[diverjohn (OP)]

I was just listening to paleontologist Peter Ward's talk on H2S role in mass extinctions, where he suggests that when people breathe H2S at 80ppm while immersed in iced water, their body temperature will drop and they then enter a hibernation-like state until they can be attended by emergency room doctors.
Video at http://www.ted.com/talks/lang/eng/peter_ward_on_mass_extinctions.html
John Berger
Canada

[Mazurka]

Whilst I would not dismess the claim without more evidence; I am not sure that administering that concentration of H2S would not cause more harm than good. 

There are numerous documented cases where people who have suffered near drowning following rapid submersion in icy water have been revived up to an hour or so later.  Curiously children have been revived many hours later, so it is always worth getting a drowned child to hospital so they can attempt to revive.

Contrary to popular myth, it takes about an hour for life threatening hypothermia to affect casualties immersed in icy water.  This is because the body keeps as much heat in the core as possible.  The effect of this is to reduce the ability to swim (as the muscles cannot get enough oxygen & energy to operate) due to the arteries constricting (vasoconstriction).  A submerged casualty, whose lungs have rapidly filled with icy water will have chilled the blood supply to the brain very quickly, which is thought to be the way in which people survive such an incident.

(for more information see “Essentials of Sea Survival by Mike Tipton and Frank Golden - an excellent evidence based approach to water realted emergencies)

At 80 ppm, H2S will cause permanent damage to eyes and may also induce pulmonary edema (i.e. fluid on the lungs) which can be fatal.

[diverjohn (OP)]

Thanks Mazurka, the dangers of H2S for the eyes and lungs are certainly serious. That puts a new perspective on the story.

[diverjohn (OP)]

Interestingly, I came across yet another TED lecture about the advantages of H2S, this time its role in saving lives of people who are frozen then recover.
Watch it here at http://www.ted.com/talks/mark_roth_suspended_animation.html
Mark Roth actually set up a commercial enterprise funded by venture capitalists, that produces a liquid form of hydrogen sulfide for medical use.

[Mazurka]

I will have to have a look at that.  Cheers