From: ((Steven B. Harris))
Subject: Re: helium inhalation
Date: 06 Jun 1995

In <admpt-0506951336300001@128.227.104.34> admpt@hrp.health.ufl.edu
(Danny Martin) writes:


>Inhaling helium from a ballon is different from inhaling straight from a
>high pressure cylinder. In the cylider scenario, the gas cools when
>going from ~ 2,000 lb/ sq in to 15 lb/ sq in and this rapid cooling may
>be the source of the "report" of damaged vocal folds.

Comment: I'd have to see data on that to believe it.  For one thing,
this kind of non-adiabatic (irreversible) expansion generates little
cooling for most gases, since it's only Joule-Thompson effect.  SCUBA
divers would freeze their lungs otherwise (you cannot help heating it
during compression, but you don't have to cool much on expansion).
Finally helium has the smallest Joule-Thompson coefficient of any
gas-- it's NOT CO2 and doesn't behave like it.  Feel a helium balloon
that's just been blown up-- it's not particularly cool, and a LOT more
work was done there by the gas, than is done when gas escapes from a
regulator and is actively breathed.

>My grad students have inhaled a lot of helium from ballons without ill
>effect- a 80%Helium 20% Oxygen mixture will produce the desired "Donald
>Duck" voice without the hypoxia problems,

Yeah, but where do you get it outside a pulmonary lab?


                                                    Steve Harris, M.D.

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.physics
Subject: Re: Helium burp
Date: 27 Mar 1998 21:50:08 GMT

In <EqH1xL.Ct7@midway.uchicago.edu> meron@cars3.uchicago.edu writes:

>In article <6ff7i7$3ql$1@flotsam.uits.indiana.edu>,
>glhansen@copper.ucs.indiana.edu (Gregory Loren Hansen) writes:
>
>>In article <1998032701431301.UAA23714@ladder03.news.aol.com>,
>>DGoncz <dgoncz@aol.com> wrote:
>>
>>>Does hydrogen produce funny burps, and is it soluble in water? Would
>>>argon or xenon produce a deep sound, the opposite of helium? And are
>>>they soluble in water? Any more compounds or elements except chlorine,
>>>astatine, and radon that might be interesting?
>>
>>Argon or xenon? I've been sniffing helium for many years, but I haven't
>>even thought of trying heavier gasses! I'm going to be looking for a
>>chance to try it.
>
>Argon isn't that much heavier than air.  As for Xenon, well, this is
>going to be one expensive burp:-)
>
>Mati Meron                      | "When you argue with a fool,
>meron@cars.uchicago.edu         |  chances are he is doing just the same"


   Sure enough, since the stuff is several bucks a liter.  It's also an
anaesthetic with properties very similar to nitrous oxide, so you might
get a little high from it.  If the stuff weren't so expensive, it would
probably be used as a the basis for all gas anaesthesia, since
obviously (being an inert gas under physiological conditions) it
doesn't have any chemical-metabolic or toxic side effects.  All this
provides a nice demonstration that some or all of the anaesthetic
effect from many kinds of gas anaesthesia, is due to physical changes
in neuronal membranes or fluids as gas disolves in them, and is not
caused by any chemical-receptor like pharamacological reaction at all.

                                          Steve Harris, M.D.

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.physics
Subject: Re: Helium burp
Date: 27 Mar 1998 22:13:19 GMT

In <6fge3g$rna$1@news.fsu.edu> jac@ibms48.scri.fsu.edu (Jim Carr)
writes:

> There is a significant danger with heavier gases that is not
> present with He.  With He, if you pass out due to insufficient
> oxygen the He escapes and special measures are probably not
> needed.  Heavy gases are, well, heavy, and they will not leave
> the lungs so easily.  One of the heavier ones, sulfur hexafluoride,
> is potentially fatal and the same is probably true of Xe.  Ar is
> probably borderline, but not so different from CO2 in mass and you
> know what happens in the candle demo.  The only effective way to
> clear heavy gases from your lungs is to hang upside down.
>
> Just because they are inert does not mean they cannot kill you.
>
> You might talk to the Low-O2 safety folks about these gases and
> their safe use since they do displace the air you need to live.



