Decompression Tables

[HowardE]

I guess my source was wrong.

Thanks Keith for the current info.

 

[kgault]

I guess my source was wrong.

Thanks Keith for the current info.

Who was your source?

If they are at NEDU or in Navy Diving Research, it would be good to ensure they have correct information.

Thanks,

Keith

 

[HowardE]

Who was your source?

If they are at NEDU or in Navy Diving Research, it would be good to ensure they have correct information.

Thanks,

Keith

PM Sent.

 

[ucfdiver]

I have never met a diver that has had a DCS hit nor have I ever met a diver who knew a diver that was rumored to have had a hit. Now, I lead a sheltered life and, personally, don't push the envelope. Nor do I know more that a very few divers who do. The dives they do border on insane (in my limited recreational view). Yet they're still walking.

Here's a poll over on cave diver forum where about 43% of 237 respondents admitted to taking a hit of some sort.
Have you gotten bent? - Cave Diver's Forum - Cave Diving Resource

 

[Shearwater]

Here's a poll over on cave diver forum where about 43% of 237 respondents admitted to taking a hit of some sort.
Have you gotten bent? - Cave Diver's Forum - Cave Diving Resource

This starts to take the thread in a new and interesting direction. After hearing many claims that no-one had been bent on XYZ algorithm, I posted a poll on RebreatherWorld http://www.rebreatherworld.com/dive-medicine/22672-trimix-diver-self-treatment.html. The response to the poll showed that almost 80% of the respondents (regular trimix decompression divers) had self-treated bend symptoms.

I think that divers underestimate the fact that dive tables are not iso-risk. Kevin and Gene presented an interesting paper at UHMS this year showing the increase in risk with commonly used models based on increasing depth/time.

I don't have a link to it at the moment, but it is well worth the time if you are planning to be an explorer

Bruce

 

[ucfdiver]

This starts to take the thread in a new and interesting direction. After hearing many claims that no-one had been bent on XYZ algorithm, I posted a poll on RebreatherWorld Trimix diver self-treatment - Rebreather World. The response to the poll showed that almost 80% of the respondents (regular trimix decompression divers) had self-treated bend symptoms.

I think that divers underestimate the fact that dive tables are not iso-risk. Kevin and Gene presented an interesting paper at UHMS this year showing the increase in risk with commonly used models based on increasing depth/time.

I don't have a link to it at the moment, but it is well worth the time if you are planning to be an explorer

Bruce

I've done quite a bit of reading, as well as talking to those who have been bent, and my conclusion is that the algorithms work, but you have to have a "subject" that's well rested, well hydrated, and in decent shape.

I've found that a conscious effort to drink as much water as possible the day before and morning of a big dive causes me to have less fatigue afterwords. It really amazes me that more people discuss computers, algorithms, and models than fitness rest and hydration.

 

[tc]

Doesn't anyone find the 1 in 2200 statistic to be preposterous?

I have never met a diver that has had a DCS hit nor have I ever met a diver who knew a diver that was rumored to have had a hit. Now, I lead a sheltered life and, personally, don't push the envelope. Nor do I know more that a very few divers who do. The dives they do border on insane (in my limited recreational view). Yet they're still walking.

It would be very interesting to find out how many chamber rides they give annually in Monterey and Catalina (just to name two places that I know have chambers). Even with those numbers, I would expect the number to be much less than 1 in 2200. Properly, I would like to know the number of discrete cases, not the number of rides.

Of course, the number could be right...

Richard

For Catalina- 19 cases last year, I think we're at 11 this year. IIRC 1 each year was a re-treat. Those include both DCS & AGE.

 

[HowardE]

For Catalina- 19 cases last year, I think we're at 11 this year. IIRC 1 each year was a re-treat. Those include both DCS & AGE.

So statistically, that would mean (for those who can't do the quick math) - that 41,800 dives (or an average of 114.5 dives per day) were made in or around Catalina.

Does that sound plausible?

 

[tc]

Totally non-scientific wild guess-

Capacity of the dive boats I could think of running to the islands (we draw from all the islands)- 300 divers times maybe 3 dives a day= 900, times two days a week= 1800.

Dive park, 200 divers times 2 dives a day= 400, times two days a week= 800.

2600 dives a week divided by 7 days= 371 a day. Looking at the 18 we had last year that would be something like 1 in 7,523.


These are summertime numbers, does not account the dive traing programs at several camps, private boats, mid week diving (far less than weekends), boats running with less than full loads or not running and mid week charters. And probably a lot of other stuff, so take for what it is- a wild guess.

One of the biggest problems with trying to analyze dive accidents is that we have no clue how many dive are actually being made.

Thinking about the DAN numbers one thing I can think of offhand is that the people reporting their dives to DAN are very likely DAN members and probably carrying DAN insurance, maybe making them more likely to go in for treatment since they have the insurance to cover the treatment.

 

[Shearwater]

I've done quite a bit of reading, as well as talking to those who have been bent, and my conclusion is that the algorithms work, but you have to have a "subject" that's well rested, well hydrated, and in decent shape.

I've found that a conscious effort to drink as much water as possible the day before and morning of a big dive causes me to have less fatigue afterwords. It really amazes me that more people discuss computers, algorithms, and models than fitness rest and hydration.

The models are probabalistic. They work most of the time. They work less well as your decompression obligation gets bigger.

I think the only real data on "other factors" are exercise during the dive and the relative temperature during the dive and during the decompression. I also think there is some pretty good data on age.

Although I don't think there's much data on hydration, I drink a lot of water when diving to prevent dehydration.

I also do other things for which there is no evidence that I am aware of. I ascend slowly between stops, keep moving during deco, am very careful to keep a continuous ascent once decompressing, ascend very slowly from 10 feet to 0 feet, do a 0 foot stop on oxygen, and pass up all my gear before climbing the ladder.

I'm not trying to say that I know the answers. I just think that a lot of divers would be surprised by how little the decompression scientists are sure about.

Bruce