August 28, 2007
Hi Andrew. A sort of medical question if you please related to a possible barotrauma. May have to post this one in the medical forum depending on your answer.
Yesterday I was at Dorathea. The first dive we descended to 50m for an ABT of 17 minutes. We then slowly ascended up and over the shelf past some houses through the 17m tunnel and then proceeded to complete a 20 minute decompression stop at 5minutes (according to the computer). The mix was standard breathing air.
1.47 hours later we descended again to 40m to see the gnome garden before ascending to swim by some old cars a van and a metal box at about 10m. Again this ascent was very slow with no ascent alarms. This tdive we did not exceed the ABT so just a standard safety stop was done at 5m.
About 1 hour later I developed a joint cramp in my left elbow that quicly spread to my left shoulder, left wrist and left hand. This pain slowly increased over the next 4 hours. I monitored myself for CENT A DIVE symptoms and displayed no others. Respiration and pulse maintained a normal rhythm.
The hospital rang Plymouth rescompression and gave them my profiles and symptom. They said it was not necessary to recompress at it was a decompression cramp.
What is a decompression cramp? The Doctor at the hospital I visited didn't have a clue. I woke up this morning with a stiff arm but the pain has stopped. What could have caused this? Any ideas?
The other two divers I was with had matching profiles and stops and they are fine.
| Posted :
August 28, 2007
Ok lets deal with the decompression profile. Firstly this sounds very boring of me but it is a good idea to plan your dive with tables or professional table generating software and then dive that plan… The computer is calculating continuously your decompression profile and it is doing so on an ideal person, or something like an average person.
I can’t go on enough about this – the computer does not know how much work has been done – few alter their decompression algorithm based on temperature and hence work function – it doesn’t know how fit you are nor how good your Cardiovascular (CV) fitness is, nor your state of hydration (or more to the point dehydration) – so give yourself plenty of contingency and cut tables before doing deco dives and dive to them – even if your computer says you have loads more time at depth – keep this as a safety margin. You will find the computer saying much less deco – yes – do what your plan says – if the computer says more then do the extra and add at least 3 to 5 minutes extra at the end as a safety margin.
So the profile you did if I’m to understand was a little short on its deco based on tables… you did 50m for 17mins then ascended, you should have done a micro bubble stop at 29m for 2 minutes, 19m for 2 minutes, then deco of 9m for 2 minutes and 6m for 29mins on Air.
The surface interval would have then resulted in the following dive being 40m for 7 minutes then a safety stop of at least 3 minutes at 6m (again ideally with 2 minutes bubble stops at 23m and 15m).
So whilst I agree your computer says you did your deco fine, and perhaps a chamber may say on balance you did your deco – I would say you cut this one a bit too fine. No two or three people dive exactly the same profile in the fine detail, nor are they exact physiologically - which is why it is so important to plan and execute dives conservatively.
You probably did have a subclinical bend – in other words you stressed your body and its joints to a state that nearly caused damage and hence would then require recompression in a chamber to resolve. Hydration is a crucial factor, as is CV fitness. Ascent rate and the quality of in water decompression (how good you hold your depth, what Gas the deco is done on, what you breathe for the final ascent and what Gas you breathe for the next five minutes at the surface and getting ashore/onto the boat).
Look up the nearest diving doctor to you on www.uksdmc.co.uk and go and see a diving medical referee ASAP. Oh and the term decompression cramp sounds very odd to me sounds a bit like someone didn’t want to use confusing jargon for what I’ve put above.
I hope this doesn’t happen again and keep safe, Best Regards Andrew.
August 28, 2007 by - ImmersionMan
Thanks for the information. The Doctor I saw rang the Plymouth recompression chamber and discussed my profile and symptom so all was checked.
Doing some research today has led me to agree that my deco time was a little too agressive. If I had the dive to do again the plane would be as follows; Dive 1; descend to 50m for 17 minutes. Ascend to 21m for 2 minutes, ascend to 18m for 2min stop, ascend to 15m for 3min stop, ascend to 12m for 3min stop, ascend to 9m for 6min stop, ascend to 6m for 8min stop, ascend to 3m for 14min stop.
Dive 2: Descend to 40m for 7min, followed by a normal ascent to 5m for a 3min safety stop.
How does this sound? I am using V-Planner as my reference.
August 29, 2007 by - ADM Diving
Urmm Ok and glad you can see it was too agressive. Be careful with the freeware tools and make sure they are fully implementing all of the relevant algorithm (eg ZHL-16B plus Pyle stops etc etc).
Your profile you are suggesting whilst it looks better it has two key warning areas...
1. By doing deco deeper it does indeed make the shallower stops shorter - however you are on gassing though too if the gas for deco is the same as the travel/bottom gas.
2. The nice shallow deco is great in a quarry or on a trapeeze - be careful on d/smb's in the open sea. For the most part you can simply add the 6m and 3m deco times and do this all at 6m
With training or if you have those qualifications already a better choice of gases to 50m would be to use air (or even better a normoxic trimix) for the decent and bottom time and deep bubble stop then carry on a stage cylinder and use 50% Nitrox for the rest of the deco and for the final surface, exit and 5minutes at the surface - this is far far safer.
This will give you a plan which looks more like...
50m 17mins Air
29m 2mins Air
19m 2mins 50%
9m 1min 50%
6m 14mins 50%
Exit and post dive breathe 50% for 5mins.
This is very significant reduction in deco but a much safer way of doing this - the elevated Oxygen in the Nitrox also greatly reduces the inert Nitrogen from the body and seriously helps remove/decrease any bubbles in your body post dive and also significantly reduces the inert Gas loading of your tissues.
Plan your dives using a professional dive table cutting tool such as ProPlanner from Delta-P.
Safe Diving, Andrew.