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Anoxia recovery times

Old 26th Jul 2018, 22:47
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Anoxia recovery times

I recently did a three-hour flight in a light plane, taking off from 2700', flying mostly at about 8000' but with an hour or so at 11,000' up to 30 minutes before descent and landing at 3700', which is the altitude I live at. I was extremely tired after landing and I wondered if I had become slightly anoxic or if I was just tired after a very turbulent flight in mountainous terrain on a hot day.

Is the recovery from anoxia rapid when descending to lower levels or are there delayed effects?
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Old 27th Jul 2018, 10:19
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You certainly were not anoxic - that is no oxygen you are asking about hypoxia.

The amount of oxygen in the blood will have fallen, and this can be measured, even in passengers on commercial flights, but it has no significant effect to a healthy person. Your flight would not cause symptoms from the relative hypoxia. Even hypoxia which leads to inattentiveness and a drunken like state resolves quickly when the oxygen levels are corrected. Severe hypoxia leads to cell death in the brain and is irreversible.
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Old 27th Jul 2018, 15:06
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Definitely mild hypoxia

On long haul flights especially at night and occasionally on short haul night flights we used to don our masks before TOD, within a minute or so vision improves markedly and that's with a max cabin altitude of 8,000ft.
I used to fly in the alps and limit time above 11,000 ft to a couple of hours and rarely climb above 13,000 but it didn't stop me from getting a massive headache.
The longer the time the longer the headache persisted.
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Old 27th Jul 2018, 15:33
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A lot depends on your physiology. I spent some time at 18,000 with an Aerox system. I needed a couple days to recover from the post flight fatigue and promptly bought a Mountain High system and pulse oxymeter.

When younger I could fly at 9,500 for hours with no more than mild fatigue after landing. Acclimation makes a difference.
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Old 27th Jul 2018, 19:18
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Radgirl,

I must have been hypoxic when I wrote my post! I do know the difference between hypoxia and anoxia.

I’ve been flying for over 50 years, so maybe my tolerance is reduced. I’ve decided I will take a portable cannula system next time I fly high. A friend of mine did a 7 hour glider flight at similar altitudes, a few days before my flight and he told me he used oxygen for the whole flight and did not feel tired afterwards.

blind pew,
I made a decision a long time ago that I would use oxygen if flying at night, but I doubt I shall need to do so in the future.


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Old 27th Jul 2018, 21:54
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You are correct Blind Pew - the one thing that is impaired at commercial pressurisation levels (which vary up to 9000ft) is night vision.
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Old 11th Aug 2018, 16:45
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Ooooh, interesting thread which I am going to follow.

I seem to remember trying to learn about "the oxygen desaturation" curve from many moons ago. All I can remember was it was very complicated and "fickle." Different people reacted very differently to similar situations.

Watched that series on ferry pilots recently, couldn't help noticing some pilots were using fingertip pulse oximeters.

Would be interesting to see how useful they are in predicting hypoxia/hypercapnoea issues.
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Old 12th Aug 2018, 16:56
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Absolutely useless Gingernut

Many moons ago when we started using pulse oximeters on patients on ventilators we were staggered to see the readings when we put them on each other in flight. You would expect over 96% on any walking patient, and on intensive care we sweat if we get down to the low 90s. Anything in the 80s......little hope

Then we saw our readings were in the 80s. Just into the 90s in a few,,,, and we were flying week in week out with little sign of brain rot....The reality is an oxygen saturation in the 80s caused by depressurisation in a healthy person causes no issues except perhaps night blindness. And that is reversible. So they cant really be used as a safety device.

The problem is that the amount of oxygen available in the blood is not a straight line relationship with the reading on the pulse oximeter. When it gets to the 80s just a tiny reduction in actual oxygen can lead to a big drop in saturation, so a pulse oximeter is worthless IMHO unless you are on oxygen when you can use the reading to titrate the flow rate against the saturation. And then you should aim for 94%...
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Old 12th Aug 2018, 17:49
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Absolutely useless Gingernut
Lol, you sound like my wife !

Fair enough comment Radgirl. We use them in primary care to affirm what we already know, I did once come across a young, athletic patient with a pulse ox reading of 78%. Which left me wondering what to do next.

A quick rub of acetone on her sparkly nail varnish soon brought it up to 98%

Did make me reflect on why on earth we do it in the first place though. I suspect, similar to clinical examination, the main purpose is to satisfy the patient, and the defence unions.Not sure about you,

In terms of affecting the management, then the story the patient tells us, is of most use :-)
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