Perhaps I am more sensitive than others, though I really I have not heard people commenting on this but...

I am 49, and in very good health (workout 3 times a week w/cardio as well) though over a few trips this year - specifically on two Delta flights - I noted periods of time where I felt like there was insufficient oxygen in the air. I tend to breathe somewhat shallow anyway, but I found that I consciously needed to do some rapid breaths just to "catch my breath". This did not occur for an extended period of time, and all was well for likely 95% of the flight.

Has anyone else noted similar issues?

THANKS