Detection of Troughs and Notches in a PPG Signal

I'm working a project which tries to determine Blood Pressure from PPG signals.I'm trying to extract the features as shown below...

I'm having problem in finding the troughs and dicrotic notch for each cycle and also the cycle start and end duration. Are there any manual method methods which can be applied ( I'm a newbie to signal processing )thereby which we can extract the trough and notch location in each cycle ?

• i hadn't seen this question before. are you confident that the notch will always be there with a slight bump to the right of the notch? what if the derivative never quite reaches zero? then where to you want to mark the notch time to calculate the Peak to Notch Time? – robert bristow-johnson Oct 25 '18 at 18:41

$y[n] = x[n] - x[n-1]$
$y[n] = x[n] - x[n-2]$