Hypoxia revisited

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ronnieh

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Ronnie
Dr. Bruce, It is only because of the high regard I and others place in your expertise that I bring this back up. If I am understanding your position correctly you do not believe hypoxia at 9500 feet or even lower in your case is cause for concern. First by hypoxia I am useing the standards set by the OP in the previous thread. Unable to function safely as PIC without supplemental O2. Also, I do not have ANY aeromedical expertise.
My question: The FAR's give guidance for supplemental O2 in both Part 91 and 135. (there is mention in other parts also). FAR135 is more stringent that 91, so for my question and example will reference 135. Dr. Bruce, if a pilot with your exact physiology came to you requesting a second class medical would you expect to be able to issue it? Maybe the question should be (since I do not know your medical condition, heck you could be blind in one eye and missing both legs:)) If a person walks in requesting a second class and his blood sugar, blood pressure and eye sight is OK along with normal hearing would you expect to issue that medical? Same pilot then leaves your office and goes to the airport, meets the client and load up in a RVSM approved KA 300 for a night flight at FL330 for 3 hours. Is it reasonable to expect that pilot to be able to safely make that flight from a medical standpoint? If that pilot has to have supplemental O2 with the cabin going through 8000 feet then it seems to me there is a problem. The FAR's seem to imply it is expected a commercial pilot can safely be PIC with a cabin up to 10,000 feet and even up to 12000 feet for 30 minutes. Can I assume the FAR's are based on some aeromedical expertise? If this is not the case then seems the FAR's should be modified to protect the flying public. My original point was I doubted the OP was hypoxic but did not know. However if and I repeat if he was then I would not consider that normal. It just seems to me the FAR's especially for commercial operations should give some safety margin. The high cabin altitude warning does not come on in my plane untill above 11K so somebody somewhere though the normal pilot should be OK up to that point. You seem to be saying hypoxia requiring supplemental O2 at a much lower altitude is normal for some people. It may happen to some people but is it normal? Again, I am not calling you out. You expertise is highly regarded and for myself being a corporate pilot already being a little long in the tooth I read your posts with much interest. I do appreciate all the help you provide!!

Ronnie
 
ronnieh said:
If I am understanding your position correctly you do not believe hypoxia at 9500 feet or even lower in your case is cause for concern.
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I don't think Bruce ever said anything of the kind. Do you have a link to a post where you think he said that?

Is it reasonable to expect that pilot to be able to safely make that flight from a medical standpoint? If that pilot has to have supplemental O2 with the cabin going through 8000 feet then it seems to me there is a problem. The FAR's seem to imply it is expected a commercial pilot can safely be PIC with a cabin up to 10,000 feet and even up to 12000 feet for 30 minutes. Can I assume the FAR's are based on some aeromedical expertise? If this is not the case then seems the FAR's should be modified to protect the flying public.
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The FAR's are only the minimum level of safety. If a pilot feels that his/her performance is improved at altitudes/times below/short of those levels, that pilot would be wise to use supplemental oxygen in those situations. There's plenty of aeromedical guidance (including from the FAA) to suggest that it is wise (if not legally required) to use supplemental oxygen above 5000 PA at night and above 10,000 PA at all times. In addition, pilots whose oxygen uptake capability is compromised by age, smoking, poor physical condition, or other causes have to recognize their own limitations and set their own standards more stringently than the FAA's minimum regulatory standard in order to be safe.

That said, I'll leave it to Bruce to defend whatever position he may have taken...
 
Ron, it would be easier for you to just review the thread that Artiom started. I think Dr. Bruce will understand the context of my question. And I agree on "the minimums". Whoever wrote that part of the FAR 135 must of had some guidance on what would be safe. My position is that is the minimum and if you can not meet that perhaps you should investigate as to why the hypoxia is setting in early. Anyway, I am not getting back into a long drawn out re hash. I am just genuinely interested if Dr. Bruce thinks it is "normal" to have hypoxia that prevents safely being PIC at cabin altitudes below the minimim standard set by the FAA. He may and I will defer to his expertise.

Ronnie
 
While we are waiting Dr. Bruce, I went to a O2 seminar at OSH given by a Dr. so that makes me an expert. :hairraise:

We all have different metabolisms, O2 intake, absorbtion rates, , smoking history, age, etc, etc., so each of our saturation levels will be different given different altitudes. The military require O2 about 8,500 MSL, and this particular DR. recommended O2 about 9,500 for anyone. Typically, pilots are older and our saturation levels change with age. I started using O2 over 9,500 and I can tell you I feel much better when I land, and for the rest of the day, less recovery time.

Carrying a finger type device to monitor saturation levels is critical. Without it you have no idea if you are getting O2. The $40 ones work just fine BTW.
 
