Research Article
Extraction of Heart Rate Variability from Smartphone Photoplethysmograms
Table 1
Commonly used HRV parameters.
| Parameter | Description |
| Time-domain | | AVNN | Average of all NN intervals | CV | Coefficient of variation of NN intervals. The ratio of the standard deviation to the mean. | SDNN | Standard deviation of all NN intervals. | SDANN | Standard deviation of the averages of NN intervals in all 5-minute segments of the entire recording. | RMSSD | Root mean square of successive differences between adjacent NN intervals. | SDSD | Standard deviation of successive differences between adjacent NN intervals. | NN50 | Number of pairs of successive NN intervals that differ by more than 50 minutes. | pNN50 | Proportion of NN50 divided by total number of NN intervals. | Frequency-domain (5 minutes) | | TP | Total power (≤0.4 Hz) | VLF | Very low frequency power (≤0.04 Hz) | LF | Low frequency power (0.04–0.15 Hz) | HF | High frequency power (0.15–0.4 Hz) | LF/HF | Ratio of LF to HF | nLF | Normalized LF = LF/(TP − VLF) | nHF | Normalized HF = HF/(TP − VLF) | Nonlinear Analysis | | SD1 | Standard deviation of short diagonal axis in Poincaré plot | SD2 | Standard deviation of long diagonal axis in Poincaré plot |
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