How to get PainCausingVolume to affect desired progress bar?

I am a student who is very new to Unreal. For a project I have decided to make a game mechanic that is based around oxygen depletion in water, and health damage as a result. I have both Health and Oxygen Bars ready, and I am using a PainCausingVolume within my waterbody. My problem right now is that I can’t figure out how to connect the damage to the Oxygen bar. This is what I have already >



Hello. I think I need a little more context to understand the issue. Do you want to take damage once your oxygen is completely depleted?

From what I’m understanding, you have your separate bars and you will need to make a function that recognizes when oxygen is at 0 and start to damage you from there, probably using an interval through a timer.