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

ABSTRACT

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.

Keywords:
Spectroscopy; near-infrared; Oxygen saturation; Oxygen consumption; Critically illness