Impact of local thermal stimulation on the correlation between oxygen saturation and speed-resolved blood perfusion

Figures

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  Figure 1. Experiment design and case subject’s raw data. (a) Thermal stimulation point. The probe was located on the forearm midline, five twelfths of the line between wrist and elbow. (b) Experiment design. From (c) to (g) are temperature (left) and oxygen saturation signals (right). (c) blank control. (d) 38 °C. (e) 40 °C. (f) 42 °C. (g) 44 °C.

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  Figure 2. Oxygen saturation at the stimulation point. (a) Oxygen saturation signals. (b) Design of the comparison. (c) Results of the comparison. (F(4,141) = 32.63, P < 0.0001). Yellow indicates P < 0.05, and blue indicates P > 0.05. BC, blank control; TS, thermal stimulation. Data are presented as the mean ± SE.

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  Figure 3. The complexity of oxygen saturation signals. The left column is the curve of MSE/MFE. The middle column is the CAI. The right column is the multiple comparisons. (a) MSE before stimulation. (b)MSE CAI before stimulation. (c) Comparison of MSE CAI before stimulation, F(4,141) = 0.5776, P = 0.6794. (d) MFE before stimulation. (e) MFE CAI before stimulation. (f) Comparison of MFE CAI before stimulation, F(4,141) = 0.5756, P = 0.6808. (g) MSE after stimulation. (h) MSE CAI after stimulation. (i) Comparison of MSE CAI after stimulation, F(4,141) = 32.38, P < 0.01. (j) MFE after stimulation. (k) MFE CAI after stimulation. (m) Comparison of MFE CAI after stimulation, F(4,141) = 39.64, P < 0.01. Yellow indicates P < 0.05, and blue indicates P > 0.05. MSE, multiscale entropy; CAI, complexity area index; MFE, multiscale fuzzy entropy. BC, blank control. Data are presented as the mean ± SE.

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  Figure 4. Relationship between speed-resolved perfusion and oxygen saturation signals. (a) Before thermal stimulation, V1 & oxygen, F(4,141) = 1.245, P = 0.34; V2 & oxygen F(4,141) = 0.540, P = 0.71; V3 & oxygen F(4,141) = 1.727, P = 0.15; (b) After stimulation, V1 & oxygen, F(4,141) = 30.923, P < 0.001; V2 & oxygen, F(4,141) = 29.146, P < 0.001; V3 & oxygen, F(4,141) = 46.659, P < 0.001; From (c) to (d) are multi comparison after stimulation. (c) V1. (d) V2. (e) V3. Yellow indicates P < 0.05, and blue indicates P > 0.05. V1: low speed component of blood perfusion, <1 mm/s; V2: mid-speed component of blood perfusion, 1–10 mm/s; V3: high speed component of blood perfusion, >10 mm/s; BC, blank control; Oxy, oxygen saturation. Data are presented as the mean ± SE.

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  Figure 5. Spearman correlation of MSE CAI between the speed-resolved blood perfusion and oxygen saturation signals. The columns correspond to the three velocity components V1, V2, and V3, and the rows to the stimulation protocol: (a) background control, and thermal stimulation at (b) 38 °C, (c) 40 °C, (d) 42 °C, and (e) 44 °C. SCC, Spearman’s correlation coefficient; CAI, complexity area index. Oxy sat., oxygen saturation.