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Table 1 Linear and Non-Linear Heart Rate Variability measurements selected in the current study.

From: Short term Heart Rate Variability to predict blood pressure drops due to standing: a pilot study

  Measure UNIT Description
Time-Domain
1 MeanRR ms Mean of RR intervals
2 STDNN ms Standard deviation of RR (NN) intervals
3 RMSSD ms Square root of the mean squared differences between successive RR intervals
4 NN50 count Number of successive RR interval pairs that differ by more than 50 m
5 pNN50 % NN50 divided by the total number of RR intervals
6 HRVtri   Integral of the RR interval histogram divided by the height of the histogram
7 TINN Ms Baseline width of the RR interval histogram
Frequency-Domain
8 LF ms2 Absolute powers of LF band, calculated with AR
9 HF ms2 Absolute powers of HF band, calculated with AR
10 LF/HF   Ratio between LF and HF band powers
Nonlinear-Domain
11 SD1 ms Standard deviation of the Poincar´e plot perpendicular to the line of identity
12 SD2 ms Standard deviation of the Poincar´e plot along the line of identity
13 ApEn   Approximate entropy
14 SampEn   Sample entropy
15 D2   Correlation Dimension
16 DFA1   Short-term fluctuation slope in Detrended Fluctuation Analysis
17 DFA2   Long-term fluctuation slope in Detrended Fluctuation Analysis
18 RPLmean beats Recurrent Plot (RP) mean line length
19 RPLmax beats RP maximum line length
20 RPREC % RP Recurrence Rate
21 RPDET % RP Determinism
22 RPShan   RP Shannon Entropy