On Tuesday, October 1, 2019 at 3:44:11 PM UTC-4, RR wrote:
On Tuesday, October 1, 2019 at 6:45:06 AM UTC-4, John McLaughlin wrote:
Does everyone stick to the 18k limit for the cannula and 25k for the mask,

or are these limits considered advisory only?

The legalitys are not so clear, but practically it is about remembering to breathe only with your nose with the cannula. Something I felt i could do, and so far have remembered. It is much easier to hydrate and communicate with the cannula. Just don't forget...

RR

There are several reasons any given person might not breathe well on a cannula at high altitude, mouth breathing is only one. Here's another: It is really easy to hyperventilate on a cannula at 20+K. Trivially easy in fact.. If you must use a cannula above 18K (which I recommend against), do not skimp on the O2, don't use a dumb ass "oxy-miser" anything above 18K. Turn up the flow. If in doubt, turn it up some more. Not a bad idea to monitor heart rate as well as O2 saturation. Tachycardia is reliable indicator of breathing problems, and it will catch hyperventilation (O2 saturation will not, key word alkalosis).

It's much easier to breathe well (and reliably) on a mask, provided the mask fits and seals acceptably well. If you aren't breathing well, hydration and communication are going to cease to matter.

T8