Rapid descent

[AquaTec]

Question for all you medicaly advanced indaviduals;

Are you aware of any Physilogical effects of rapid descents

By rapid I am talking about 100 feet per minute say for three minutes.

I have heard of a couple of thing but they don't make since to me, so I am seeing what other view points there are out there

 

[sheck33]

i have never heard or read anywhere that a rapid descent would have any ill effects. The only thing i can think off would be being hit like a rock by narcosis if you were to do a fast descent to more than 100' on air.

just make sure you'r ears/sinuses are cleared

 

[AquaTec]

Yes I agree, the narc hit is very intence.
I should have clarified. I mean using the appropriat gas for the depth. so lots of helium

 

[Dr Deco]

Dear AquaTec:

With respect to decompression sickness, I am not aware of any problems with rapid descent. Commercial (deep) divers do experience such effects are “high pressure nervous syndrome” and “hyperbaric arthralgia” from a too rapid descent. This would not be seen at less that 400 fsw.

Ear barotrauma, if you can not clear, is a different problem.

Dr Deco :doctor:

 

[JDostal]

When we dive shipwrecks in the deeper depths (100+) range, we usually rocket down to the wreck as fast as we can. All air out of BC and dry suit, go down head first kicking the whole way. The quicker we can get down there, the more time we will have on the wreck. Doing the dives on air, if you want to stick to NDL's, doesn't give you much time so we try and get down to the wreck as fast as we can. We've done it quite a few times to no ill effect...of course, you get the occasional buzz doing it, but hey.

And granted...this is quite far away from a scientific answer as well =)

 

[Bob3]

You'll be OK as long as you start off on bottom gas, you'd risk an oxtox hit otherwise.

 

[Jarhead]

That the Navy tables list a Max. descent rate of 72 fpm. Don't know if there is a reason behind it though.

Jarhead

 

[Dr Deco]

Dear Omicron:

“Bends/no bends limit”

It is important to recall that there does not exist a “wall of DCS” at the end of the NDL. One does not encounter a “bends/no bends” situation when you hit the “table limit.” Such a concept is discussed, but it is not a physical reality.

Kicking to the Bottom

On the other hand, vigorously kicking to the bottom (if that is indeed what is done) would probably do more to add tissue gas through the mechanism of increased blood flow to the body, especially the legs. This is not a theoretical concept; it has been known since the time of the physiologist Krough (about 1920). He received a Nobel Prize for his studies of blood flow and exercise.

Some increased blood flow continues for a while (about 20 minutes) even when you have stopped kicking. When you then make the ascent, you are generally less active than when descending (in this particular case). This arrangement could lead to potential DCS problems. I would recommend that vigorous activity to reach the bottom carries with it a potential penalty.

Dr Deco :doctor:

 

[JDostal]

Dr. Deco - as far as there not being a wall of DCS, that I most definitely realize. I work in a "computer science" field...although we call it computer "science", it's more of a black art than anything. I've come to understand that some of the theories on DCS should be taken in the same meaning

Thank you for the information on the effects of kicking and increased blood flow - I've read similar theories and have wondered about the potential impacts of this on on-gassing....definitely something I will consider in future dives!

 

[AquaTec]

Bob3 once bubbled...
You'll be OK as long as you start off on bottom gas, you'd risk an oxtox hit otherwise.

On a Hypoxic mix you will need to start on a travel gas, but the switch is very simple and can be done on the fly as long as it is completed prior to the MOD of that gas

As for the onset of HPNS, a bit of nitogen wards off the effects. and I beleive that the commercial divers you speak of tend to continue on deeper and are traveling at rates faster than 100 ft/min

Doc tell me more of what you know about HPNS, it is an interesting subject

and as for kicking hard to the bottom, this will dramaticly increase ongassing, which isn't a problem on the way down. but you can thow away your tables or computer on the way up. increase your decompression times exponentialy