safe CO levels

[N201MKTurbo]

I’ve told this story before, but I was flying in the dead of winter from Denver to Rapid City. When I got there, I felt awful, nauseous, and a splitting headache. My eyes were very sensitive to light. Before I flew back I bought a CO spot detector and some sun glasses (there were no Sensorcons). I put the spot next to the heater vent after I started the engine and it turned pitch black in about 3 seconds. I turned the heater off and opened all the vents, the spot eventually went back to its normal color. So I flew back to Denver with all the vents open and the heater off. It was 15F outside. I was shivering to much to pass out. I had my winter coat and gloves on , but it was still F’in cold.

I felt like I had a severe hangover for the next three days. The muffler had a 3 inch crack about 1/8 inch wide.

[A64Pilot]

Ref supplemental O2. 

it hurts nothing at all to have it on and not need it, heck why not don it on the ground especially if punching into an 800 ft overcast? One less thing to worry about while getting reroutes IMC.

Secondly the 10,000 ft thing is based on young healthly people, some of who are older may benefit even lower.

Lastly from memory, even young healthy Military pilots start to lose night vision at 6,000 ft without supplemental O2.

[jaylw314]

2 hours ago, A64Pilot said:

Ref supplemental O2. 

it hurts nothing at all to have it on and not need it, heck why not don it on the ground especially if punching into an 800 ft overcast? One less thing to worry about while getting reroutes IMC.

Secondly the 10,000 ft thing is based on young healthly people, some of who are older may benefit even lower.

Lastly from memory, even young healthy Military pilots start to lose night vision at 6,000 ft without supplemental O2.

IIRC the AIM suggests, but does not require, supplemental O2 at night above 5,000' MSL

[ilovecornfields]

4 hours ago, A64Pilot said:

Ref supplemental O2. 

it hurts nothing at all to have it on and not need it, heck why not don it on the ground especially if punching into an 800 ft overcast? One less thing to worry about while getting reroutes IMC.

Secondly the 10,000 ft thing is based on young healthly people, some of who are older may benefit even lower.

Lastly from memory, even young healthy Military pilots start to lose night vision at 6,000 ft without supplemental O2.

It probably won’t hurt you to have it and not need it in an airplane, but why even do that when for $20 you can know if you need it, when you need it and how much you need? I use an O2D2 set at 5000’ and just put it on before takeoff. Then I check my oxygen level a few minutes after leveling off and every hour. I usually get the tank filled every annual flying 100-150 hours/year.

My wife doesn’t like wearing the cannula if she doesn’t have to so she just uses the pulse ox and uses oxygen when she needs it. Having the pulse ox makes you realize that those altitudes the FAA chose were more about terrain and convenience than human physiology.

It makes no sense that the altitudes are based on MSL altitudes and not density altitudes especially out West when the density altitude (what you’re actually breathing) can be a couple of thousand feet higher than your indicated altitude. With the pulse ox you can also see the day to day variation- for example I’m usually 92-95% at 8000’ MSL without oxygen but I’ve seen it as low as 88%.
 

I understand cheap reliable pulse oximeters weren’t available when the regs were written, but they are now. Seems kind of ridiculous to make all these rules based on altitudes and times when all you really care about is what your individual SpO2 is. I can’t prove it, but I suspect a lot of poor decision making and accidents at the end of trips had hypoxia as a contributing factor with people thinking that because they were following the regs they were safe.

In a medical setting (or underwater) there are clear harms to having a higher concentration of oxygen than you need but those are different topics entirely. 

Edited November 8, 2021 by ilovecornfields

[Marauder]

Just an opinion from a pilot who has aged over his flying career. All the points about youth are true. When I was a young aviator, going up to high altitudes never had an impact on me. When I was in my early 50s a friend of mine gave me a bottle of O2 to try for night flying. It was the first time I realized that O2 can bring the lights of Broadway back into the cockpit. I became a believer for night flying.

Then I started noticing I was getting headaches while flying. Thought it was related to my headset so I bought a set of Halos and realized, I still had the headache. And for the first time at my usual 8k to 9k altitudes I found flying with supplemental O2 was making a difference. I have a couple of O2 pulse oximeters in the plane and through my experimentation (not peer reviewed  ), I concluded that when my pulse ox was in the 90 to 92 range, I started getting the headaches. So I am that guy you see who gets out of his plane with his cannula still attached to him. 

 

[N201MKTurbo]

For anybody that doesn’t think oxygen is important, try this:

Go flying at night away from the city on a moonless night at about 10,000 feet. Dim the lights as much as you can, wait till your eyes accommodate the darkness and then dim some more, till you can barely see the instruments.

Then put on the oxygen. It is amazing.

[aviatoreb]

34 minutes ago, Marauder said:

Just an opinion from a pilot who has aged over his flying career. All the points about youth are true. When I was a young aviator, going up to high altitudes never had an impact on me. When I was in my early 50s a friend of mine gave me a bottle of O2 to try for night flying. It was the first time I realized that O2 can bring the lights of Broadway back into the cockpit. I became a believer for night flying.

