Hi Pedro,
I am not sure if you are looking for an IC to create a new product or you are working on a one-off unit. If this last is the case, you can get a very cheap pulsioximeter that has internal serial data that you can read easily. I was working in a (for fun) project and getting the data out was quite easy, you can then do whatever you need with it.
I haven't done an article yet, but it is very similar to this:
http://www.thinkering.de/cms/?p=864You don't need to get a pulse oximeter with serial output, the data is available inside anyway, in a pulse oximeter like this one (for example):
https://www.amazon.com/Innovo-Fingertip-Oximeter-Plethysmograph-Perfusion/dp/B01NATPX6I/ref=sr_1_6_a_it?ie=UTF8&qid=1526312381&sr=8-6&keywords=pulse+oximeterRegards,
rosetta