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Fig. 8.
Confusion matrix between RRIV and SSIV in the resting and deep breathing phases_
| Phase | SSIV | RRIV Abnormal [ms] | RRIV Normal [ms] |
|---|---|---|---|
| Resting | Abnormal | 44 | 2 |
| Normal | 8 | 190 | |
| Deep breathing | Abnormal | 44 | 3 |
| Normal | 7 | 190 |
SSIV assessment range of normal cardiac autonomic function in each age group based on PPG_
| Age [y] | 20 ∼ 29 | 30 ∼ 39 | 40 ∼ 49 | 50 ∼ 59 | 60 ∼ 69 |
|---|---|---|---|---|---|
| Rest [ms] | 13 ∼ 45 | 7 ∼ 31 | 7 ∼ 35 | 6 ∼ 22 | 8 ∼ 18 |
| Breath [ms] | 20 ∼ 61 | 10 ∼ 53 | 15 ∼ 47 | 12 ∼ 58 | 9 ∼ 27 |
The sensitivity and specificity of SSIV in different assessment ranges_
| Phase | Rate [%] | Out+2 | Out+1 | RRIV source | In-1 | In-2 | In-3 | In-4 |
|---|---|---|---|---|---|---|---|---|
| Rest | Sensitivity | 36.54 | 63.46 | 84.62 | 96.15 | 96.15 | 100.00 | 100.00 |
| Specificity | 98.96 | 98.96 | 98.96 | 91.67 | 79.69 | 70.83 | 59.90 | |
| Breath | Sensitivity | 54.90 | 70.59 | 86.27 | 94.12 | 94.12 | 96.08 | 96.08 |
| Specificity | 99.48 | 99.48 | 98.45 | 95.85 | 91.19 | 84.97 | 78.24 |
A descriptive listing of PPG signal processing methods_
| No. | Filter name | Description |
|---|---|---|
| F01 | Butterworth | The passband frequency is from 1 Hz to 5 Hz, and the filter order is 2. |
| F02 | Bessel | |
| F03 | Chebyshev | |
| F04 | Elliptic | |
| F11 | Savitzky-Golay | The polynomial order is 3, and the window size 401. |
| F12 | Average | The passband frequency is from 1 Hz to 5 Hz. |
| F13 | Periodic moving | After normalizing each cardiac cycle with the same number of sampled signals, the ith sampled signals of each of the 5 cycles are averaged, where 1 ≤ i ≤ the normalized cycle length. |
| F21 | Daubechies | Use the inverse DWT of Daubechies db6 and Coiflet C3 to reconstruct the selected band from 1 Hz to 5 Hz. |
| F22 | Coiflet C3 | |
| F23 | Morlet (CWT) | Apply the inverse WT of Morlet to reconstruct the selected band from 1 Hz to 5 Hz. |
RRIV assessment range of normal cardiac autonomic function in each age group based on ECG [38]_
| Age [y] | 20 ∼ 29 | 30 ∼ 39 | 40 ∼ 49 | 50 ∼ 59 | 60 ∼ 69 |
|---|---|---|---|---|---|
| Rest [ms] | 12 ∼ 46 | 6 ∼ 32 | 6 ∼ 36 | 5 ∼ 23 | 7 ∼ 19 |
| Breath [ms] | 19 ∼ 62 | 9 ∼ 54 | 14 ∼ 48 | 11 ∼ 59 | 8 ∼ 28 |
Average absolute errors between the RRIV/ECG SDNN/ECG, NN50 at 1000 Hz and the SSIV/PPG SDNN/PPG NN50 at different sampling rates_
| Filter/Sample rates | Phase | Parameter | 1000 [Hz] | 500 [Hz] | 250 [Hz] | 200 [Hz] | 125 [Hz] | 100 [Hz] | 50 [Hz] | 40 [Hz] | 25 [Hz] | 20 [Hz] |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| F01 | R | SSIV [%] | 0.6 | 0.6 | 1.2 | 1.3 | 1.3 | 1.4 | 1.8 | 2.2 | 3.4 | 4.4 |
| F11 | R | SSIV [%] | 1.4 | 1.5 | 2.1 | 2.2 | 2.3 | 2.3 | 2.8 | 3 | 4.1 | 7.3 |
| F23 | R | SSIV [%] | 2 | 2.2 | 3 | 2.5 | 2.9 | 2.8 | 3.2 | 4.7 | 4.6 | 5.8 |
| F01 | B | SSIV [%] | 0.9 | 1.1 | 1.2 | 1.1 | 1.2 | 1.2 | 1.8 | 2 | 2.9 | 3.8 |
| F11 | B | SSIV [%] | 2.5 | 2.3 | 2.3 | 2.5 | 2.6 | 2.7 | 3.1 | 3.3 | 4.2 | 14.4 |
| F23 | B | SSIV [%] | 2.6 | 2.7 | 2.9 | 2.5 | 2.9 | 3 | 3.4 | 5 | 4.3 | 5.6 |
| F01 | R | SDNN [ms] | 0.6 | 0.6 | 0.6 | 0.6 | 0.8 | 0.9 | 2.1 | 3.1 | 6.5 | 9.5 |
| F11 | R | SDNN [ms] | 1.3 | 1.4 | 1.5 | 1.6 | 1.7 | 1.9 | 3.2 | 4 | 7.3 | 12.4 |
| F23 | R | SDNN [ms] | 2.7 | 2.6 | 2.8 | 2.1 | 2.7 | 2.3 | 3.4 | 6.9 | 7.5 | 10.8 |
| F01 | B | SDNN [ms] | 1.2 | 1.2 | 1.3 | 1.3 | 1.3 | 1.4 | 2.2 | 2.7 | 5 | 7.2 |
| F11 | B | SDNN [ms] | 2.2 | 2.2 | 2.2 | 2.4 | 2.4 | 2.6 | 3.3 | 3.9 | 6.3 | 15.3 |
| F23 | B | SDNN [ms] | 2.7 | 2.7 | 2.9 | 2.4 | 2.7 | 2.6 | 3.3 | 6.1 | 5.6 | 8.1 |
| F01 | R | NN50 [%] | 0.8 | 0.9 | 0.8 | 1 | 1 | 1.3 | 1.7 | 1.7 | 3.6 | 3.1 |
| F11 | R | NN50 [%] | 1.7 | 1.6 | 1.8 | 1.6 | 1.9 | 2 | 3.5 | 2.2 | 5.1 | 4.3 |
| F23 | R | NN50 [%] | 1.5 | 1.5 | 1.5 | 1.6 | 1.6 | 1.8 | 2.2 | 2.1 | 4.1 | 3.3 |
| F01 | B | NN50 [%] | 0.8 | 0.8 | 0.8 | 0.9 | 0.9 | 1.1 | 2.2 | 1.8 | 3.6 | 3.1 |
| F11 | B | NN50 [%] | 2.4 | 2.4 | 2.8 | 2.3 | 2.7 | 2.3 | 4.9 | 2.8 | 5.9 | 5.3 |
| F23 | B | NN50 [%] | 1.6 | 1.6 | 1.7 | 1.6 | 1.7 | 1.9 | 3.1 | 2.5 | 4.8 | 4.1 |