I have a few thoughts and a question or two about CPAP and aircraft.
Does anyone here use a bipap or a vpap?

I had my annual sleep study a few weeks ago. I had been using CPAP for about 18 months. The good news is that my AHI index was halved from mid 90's per hour to mid 40's per hour. I have lost about 45 lbs during that period.
Despite my AHI index going down, the pressure setting had to be increased. Prior setting of pressure I was using did not eliminate all obstructive events, but the doctor had recommended that pressure since I was new to CPAP and the pressure setting of 16cm was high enough that a new user might not be able to tolerate the pressure. Now my pressure setting is 20 cm of water column. I was unable to tolerate it during exhalation. So within three weeks of the last sleep study, I was sent in for another titration using a bibap.
I was curious about the significance of the pressure. What does a pressure of 20 cm of water column in access of the atmospheric pressure mean?

I have two practical answers.

1. My brother, who was a chief engineer on oil tankers told me, they used a pressure of 20 cm in piping for air supply, on the ships to keep the pipes clean, i.e. to keep corrosion from building up on the inside walls of the pipes.
   
2. For Flyertalk, a better analogy would be in terms of aircraft. I did a simple calculation and the result was quite impressive. I had an inkling the pressure would be within an order of magnitude of that required to lift an aircraft off the ground. If the pressure of 20 cm of water column (2% of the atmospheric pressure) was uniformly applied to the underside of the wings of a Boeing 747-400 ER, i.e., the pressure difference between the upper and the lower surface of the wings was 20 cm of water column, it would be sufficient to lift an aircraft the size of a Boeing 747-400 ER that weighed 26% of the maximum take off weight of the aircraft. Quite a daunting thought.
3. Even an empty Boeing 747-400 ER weigh more than the weight that could could be lifted by a pressure of 20 cm of water column. The pressure is enough to lift a weight more than twice the number of passengers and their luggage of a fully loaded Boeing 747-400-ER

I was using a Respirnoics CPAP, but now I am using a Resmed Vpap Auto25, that the vendor has loaned me pending results of the second titration.