From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: alt.med.ems,alt.survival,misc.rural,misc.survivalism,sci.med
Subject: Re: carbon dioxide poisoning / suffocation : (was power outage)
Date: 4 Jan 1999 16:37:35 GMT

In <3690E0FF.3C9F2BB1@gw-tech.com> Carey Gregory <cgregory@gw-tech.com>
writes:

>CO2 levels aren't the culprit exactly. It's the lack of O2 that normally
>accomanies high CO2 levels. Since ambient air carries 21% O2, any
>significant increase in CO2 results in a corresponding decrease in
>available O2. This is a much different mechanism than CO poisoning, which
>can occur at very low levels due to its highly efficient displacement of
>O2 in the blood. Unlike CO2, if you had CO levels high enough to
>significantly reduce ambient O2 levels, probably a single breath would
>kill you.


    All true, but the subjective distress is almost entirely caused by
the high CO2.  Humans don't have good hypoxia sensors, and people have
walked into nitrogen filled rooms and died, before they even realized
there was anything wrong.  You can breathe into a closed circuit which
takes out the CO2 until you pass out from hypoxia, without much
discomfort at all.  On the other hand, in a submarine or someplace
where CO2 is building up but there's plenty of oxygen, it's intensely
uncomfortable, and feels like dying.  So does breathing that 5% CO2 95%
O2 medical mix they treat CO victims with.

   And when the CO2 hits about 7% to 10% of your ambient air, you DO
die.  Even if the rest is O2.  It's CO2 narcosis, and it shuts you
down.  5% CO2 is about 40 Torr, your normal blood level.  So if you
breath that, you go up to 80 Torr, enough to black you out unless you
hyperventilate.  Double your minute volume and you can get down to 60
Torr, but you feel crumby.  At 10% there's no way to keep below about
90 Torr, and (unless you're a chronic COPD patient who's used to high
CO2s and has a high bicarb and other compensatory mechanisms) you black
out.  Then quit hyperventilating.  Then quit breathing entirely.


>Ultimately, hypoxia is the cause of death in either case, but death by CO
>poisoning wouldn't be called suffocation whereas death by CO2 (ie, lack of O2)
>would.


   Again, death by CO2 is not always death by lack of O2.  Though quite
often it is.


>> > I'd love to see a solid reference for this statement. Carbon Dioxide per
>> > se is not toxic,


   No, it's toxic.  Just not as toxic as CO.  But a much more
unpleasant way to die.  Fer sure.


>> > so I believe if such deaths occured it was from the displacement of
>> > available oxygen... however I would think this would leave one short
>> > of breath and gasping

   Nope.  Loss of O2 alone for humans is not bad.  However, if you put
a rabbit in nitrogen atmosphere, he'll go nuts.  Critters that live in
holes have VERY good low O2 sensors.  By contrast us monkey-descendents
are not so good at it.



>> > - not quite as subtle as CO which
>> > binds with the 02 AFTER it's in your blood stream.
>
>I've also never heard of a CO2 death from heating systems and I'm highly
>skeptical that it has ever occured.  Someone is confusing CO and CO2.


   Probably, since any heating system that puts out enough CO2 to be
toxic will kill everybody by CO first.  CO2 deaths occur only in exotic
places like subs and spacecraft, where absorbers fail but O2 supplies
don't.  It would have happened in Apollo 13, for instance, if not for
some some quick fixes with duct tape and the like to get one kind of
LiOH CO2 absorber mated with another system.

                                       Steve Harris, M.D.

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: alt.med.ems,alt.survival,misc.rural,misc.survivalism,sci.med
Subject: Re: carbon dioxide poisoning / suffocation : (was power outage)
Date: 5 Jan 1999 11:15:41 GMT

In <369187C6.7396@netcom.ca> Tom Matthews <tmatth@netcom.ca> writes:

