On Wednesday, October 2, 2019 at 8:52:12 AM UTC-4, Eric Greenwell wrote:
Tango Eight wrote on 10/1/2019 3:47 PM:
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.

Does it matter which face mask is used? The one that came with the Mountain High
EDS units I have is very basic, with a very small cavity, so I think it would not
increase the amount of CO2 you breathe. I'm assuming it's the CO2 content that's
the important factor - is that true?

They do have a mask with a rebreather bag, so perhaps that's the one you should use?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

I've had good luck with (decent quality, form fitting) re-breather mask systems on constant flow. I don't breathe well on the EDS / cannula system at high altitude. My breathing tends to get sort of "lazy" by 16 - 18K and I find I have to use one of the higher delivery modes to maintain high saturation. Re-breather mask fixes that and CO2 seems the most likely reason.

I have not tried the MH masks. I've seen one (blue rubber, apparently decent quality) that looked like it might be worth a try.

Minor rant: *Any* hard plastic mask (Aerox & Mountain High are both guilty of selling such) that looks like an emergency medical single use mask has no place in the cockpit... you would honestly just be better off sucking on the end of the hose. I've seen these things literally fall apart before first use as someone unwrapped the sealed plastic bag it was shipped in. It's completely unconscionable that anyone would sell you something this crummy as part of a life support system.

While I'm at it, I'd encourage folks to take a skeptical look at their oxygen delivery gear. The old style Aerox needle valve/rotameter is notorious for breaking under normal handling, as are the old green plastic barbed fittings. Expect anything plastic or rubber to become more fragile when cold soaked, don't expect that these O2 system manufacturers have done any durability or cold soak testing of their products: they obviously haven't. Again... I find it completely unconscionable that anyone sells such rubbish for life support purposes, but it's out there, beware.


T8