Bent... but why?

[Dr Deco]

Dear Zept :

Here are my thoughts on this.

1) Just too much diving.

If one is within the table, the gas loads should be acceptable (for an individual exiting the pressure environment and sitting down).


2) Just naturally more susceptible. I was near the edge of the table, and I know the models are only theoretical.

The models may be theoretical, but they are based on actual data. The data is correct independent of the model. It is a definite possibility that you are a DCS-sensitive diver. There is not a good way to check this currently. Please remember that DCS probability increases with the dosage of nitrogen; there are no “table limits” in physical reality.


3) Just bad luck.

I would call it a “chaotic” response. This means that several factors happened to occur at one time and led to a very bad outcome. This is also called “just bad luck” in common parlance.


4) The reverse profile. Fifth dive on Day 3 was deeper than the third and fourth dives. Then again, I’ve read several articles that say reverse profiles are okay.

I truly doubt this played any role.


5) Exertion. After each dive I had to get off the boat and walk up the beach, wearing all my gear, and then change tanks. Kind of strenuous for a small person. Otherwise, I didn’t do anything more energetic than walking.

I have indicated before in this FORUM that one factor that can increase DCS risk in a very visible manner is heavy physical exercise both during and following a dive.


6) Hot showers. I did have hot showers after some of the dives, but they were brief. I can see how they might cause a skin bend, but would they cause a joint hit?

I doubt that this is a big factor.

I put my money on gas loads and physical exercise.

Dr Deco
:doctor:

 

[Zept]

Putting my own thoughts into words and then reading your responses has been very helpful. As Dennis said, I'll never know exactly what caused the problem, but diving too hard, diving too close to the limits and exertion after the dive seem to be the candidates.

The models may be theoretical, but they are based on actual data. The data is correct independent of the model. It is a definite possibility that you are a DCS-sensitive diver.

My bad. What I meant was that I know the computer is not measuring anything (other than depth and time), it is predicting the nitrogen load based on its model, which may not reflect my individual physiology. I guess I could find out whether I am DCS-sensitive by repeating the dives and monitoring the outcome... but I am not that dedicated to the advancement of science! Diving more conservatively seems like a thoroughly excellent idea.

I'm still waiting for the PC interface for my dive computer. I don't expect the profiles to reveal anything new, but it'll be interesting to see how close I was to the computer's limits.

Thank you all for your input,

Zept

 

[Liquid]

Getting bent during rec. diving, within the table limits is usualy not the outcome of a single reason, rather, it is the outcome of combined reasons. Probobly all the reasons you stated did it together, while any alone would not be enough. Might also be anotherone or two you didnt even notice.

 

[Zept]

Downloaded the dive profiles from my Vyper last night.

The closest I came to the NDL was five minutes of no-deco time remaining at 33m. Looking at the tissue saturation estimates, the highest saturation at any time over the two days was 88%; the highest on exiting the water was 79%.

The question is, now what? How do I decide how far from the computer/table limits I need to be to avoid getting bent again?

Zept

 

[Liquid]

The more factors you know you have- the more conservative you should be. As you are using a Vyper (mighty good computer by the way!!! I love it) you can simply choose to make it more conservative.

 

[Dr Deco]

Dear Zept:

It is always nice to think that a dive table can be written that will make the dive safe. You would do better, in my experience with decompression, to avoid the “other side of the coin” that is also responsible. That is the much-referred to micronucleus. This aspect has not be stressed, or even noted, by other diving physiologists. While we often see decompression before the dive, we only get a passing nod (or nothing at all) to exercise after the dive. THE DECOMPRESSION IS NOT OVER WHEN YOU REACH THE SURFACE. Somewhere along the line, recreational scuba diving became referred to as no-decompression diving . This is because a decompression stop before the surface is not required - - not because there is not any decompression or off gassing.

There is not any question that reducing the gas loads will help is avoidance of DCS. Never going underwater, or never coming up, are two sure ways to eliminate supersaturation altogether. This aside, reducing gas loading is always good.

Other things that can be done are hydrating as well as possible since this effectively will reduce the concentration of the surfactant biomacromolecules that surround the micronuclei. This mechanism has not be vigorously proven but hydration state is definitely and important factor.

Individual susceptibility is important but not currently testable. Maybe someday.

