Talk:High-pressure nervous syndrome

Does Helium cause this?
Is this caused by Helium? Or just by the high pressure? -- 77.7.136.157 (talk) 14:02, 1 October 2010 (UTC)
 * HPNS has only been observed when breathing helium-based gas mixtures under very high pressure (more than 16 atmospheres, a depth of 150 metres). It's probably a pressure effect, but we don't know for sure. All other gases (with the possible exception of neon) at those sort of pressures have a narcotic effect, which seems to "cancel out" HPNS. Even hydrogen is narcotic at these pressures, so it becomes difficult to isolate what causes HPNS. Experiments in Ultra-deep diving undertaken by Comex have used breathing mixtures containing predominately helium, with a small fraction of oxygen (to avoid oxygen toxicity), and some hydrogen (to 'balance' the HPNS). Divers at Comex have succeed in breathing these sort of mixtures under controlled conditions to an equivalent depth of 701 m, which is over 70 atmospheres. --RexxS (talk) 16:07, 1 October 2010 (UTC)

Temporary or permanant?
The article doesn't make it clear how long the symptoms stay with the diver. It would be nice to have some clarity on that point. Dennis Brown (talk) 14:34, 31 May 2011 (UTC)
 * The symptoms are most noticeable on descent, but generally lessen somewhat over a matter of hours after reaching a stable depth. The depths are such that returning to surface pressure is likely to require many hours (or possibly days) of decompression, during which time the symptoms of HPNS will fade away. There's a table at List of signs and symptoms of diving disorders (derived from Bennett and Elliott's physiology and medicine of diving) that really needs to be copied into this article, and which may clarify the duration of symptoms. As far as is known, the effects of HPNS are completely reversible when the pressure is restored to normal. --RexxS (talk) 03:31, 1 June 2011 (UTC)
 * I was also confused about whether this is temporary or permanent, especially given this sentence in the article: "The effects [...] remain regardless of the time spent at that depth." @RexxS, could you please add your description of the temporary nature of this syndrome to the article?  (Since I assume you have the source(s) to cite and I do not.)  69.36.132.252 (talk) 01:41, 30 June 2020 (UTC)
 * According to Bennett, the effects always disappear on ascent back to the surface. This is consistent with an effect caused by the pressure at extreme diving depths.
 * The sentence you quote needs to be read in conjunction with the previous two sentences. What it is saying is that some symptoms occur when descending below 150 metres, and these are more severe with rapid descents, but will fade when the diver reaches their target depth and stops descending. However, below 300 metres, a secondary mechanism comes into play which causes symptoms that remain as long as the diver stays at that depth, only being alleviated when they ascend to much shallower depths. I've added a sentence to help dispel any ambiguity about the temporary nature of the syndrome. Does that help? --RexxS (talk) 17:48, 30 June 2020 (UTC)

Use of anesthetics for preventing HPNS
It seems anesthetics are used by some divers for preventing HPNS. Hallephi1 (talk) 09:53, 13 December 2016 (UTC)