Flying with oxygen : recommended also for 20.000 plus feet?

[jaylw314]

Just one small point, the typical common oxygen conserving nasal cannula are only useful up to about FL150, at which point they become oxygen-wasting like normal nasal cannula.  That might be why your instructor specifically mentioned that altitude, even if it's not a very important reason

[Schllc]

3 hours ago, jaylw314 said:

Just one small point, the typical common oxygen conserving nasal cannula are only useful up to about FL150, at which point they become oxygen-wasting like normal nasal cannula.  That might be why your instructor specifically mentioned that altitude, even if it's not a very important reason

That seems incongruent, because if the oxygen is flowing when you are not inhaling it is obviously wasted,  but when inhaling distribution is the same as constant flow. 
I took a trip a few years ago from Florida to Oregon and back. I flew with a friend and very little of that trip was below 19k. We used conservers the entire time and never had any issues with saturation. 
What does oxygen wasting mean?  
Are you saying conservers deliver less o2 above 15k?  
I would like to read the source of this, can you share?

[Fly Boomer]

10 hours ago, wombat said:

I am looking at buying a pulse oximeter with an alarm, which would help protect against my failure to continuously monitor the O2 saturation.   Humans are really bad at monitoring something that doesn't change much, and I'm no exception

I have not followed your links yet, but wanted to say that my thinking has been going down that same path.  Ideally, it would be something that I wear (maybe on my wrist) that does not interfere with finger dexterity, AND alerts me to a problem through my audio panel.

[hais]

Suppose you have VNAV capabilities, would this be an effective poor man's hypoxia mode?

1. Dial up a VNAV waypoint in your navigator down to 12K

2. When you get close to TOD, change the VNAV waypoint to the next

If you don't respond, the A/P will take you down. 

 

 

 

[hais]

7 hours ago, ilovecornfields said:

If you factor in the time for the device to alarm, your response time (while hypoxic) to the alarm and the time it takes to take corrective action (while hypoxic) then it may be too late

How long does it take to regain consciousness, say, if the A/P were to descend down to breathable altitude? 

[Fly Boomer]

1 minute ago, hais said:

Suppose you have VNAV capabilities, would this be an effective poor man's hypoxia mode?

1. Dial up a VNAV waypoint in your navigator down to 12K

2. When you get close to TOD, change the VNAV waypoint to the next

If you don't respond, the A/P will take you down. 

 

 

 

Similar to something another MooneySpacer did.  He set his altitude preselect to 10,000 and vertical speed preselect to 1,000 or something like that.  His strategy was that his last cogent thought would be to punch the "do it" button before he passed out.

[ilovecornfields]

20 minutes ago, hais said:

How long does it take to regain consciousness, say, if the A/P were to descend down to breathable altitude? 

Hopefully in time to recover from the Vne dive and not break the wings!

It really depends on individuals and how long you’ve been hypoxic as well as the degree of hypoxia. Most of my experience with this is with opiate overdoses and although they regain consciousness quickly they remain confused and disoriented for quite some time. You might wake up pretty quickly back down at a normal altitude but you probably won’t function well for a while.

[Fly Boomer]

6 minutes ago, ilovecornfields said:

Hopefully in time to recover from the Vne dive and not break the wings!

It really depends on individuals and how long you’ve been hypoxic as well as the degree of hypoxia. Most of my experience with this is with opiate overdoses and although they regain consciousness quickly they remain confused and disoriented for quite some time. You might wake up pretty quickly back down at a normal altitude but you probably won’t function well for a while.

That would be a great time to let Otto fly for a while -- even if we weren't headed anywhere in particular.  I live in the Midwest, so just pointing the airplane west would be pretty safe for a couple of hours.  Other parts of the country, not so much.

[wombat]

@Fly Boomer I can't find many wrist-only devices that have oxygen saturation.    For example the fitbit charge 5 *can* but it is geared toward sleep oxygen measurements.

But there are some that have the sensor near the base of the thumb.    I still don't know what (if anything other than my regular oxygen sensor) I'll get.

 

@hais  Regarding setting a vertical descent rate in hopes of regaining consciousness....  I worry that will be ineffective because I think what would happen to me is that I'd fall asleep.  Then as I descend I'll remain asleep, not unconscious.   I know the times I've felt more severe symptoms of hypoxia I've been really sleepy.   But that's a heck of a better option than doing nothing at all.  And it's free!

