutchinson Technology Inc., MN, USA) with a multiprobe (15/25mm) in the thenar position. A venous occlusion test in volunteers was applied in the upper arm to test the tolerability and pattern of StO2 changes during the venous occlusion test. A sphygmomanometer cuff was inflated to a pressure 30mmHg above diastolic pressure until StO2 reached a plateau and deflated to 0mmHg. Tissue oxygen saturation parameters were divided into resting StO2 (r-StO2) and minimal StO2 (m-StO2) at the end of the venous occlusion test. In patients, the cuff was inflated to a pressure 30mmHg above diastolic pressure for 5 min (volunteers’ time derived) or until a StO2 plateau was reached. Tissue oxygen saturation parameters were divided into r-StO2, m-StO2, and the mean time that StO2 reached ScvO2. The StO2 value at the mean time was compared to ScvO2. Results All 9 volunteers tolerated the venous occlusion test. The time for tolerability or the StO2 plateau was 7 ± 1 minutes. We studied 22 patients. The mean time for StO2 equalized ScvO2 was 100 sec and 95 sec (15/25mm probes). The StO2 value at 100 sec ([100-StO2] 15mm: 74 ± 7%; 25mm: 74 ± 6%) was then compared with ScvO2 (75 ± 6%). The StO2 value at 100 sec correlated with ScvO2 (15 mm: R2 = 0.63, 25mm: R2 = 0.67, p < 0.01) without discrepancy (Bland Altman). Conclusion Central venous oxygen saturation can be estimated from StO2 during a venous occlusion test.