It was an older passenger about 5 seats across from me in Premium Economy. He looked to be having some kind of illness, age, or pre existing condition difficulty, not anything I could deal with (I know trauma care reasonably well from SF medics and working in a hospital, and some dive medicine stuff, but do t have any certification beyond first responder stuff), so I didn't do anything.

I was fairly surprised there were no medical people on the flight. I did notice some of the flight crew checking in on him periodically, and he seemed to de-plane normally, wasn't met with an ambulance, etc.