Baseline StO2 and VOT parameters for healthy volunteers were coll

Baseline StO2 and VOT parameters for healthy volunteers were collected in a semirecumbent position after 10 minutes of rest. Data from days 1, 2, and 3 were pooled for a correlation study between NIRS parameters, macrohemodynamic data, metabolic data and LD data. In addition, baseline StO2 values were compared with other oxygen saturations and the gradients between StO2 and SvO2 and between SpO2 and StO2 were computed.Laser DopplerThe skin blood flow velocity was measured upstream of the StO2 probe, on the inner side of the homolateral wrist, using the LD technique. The probe was secured and connected to a dual-channel flowmeter (BLF21D; Transonic Systems, Ithaca, NY, USA). Cutaneous blood flow velocity (1.

2 mm deep, in arbitrary tissue perfusion units (TPU)) was continuously measured and recorded as a numerical signal onto a computer with an analog/digital transducer (Biopac Systems MP100; BIOPAC Systems, Inc, Goleta, CA, USA) and with data processing software (Acqknowledge 3.81; BIOPAC Systems, Inc).The same occlusion test used for StO2 was applied for LD measurements (Figure (Figure1).1). After baseline data registration, the stop flow (VOT) and the post-ischemic reperfusion flow were registered. As shown in Figure Figure1,1, the LD flow signal shows a reperfusion peak flow before coming back to baseline. In addition to baseline values, the slope of reperfusion was calculated as described for StO2 using linear adjustment (normal value �� standard deviation: baseline, 30.49 �� 21.30 TPU/seconds (local data) [35]; reperfusion slope, 48.62 �� 32.08 TPU/seconds).

The relative reperfusion hyperemia was also calculated from baseline to peak (absolute TPU value). Data from reperfusion were expressed as absolute changes, as well as the percentage of variation from the preocclusion value.Figure 1Tissue hemoglobin oxygen saturation and laser Doppler measurement. Example of a real tracing for tissue hemoglobin oxygen saturation (StO2) and laser Doppler measurements obtained before and during the occlusion test. TPU, tissue perfusion units.Statistical analysisData are summarized as the incidence and percentage for categorical variables. Quantitative variables are summarized as the median (25th to 75th percentiles). The reperfusion slope was dichotomized using the median value, which allowed fixing the threshold difference.

The relationship between variables at day 1 (scores, macrohemodynamic, metabolic, NIRS and LD) and death within 28 days were tested by Wilcoxon test or Fisher exact test. Multivariate GSK-3 models were performed using multiple logistic regression. In model checking, we examined potential interactions and colinearity. Goodness of fit was evaluated using the method proposed by Le Cessie and Van Houwelingen. Models were compared using the log-likelihood ratio test.

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