    Sorry, but this is incorrect.  The forces of mixing caused by gas
inhalation and exhalation in normal lungs are HUGE.  More than enough
to stir up any mix of mere gases, even when one is 5 times heavier than
air, as in SF6.  Heck, I've done fluoroscopy of living dogs being
ventilated with oxygen while their lungs were full of *liquid
fluorocarbon,* which has twice the density of water, and several
thousand times the density of air.  The mixing is still excellent, and
the bubble jets get all the way to the ends of the airways with every
breath (and the dogs are fine).  An inert gas like xenon will simply be
mixed up and purged in a breath or two (xenon has been successfully
used as a gas anaesthetic).  If it has enough concentration to produce
an anaesthetic effect before then, you'll feel it.  And you can always
asphyxiate yourself with it.  But on the whole, xenon is no more, and
no less dangerous than nitrous oxide.

   Pure CO2 is considerably more toxic because of the problem with CO2
narcosis at high partial pressures (anything over about 40 Torr).   I
don't know about SF6, but I from what I've read, it's probably inert
enough to be breathed like the freons, and has suffocation potential
only (and then only in a room full of it, NOT if you just get a lung
full of it-- see above).  It's thermodynamically unstable toward SF4
plus F2, but this doesn't happen fast enough to matter (it's
kinetically stable).  For UF6 the kinetics are such that is a certain
equalibrium toward the decomposition to SF4 and F2, and of course the
F2 destroys any tissue it contacts.  It's the F2 that makes UF6
dangerous.

                                        Steve Harris, M.D.

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.physics
Subject: Re: Helium burp
Date: 29 Mar 1998 01:57:44 GMT

In <6fjvpu$4oc$1@news.fsu.edu> jac@ibms48.scri.fsu.edu (Jim Carr)
writes:
>
>jac@ibms48.scri.fsu.edu (Jim Carr) writes:
>|
>| Just because they are inert does not mean they cannot kill you.
>| You might talk to the Low-O2 safety folks about these gases and
>| their safe use since they do displace the air you need to live.
>
>sbharris@ix.netcom.com(Steven B. Harris) writes:
>>
>>    Sorry, but this is incorrect.  The forces of mixing caused by gas
>>inhalation and exhalation in normal lungs are HUGE.
>
> True, but we are talking about a situation where someone inhales
> a large amount of (say) sulfur hex, speaks, and then maybe tries
> it again and passes out.  This is a serious situation.
>
>>More than enough
>>to stir up any mix of mere gases, even when one is 5 times heavier than
>>air, as in SF6.  Heck, I've done fluoroscopy of living dogs being
>>ventilated with oxygen while their lungs were full of *liquid
>>fluorocarbon,* which has twice the density of water, and several
>>thousand times the density of air.  The mixing is still excellent, and
>>the bubble jets get all the way to the ends of the airways with every
>>breath (and the dogs are fine).
>
> Interesting, and useful, since it means fast action can help the
> person who collapses if a bystander knows the nature of the problem.
>
> However, it is also true that people have suffocated _outdoors_ from
> SF6 accumulating in a low area.  Heavy inert gases are dangerous.
> A tank leak in a lecture hall could be very serious.


    Obviously you're in trouble if you collapse in any place where the
asphyxiating gas is still available to be breathed after you're down.
Where we disagree is the situation in which you breathe enough gas to
lose consciouness, and then collapse to the floor or someplace where
any further air you breathe is pure.  I think that it would be very
hard for someone to die that way.

    I can't prove it, but my impression from watching lots of hypoxic
animals and people is that the system is just too robust for that.
"Agonal gasping" goes on for quite a long time, even in full cardiac
arrest-- as long as 30 seconds in our dogs, and a fair amount of mixing
happens with that much gasping.  So even pretty complete anoxia to the
brain is not enough to prevent such gasping-- you'd have to have some
anaesthetic action also.  Perhaps with anaesthetic asphyxiant gases
like Xe or N2O or CO2, but I think less likely with SF6 or Freons.