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Geico266 said:
I started using O2 over 9,500 and I can tell you I feel much better when I land, and for the rest of the day, less recovery time.
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What are your age and cardiovascular condition, and at what point (age, altitude, etc) did you begin to notice the lack of oxygen at altitude?

Just curious because I'm 46, never smoked, do a little running, and otherwise keep myself in decent shape. In the RV, I do long flights (3-4 hours) at 8 - 12K, and have never noticed any sign of hypoxia, fatigue, or tiredness after landing. So I wonder if I'll get to an age where that changes, or if I stay in shape, will I ever *need* oxygen for the flying I do.

And I'm not discounting the idea that I might feel better on O2 than without it, but based on how I feel at altitude today, I don't see any pressing need for O2.
 
Would you fly your RV without an oil temp gage? Then why would you fly high without monitoring the O2 saturation level of the pilot in command? Get an O2 pulse oximeter and take readings at different altitudes. If your saturation level remains above 92 you are good to go, if you are below 90 you are kidding yourself. Get a monitor!

Hypoxia is something you cannot feel! Mamals are not meant to fly unless you are a bat.

We are all different so my particulars are not relevant to compare with yours. Not being secretive, but it just does not matter. The point is we all are different. Measure the amount of O2 in your body.

This DR I listened to starts breathing O2 when he starts his preflight! No, I am not kidding!

BTW women are much more susceptible to hypoxia than men.
 
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Ronnie,

I don't think I ever said what you say I have said.

There are no requirements to check oxygen saturation at a flight physical for any class, let alone in an altitude chamber at 10,000 feet.

As for the operational aspects of a King Air 200 (I have no OE in the -300), it would be pretty unlikely to be able to remain in flight at FL 33, and is pretty well topped out at FL 28. Most versions will maintain a 10,000 foot cabin through FL 25 (but that also depends on the -XX designation of the turbines installed).
******

The FAA's body of research on the topic resulted in them taking no, ZERO position on the dosage of oxygen and at what minimal level it is appropriate. The maximal level was as I will mention (below), was determined by politics.

FAR 91.211 was not arrived at by scientific grounds. It was a compromise between the Colorado Pilot's Assn who thought it was just egregious that they should have to equip with oxygen for a short trip over the mountains, and they lobbied their POWERFUL senator in the late 60s early 70s to get the proposed requirment changed first from 8,000 to 10,000 for part 135 and 14,000 for part 91.

The then Director at CAMI, a distinguished guy named Audie Davis is still alive to recount the tale and he was....horrified. I know Audie personally, who is now in his early eighties.

But the Senator Dominick was a powerful man. To get a sense of what the popultation averages are, look up Nestus, T, et. al. DOT FAA AM 097/9 . 12,500 for 30 minutes is clearly associated with increases in decision making errors for the next 30 mintues following descent. AND THIS WAS IN YOUNG ERAU students who were not having colds or viral issues that day.


Polling more senior aviators who fly unpressurized GA for utility, I'd say most decide to wear O2 at 8,000 at night. They know where the bones are and would like to leave them there. So to answer one of your many questions, the OP could be perfectly normal on pulmonary function and blood studies, cardiac output and stroke volume, and still desaturate below 90% at 9,500. We just don't have good population studies in the alittude chamber so we can't say.

If safety was to rule the day, Oxygen would indeed be required at 8,000 as passenger cabins in part 121. 10,000 would be the absolute limit. But under part 91 we are subjected only to the most genteel requirments, which you should not take as "gospel" that you're OK 'cause 91.211 says you're legal. Safe, and Legal as always in aviation are two completely separate items.

Bottom line: You would be amazed how many Philistines there are out there- until recently Paul Bertorelli maintained, "wee don't need no steenkin pulse oximeter".
 
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Military requires the use of O2 at cabin altitudes above 10,000MSL.
At least when I was still flying on active duty.
 
Geico266 said:
Would you fly your RV without an oil temp gage? Then why would you fly high without monitoring the O2 saturation level of the pilot in command? Get an O2 pulse oximeter and take readings at different altitudes.
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I've had one for several years. But the issue is/was whether there are biomedical issues that are likely to impact my no-O2 performance as I age. Therefore the questions to you.
 
BillTIZ said:
Military requires the use of O2 at cabin altitudes above 10,000MSL.
At least when I was still flying on active duty.
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I have been told it is now 8,500 MSL. Maybe one of America's finest will let us know.

In my military career I was never above 40' MSL, and most of the time I was -10' MSL sleeping in my rack! :D
 
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kyleb said:
I've had one for several years. But the issue is/was whether there are biomedical issues that are likely to impact my no-O2 performance as I age. Therefore the questions to you.
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How're you gonna know without a $39.00 pulse oximeter?