Dr Deco :doctor:

 

[landlocked]

Originally posted by Zept
On the evening on Day 4 I was sitting on my bed reading when my shoulder started to hurt. I didn’t think anything of it, because normally something hurts when I’m sitting awkwardly (I often get a sore neck sitting at the computer). When the pain spread up my neck and down my arm and over on to my back, I figured I’d pinched a nerve.

Got back into the water on Day 5 and the pain went away. It was only when it returned that evening that I started to worry. Spoke to the resort’s instructor the next morning, but by then the pain was subsiding. He said it ‘might’ be something, and to call them if it got worse. By the time I got back to Singapore, I was pretty sure it had been something, and my doctor agrees.

A similar thing happened to me two days ago. I believe it was tendonitis in my left shoulder which spread down my left arm and across my neck. It felt like tendonitis and responded to treatment for tendonitis. It did start to worry me though as I had been diving that day in cold water with a new hood giving me fits. (Since I was struggling with the hood instead of paying attention my boyancy control was horrible until I took the thing off, under water.) We also had quit a hike back up to the car afterwards, etc., etc., A very poorly planned dive, but you learn from them all right?

My question is.... did your problem just go away? Why do you and your doctor think that it was DCS instead of say.... tendonitis from walking up the beach carrying a lot of weight on your shoulders and then sitting in an ackward position?

 

[Zept]

Originally posted by landlocked
My question is.... did your problem just go away? Why do you and your doctor think that it was DCS instead of say.... tendonitis from walking up the beach carrying a lot of weight on your shoulders and then sitting in an ackward position?

The main reason for thinking it was DCS is that it went away -- completely -- when I got back in the water the next morning, and then came back that evening. Wasn't as painful the second time around and the pain gradually eased over the next few days (and then I washed my gear, and after that it hurt a lot -- my doctor thinks I tore some of the damaged tissue). Plus it didn't feel like a strained muscle. It didn't respond much to movement, for example.

I can't be sure it was DCS, but... I did a lot of diving, I had a pain in my shoulder that felt and behaved a lot like DCS, people do get DCS while diving within table limits... so it seems the most probable explanation.

Originally posted by Dr Deco
It is always nice to think that a dive table can be written that will make the dive safe.

I really don't think that . People vary, individual physiology varies from day to day, conditions vary... dive tables look very neat and precise, but real life is a messy and unpredictable business. OTOH, I still have to decide how deep I'm going to dive and how long I'm going to stay down.

Originally posted by Dr Deco
You would do better, in my experience with decompression, to avoid the “other side of the coin” that is also responsible. That is the much-referred to micronucleus.

I can appreciate the importance of the exercise issue, I'm just having a hard time figuring out how I can do much less between dives. I have to get back on to the boat, that's just unavoidable. I guess I can take it easier on the gear-wrangling front. Otherwise I spend the time between dives sitting around, writing in my log book, drinking lots of water and taking it easy.

Originally posted by Dr Deco
There is not any question that reducing the gas loads will help is avoidance of DCS.

Originally posted by Liquid
As you are using a Vyper, you can simply choose to make it more conservative.

After looking at the profiles from this trip, and from a previous trip where I did a similar number of dives (but didn't come as close to the limits), and running some simulations, I've put my computer into the more conservative P1 mode. I'll still be able to do the dives I've done routinely without any problems, but I won't be able to dive as hard as I did a couple of weeks ago. I still have to decide what I'm going to do with my tables (I plan my dives using tables or the Wheel), but probably I'll just set a limit for the ending pressure group.

I know I'm just flailing around in the dark, but at least I can say I've explored all the issues and looked at all the ways I can modify my diving. Of course there are no guarantees it'll never happen again, and maybe it wasn't even DCS in the first place, but life's just like that... uncertain.

Thank you all for your help and your patience!

Zept

 

[Dr Deco]

Dear Zept:

There is definitely a limit to how little you can do following a dive. Certainly you must return to the boat. One can ask assistance in climbing the ladder, or, if possible, have someone help in getting the tanks aboard. All of this work in climbing a ladder will produce the micronuclei.

During the surface interval, it is also important to move about somewhat rather than just sit - and definitely not sleep.:mean:


Dr Deco :doctor:

 

[The Hamburger]

Dr. D,

Could you please expand on your last post a little.

Makes sense but I'd like to know a bit more.

Cheers