Table 5 BPV parameters used in the selected papers
BPV parameters | Definition | Physiological Interpretation |
|---|---|---|
Time-domain measure | ||
Standard deviation of SBP or DBP \(\sqrt{\frac{1}{n-1}\sum_{i=1}^{n}{({X}_{i}-\overline{X })}^{2}}\) | Measures the absolute magnitude of overall variability of BP | |
 Coefficient of variation, CV [51] | Dividing the SD by the average SBP or DBP level \(\frac{SD}{\overline{X} }\) | Relative measure of variability that normalized the standard deviation of BP against mean of BP |
 Residual standard deviation, RSD [20] | Square root of the total squared differences of data points from a linear regression of SBP or DBP values against time \(\sqrt{\frac{1}{n-2}\sum_{i=1}^{n}{({X}_{i}-\widehat{{X}_{i}})}^{2}}\) | Quantifies the extent of variability in blood pressure over time by excluding the impact of the possible drift in mean BP |
 Average real variability, ARV [20] | Average of absolute difference between adjacent SBP or DBP values \(\frac{1}{n-2}\bullet \sum_{i=1}^{n}|{X}_{i+1}-{X}_{i}|\) | Quantifies the BP measurements over time by considering the sequence of measurements |
 Variation independent of mean, VIM [20] | Proportional to SD/meanx, with x derived from curve fitting \(k\bullet SD/{\overline{X} }^{m}\) | Quantifies BP fluctuations that occur independently of mean BP level |
 Time Rate, TR [48] | First derivative of SBP or DBP values against time | Quantifies the degree and rate of BP fluctuation, often used to assess the speed or dynamics of BP fluctuations |
Frequency-domain measure | ||
 Spectral power density at frequency of 0.1Hz (in absolute, mmHg2/Hz and relative units) [40, 41] | – | Reflects the 10 s oscillation related to BP and vasomotor tone regulation, which refers to Mayer wave |
Non-linear measure | ||
 Multiscale entropy [51] | Entropy or recurrence in physiologic series over different temporal or spatial scales | Captures the irregularity of BPV fluctuations across multiple time scales |