Hpns

[tekdiver1]

Ok let's have a discussion about High Pressure Nervious Syndrome "HPNS". I read in posting somewhere around here, stating that HPNS is brought on by the use of He at extreme depths, 400+FSW.

When I took the IANTD course the book I read stated that at first it was thought that He caused HPNS, however, recent research theorizes that HPNS is brought on due to the rapid onset of pressure.

The book stated that divers could reach depths below 1000+FSW on He02 if the pressure was increased slowly. This means a slow decent.

It was believed that when Sheck Exley and Jim Bowden dove Zacaton in 93 that Sheck died from HPNS. Not suprising, the dive plan put them at 1080FFW in 12 minutes. Sheck died at 800+FFW and Jim made it to 926FFW before calling it quits and returning to the surface. Now it is believed that Sheck died from C02 rather than HPNS. "Who knows"...

My point is that I believe that HPNS is brought on by rapid onset of pressure not by He.

Any views on this subject would be great.

Thanks again.

 

[Norm]

I agree with you td1. From all that I have read I think that HPNS is brought about primarily by the compression rate, not necessarily the gases being breathed. However, it must be understood that this rapid pressure increase can only be brought about by the use of "other gases". I have read that on very deep commercial and chamber dives they have found that at extreme depths (1000' - 2000') a minute amount of nitrogen added to the mix actually helps fight the symptoms of HPNS and improves motor skills. Go figure?
It just goes to show what we as divers already know: No one knows it all and diving is still not an exact science. "Any one can get bent on any dive on any day." There are "freaks" (and I say that with total respect) amoung us that can break ascent rules, break deco rules, break all kinds of the rules we adhere to as "carved in stone", and get away with it, (some repeatedly). There are also many divers that have been diving totally within the confines of safe diving practices, (with no physical defects, hangovers, or dehydration), and get bent like a pretzel! Although I have read that there is no physiological possiblity that our bodies can adapt to pressurization depressurization, many of us believe otherwise. There is evidence that frequent divers can "get away with more" than infrequent or new divers. Supposedly that is impossible but I have read that this too, is a distinct possiblity. Our bodies acclimating/adapting to frequent pressurization? (I think so)
The issue of frequent deep divers gaining an increased resistance to narcosis verses our learning to function under the effects of narcosis? I don't even want to go there! - Norm

 

[Arduous]

Hi tekdiver1 & Norm:

I think both of you have some valid points. I think the human body is capable of adapting to all sorts of conditions and I don’t mean over the course of millions of years. If you live in an area of the world that has seasonal changes, like I do here in New England. You find that after a long hot summer, when the temperatures start to get down around 50 degrees , everyone is wearing sweaters and jackets. However at the end of a long cold winter, when the temperatures get up to about 50 degrees, everyone’s walking around in t-shirts. Our bodies simply adapted to the changes in climate. Similarly when we first start diving we may have trouble clearing our ears. After becoming a seasoned diver, we clear our ears almost with out notice. Are we really just that much better at it, or has our bodies adapted in such a way to make equalizing easier for us ?? Interesting questions.

Dive Safe………………..Arduous