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. 2023 Apr 19;23(8):4111. doi: 10.3390/s23084111

Table 1.

Chosen amplitude-based features.

	Feature	Feature Description
1	Systolic blood pressure (SBP)	maximum value of the extracted pulse waveform [5]
2	Diastolic blood pressure (DBP)	minimum value of the extracted pulse waveform [5]
3	Pulse Pressure (PP)	$P P = S B P - D B P$ [5]
4	Dicrotic Notch	trough between SBP and secondary upstroke
		due to pressure wave reflection [5]
5	Pressure at time of reflection (PR)	value at the beginning of the backward
		reflection of arterial pressure
		inflection point PR occurs after the SBP point
		in young subjects and before in old subjects
		due to increased arterial stiffness [10], see Figure 8
		different types of PR occurrences are visualized in Figure 9
6	Augmented pressure (AP)	describes the BP increase due to early
		arrival of the reflected wave, as visualized in Figure 8.
		$A P = (S B P - P R) \cdot A I_{x}$
		$A I_{x} = 1$ marks arrival before systole
		and $A I_{x} = - 1$ after.
		AP is thus positive for older subjects and
		negative for younger ones and
		indicates arterial stiffness due to age [5,44].
		Figure 9 shows four different types of PR
		and their resulting AP that increases with age
		as the reflection of the pressure wave occurs
		increasingly earlier (type B and A) before it
		eventually vanishes (type D).