Oddly enough, Kyle, I used to think just like you....until I did a FSDO video in 1994. If you read Nestus, et. al, even if you think you're healthy, you'll realize you get too dumb to realize you're dumb. And so it goes.
 

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bbchien said:
How're you gonna know without a $39.00 pulse oximeter?

Oddly enough, Kyle, I used to think just like you....until I did a FSDO video in 1994. If you read Nestus, et. al, even if you think you're healthy, you'll realize you get too dumb to realize you're dumb. And so it goes.
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I clearly wrote "I've had one <an oxymeter> for several years." My sat's have been fine (>90) every time I've checked up to about 12k feet. Above that, well, they get lower than I like (I think the lowest I've seen was 87 at 14,500 for ~20 minutes).

My question about likely biomedical changes is still out there if anyone wants to answer it...
 
ronnieh said:
Ron, it would be easier for you to just review the thread that Artiom started.
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If you'd referenced that thread, I might have known that.

I am just genuinely interested if Dr. Bruce thinks it is "normal" to have hypoxia that prevents safely being PIC at cabin altitudes below the minimim standard set by the FAA. He may and I will defer to his expertise.
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My money's on Bruce saying that it may be "normal" for some people depending on their physical/medical condition even if they qualify for an unrestricted medical certificate. Let's see what he says...

<edit>...and now that I've read his post, that seems to be what he said.
 
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Sorry, Kyle, I missed that. Then just pray for continued good fortune. I didn't deteriorate until my 52nd year. But it was pretty remarkable because I spend lots of unpressurized time in the upper teens. I learned the hard way to not take if off until 8,000.

I can run a 6:45 mile and have a BMI of 18.
 
Bruce, thanks for your response. That was very interesting and a little disconcerting. I do own and use an oxymeter. I have never seen it below 91 and that was in a non pressurized at 12,000 feet. I too can run a 6:45 mile but, it would take me at least a week to do it:)
BTW, a 300 on a standard day at gross TO will go straight to FL330 without a step climb. The cabin would be around 9500 feet. The 300 is basically a 200 with 1050 HP per side.The Cheyenne IIIA I fly with the same conditions (gross TO and standard temp) will still be climbing around 700 fpm when leveling at FL280, and will be truing about 288K at the end of the first hour, I am not RVSM. A B200, 300 or a IIIA will hold about a 8000 foot cabin at FL250. (little over 6 psi differential)
Just FYI:
KA300 -60A Flat rated 1050 HP
B200 -42 Flat rated 850 HP
IIIA -61 Flat rated 720 HP
Again, thanks for the response, I always look forward to reading your posts.

Ronnie
 
See post 7. Dr. Audie Davis passed away last weekend in Norman OK. :(
 
Here's a question for you - Lets say that you normally live at 5000MSL, would your limits be higher?

When I first moved to Az, getting up to Flagstaff (7000MSL) and under some physical stress would get me breathing heavy.
It doesn't anymore, so did i "get used" to elevation?

Just curios.
 
gil_mor said:
Here's a question for you - Lets say that you normally live at 5000MSL, would your limits be higher?

When I first moved to Az, getting up to Flagstaff (7000MSL) and under some physical stress would get me breathing heavy.
It doesn't anymore, so did i "get used" to elevation?

Just curios.
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Curios? Kokopeli maybe? Yes, your body adjusts the number of red blood cells in circulation as you change the altitude of residence. Typically takes less than six weeks, BuT there are drugs to speed the process up... And most folks note improvement even without drugs in under a week.

Paul, recalling a 1973 physiology course
 
I live down near sea level, I just spend a bunch of time at altitude.

Another chapter for the "Hey, I used to think that way, but I know better now" book: I used to be in the "Don't need no stinkin' O2 or pulse ox" camp. I'm 27, never smoked, healthy (although not as active as I should be). The reality is that, especially at night, I'll notice a difference above 10K. Now I carry a portable O2 bottle and a pulse-ox in the winter (in the summer, the planes really won't be happy with flight above 10K) and use them regularly. Sometimes, I'll put the O2 on just because I'm starting to feel a little tired, even though my O2 sat is good. Wakes me right up.
 
Dr. Bruce,

I'm curious on your thoughts about the effect of cardiovascular fitness on this. My main hobby is running, and I average 70 ~ 75 miles per week. My resting heartrate is 39bpm and my most recent VO2Max test was 63 ml/kg/min.

So I know I have a higher than normal 'fitness,' but doesn't that mean my muscle tissue is sucking up oxygen like a vacuum while I'm guessing the brain receives the same amount as an average person? How do you think this would affect my O2 levels when the air starts getting thin?

Cheers,
A
 
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