Oxygen deficient atmospheres (Physiologists/Meds)???

[Tangent Police]

I have been debating this with friends for a while and have got no further forward with an actual answer. I place my faith in PH to enlighten me.

I explore old metal mines as a hobby and one of the hazards is low oxygen. Not particularly hydrogen sulphide or methane, just low oxygen.

I've debated this with meds, trainers and am myself a chemist/science teacher. Of course, the military have invested heavily in diving gases and everyone knows about mountaineering. Not too many people know about oxygen deficient atmospheres.

I either carry a Davy Lamp which goes out at about 15% (and it's time to leave) or a 4-gas meter.

[i]Here is what the "witch doctor of the interweb" says.

O2% by volume. Symptoms during reduction from :-


21 to 14% First perceptible signs with increased rate and volume of breathing, accelerated pulse rate and diminished ability to maintain attention.
between

14 to 10% Consciousness continues, but judgment becomes faulty. Rapid fatigue following exertion. Emotions effected, in particularly ill temper is easily aroused.

10 to 6% Can cause nausea and vomiting. Loss of ability to perform any vigorous movement or even move at all. Often the victim may not be aware that anything is wrong until collapsing and being unable to walk or crawl. Even if resuscitation is possible, there may be permanent brain damage.
below

6% Gasping breath. Convulsive movements may occur. Breathing stops, but heart may continue beating for a few minutes - ultimately death. [/i]

Interesting read:- http://wasg.iinet.net.au/Co2paper.html

People are a bit nebulous about limits, probably because of the variation between people and the exertion being done.

I'd like to know a lot more about what the safest minimum amount a person can tolerate "at rest" and why this has been arrived at.

Clearly the partial pressures are different and so it's not quite as simple as saying "well, it's got to be similar to climbing a mountain". It's slightly different as there is no CO2 present as would be if combustion had lowered the level. CO2 messes with respiration. Here it would be absent.

It's all very well having a gas meter, but it's a better idea to know what it means. It would be nice to sit down and be able to recouperate without being in too much danger. The biological oxidation of pyrite minerals can drag the oxygen level down to about 9% where there is no ventilation. Clearly this may sound bloody dangerous but we are trained and careful.

The bad air stories can be quite entertaining with people getting blue lips, pins and needles, tunnel vision, headaches, symptoms of intoxication, etc. In certain cases (usually with coal mines-which is bloody stupid) abseiling into shafts presents this hazard.

Here's a photo of one of the chaps note bad air warnings. Goes below 10% there.

Removed by Mod

So, the question is "how low can a healthy human go" if you make any assumptions, outline where.

One of our lot is considering doing some pukka medical research at some point. I'd like to get amongst the theory first though.....

Cheers, TP

Edited by ThatPhilBrettGuy on Friday 12th February 18:01

[tank slapper]

The children at 28dayslater don't like PH for some reason, so linking to them isn't usually the best idea.

[maddog993]

Tangent Police said:

Removed by Mod

I'd say that link is NSFW but that's a bit of an understatement

Edited by ThatPhilBrettGuy on Friday 12th February 18:02

[Tangent Police]

tank slapper said:

The children at 28dayslater don't like PH for some reason, so linking to them isn't usually the best idea.

I don't post pictures myself as there are potential access/rescue consequences. It was relevant to my post (bad air). You can't just go swanning into one of these places without putting yourself in huge danger. Rotten false floors above hundreds of feet drops are possible.

I'm interested in the air "truth" though.

[tank slapper]

I wasn't referring to the content of their site, but that they are redirecting links from PH to unsavoury sites.

[Munter]

maddog993 said:

Tangent Police said:

Removed by Mod

I'd say that link is NSFW but that's a bit of an understatement

Thank god I'm not at work!

The Boss Is a "whatsit" at full volume could have caused trouble!

Edited by ThatPhilBrettGuy on Friday 12th February 18:04

[ucb]

I dont understand why you believe going down a mine shaft with a lower partial pressure of oxygen is different to climbing a mountain. Is there significantly more C02 in the air? If not, then CO2 is not an issue.

Normal ventilation is blood-CO2 sensitive at ground-level o2 levels. Oxygen only begins to stimulate respiration at very low blood partial pressures, such as <8kPa. The issue is therefore the partial pressure of oxygen in the air you are breathing, and not the percentage content. Therefore, whether you are at 4000m (atmospheric pressure 85kPa, O2 partial pressure 17kPa, blood o2PP approx 6-8kPa) or 200m underground (atmos pressure 102kPa, O2 partial pressure 21kPa, blood o2 partial pressure 10-12kPa) the effect of hypozaemia is the same.

What's the lowest you can tolerate at rest? Probably around 5-6 kPa, but you will get marked physiological changes. What is the lowest you can recuperate from after a period of activity? Conjecture, but I wouldn't want to try to recuperate in a hypoxic environment which is subjecting my body to a physiological stress in itself.

[ThatPhilBrettGuy]

Yes, linking to 28dayslater has unfortunate results. Best not to....

[Tangent Police]

Interesting stuff. Thanks.

Right. So the saturation of haemoglobin is directly proportional to the effective pressure of Oxygen and that's it.

Interesting stuff, makes things a lot more simple. Hypoxia and wikipedia was my friend.

