Oxygen - ANO question
 

I'm trying to find the regulations for oxygen requirements on GA flights but the CAA search engine is throwing up too many returns for the various terms I've tried.

I know the regs for flying crew to be on oxygen for any sector greater than 30 mins above FL100 and below FL130 and oxygen continuously above that. What I'm trying to find are the criteria for oxy systems applicable up to & inc FL200.

The a/c I want to fly is a TB21 with a time expired oxy system on the bottle which the manufacturer no longer makes (Puritan Bennett). The cost of recertification of a new bottle is prohibitive so I want to know what options are available for portable oxygen and the rules for cannulae vs masks, certification if any of portable bottles etc.

Does anyone have any pointers or experience with portable systems in GA a/c between 10 and 20 thousand feet?

Check out www.peter2000.co.uk for a detailed description of the selection, purchasing and use of oxygen.

HWD - exactly what I was looking for, first hand experience and no jargon explanation and relation between FAA/CAA (I travel to the US regularly so it makes sense to buy the kit at half price there!).

Thanks for the link.

Interestingly there are no rules on what kit is actually used just that you must use O2 at 10,000ft.

I use the mountain high O2D2 unit which will give 36 man hours from a 2.2l cylinder more than twice the nearest competitor.

You should buy the kit with a Euro cylinder not a US DOT spec and with a DIN477-9 fitting not the US CGA540 thread. This will make it easier to fill in Europe.

The MH kit comes with both cannulla and face mask. The rule of thumb is cannulla are fine to 18,000ft and then a full face is required.

PM me for details.

I have not yet found a reference for cannulas being not approved above 18k feet (obviously this is FAA - the CAA never got this far into general aviation) but it is a widely quoted figure.

But they certainly work. I was at 95% saturation, 75 heart rate, at FL190 the other day, using straight cannulas with demand regs, for an hour or two. The bottom line is the blood saturation - if you are getting above 90% than whatever you are doing is obviously OK. If you could get 95% by sticking the cannula up your back orifice, that would be fine too ;)

A TB21 has an official ceiling of 25k feet and I am certain cannulas would work there just fine. One will be using a LOT of oxygen up there, but a mask will use a LOT of oxygen anyway, a) because it works inefficiently and b) because one can't use it (supposedly) with a demand regulator.

EDDNR - there was some discussion of this on the socata.org users group. You aren't the only one stuck with the fitted system. There may be other bottle options, perhaps even with a kevlar bottle which I believe was fitted to later TB21s. But to be honest most fitted-oxygen owners find refilling so difficult around Europe that they use portable kits anyway :)

I was off the understanding that the FAA required full face mask above 18k and I did actually have one of your favorite references for this IO but just not on my laptop! The CAA have made no recommendations other than the requirement to use O2.

However you are right, there is no reason why a cannula won't work well above this level, it depends on the individual. I have no idea if they will work at 25k, I have not been that high un-pressurised but await the results of your self experiments with eager anticipation!

But the rules are supposed to be aimed at the mean average....

Just curious how the stipulation for a mask above 18k would be regulated (no pun intended) given that portable equipment is generally exempted from all regs.

(In the UK, i.e. G-reg aircraft, where if the ANO prescribes carriage/usage of some portable item (in this case o2) the kit has to be type approved, and that was the mistake in the initial o2 legislation (because the CAA o2 regs were brought in without anybody realising that no type approved o2 kits existed....) which was subsequently repealed by an AIC.)

It's an interesting scenario versus insurance. If you file a flight plan for FL200 but don't carry a mask... But then under the FAA regs (N-reg now) you always have to carry at least one mask, in case somebody gets a blocked nose.

I know of cases where US pilots wrote stories about flights on which they climbed to say 14k feet, on a flight plan stating as much, without carrying o2, and then when somebody pointed out the obvious, they edited them rather fast ;)

Some usefull links:

http://www.aircraftspruce.com/menus/...ensystems.html

This one's good for system comparison:

http://www.airportshoppe.com/aviatio.../compared.html

We have a portable bottle, I turn it on when climbing above 8K on the way to FL180. Keeps the saturation levels up....:}
We use the Oxysaver cannula.

Does anyone know what the regs are on N-reg in Europe. As I recall, FAA regs require that the flight crew require o2 if between 12,500' and 14, 000' for >30 mins. whereas it was pointed out earlier in the thread the CAA require the flight crew require o2 from FL100 to FL130 for >30 mins. Therefore, you could file at FL120 (provided it is not above alt 12,500') in an N-Reg operating on an FAA licence without o2 but you could not file above FL100 on a JAA license without the PIC having o2 (assuming of course you were up there for 30 mins+). Is that right or have I got it all wrong (as usual!:})

You have it right.

