Hydrogen Sulfide

[jome]

It's not entirely new concept, but most "freediving nerds" will probably find this interesting.

The Journal of the American Society of Anesthesiologists, Inc. - Anesthesiology Fulltext: Volume 108(4) April 2008 p 659-668 Inhaled Hydrogen Sulfide: A Rapidly Reversible Inhibitor of Cardiac and Metabolic Function in the Mouse.

Money quote:
Results: Breathing H2S at 80 parts per million by volume at 27°C ambient temperature for 6 h markedly reduced heart rate, core body temperature, respiratory rate, and physical activity, whereas blood pressure remained unchanged. Echocardiography demonstrated that H2S exposure decreased both heart rate and cardiac output but preserved stroke volume. Breathing H2S for 6 h at 35°C ambient temperature (to prevent hypothermia) decreased heart rate, physical activity, respiratory rate, and cardiac output without altering stroke volume or body temperature. H2S breathing seems to induce bradycardia by depressing sinus node activity. Breathing H2S for 30 min decreased whole body oxygen consumption and carbon dioxide production at either 27° or 35°C ambient temperature. Both parameters returned to baseline levels within 10 min after the cessation of H2S breathing.


Bit hesitant to post it, but since it's only a matter of time someone discovers it, I guess I might as well...

The good news is that you should be able to spot cheaters pretty easily from the stink

[efattah]

This was discussed earlier, and is an obvious thing to try. Similar to using cyanide, which has also proven effective by some divers. Don't try at home!

[truik]

Althought it is mentioned in the topic of the article, I must emphasize more the fact that these test were done with mice. Also the toxicity of H2S should have been mentioned when posting this kind of links to forums IMHO, if this kind things need to be posted here.

The concept is really something that nobody should ever even imagine to try in real life.

Human can smell (detect) the H2S in about concentration of 5 ppb = 0.005 ppm and one get used to that concentration pretty quickly (doesn't detect it anymore) and that is when it becomes real danger.

Tests were done with 80 ppm, whereas the limit for concentarion that are Immediately Dangerous to Life or Health (IDLH, meaning irreversible damages) is 100 ppm / 30 min.

http://www.airgas.com/documents/pdf/001029.pdf

[jome]

I agree, I should have put more warning stickers on the post which I mostly meant as a joke.

It is dangerous to draw direct conclusions, but at the same time I find this an incredibly cool thing (not so much as a tool for freediving, but as a general observation and medical implications). But since I picked it up from one of the biggest news sites on the net, I figured it already available information. Of course posting it on a freediving forum twists the context a little bit and may make the exactly same information more dangerous.

So thanks for the corrections - absolutely agree - don't try this at home (and this really doesn't have real implications for diving, but in the land of science fiction, it could enable some really really really long breath holds)

Perhaps more in the category of "beach bar"?