Emergency Surface from 250 FT and reascent procedures

[Jerrod]

I have been reading the book Fatal Depth about the Andrea Doria and all the people that have died diving it.

In the book there is a story about a guy that freaked out and shot to the surface from 250 ft. The book states the captain "ran some software" to determine that the diver needed to descend for four hours to decompress. With the remote location, I guess this is the only option, since a helicopter ride would be 2 hours to the nearest chamber.

My question is what would this look like? What depth(s) would he/she need to descend to and what gasses would he/she need to breath? The book seems to indicate the average decompression time was about 1 hour, so why 4?

The only technical information it provides is the diver was diving a trimix and it was the second dive of the day. The book also indicates its about a 4 hour interval between dives.

Thanks,

Jerrod

 

[decompression]

You may find answers from the board come slowly, reason being is one of liability. Many are reluctant to share potentially deadly information. Certainly training in these types of dives will be recommended. You are asking about decompression theory and mixed gases, with some googling on the interweb, you should find a wealth of information.

 

[Jerrod]

Yeah I tried googling and found a bit of information. I understand the liability and I understand that doing this is very dangerous, why the guy didn't die or suffer some type of problem seems almost shocking. The book, a book written by an journalist, so who knows how accurate that is, says he held his breath, but that seems like an injury for sure.

Someone can PM the basic idea if they are concerned with providing information.

 

[PfcAJ]

I won't give you specifics, but for starters, deco time is a function of depth and time.

A 20min botom time at (x) depth might give you the same deco time as 10mins at (y) depth because (y) is deeper than (x).

Accordingly, 30mins spent at (x) will give you a longer deco than 20mins at (x).

The procedure you're describing is called "omitted deco procedures" or "in water recompression" (if the diver was showing DCS symptoms). IWR is very controversial and can be quite risky. In a nutshell, omitted deco just means quickly redescending and completing your missed deco. IWR is a DCS treatment that may be used by trained, experienced, and properly equipped divers if a recompression chamber is unavailible.

 

[Bombay High]

In water recompression can be done, but is best done with surface supplied gas, with full face mask or better - hard hat, with communications to support divers and to topside support. In the open ocean such as the north atlantic, where the Andrea Doria lies, Its a tremendously risky procedure, particularly if DCS symptoms are already seen.
Akimbo, on the board here, has spent a lot of time on the Andrea Doria. Maybe he can chime in with what an in water recompression in those seas would be like.

 

[Centrals]

The only technical information it provides is the diver was diving a trimix and it was the second dive of the day. The book also indicates its about a 4 hour interval between dives.

Mininum of 3 hrs surface interval for air/nitrox deco dive and 4 hrs for trimix dive.
That was my training(IANTD).

 

[TSandM]

One of the reasons why going back down results in longer decompression than doing it right the first time is that coming up too fast creates bubbles (and grows the ones you already have). Gas in bubbles is eliminated more slowly than gas that is still in solution, so the time you have to spend decompressing once you have a lot of them is longer than if you had done proper deco and kept the gas dissolved.

 

[waterpirate]

Omited deco from that depth on trimix yeilds a result that is very predictable and documented. Given the remoteness of the location from treatment, IWRC was the only option left for that diver, risky or not it was better than the alternative. I think I remember from the book that it worked?? Usually it does not and the patient drowns.
Eric

 

[ajduplessis]

I will depend on gasses used and BT. IWRC should only be considered if the skill, equipment, support divers and required gas to perform this is immediately available. The other problem is that you need to get the diver back in the water within minutes with a very clear and detailed plan.

IWRC really works, but as stated you need the equipment, gas, plan and divers in the water very, very, very quickly with some luck!!

Coming to the surface from 250ft is not a simple type1 hit!! If you are lucky a wheelchair would be nice.

 

[DCBC]

The severity of DCS depends on many factors (as discussed). Depth is only one factor, time at depth, dehydration, a high degree of exercise (before and after the incident), age, fat percentage and other factors play a role. Just because the depth was over 200 FSW isn't the main factor. Generally speaking, in-water recompression can make the situation worse. The Andrea Doria lies in cold water (it was 42 degrees when I made that dive). Putting a person with a type II DCS hit into cold water, isn't a good idea. Nausea & vomiting often accompanies an injury of this type and even with a full-face mask, the safety of such treatment is questionable to say the least. Obviously someone would have to make the call, but if I suffered a hit like this, I'd want to be evacuated by air ASAP.