N-reg are governed by FAA rules, worldwide.

G-reg are governed by CAA rules, worldwide.

In this case, the CAA requirements are specific to G-reg. I don't recall how the ANO defines this but IIRC you will find there is a group reference to some annex which, if you read it, is basically "G-reg".

Other requirements, e.g. equipment carriage like ADF, DME, Mode S, is applicable to any reg flying in UK airspace.

:eek: I got something right!!

Thanks for the confirmation IO540 - I wasn't aware of the CAA FL100 rule before seeing this thread!

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.

"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."

You are absolutely right, I used to frequently work with a (recently retired) consultant anaesthetist who was a keen pilot and very much up on high altitude physiology.
His advice was that nasal cannulae are fine at low(ish) levels but that the rebreathing bag that you get with the mask makes a big difference to CO2 levels and some improvement in O2 sats as you climb higher.

Personally, I just stick with masks (and carry a sats probe). The masks go on at around FL100 and stay on until I pass back down through FL100 again. I say "around" as density altitude can make 8000' feel like 12500' so adjust as required.

Advantage of masks - inbuilt rebreathing bag helps with CO2 and O2 levels when you are higher.

Downside of masks - sweaty face and poor seal with mic poked inside. Using the mask with inbuilt mike makes u sound like a constipated dalek in an echoey room.

Advantage of cannulae - won't spoil your makeup. Less burdensome.

Downside on cannulae - better make sure you don't share them if you reuse them!! YUK.

Chacun a son gout as the French rugby team might say (amongst other things!:)),

SB

SB do you use the factory fitted in oxygen ? or use portable one ?

I think most people that have fitted oxygen tend to use that, but sometimes they can't because if say a plane is moved from N to G the CAA certification can be prohibitive so they use a portable kit.

Re masks, they also use a lot more o2 than a cannula - of the order of 2x to 5x more. That is a serious problem, but luckily there is rarely a need in N Euro weather to be above FL200 for more than say an hour at a time.

Reservoir bag
 

The purpose of the bag used with the mask is not rebreathing CO2.
It is a reservoir for pure oxygen, and if the mask is working as designed, no exhaled gases should enter the bag.
Inspiratory flow rates exceed 10 l/minute and comprise about 1/3 of respiratory cycle, the reservoir "traps" the flowing oxygen during exhalation and makes it available for the next inhalation. Otherwise, 2/3rds of flowing oxygen is simply lost into the cabin. To inhale (mostly) pure oxygen from a mask without a reservoir bag would require flow rates that would deplete most systems in short order.

Indeed, which is why the oxysaver cannula has a reservoir.

I don't think one needs to re-inhale any exhaled air for the human system to function.

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)

My question is 'What drives the certification limit of 18000 feet for use of cannula in FAA land?'

More specifically, is the only requirement that o2 saturation remains above say 90% or are there other physiological issues to be considered in the space between 18k and 25k

Forum answers would be good, but it would be even better for a reference to some authoritative on line text that explains this.

The only reference I ever saw on this subject was an FAA requirement specifying a minimum o2 flow rate.

I haven't got a clue where the 18k cannula "limit" comes from. It might possibly apply to some installed o2 systems. I don't see portable kits being legislated in this way.

Here is some text. Here is some more :)

This part of FAR 23.1447
(c) If certification for operation above 18,000 feet (MSL) is requested, each oxygen dispensing unit must cover the nose and mouth of the user.
Ian

Nasal cannulae will always have outside air entrained into the inspiratory stream, diluting the oxygen. A very high flow rate would help this, but >4-5 l/m becomes very uncomfortable and uses oxygen supply quickly. Nasal reservoir bags work to some degree, but without a gas tight fit in the nare, it is not as efficient as a well fitted mask with bag. A beard dramatically reduces the efficiency of a mask for the same reason.
4 liters O2 by nasal cannula at 18,000' will result in a sea level equivalent of approx 25% oxygen, 2 liters, about 18%. The 18,000' is arbitrary, but coincides with FAA Class A airspace and is a reasonable estimate of where a cannula is unable to reasonably provide the normal 20% (sea level equivalent) O2.
An on-demand system with cannula, such as Mountain High, is superior at higher altitudes. Flow occurs only on inspiration, reducing drying, usage, also, the oxygen delivered comes early in the I/E cycle, and most of it reaches gas exchanging portions of the lung.
P

The assembled wisdom seems to be that IO's comment that as long as your O2 saturation is ok (say above 90) that is all that is necessary to be safe - even if you are achieving this using a cannula (or a pipe 'up your back orifice') or some other method. (obviously not legal in FAA land)