I don't know exactly when it started, but it's since I last saw my Dr in March. I will, of course, bring it up when I see him next week, but I'm wondering if anyone else goes through this. By excessive, I mean 2-3 yawns a minute. It also seems to happen only when I am doing pursed lip breathing, even though my 02 is over 95. Yes, it stops when I put my cannula on and get my 02 from a machine.