[jaylw314]

50 minutes ago, Schllc said:

That seems incongruent, because if the oxygen is flowing when you are not inhaling it is obviously wasted,  but when inhaling distribution is the same as constant flow. 
I took a trip a few years ago from Florida to Oregon and back. I flew with a friend and very little of that trip was below 19k. We used conservers the entire time and never had any issues with saturation. 
What does oxygen wasting mean?  
Are you saying conservers deliver less o2 above 15k?  
I would like to read the source of this, can you share?

The nasal cannula with reservoirs (Oxymizer) 'store' oxygen in the small reservoirs while your exhaling, so in theory none is wasted.  Once you get above a certain volume flow, though, the excess flow gets wasted during exhalation like a normal nasal cannula, so you start wasting an increasing fraction of your oxygen. 

I did the back-of-napkin calculations a few years ago, but IIRC the reservoir volume on my oxymizer is about 30cc, so for 10 breaths/min, that's about 300cc.  So if your flow is above 0.3 L/min, you're starting to waste some oxygen between breaths.  That tends to happen between 10-15k' 

You can still keep your O2 sats up by turning up the flow further, it just means your O2 supply doesn't last as long as you'd expect.

[wombat]

Let's talk rules for a moment...  Not talking safety here, just talking about legality.

 

What says I can't use a cannula above 18,000' ?  Conversely, is there anything that explicitly allows me to use use a cannula only below 18,000'?  And also prohibits me from using a homebuilt system? Or just breathing in on the end of the hose?

FAR 91.211 does not have anything to say about this

FAR 25.1447 is about transport category aircraft

FAR 23.1443 is about continuous flow oxygen equipment installed in aircraft (Normal, Utility, Acrobatic, and Commuter Category)

[N201MKTurbo]

32 minutes ago, wombat said:

Let's talk rules for a moment...  Not talking safety here, just talking about legality.

 

What says I can't use a cannula above 18,000' ?  Conversely, is there anything that explicitly allows me to use use a cannula only below 18,000'?  And also prohibits me from using a homebuilt system? Or just breathing in on the end of the hose?

FAR 91.211 does not have anything to say about this

FAR 25.1447 is about transport category aircraft

FAR 23.1443 is about continuous flow oxygen equipment installed in aircraft (Normal, Utility, Acrobatic, and Commuter Category)

I remember talking to an old airline pilot. When he started flying DC3s, if he flew above 12000 feet he had a pipe stem fixed to the end of an oxygen hose. He said you just stuck it in your mouth and sucked on it. He said it worked fine. He also said all the passengers would fall asleep.

[Schllc]

1 hour ago, jaylw314 said:

The nasal cannula with reservoirs (Oxymizer) 'store' oxygen in the small reservoirs while your exhaling, so in theory none is wasted.  Once you get above a certain volume flow, though, the excess flow gets wasted during exhalation like a normal nasal cannula, so you start wasting an increasing fraction of your oxygen. 

I did the back-of-napkin calculations a few years ago, but IIRC the reservoir volume on my oxymizer is about 30cc, so for 10 breaths/min, that's about 300cc.  So if your flow is above 0.3 L/min, you're starting to waste some oxygen between breaths.  That tends to happen between 10-15k' 

You can still keep your O2 sats up by turning up the flow further, it just means your O2 supply doesn't last as long as you'd expect.

The precise flight conserver has altitude settings. 
Presumably this increases that flow rate right?
I have never used the mountain air or any other ones, but they appear to have fixed rate disbursement. 

[T. Peterson]

23 hours ago, Schllc said:

Years ago I was flying home and while planning my flight realized there was a 70knt tailwind at 25k, directly on my tail. Pretty hard to pass up in a plane capable..
I was alone, had the nice blue silicone mask with a microphone, so I filed for 25k and off I went. 
I was cruising along and I looked down in my lap and saw this little black disk. 
At the time the plane I was flying was an ultra with the precise flight conservers, and I thought the disk looked like the adjustment dial on the outside of the unit. 
After a few seconds of fiddling with it, I realized I was trying to put it back together, but it wasn’t apart…. By the grace of god I realized that what I was doing made no sense whatsoever and I engaged the vertical descent for 1400fpm and still to this day do not recall the next two or three minutes. 
What I do recall is being level at 8,000 ft with atc calling me asking intentions. I hit replay on the g1000 and listened to me responding to them and taking instruction. I did not sound like myself, but I was responding. I do not remember any of this…

After my wits were about me again I looked down and realized my arm had gotten wrapped around the o2 hose going to my mask and had inadvertently pulled the grommet out of the front of my mask at 25,000ft.  The disk was the grommet, and if one was completely cogent, would never had mistaken it for anything else.
I don’t know how long it had been pulled out, or how long it took me to notice something was wrong.  The flight recorder only goes back about 2.5 minutes on a constant loop, so that’s all I could listen to.  I don’t know how long the entire event lasted, but I did realize how close I came to being a bad story. 
 

