I really must learn to quote the full context of a reply. OP said: > just due to lower oxygen levels in your blood So my comment is in response to that. PS.

I really must learn to quote the full context of a reply. OP said: > just due to lower oxygen levels in your blood So my comment is in response to that. PS. The downvote button isn't a disagree button. (Although how you can disagree with the fact that Apple watches have a blood oxygen sensor I don't know).