IO540-
Replied with respect to:
"I was under the impression that the reason cannula were 'required above 18000 feet was an issue with excessively low CO2 if you didn't re-breath some of the exhaled air."
"Advantage of masks - inbuilt rebreathing bag helps with CO2 and O2 levels when you are higher."
Just trying to clear up the "reservoir" vs "rebreathing" concept.
P (M.D. anesthesiologist)