Table 1.
Definitions, units, description of variables used in the analyses.
| Biosignal (Units) | Variable | Description |
|---|---|---|
| SBP (mmHg), HR (bpm), TSI (%) | Baseline | Mean value 30–60 s before standing |
| SBP (mmHg), TSI (%) | Nadir | Largest trough after standing (in first 30 s) |
| SBP (mmHg) | Overshoot | First peak found between SBP nadir time +5 s and 60 s after standing |
| TSI (%) | Overshoot | First peak found between TSI nadir time +2 s and 60 s after standing |
| SBP (mmHg), TSI (%) | Steady-state | Mean value 60–120 s after standing |
| SBP (mmHg), TSI (%) | Delta | Nadir—Baseline |
| SBP (mmHg), TSI (%) | Nadir to overshoot | Overshoot—Nadir |
| SBP (mmHg), TSI (%) | Steady-state change | Steady-state—Baseline |
| SBP (mmHg/s), TSI (%/s) | Maximum recovery rate | Largest difference between consecutive points divided by the time between points (within the time interval between the nadir and overshoot) |
| TSI/SBP (%/mmHg) | Normalized TSI recovery rate | Maximum TSI recovery rate/maximum SBP recovery rate |
HR: heart rate (units: beats per minute (bpm)), SBP: systolic blood pressure (units: mmHg); TSI: tissue saturation index (units: %).