Dynamic evaluation of near-infrared peripheral oximetry in healthy volunteers: A comparison between INVOS and EQUANOX

Abstract Purpose The present study aimed to compare peripheral regional tissue oxygen saturation (rSO2 ) values and desaturation/resaturation rates given by INVOS and EQUANOX devices. Materials and methods Twenty healthy volunteers were investigated during 4 experimental steps: baseline, hyperoxia, ischemia, and reperfusion. For each volunteer, 2 sensors INVOS and 2 sensors EQUANOX were placed on both left and right calves. Blood pressure, heart rate, and peripheral pulse oximetry were monitored. Results Peripheral rSO2 ranged from 40% to 95% (INVOS) and from 47% to 100% (EQUANOX): 81 ± 12 vs 82 ± 9 ( P = .469). A significant relationship was found at baseline between absolute values of INVOS and EQUANOX (n = 40; R2 = 0.159; P = .011). Bias was − 0.4%, and limits of agreement were ± 15.1%. The percent maximum differences vs baseline values during dynamic maneuvers were 33% ± 19% (95% confidence interval, 24-42) and 21% ± 14% (95% confidence interval, 15-28) for INVOS and EQUANOX, respectively. No significant relationship was observed between percent maximum differences in INVOS and EQUANOX (n = 20; R2 = 0.128; P = .122). Rates of desaturation/resaturation during occlusive vascular tests were 3.65% per minute vs 2.36% per minute ( P = .027) and 30.42% per minute vs 16.28% per minute ( P = .004) for INVOS and EQUANOX, respectively. Conclusions INVOS and EQUANOX are not comparable in measuring both absolute values and dynamic changes of peripheral rSO2 and near-infrared spectroscopy–derived parameters during occlusion vascular tests.