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