Converting antiquated charts with both temp. and pulse. lines

Hi! I’m new here so please be gentle! I’m working on converting charts of patient fevers from 1910 - 1913, from Wellcome Collections (see the image below as I could not attach in a first-time post). I used ImageJ previously to extract only temperature data, through figure calibration to define axes → multi-point tool → exporting as a .csv of time and temp data to → turn into a format in R for Rethomics and circadian analyses.

This time, I am wanting to record the points for pulse too, so that I can look at corresponding changes in rhythmic features. The work-around I am considering is to always add points sequentially, and write code in R that will recognise all odd-numbered points as temp and even as pulse. at some intervals there is a recorded temp but not pulse, and vice versa. In this case I was planning to add a point at the proper top of the selection limit and then write code to turn any of these points into NA for missing.

Essentially, hoping you can tell me if there is a way through ImageJ to record both at a time, from the same image, as distinct columns to prevent further hassle down the line!
Thank you!

Image attached for reference! In this case there are no times when temp is recorded without pulse or vice versa, but in other charts this does happen…

Have you considered an R based plot digitizer?
Especially since you want to get the data into R anyways, using a more specialized tool may make your life easier.

Or {digitize}

Hi Thanks!
I had a look at both of those and neither seems to mention how to specify a Z axis?