Oxygen Saturation Measurements from Green and Orange Illuminations of Multi-Wavelength Optoelectronic Patch Sensors

Figures

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  Figure 1. Optical penetration depth δ shown for a range of light sources of different wavelengths [21].

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  Figure 2. Absorption of Hb and HbO2 at green and orange illuminations [22].

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  Figure 3. Data obtained from the mOEPS system (a) the raw green and orange signals; (b) the signals from the four wavelength illuminations after the band pass filtering (0.8–5 Hz). The peaks and troughs in the signals can be used to obtain SpO2.

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  Figure 4. Measurement of PPG signals to extract the DC and AC components. (a) the raw data contains both information of non-pulsatile (DC) and a relatively small variation resulting from pulsatile (AC) absorption; (b) filtering of the raw data can be used obtain the dynamic AC change.

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  Figure 5. Microcontroller control of the multi-wavelength illumination and de-multiplexing operations. In the mOEPS, the detail of four illumination are: the channel 1: green, the channel 2: orange, the channel 3: red, and the channel 4: near infrared(IR).

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  Figure 6. SpO2 data obtained from the mOEPS and a standard pulse oximetry device. The graphs of (a–c) display a line correlation for subject I, subject II and all 15 subjects respectively.

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  Figure 7. Bland–Altman plot showing differences in SpO2 between the green and orange illuminations of mOEPS and the pulse oximetry device. The graphs display a scatter diagram of the differences against the averages of the pulse oximetry and the green and orange illuminations of mOEPS for all 15 subjects.

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  Figure 8. SpO2 readings with box-and-whisker plots and median values of the pulse oximetry device and the green and orange illuminations of mOEPS. Subject I (Pulse Oximetry: 97% and mOEPS: 96%), subject II (Pulse Oximetry: 98% and mOEPS: 96%) and all 15 subjects readings (Pulse Oximetry: 98% and mOEPS: 98%). All SpO2 data sets were processed with box-and-whisker procedures to obtain the lower, median and higher values.

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  Figure 9. SpO2 data obtained from the mOEPS (green/orange) and the mOEPS (red/infrared) for different exercises.

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  Figure 10. Bland–Altman plot showing differences in SpO2 between the green and orange illuminations of mOEPS and the red and infrared illuminations of mOEPS for (a) cycling and (b) walking. The graphs display a scatter diagram of the differences against the averages of the green/orange and red/infrared illuminations of mOEPS for 16 subjects.