TABLE 3.

Parameters chosen for statistical analysis of HRV SA (spectral analysis of heart rate variability).

Parameter	Area of analysis	Significance
SDNN	Time domain	Standard deviation of NN intervals
pNN50	Time domain	Percentage of successive RR intervals that differ by more than 50 ms
LF/HF	Frequency domain	Ratio of low frequency-to-high frequency power
ApEn	Non-linear domain	Approximate entropy (which measures the regularity and complexity of a time series)
DFA-α1	Non-linear domain	De-trended fluctuation analysis (which describes short-term fluctuations)