There is certainly more elevated risk at those altitudes, and one must be very vigilant, aware and have some routine to check yourself very regularly. 
I personally stay 19k or below if I am alone, and will only go to 25k with someone else and if we pick up enough time to really make a difference. 
This isn’t my recommendation or suggestion, it’s merely a personal minimum in my Mooney, or any non pressurized airplane. Things can deteriorate much quicker than you would like to believe…

Last thought on this story…    
I was embarrassed by this.  I felt foolish, like my arrogance and confidence led me to a bad choice that could have killed me.
I finally opened up and told the story to a pilot friend of mine and he told me I should share, because perhaps someone could benefit from hearing my mistake.  I sure hope it does, because I still feel foolish. 

You may feel foolish, but the rest of us just feel grateful you’re here. I am also thankful for the sobering reminder that even being careful may not be enough. No way you can be faulted for a grommet falling out!

[ilovecornfields]

1 hour ago, wombat said:

Let's talk rules for a moment...  Not talking safety here, just talking about legality.

 

What says I can't use a cannula above 18,000' ?  Conversely, is there anything that explicitly allows me to use use a cannula only below 18,000'?  And also prohibits me from using a homebuilt system? Or just breathing in on the end of the hose?

FAR 91.211 does not have anything to say about this

FAR 25.1447 is about transport category aircraft

FAR 23.1443 is about continuous flow oxygen equipment installed in aircraft (Normal, Utility, Acrobatic, and Commuter Category)

Because the FAA said so in their pamphlet. 
https://www.faa.gov/pilots/safety/pilotsafetybrochures/media/oxygen_equipment.pdf

[Schllc]

I don’t feel foolish for the random act of the grommet being yanked out. 
That was the one link in the chain that wasn’t a factor of my negligence. 
I had a pulse oximeter I didn’t utilize enough, I didn’t set up a backup mask or cannula, which I did have with me, I didn’t have any checklist to confirm my function. I was alone.

Any one of these other items may have been ok, but all of them was just a lack of preparedness and awareness, that happened to coincide with an equipment failure. 
I didn’t say I felt foolish to be self effacing or elicit sympathy. The story reads like so many of the accidents we read about, only it ended well.  
It is easy for confidence and arrogance to be conflated. 
I am fortunate and I will not forget the lesson.

[wombat]

I read that brochure, but it's not regulatory.  And the brochure says that cannulas are restricted by federal aviation regulations, which may be true,  but... Which regulation? 

The best idea I have right now is that all of the manufacturers of cannulas are trying to get some sort of FAA certification for their equipment for all of the part 135 operations,  and in order to do that they need to meet specific requirements,  and those requirements include prohibiting use above 18,000'.

So if you buy one for aviation use, you would be using it against the manufacturer's requirements above18,000'.   But how does this limit a part 91 pilot?

 

If I simply sucked on a pipe end attached to the end of a hose plugged into the oxygen system, would that be illegal as a part 91 flight?

 

Again, I'm completely ignoring the question of if this safe, or a good idea, or anything other than just the legal aspect.

[ilovecornfields]

3 hours ago, wombat said:

I read that brochure, but it's not regulatory.  And the brochure says that cannulas are restricted by federal aviation regulations, which may be true,  but... Which regulation? 

The best idea I have right now is that all of the manufacturers of cannulas are trying to get some sort of FAA certification for their equipment for all of the part 135 operations,  and in order to do that they need to meet specific requirements,  and those requirements include prohibiting use above 18,000'.

So if you buy one for aviation use, you would be using it against the manufacturer's requirements above18,000'.   But how does this limit a part 91 pilot?

 

If I simply sucked on a pipe end attached to the end of a hose plugged into the oxygen system, would that be illegal as a part 91 flight?