>>     All true, but the subjective distress is almost entirely caused by
>> the high CO2. Humans don't have good hyoxia sensors, and people have
>> walked into nitrogen filled rooms and died, before they even realized
>> there was anything wrong. You can breathe into a closed circuit which
>> takes out the CO2 until you pass out from hypoxia, without much
>> discomfort at all. On the other hand, in a submarine or someplace where
>> CO2 is building up but there's plenty of oxygen, it's intensely
>> uncomfortable, and feels like dying.
>
>I learned this as a youngster, trying to swim long distances underwater
>(no fins, snorkel or scuba gear). I only succeeded in attaining a full 3
>pool lengths (75 yards), by blowing my lung air out during the less 10-15
>yards to prevent the intense discomfort of the CO2 build-up.
>
>--Tom
>Tom Matthews



   And it's still damned dangerous to so stuff like that, because you
can lose consciousness from hypoxia before your CO2 levels force you to
breathe.  This mostly because of the training effect which allows people
to get used to higher levels of CO2.  It's only really safe to do long
breath holding experiments underwater if you use pure oxygen.

    BTW, I wonder why blowing out the gas helps the subjective CO2
dyspnea effect (which I also have observed from lots of swimming)?
That wouldn't effect the concentration.  So the effect just be some
combination of concentration and lung stretch receptor firing.  If
you're breathing out, also your medulla probably "resets" its demands a
bit, thinking that you've now started to pay attention, and are
complying with orders to breathe.  Whereas, you're really just stalling
some more.

                                       Steve

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: alt.med.ems,alt.survival,misc.rural,misc.survivalism,sci.med
Subject: Re: carbon dioxide poisoning / suffocation : (was power outage)
Date: 17 Jan 1999 09:07:39 GMT

In <369c2af0$4$ovryyvat$mr2ice@news.datasync.com> bielling@datasync.com
writes:

>An increase in CO2 in the air, then, would tend to increase the driving
>force for the CO2 to go into water, or in this case blood. This much I
>understand but I'm guessing the result, metabolically, would be that the
>blood pH would drop once the buffer was overcome. IF this occurs does it
>essentially corrode the blood vessels until they weaken and burst?
>
>Take care,
>Duane



   No, your body defends your pH by having the kidneys make more buffer
(bicarbonate) over the course of a few days.  The problem with CO2 in
the air is that your body depends on the difference in CO2 pressure in
the blood and CO2 pressure in the air, to get RID of it.  Run one up
much and just can't breathe fast enough to do it.  The CO2 builds up in
your blood and acts as a direct anaesthetic.  Eventually, you lose
consciousness and respiratory drive, and it's a viscious circle from
there.

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: alt.med.ems,alt.survival,misc.rural,misc.survivalism,sci.med
Subject: Re: carbon dioxide poisoning / suffocation : (was power outage)
Date: 17 Jan 1999 09:28:45 GMT

In <369c20a8$1$ovryyvat$mr2ice@news.datasync.com> bielling@datasync.com
writes:

>>I haven't researched this at all, but I don't really think that carbon
>>dioxide simply coming into contact with water would produce carbonic
>>acid; not at normal atmospheric pressure, anyway.


Well, it does.  But it's an equilibrium thing.  There are 100 CO2
molecules floating around intact for every one that has reacted with
water for form H2CO3.


>So at any pressure or temperature there will be a certain solubility of
>the CO2 in water. But increase the pressure or decrease the temperature
>(or both) and you favor the CO2 staying in the water. But to sort of
>answer your statement, you can't get a whole lot of CO2 into water at
>ambient conditions but you can get some.



   Right.  One way is to have a base in the water to turn H2CO3 into
HCO3- as soon as made.  The body does this.   Pobably 70% of your CO2
is transported just this way, with an enzyme (carbonic anhydrase) which
hastens the conversion from CO2 to H2CO3 so it can be neutralized.  The
other 30% is carried attached to proteins, such as hemoglobin.  You
have about 27 ml CO2 per liter of blood, and only 7% of it gets out in
the lung on any pass.

   The process of CO2 + H2O --> H2CO3 is a slow one, requiring several
minutes.  You can watch it happen on this scale by neutralizing a weak
red-indicator base solution with soda.  It goes clear in a few minutes.
Add a drop of blood from your finger with that little bit of carbonic
anhydrase, and it happens immediately.  Makes a nice demo for kids.  Or
it did before Atari.


                                      Steve Harris, M.D.