Blood Oxygen Levels at Altitude

[Milt]

Blood Oxygen Levels at Sustained Altitude

Does anyone know how low the blood oxygen levels go at sustained cruising altitudes?

The medics use a finger sensor connected to an oxiometer which registers 100% for a sea level norm.
They strive to get a patient over 98% when recovering from an anaesthetic.

Do our lungs compensate during a long haul unpressurised at say FL 10 to keep our blood oxygenated
at a level where our human performance is not significantly degraded?
I believe that we are designed to breathe to expell carbon dioxide and little notice is taken by the body over depleted oxygen levels.

At what % of sea level blood oxygen do we start to be significantly impaired?
At what level is the average aircrew when on the edge of unconsciousness?
Having been to that edge of unconsciousness on several occasions following oxygen supply system malfunctions you can be assured that each occasion has you with one foot into the big hangar in the sky.

[Islander Jock]

One of the biggest dangers with hypoxia is its insidious nature and euphoric effects it has especially in mild cases.

I did the RAAF 1 day chamber course about 3 times and experienced the effects of hypoxia from F250. It's amazing how you feel quite good but cannot perform the simplest of mental tasks ie write down the number 340 and subtract 6 from each successive answer.

When I was jump flying with regular sorties to F120 I knew from the chamber training I was starting to experience very mild symptoms of hypoxia. Different people would have different reactions at certain levels. One of my first sensations was the tingling of the lips. Smokers (myself included), will succumb to the effects of hypoxia earlier than non smokers due to the residual effects of carbon monoxide on the blood.

Pleny of good information http://www.cami.jccbi.gov/aam-400/beware.htm (here)

[QDMQDMQDM]

Altitude in Feet Saturation (%)

0 to 10 000 95 to 90
10 000 to 15 000 90 to 80
15 000 to 20 000 80 to 70
20 000 to 23 000 70 to 60


http://www.aviationmedicine.co.za/hypres.php

Basically, much above 10K and you are starting to deteriorate with an exponential curve. In aviation, of course, you have no opportunity to adapt as the exposure is so short-term, as compared to say trekking in the Himalayas. That makes the effect more dramatic.

WW1 pilots used to patrol at up to 22K without supplementary O2 for up to two hours, but how they did it I do not know.

QDM

[Speedbird777]

I actually though smokers did better at altitude due to them being used to a more hypoxic state under normal circumstances????

[Corporate Yank]

Here's some info everybody who flies high needs to read. I bought a pulse/oximeter 2 years ago, and it helped me make up my mind to go to the hospital emergency room early one morning after I had suffered a DVT and resulting pulmonary embolism.

<http://www.avweb.com/news/aeromed/181936-1.html>

here's another, should be required reading for anybody flying pressurized airplanes.

http://www.avweb.com/news/aeromed/181934-1.html

and another...

http://www.avweb.com/news/aeromed/181893-1.html

Blue skies,
CY

[QDMQDMQDM]

I actually though smokers did better at altitude due to them being used to a more hypoxic state under normal circumstances????

This seems very unlikely to be true. Total O2 transport capacity is reduced in smokers and although there may be some intracellular adaptations to chronic hypoxia as a result (and also the Hb-O2 dissociation will presumably be shifted, making Hb give up O2 more easily), it seems unlikely these would be sufficient to make any useful difference in hypoxia at altitude.

I stand to be corrected.

QDM