I'll have to do some calculations and relate people's experiences at height (preferably with no altitude training) with %O2 at STP.

Edited by Tangent Police on Friday 12th February 18:41

[ucb]

If you google 'haemoglobin-oxygen dissociation curve' you should get the relationship between o2 and Hb .
It is a sigmoid shaped curve, with o2 almost fully saturated above 8kPa (approx 93% sat). The pO2 at 50% saturation is about 3.5kPa.

Glad if this has helped.

[Tangent Police]

Yep, thanks a lot

[JumboBeef]

If I'm understanding you correctly, you want to make sure that you are not personally affected by low O2....?

Rather than measuring how much O2 there is there to breath, why not measure how much there is inside you?

You should buy a SPO2 meter (Oximeter), like one of these:

http://www.amazon.com/Choice-Med-MD300C13N-Finger-...

[Tangent Police]

That is the plan from my Med mate. I don't like the idea of tapping an artery though

Clearly, people respond to altitudes/low O2 differently due to fitness but there will be a level which fits all.

Reading more about hypoxia, I must have been fit at the time as when I've heard people moaning about headaches/pins and needles/tunnel vision/drunkness, I've felt fine.

I'm going to do some research and calculations and then test it. We may need bottled air for some of it, but it will go further knowing when to use it.

[ShadownINja]

Tangent Police said:

Clearly, people respond to altitudes/low O2 differently due to fitness but there will be a level which fits all.

I understand it has nothing to do with fitness but physiological make-up. Some people can handle high altitudes no problems while others who are much fitter suffer from oedemas.

Have a look at this: http://en.wikipedia.org/wiki/Altitude_sickness

I know someone studying mountain medicine so if you mail me via my profile with questions I can forward them...

Edited by ShadownINja on Saturday 13th February 00:41

[Tangent Police]

Good link, I'll have a peruse.

There is some interesting work to be done here. I'm up for some collaboration/discussion/criticism with anyone who is interested in the area.

We have some good research areas as well. (which are very difficult to create artifically-this coincides with altitude research)

I've learned a lot today.

Edit:- Quite a few of my chaps are involved in underground rescue and so this research is very relevant in a field with the dogma of "If it's lower than 19.5% you can't go in". We need to be looking around the 11-12% mark and gaining proper insight into how people behave.

Edited by Tangent Police on Saturday 13th February 02:35

[ShadownINja]

I think one "issue" you could look at is how the body adapts to suit the conditions. For instance, if you were helicoptered up to the top of Everest (not sure it's possible given how thin the air is... heli might crash) and stepped out, there's a very good chance you'd go unconscious and unless you were brought down to a lower height immediately, would die. So, when someone is preparing to summit Everest, they will spend a few weeks acclimatising by perhaps spending some time at Namche Bazaar in Nepal. That's why mountain sherpas rarely have problems - they're used to the altitude.

http://www.google.co.uk/search?q=mountain+training...

[Tangent Police]

The rate of onset appears to vary with the gradient of the oxygen. I'm going to do some more research/maths over the weekend and then actually trial myself in some various atmospheres. What I want to do is to get a safe lower limit. Obviously, you could go into 14% and exert yourself silly and pass out, but I would want to be able to have enough reserve to back myself right off, relax and not black out/collapse.

Unlike black damp (CO2) there is very little variation in actual height from teh floor. If you were to wander into a low air/CO2 mix and pass out, you'd probably suffocate on the floor in the CO2.

I imagine it's around the 11.5% mark (off the top of my head) to be marginal.

Since there will be a lot written about altitude sickness, all I have to do is work the maths backwards to an effective pressure of O2 and then turn that into a ratio at ground level.

I'll post my results as I get them.

The biggest danger is hitting low oxygen when abseiling in a shaft. It's all very well having a meter, but you need to be 100% certain you have a margin to get yourself out. What is more odd is that when you start an ascent in low O2 and work your way up, it feels that you are getting fitter/fresher/more able with exercise. Very odd indeed.

[ShadownINja]

Did you see the episode of Top Gear when they went across South America and up some big mountain range? Same thing happened.

http://www.youtube.com/watch?v=tCEqksAKt_c

[ucb]

If you acutely ascend to the Everest summit and get out, you'd have around half a minute before you would die.
Altitude = 8800m
Air pressure is apparently 30kPa, and therefore there will be an insufficient partial pressure of oxygen to maintain oxygen diffusion into the blood.

Altitude conditioning produces cardiovascular, pulmonary and haematological changes. Cardiac output increases to maintain o2 delivery to organs, respiratory minute ventilation increases initially, but over a period of weeks reduces. The response of ventilation to hypoxia also changes over time. There is an increase in red blood cell mass in order to increase O2 carriage in the blood, but again that takes days-weeks to produce change.
I do have a textbook which contains a chapter on such changes, but I haven't got it with me an it is probably in storage until July.
I'll try and get some links for you.

[ucb]

This one seems to explain acute/chronic changes:
http://www.bio.davidson.edu/courses/anphys/1999/Yu...

Use the US National Medicine Library's search function:
http://www.ncbi.nlm.nih.gov/sites/entrez

and select for 'Review' articles for several hundred articles.

Edited by ucb on Saturday 13th February 16:00