With all due respect, if you're not going to trust me, then why am I even bothering to be here. I don't have a full physics lab to do the measurements you ask for. My CPAP worked correctly for several months. Now the pressure is lower. How do I know it's lower? Because I've been using it for several...

Sorry to dredge up an old post, but I'm having the same problem. My CPAP was working fine for a few months. Then I took out the big blue reusable filter, rinsed it, let it sit overnight, and put it back in. Now my air pressure is extremely low. You asked the OP "how do you know the pressure is low"....