Then I started noticing I was getting headaches while flying. Thought it was related to my headset so I bought a set of Halos and realized, I still had the headache. And for the first time at my usual 8k to 9k altitudes I found flying with supplemental O2 was making a difference. I have a couple of O2 pulse oximeters in the plane and through my experimentation (not peer reviewed  ), I concluded that when my pulse ox was in the 90 to 92 range, I started getting the headaches. So I am that guy you see who gets out of his plane with his cannula still attached to him. 

 

That forgetfulness is another problem.  That is your old brain forgetting that... forgetting that... what were we talking about again?

I have a different problem.  I DON'T get headaches at a nice still not crazy O2sat like 90-92.  Instead I am perfectly comfortable at 80 - so I think!  But of course I am not ok at 80.  I just don't get obvious easy to notice problems like headache.  Instead more subtle problems.  So I have an O2sat ring I wear that buzzes/alarms if I dip below 90.

[N201MKTurbo]

I had a friend who flew to Oshkosh with me in 2013. On the way, we were on oxygen and I put the pulse ox on him. It read 75%! I said Oh Crap! are you OK? He tells me that those things never read over 80 on him and 75 is normal for him. He says that every time he goes to the hospital and they put pulse ox on him they all panic. His doctor says that he is just weird that way. 

Can any of the physicians on here explain that?

[N201MKTurbo]

9 minutes ago, N201MKTurbo said:

I had a friend who flew to Oshkosh with me in 2013. On the way, we were on oxygen and I put the pulse ox on him. It read 75%! I said Oh Crap! are you OK? He tells me that those things never read over 80 on him and 75 is normal for him. He says that every time he goes to the hospital and they put pulse ox on him they all panic. His doctor says that he is just weird that way. 

Can any of the physicians on here explain that?

OK, I went to the bathroom with my IPad and this is what I came up with: He could have some genetic trait that leads to hypoxemia and he has compensated for it with increased cardiac output so he doesn't have hypoxia. 

Wait a sec, I have to flush.....

[PT20J]

I notice that my pulse oximeter has a lot of measurement-to-measurement variation when it gets in the lower 90's. Upper 90's it's consistent within 1%. But in the lower 90's it can read 92, 86, 88, 94 on successive measurements. Switching fingers doesn't seem to make much difference. I was planning to buy another model and see if it does the same thing, but I wonder if this is just the way they are.

Skip

[exM20K]

2 minutes ago, PT20J said:

I notice that my pulse oximeter has a lot of measurement-to-measurement variation when it gets in the lower 90's. Upper 90's it's consistent within 1%. But in the lower 90's it can read 92, 86, 88, 94 on successive measurements. Switching fingers doesn't seem to make much difference. I was planning to buy another model and see if it does the same thing, but I wonder if this is just the way they are.

Skip

This has been my experience, too.  I do get some finger-to-finger variability, and sometimes the mid 80's readings will creep up to low 90's over 5-15 seconds.

Must be my nail polish lol

-dan

[EricJ]

8 minutes ago, PT20J said:

I notice that my pulse oximeter has a lot of measurement-to-measurement variation when it gets in the lower 90's. Upper 90's it's consistent within 1%. But in the lower 90's it can read 92, 86, 88, 94 on successive measurements. Switching fingers doesn't seem to make much difference. I was planning to buy another model and see if it does the same thing, but I wonder if this is just the way they are.

Skip

Mine goes down into the 80s and even 70s sometimes, and usually I'm feeling fine when it does.   I get some reliable tell-tale signs when I'm actually getting a little hypoxic, but use the pulseox to try to stay ahead of that.   I do notice that when it is reading that low if I do a few deep breaths it'll come back up to the low 90s, and I don't really feel much different by doing so.    Likewise I've been going to try a different pulseox unit to see if it makes a difference.   Fresh batteries don't seem to matter.

 

[jaylw314]

1 hour ago, N201MKTurbo said:

OK, I went to the bathroom with my IPad and this is what I came up with: He could have some genetic trait that leads to hypoxemia and he has compensated for it with increased cardiac output so he doesn't have hypoxia. 

Wait a sec, I have to flush.....

Ewww 

People with chronic lung diseases that are chronically hypoxic end up stabilizing with lower oxygen pressures and saturations.  However, I'm not sure they would be feeling "fine" up at altitude, since their margin is thinner than the average person.

Other things include peripheral circulation, being a smoker, skin thickness and pigmentation, but I don't recall any of them commonly reducing the value by that much.

[aviatoreb]

47 minutes ago, exM20K said:

This has been my experience, too.  I do get some finger-to-finger variability, and sometimes the mid 80's readings will creep up to low 90's over 5-15 seconds.

Must be my nail polish lol

-dan

Mine also seems to settle in to a measurement over 5-15 sec or so.  So 86 day initially drifts up to say 94 over 15 sec.