Can Deco-Sickness occur during the dive?

[Increase1]

As an inexperienced scuba diver I would like to ask about how decompression sickness takes place. More specifically, when does death occur.
Does it or can it occur during the dive, during ascent? Or does it only actually take its tolls after the dive.

 

[mathauck0814]

Welcome to ScubaBoard. The "bends" typically presents after surfacing. It's my understanding that lung overexpansion and/or embolizing can occur as a result of a rapid ascent so if the scenario were that diver A were to rapid ascent from a certain depth and either have sufficient inert gas come out of solution, or were to hold their breath, and then stop ascending prior to breaking the surface; the injury could occur in water. I doubt this is very likely though.

Is your question specific to bending? There's a lot of good data at DAN and a short article at Decompression sickness - Wikipedia, the free encyclopedia that might be helpful. Hopefully yours is an academic inquiry, otherwise I'd encourage you to contact DAN immediately if you have reason for concern that's more... "tangible"

 

[TSandM]

DCI is an umbrella term, used to cover all decompression-related medical problems.

The term includes arterial gas embolism, or AGE, which occurs when the diver holds his breath during ascent and experiences lung barotrauma that results in air in the arterial circulation. If death does not occur during ascent, it can be essentially immediate on surfacing.

DCS due to inadequate decompression is rarely, if ever fatal for recreational divers, and usually presents with symptoms on surfacing or after exiting the water. DCS due to massive omitted decompression, as with the Rouses on the Doria, can be fatal in a short period of time, and can be symptomatic while still underwater. This is not usual for recreation diving DCS cases.

 

[Bubbletrubble]

Wikipedia article on Decompression Sickness

If you're asking whether the onset of decompression symptoms can occur prior to surfacing, the answer is absolutely.
However, in most cases, DCS symptom onset occurs after surfacing and within 24 hours of the conclusion of the dive.

Death does not occur in 100% of DCS cases.
Although several hypotheses exist, the exact pathogenetic mechanism that underlies clinical DCS in humans remains unknown.

I would think that, at a bare minimum, any basic OW class would teach students how to prevent DCS, what symptoms could be DCS-related, and how to treat/what to do with a diver suspected of being afflicted with DCS.
Are you a certified scuba diver?

 

[Increase1]

Welcome to ScubaBoard. The "bends" typically presents after surfacing....

Is your question specific to bending? ...Hopefully yours is an academic inquiry, otherwise I'd encourage you to contact DAN immediately if you have reason for concern that's more... "tangible"

Hey, thanks for the prompt reply.
My question is specific to a diver ignoring the decompressing stop during a moderate dive (around 100ft). Basically, from my understanding, symptoms set in during the dive, and unconsciousness occurs after resurfacing.

The dive in question is a 100ft air dive for 40minutes. (The 10msw 7min stop is ignored) Followed by a repetitive dive (SI=01:00) of 70ft 45 minutes and so is definitely an academic concern rather than something I actually want to do..
I'm looking at getting certified before I even think of conducting a 100ft dive.
Thanks Again!

DCI is an umbrella term, used to cover all decompression-related medical problems.

The term includes arterial gas embolism, or AGE, which occurs when the diver holds his breath during ascent and experiences lung barotrauma that results in air in the arterial circulation. If death does not occur during ascent, it can be essentially immediate on surfacing.

DCS due to inadequate decompression is rarely, if ever fatal for recreational divers, and usually presents with symptoms on surfacing or after exiting the water. DCS due to massive omitted decompression, as with the Rouses on the Doria, can be fatal in a short period of time, and can be symptomatic while still underwater. This is not usual for recreation diving DCS cases.

As I mentioned, I'm focusing on a dive where safety is completely ignored. More specifically I am focusing on DCS due to ignored safety stops. Thanks for the reply!

Wikipedia article on Decompression Sickness

If you're asking whether the onset of decompression symptoms can occur prior to surfacing, the answer is absolutely.
However, in most cases, DCS symptom onset occurs after surfacing and within 24 hours of the conclusion of the dive.