 

Again, I'm completely ignoring the question of if this safe, or a good idea, or anything other than just the legal aspect.

I’ve never found the regulation that it refers to either but I think it’s good advice. You could always ask your friendly neighborhood FSDO.

 

[N201MKTurbo]

How would anyone know if you are using a cannula above 18000 feet? Even if the airplane cops pulled you over, you would be on the ground before they could check.

[LANCECASPER]

3 hours ago, ilovecornfields said:

I’ve never found the regulation that it refers to either but I think it’s good advice. You could always ask your friendly neighborhood FSDO.

 

FAR 23.1447 says that above 18,000 feet it must cover the nose and mouth.

https://www.govinfo.gov/content/pkg/CFR-2012-title14-vol1/pdf/CFR-2012-title14-vol1-sec23-1445.pdf

[A64Pilot]

3 hours ago, N201MKTurbo said:

How would anyone know if you are using a cannula above 18000 feet? Even if the airplane cops pulled you over, you would be on the ground before they could check.

That’s the bottom line with pretty much everything, that is we Police ourselves.

‘I’ve only been above 180 a few times and then to 250, and wore the not inexpensive mask, nor very comfortable mask, and if you wear bifocals like me the mask may interfere with your vision. I didn’t check that before the flights. So I flew the flights looking through the bottom of the bifocals.

 

‘The only thing I’ll add to this conversation is when something happens that needs immediate action, like O2 failure at altitude, engine failure etc, contact ATC when able and inform them what your doing, don’t ask. If you ask it’s likely they will fumble around. I’ve rarely had to do it, but have never had them say no and have never had any issue.

[aviatoreb]

20 hours ago, ilovecornfields said:

One of my first Mooneyspace posts was on pulse oximeters and I basically got attacked for suggesting people get one and use it to adjust their oxygen delivery. I feel more used to the “feedback” now so I’ll comment again on things that have been said before:

1. Pulse oximeters are great, but to paraphrase Dirty Harry, you have to know their limitations.

2. They will read artificially high in the presence of CO.

3. They are inaccurate in the setting of poor perfusion (cold, poor circulation).

4. They tell you what happened in the past, not what’s happening now. This study showed it took almost a minute to detect acute hypoxemia in the foot (compared to ear) but a cold hand could easily have the same problem. 20-30s delay is not uncommon even in normal warm patients. https://pubmed.ncbi.nlm.nih.gov/10386281/

5. #4 is worse than it seems because the fall in oxygen levels once you start to get hypoxic isn’t linear. Once you detect hypoxemia on the pulse ox, you’re on a very steep part of the curve and likely much more hypoxic than the number is reading. If you factor in the time for the device to alarm, your response time (while hypoxic) to the alarm and the time it takes to take corrective action (while hypoxic) then it may be too late.

6. Hyperventilation doesn’t cure hypoxia. You’re just going to introduce another respiratory disorder (respiratory alkalosis) by blowing off CO2 and increase your chances of passing out.

7. Be careful out there.

CP thoughts only. Not a flight level flyer or flight surgeon.

Edit: Cool dog study showing how hyperventilation actually makes cerebral hypoxia worse (I guess not so cool if you were the dog).https://pubmed.ncbi.nlm.nih.gov/6774644/

Yes - you aren't a flight surgeon - but you are a doctor and a flying doctor who probably learned more on the topic than most doctors - so I sit up and pay attention.

[aviatoreb]

3 hours ago, N201MKTurbo said:

How would anyone know if you are using a cannula above 18000 feet? Even if the airplane cops pulled you over, you would be on the ground before they could check.

Well if you get busted for breaking a TFR and the F16s pull beside you AND you are wearing a cannula at FL19 - then - lookout!

[A64Pilot]

39 minutes ago, LANCECASPER said:

FAR 23.1447 says that above 18,000 feet it must cover the nose and mouth.

https://www.govinfo.gov/content/pkg/CFR-2012-title14-vol1/pdf/CFR-2012-title14-vol1-sec23-1445.pdf

From a purely legal perspective, I don’t think FAR 23 is applicable to our aircraft

[LANCECASPER]

25 minutes ago, A64Pilot said:

From a purely legal perspective, I don’t think FAR 23 is applicable to our aircraft

Perhaps, but since it’s in the AFM supplement for recent Mooneys I think we’re good