    To spell curtains you really need the situation in which the
hypoxia is so severe that you get not only unconsiousness, but also
cardiac arrest, which happens only (in the healthy) when SEVERELY
deoxygenated blood hits the heart.  If your heart has stopped, it won't
recover without some brief recirculation (chest compressions, etc),
even if the lungs have been reoxygenated (no heartbeat without
oxygenated blood in the coronaries). However, again, it takes a lot of
anoxia-- almost complete loss of blood oxygen content-- to stop the
heart in a healthy person.  For this reason, I believe this kind of
thing (relatively sudden and early cardiac arrest due to anoxia-- in a
few seconds) happens only in explosive decompression, or situations of
true poisoning of hemoglobin (such as with HCN, H2S, CO--- where a good
lungful really can kill you).  In other situations, it just is too hard
to get oxygen out of the blood fast enough.

   For the inert asphyxiant gases, I would expect cardiac arrest to be
long delayed, since the oxygen content of the blood would insure that
even lungs filled initially full of pure asphyxiant would come to some
kind of equilibrium low alveolar O2 after a bit, and that would be
enough to run the heart for awhile.  Remember, you've got enough oxygen
in your blood to run your circulation for several minutes without any
contribution from the lungs at all, and that is why cardiac arrest due
to an asphyxiant gas happening sooner than a minute or two requires
active breathing of the asphyxiant for a good portion of that time---
not just to flush the lungs of O2, but also to flush the *blood* of O2.
If you asphyxiate an anesthetized animal with pure nitrogen, for
example, it can take as long as 45 seconds for cardiac arrest to occur.
(In a person walking into a nitrogen filled room, as at NASA, loss of
consciousness can take only a few seconds, though).

   (Of course, when you "breathe" vacuum during an explosive
decompression, complete deoxygenation of blood happens in only one pass
through lung with no equilibrium possible, so again the situation is
different: there the dog experiments done for the Apollo program show
a column of completely deoxygenated blood getting about halfway down
the aorta before the heart stops from the deoxygenated blood flowing
though it.  So you get oxygenated blood in the periphery but completely
deoxygenated blood centrally.   With explosive decompression you can
see cardiac arrest in 10 or 15 seconds, much faster than with any other
kind of hypoxic state).

    Anyway, the bottom line is that whether you're conscious or not
with an asphixiant, so long as your heart is beating, you're going to
be agonally gasping and bootstrapping your lung oxygens up (if you're
gasping in air).  And in the absense of poisonm, your heart will beat
until your blood oxygen goes to almost nothing, a situation it's
impossible to force acutely with a couple of lungfuls of an asphyxiant
gas.   Basically, you can't die that way from a pure asphyxiant.  Too
much body oxygen reserve.

                                            Steve Harris

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.physics
Subject: Re: Helium burp
Date: 29 Mar 1998 08:52:52 GMT

In <6fko68$j8f$1@news.fsu.edu> jac@ibms48.scri.fsu.edu (Jim Carr)
writes:
>
>>   For the inert asphyxiant gases, I would expect cardiac arrest to be
>>long delayed, since the oxygen content of the blood would insure that
>>even lungs filled initially full of pure asphyxiant would come to some
>>kind of equilibrium low alveolar O2 after a bit, and that would be
>>enough to run the heart for awhile.  Remember, you've got enough oxygen
>>in your blood to run your circulation for several minutes without any
>>contribution from the lungs at all, ...
>
> but, I presume, not the brain.  Which is why prompt rescue from a
> low O2 environment is essential but must be done safely.


   Yes, in low oxygen environs you lose consciousness or useful
function for some minutes before you get hypoxic enough for your heart
to stop.  You get very little brain damage ordinarily, until you get
actual circulatory arrest.   Since the amount of O2 necessary to keep
the brain going, at least in the short term is a lot less than it takes
to keep it conscious.  Even after full circulatory arrest at normal
temperatures (explosive decompression would be a good example), the
damage is reversable for an amazingly long time.  It used to be said
that the brain only lasted 4 to 6 minutes without blood flow.  But
lately it's become clear that this is only the amount of time before
which damage cascades start which result in neuronal death much later
(many hours later).  Neurons don't blow up or something after 5
minutes-- they're fine for hours.  In fact a recent paper in Lancet
reported being able to culture working neurons from human brains as
long as 8 hours after death, even with no special attempt at cooling.