Death does not occur in 100% of DCS cases.
Although several hypotheses exist, the exact pathogenetic mechanism that underlies clinical DCS in humans remains unknown.

'Basically, from my understanding, symptoms set in during the dive, and unconsciousness occurs after resurfacing.'
Just btw, I am not certified

 

[Increase1]

Any feedback ?

 

[Rhone Man]

That is pretty darned unlikely. The majority of DCS hits occur over an hour after surfacing. The only situation where I could see it as a live possibility is where a DCS hit occurs during a repetitive dive, but even that must be hugely unlikely because if you are below about 15 feet or so, the water pressure will keep the majority of the nitrogen (or helium) dissolved in your body tissues.

Physiologically, the bends is caused by micro bubbles coming out of solution and then slowly aggregating over time until they form big enough bubbles to do damage. For a dive around 100 feet unless it is like a 2 hour dive, you are going to have relatively modest nitrogen absorption, and unlikely you would get that kind of aggregation in less than about 2 hours after surfacing.

Situations where you are likely to have rapid onset DCS are going to involve very deep technical dives, normally using helium based gas mixes, and involving long decompression stops on oxygen enriched gases. A very famous example is Chris Rouse, a young diver who shot to the surface blowing off over an hour and a half of deco obligations, and he had onset of symptoms at the surface before he got on the boat. He later died in the chamber.

I won't go so far as to never, but it must be staggeringly unlikely a diver on a 100 foot dive (excluding saturation type commercial dives) could ever get a DCS hit before they actually broke the surface.

Also: I don't have any scientific basis for saying so, but my understanding is that rapid onset DCS is disproportionately more often "skin bends". Whilst uncomfortable, it won't of itself cause you to lose consciousness.

If you want to read more on the subject, I strongly recommend Deco for Divers by Mark Powell (Link).

EDIT: One big exception to this would be Audiovestibular DCS (inner ear). There are a number of recorded instances of divers switching from helium based mixes to nitrogen based mixes for decompression and a bubble being formed in the inner ear which causes serious nausea and vomiting during the dive. This nearly killed two particularly famous divers: John Bennett (when he set his world record dive at 1,000 feet) and Don Shirley, during the dive that killed Dave Shaw. But those are seriously deep dives.

 

[RonFrank]

You can find plenty of DCS discussions on this board that are real. Discussion on a hit that never occurred is kinda foolish as DCS is difficult to predict.

 

[Bubbletrubble]

Any feedback ?

Based on your posts, I'd highly recommend that you re-read the Wikipedia page on DCS.
Then re-read TSandM's post because it sounds like you are more interested in decompression illness (DCI; which includes both DCS and arterial gas embolism).
For the majority of DCI cases, symptomatic onset occurs during or after surfacing.

Most dive computers nowadays are programmed to recommend an optional 3 minute safety stop in the depth range of 10-20 ft.
Safety stops are optional but recommended. Deco stops are obligatory stops. When a divers skips deco stops, he increases his risk of DCS significantly.

When you take your basic OW scuba class, the instructional materials and your instructor will teach you about dive tables (hopefully) and what kinds of precautions to take to avoid DCI.

Hope this helps...

 

[Increase1]

Thanks for the replies! If you are wondering, the reason for this topic is that I am trying to teach someone about decompression sickness. A dive of this sort was raised, and I'm trying to figure out the theoretical issues involved. I know DCS is statistically based and can occur randomly but I'm going off likelihood.


Anyway, I'm going to try to be specific here.

Say this was the schedule:

100ft air dive for 40minutes. (The 10msw 7min stop is ignored)
Followed by a repetitive dive (SI=01:00) of 70ft 45 minutes

What is the likelihood of NCS occurring during these to dives?
How can these dives be modified to caused likely death? Or unconsciousness?

Thanks For You Help!

PS: About the Deco for Divers book, if it's at my local library I'll see if I can get it tomorrow.