TABLE 1.

Characteristic points of the PPG signal and its derivatives.

Waveform	Fiducial points	Description
PPG	O	Onset
	S	Systolic peak
	N	Dicrotic notch
	D	Diastolic peak
VPG	w	Global maxima in the systolic phase
	x	Local minima in the systolic phase
	y	Global minima in the systolic phase
	z	First local maxima in the diastolic phase
APG	a	Early systolic positive peak
	b	Early systolic negative peak
	c	Late systolic re-increasing wave
	d	Late systolic re-decreasing wave
	e	Early diastolic positive wave
	f	Diastolic negative wave