   So the resuscitation cocktail and protocol is the key, and (as the
cryonicists have long said) you're only as dead as the resuscitation
technology of your time is ignorant (again, see the Day the Earth Stood
Still).  We've gotten dogs back to basically normal kennel behavior
after normothermic complete circulatory arrests of more than 16
minutes-- a LONG time to be clinically dead.  And we've got a long,
long way to go at this before we hit any fundamental limits.

                                           Steve Harris

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.physics,sci.med,sci.med.pharmacy
Subject: Re: Perverse question about playing wind instruments
Date: 18 Oct 1999 14:14:39 GMT

In <380B03CA.545C3DE9@home.com> Mark Fergerson <mfergerson1@home.com>
writes:

>> >Has anyone ever tried playing a wind instrument in a helium-oxygen
>> >atmosphere?
>>
>  Are there things about the size of sleeping bags? Rig them so you're
>standing up, or even drape it over a chair...
>
>> A recording studio with several of these chambers might make some
>> money. The cost of operation is low, and sales of recordings might
>> amortized the equipment. I wonder if the Andrews Sisters would be
>> interested. They were on the Joey Bishop Show the other morning. I
>> don't know if they are still together, or even alive.
>
>  Yow. A barbershop quartet on helium... (shiver)... Helium Rap? Those
>guys doing the new "Folgers'" commercial...



   I'm thinking of a return of the late 50's Chipmunks albums.


>  How about "Hyperbaric Chamber Music"? Hell, an entire hyperbaric
>orchestra!
>How about "open air" so to speak, in an eventual Lunar colony?
>Underpressure would produce the opposite; an attenuation of highs, and
>a perceived enhancement of lows, no? How would the much lower Lunar
>gravity affect musical instruments' aural properties? For instance, a
>gong or a cymbal should produce a longer sustain because of the
>reduced damping in their supports, no?


   Sure: conservation of energy.

>> Use of a nasal catheter will demonstrate the effect, but musicality
>> will suffer. The gas composition will vary considerably with breathing
>> patterns, related to musical phrases, and otherwise not uniform.
>
>  Scuba tanks for those difficult notes? Several tanks with various
>(nontoxic) gases for different octaves? How much higher/lower could
>you go? This would really screw up Olympic Flute Solo...


   Would work.  Such stuff has been used by radio personalities for
prolonged chipmunk-like dialogs. "Alvin!"

   On the other hand, most of it also ends up sounding a lot like the
midgets from Munchkinland.  "We represent... the Lollypop Guild, the
Lollypop Guild, the Lollypop Guild..."



>> Without a detailed understanding of alveolar fluid mechanics, these
>> experiments can be dangerous. One does not breath deeply if
>> conciousness is lost.


   No problem if you always makes sure that all your mix gases are at
least 15% O2.  One reason dental N2O is always 20% O2.


> Deep, controlled breathing can clear almost any contaminant gas. This
> requires concious control.
>
> Natural discipline for even an amateur wind musician.


   You'll clear any gas with any breathing, since diffusion is
responsible for moving gases from small airways to alveoli in even
tidal breathing, and works quite well.  You can survive on O2 run down
your trachea through a small catheter at 10 L/min with NO respiratory
movement.  Although your CO2's climb sky-high.  This is a standard test
for brainstem function, and one of the panel used in clinical diagnosis
of brain death.

   As for conscious control of gas mix, it is again one of the things
dentists rely on when using N2O mixes through a nosepiece.  When you go
under too far, you breathe through your mouth (normally inhibiting this
somewhat when someone is working in your mouth), and this clears the N2O
from your lungs.  On the other hand, the savvy patient can consciously
control level of sedation during especially painful parts of any
procedure by breathing *very* slowly from the nosepiece ONLY (so as not
to exceed its flow capacity), and holding the resulting expired gas as
long as possible before exhaling.  Since (again) the dental stuff never
has less than 20% O2 in it, this does not produce hypoxia. It can,
however, produce quite an impressive level of anaesthesia/analgesia.