Table II.
Summary of methods and results of studies that have employed ECG and finger PPG (RMSE is root-mean-squared error; LOA is limits-of-agreement).
| REF # | Waveform Detection | Calibration (Model/BP Perturbation/Period) |
Evaluation (# of Subjects/Interventions) |
Results | |||||
|---|---|---|---|---|---|---|---|---|---|
| Correlation (r Value or RMSE [mmHg]) |
Calibration Error (Various Metrics) Mean (SD) |
||||||||
| SP | MP | DP | SP | MP | DP | ||||
| [169] | R→Minimum | Linear in PTT Change Surgery/5-min |
20/Surgery | - | - | - | RMSE 3.7 (1.9) |
- | - |
| [94] | R→Threshold | Log & Quadratic in PTT−1 Population Parameter/One-Time |
85/Natural Variability (Weeks) | - | - | - | 0.6 (9.8) | - | 0.9 (5.6) |
| [142] | R→Minimum | - | 10 Normal/LBNP - Hand Grip | 0.73–0.92 | - | - | - | - | - |
| [98] | R→Minimum | - | 12/Hemodynamic Drugs | 0.62 | 0.28 | 0.14 | - | - | - |
| [179] | R→Max Tangent | - | 18/Exercise | RMSE 3.6 |
- | - | - | - | - |
| [170] | R→Maximum | Linear in PTT Cuff Deflation/One-Time |
11/Exercise | - | - | - | - | 4.5 (6.6) | - |
| [148] | Max Deriv→Max Deriv | Linear in PTT Exercise/One-Time |
14/Exercise | 0.90 | - | 0.34 | First: 0.0 (5.3) Repeat: 1.4 (10.2) |
- | First: 0.0 (2.9) Repeat: 2.1 (7.3) |
| [92] | R→Minimum | - | 22/ICU | 0.43 | 0.42 | 0.37 | - | - | - |
| [172] | R→Max Deriv | Linear in PTT & HR ICU/60-min |
25/ICU | - | - | - | −0.4 (7.8) | - | −0.1 (5.0) |
| [180] | SP: R→Max Deriv DP: Diastole Duration |
Linear in PTT Step Climbing/One-Time |
5/Step Climbing | 0.74–0.89 | - | 0.44–0.74 | Absolute % 9–14 |
- | Absolute % 4–11 |
| [208] | R→Max 2nd Deriv | - | 18/Exercise | RMSE 4.1 |
- | RMSE 2.3 |
- | - | - |
| [174] | R→Minimum | Linear in PTT−1 Exercise/One-Time |
33/Exercise | 0.79 | - | 0.77 | LOA −13/+13 (ST) −17/+13 (MT) |
- | LOA -11/+11 (ST) -12/+11 (MT) |
| [149] | R→Minimum | - | 10/ICU | - | 0.45 | - | - | - | - |
| R→10% Height | - | 0.39 | - | - | - | - | |||
| R→Max Deriv | - | 0.27 | - | - | - | - | |||
| R→90% Height | - | 0.33 | - | - | - | - | |||
| R→Maximum | - | 0.32 | - | - | - | - | |||
| [145] | R→Max Deriv | Nonlinear in PTT−1 Population Parameters/One-Time |
63/Exercise | 0.75–0.99 | - | - | LOA −20/+20 |
- | - |
| [143] | R→Minimum | Linear in PTT ICU/60-min |
25/ICU | 0.09 | - | −0.02 | 3.1 (6.3) | - | 1.9 (3.9) |
| R→50% Height | 0.32 | - | 0.22 | ||||||
| R→Maximum | 0.71 | - | 0.69 | ||||||
| [185] | R→Maximum | Linear in PTT Change Population Parameter/6-min |
15/Natural Variability (Minutes) | - | - | - | 1.0 (2.4) | - | - |
| R→Maximum | Log & Quadratic in PTT−1 Population Parameter/8-min |
- | - | - | 1.1 (9.7) | - | - | ||
| [150] | R→Maximum | Linear in PTT Exercise/One-Time |
5/Exercise | - | - | - | 0.0 (12.0) | - | - |
| R→Max 2nd Deriv | 1.8 (14.0) | ||||||||
| R→Minimum | 5.2 (40.4) | ||||||||
| [182] | R→50% Height | Linear in PTT & HR Natural Variability (Hours)/~110 min |
10/Natural Variability (Hours) | - | - | - | RMSE 1.7 |
- | RMSE 1.0 |
| [183] | R→Maximum | Linear in PTT−1 & PTT Variations Posture Change/One-Time |
30/Posture Holding (Sitting) | - | - | - | −0.2 (2.4) | - | −0.5 (3.9) |
| [184] | R→Max Deriv | Linear or Nonlinear in PTT−1 Valsalva/One-Time |
4/Valsalva | - | - | - | RMSE 12.6–15.4 |
- | - |
| [209] | R→Maximum | - | 25/Step Climbing | 0.90 (.03) | - | 0.82 (.04) | - | - | - |
| [187] | R→Max Deriv | - | 20/Exercise | 0.93–0.99 | - | 0.10–0.89 | |||