Table 1.
HRV parameters used in this trial.
| Variable | Units | Description |
|---|---|---|
| Time-domain parameters |
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| SDNN | msec | the standard deviation of all NN intervals, an estimate of overall variability |
| rMSSD | msec | the square root of the mean of the squared differences between adjacent NN intervals, an estimate of the short-term components of variability |
| pNN50 | % | the proportion derived by dividing NN50 (the number of interval differences of successive normal-to-normal intervals greater than 50 ms) count by the total number of normal-to-normal intervals |
|
| ||
| Frequency- domain parameters |
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|
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| TP | msec2 | total power, frequency range <0.4 Hz |
| HF | msec2 | power in the high-frequency range (0.15–0.4 Hz), considered to be mediated mainly by vagal activity |
| LF | msec2 | power in the low-frequency range (0.04–0.15 Hz), suggested to be mediated by both sympathetic and parasympathetic activities |
| LF/HF | Ratio | an indicator of the balance of the sympathetic and parasympathetic systems |