Relationship Between Finger Photoplethysmographic Pulses and Skin Blood Perfusion

Figures

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  Figure 1. Measurement setup Laser Doppler flux (LDF) is measured on the pulp of the ring finger using a multifiber LDF probe. The photoplethysmographic (PPG) signal is obtained from the index finger with the PPG sensor secured to the finger firmly but gently with Velcro.

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  Figure 2. Example measurement sequences LDF is the laser Doppler flux measured on the pulp of the ring finger. PPG is the photoplethysmography signal from the index finger. Both are shown as a function of time. In A, the 30-pulse sequence that was analyzed was captured 1496 seconds into the experiment. In B. the 30-pulse sequence that was analyzed was captured 4.5 seconds into the experiment. In both cases there is a spontaneous waxing and waning of the PPG signal with associated changes in the pattern of the LDF signal.

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  Figure 3. Parameter definitions LDF is the laser Doppler flux measured on the pulp of the ring finger. PPG is the photoplethysmography signal recorded from the index finger of the same hand. Both are shown as a function of time. PALDF is the peak-to-peak amplitude of the LDF and PAPPG is the peak-to-peak amplitude of the PPG pulse. TLDF is the duration of the LDF pulse. The area with the diagonal lines in the LDF signal is the total LDF per pulse (LDFTOT). The area enclosed by the pulsatile part and labeled PF is the pulsatile flux component.

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  Figure 4. Best and worst correlations for LDF pulse amplitude The pulse amplitude of the laser Doppler flux (PALDF) is shown versus the pulse amplitude of the PPG (PAPPG) along with the linear regression line (dotted) and corresponding regression equation. Part A is the best correlation among the 10 subjects (R = 0.937) and part B shows the least good correlation among the 10 subjects (R = 0.468). Data is for the sequence of 30 pulses, and R is the correlation coefficient.

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  Figure 5. Best and worst correlations for total LDF The total LDF per pulse (LDFTOT) is shown versus the pulse amplitude of the PPG (PAPPG) along with the linear regression line (dotted) and corresponding regression equation for the same two subjects (A and B) as shown in Figure 4. Data is for the sequence of 30 pulses, and R is the correlation coefficient.

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  Figure 6. Best and worst correlations for pulsatile component of LDF The pulsatile flow component (PF) is shown versus the pulse amplitude of the PPG (PAPPG) along with the linear regression line (dotted) and corresponding regression equation for the same two subjects (A and B) as shown in Figure 4. Data is for the sequence of 30 pulses, and R is the correlation coefficient. Subjects A and B are the same as shown in Figure 4.

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  Figure 7. Correlation among all subjects for LDF pulse amplitude The pulse amplitude of the laser Doppler flux (PALDF) is shown versus the pulse amplitude of the PPG (PAPPG) along with the linear regression line (dotted) and corresponding regression equation for all subjects. The p-value for the regression is < 0.0001.

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  Figure 8. Correlation among all subjects for just the pulsatile LDF component The pulsatile flow component (PF) is shown versus the pulse amplitude of the PPG (PAPPG) along with the linear regression line (dotted) and corresponding regression equation for all subjects. The p-value for the regression is < 0.0001.

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  Figure 9. Average blood perfusion comparison Average LDF during the 30-pulse sampling interval (LDF30-PULSE) in relation to the overall 30-minute average LDF perfusion (LDF30-MINUTE) is shown for each of the 10 subjects. The dotted line is the linear regression with the equation shown in the inset. The p-value of the regression is < 0.001. Error bars are the standard error of the mean (SEM).

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  Figure 10. LDF pulsatility index The LDF pulsatility index (PLI = PALDF/MEANLDF) is shown for each of the 10 subjects compared to their PAPPG averaged over their 30-pulse sampling interval. The dotted line is the linear regression with the equation shown in the inset. The p-value of the regression = 0.014. Error bars are the standard error of the mean (SEM).