Bent... but why?

[pasley]

The final answer is sometimes S*** happens. Recent readings indicate that the computers just do not handle multiple dives over multiple days all that well. The deep tissue gasses are the problem. I have read recently (From DAN I think) that it is recommended to skip a day of diving in the middle of the week if you are doing the multi-day, multi-dive routine. There is growing evidence that Multi-day, Multiple dive profiles, are at a higher risk of DCI. Perhaps you could snorkle for a day, or else stay above 30 feet on all dives for one day and only do one.

Five dives in one day after a week of diving is a heavy gas load on a body that already has quite a lot or residual deep tissue nitrogen to off gas. The hot tub or hot showers ( or maybe just a hot climate) causes the blood vessles to move to the surface to disipate heat, this slows the off gassing of the deep tissues and may contribute to DCI. The two factors of 3-5 dives a day with profiles near the limits, and multiple days of the same, probably just caught up to you. Give the body a chance to off gas.

As for going diving after the first symptoms, the fact that you got better under pressure should have tipped you off to consider DCI. Like you, I did a dive, close to the edge but not violating the computer, and I got bent. Sometimes it happens. I am 48, 150 bls at 6 feet tall, and 13.7% measured body fat. But, I had old injuries from parachuting for years (military) and evidently I am more prone to DCI. You may also exlplore PFO. This is a heart thing that occurs in about 1/3 of the population. Another problem is that we all expect DCI to be intense pain, like we saw on TV with Lloyd Bridges on the deck of his boat in Sea Hunt every single episode. DCI can be a subtle, minor discomfort-- at first, which we often dismiss as somthing else. Bottom line is, DCI does not mean you are a bad diver, or that you did anything wrong. It just means, you got DCI.

I do think that studing your profile is also helpful. DAN is encouraging we avoid going up and down in a saw tooth pattern during our dives. I now work at haveing a profile that goes deep first and then slowly accends from that point, or at least does not go up and down a lot.

Melvin Pasley
Not a doctor, and the above is just my two cents.

 

[Dr Deco]

Dear Readers:

Remember that the two things you wish to avoid to prevent DCS is MICRONUCLEI and GAS LOADS.

MICRONUCEI and reduced in number by minimizing the amount of muscle work that you do an hour or so before the dive, during the dive itself, and following the dive on the surface for a couple of hours. Laboratory tests indicate that these statements are valid and not just someone’s idea of what is good and what is bad. Here we are not worried about light activity such as walking, but rather strenuous activity such as lifting tanks.

GAS LOADS depend on blood flow to the tissues. These are variable dispite the fact that they are fixed in the decompression algorithms. During the bottom interval the more swimming activity, the more tissue gas loading occurs. When on the surface, activity such as walking is good as it promotes an increased heart rate, open the capillary beds and promotes the “muscle pump” so important for circulation. Thus we see that siome activity is generally good for the diver but stressing and straining is not. It is always important to remember that the decompression is not over when you reach the surface!

Dr Deco :doctor:

 

[Zept]

Originally posted by pasley
Another problem is that we all expect DCI to be intense pain, like we saw on TV with Lloyd Bridges on the deck of his boat in Sea Hunt every single episode. DCI can be a subtle, minor discomfort-- at first, which we often dismiss as somthing else.

Definitely I expected DCS to be more painful. I also expected the pain to stay in the joint... if anything, I was reassured when it started to spread. It was only when the pain went away and then came back again that I started to get concerned.

If there is a next time, I will know better... but I still hope that there won't be!

Zept

 

[Dr Deco]

Dear Readers:

It is often believed by divers that DCS pain will always be so intense that you will definitely know it. This is not true. :nono:

Mild problems are often referred to as “the niggles.” There is a progression of DCS pain depending upon [I suppose] the amount of nitrogen gas that has exsolved (= come out of solution). If there is none, then nothing happens. It there is a marginal amount, then you get “marginal” pain, but if there is more, you get definite symptoms. When the separated volume is large, the pain is quite intense.;-0

After a period of a few hours, the problems generated by the gas phase become more permanent because of biochemical sequelae (e.g., inflammation). If the problem occurs in nerve tissue, and treatment is delayed, then the damage could be permanent. Pain following diving is often difficult to diagnose is being DCS. In the laboratory setting, it is always checked by pressurization to see if the pain remits; this is referred to as a “test of pressure.” It is not always easy to tell without the repressurization.

Dr Deco
:doctor:

 

[Christian]

Dear Zept

After reading your posting I can't really see that you did anything wrong. So you could categorize it as "bad luck". It can happen even if you play by the rules. The only thing I would have done different is stretching thoose SI:s (some of yours where only a little bit more than 1 hour). When I do multiple dives for multiple days, I always do around 3 hours of surface interval in between dives. This puts quite some demands on the planning, but in a place like Sipadan it's no problem.

Cheers

Christian

 

[Dr Deco]

Dear Zept:

Individual Risk of DCS

There is a large degree of variability among individuals with respect to DCS . In the ATTACHMENT is a graph abstracted from a recent paper (Dervay, Powell, Butler, Fife. The effect of exercise and rest duration on the generation of venous gas bubbles at altitude. Aviat Space Environ Med 2002 Jan; 73 (1): 22-7). In this study, all test subjects performed the same exercise activity, a series of 150 deep knee flexes over a period of ten minutes, and then they were depressurized to 22,000 feet of altitude. Doppler monitoring was performed while in the chamber for the two-hour depress.

The vertical axis is the amount of Doppler bubbles measured and the horizontal axis is the individual test subject. Each person did the test three times (shown as colored bars). One test was performed with no waiting period before entering the hypobaric chamber (blue), once with a one-hour interval (tan) and once with a two-hour interval (red checks). The number of bubbles that formed during depress reduced with the duration of the rest interval , as we might expect on the basis of the short-lifetime micronuclei hypothesis. It is easy to see that some subjects produced many bubbles on this profile but many (about ½ produced none at all.)

Selection Criteria

Currently we do not know why some individuals differed from their fellows with respect to bubble formation and DCS. In this study, some aspects were checked but nothing was found in the laboratory.

We do not know how repeatable this test might be, but I expect that, with proper controls, there would be good repeatability. NASA is not currently interested in testing its astronauts for DCS susceptibility, as it really wishes to put the weight on decompression procedures and not selection criteria within the astronaut corps.

Self Selection

There are many commercial divers who have self selected, I am sure. We hear of many very aggressive dive procedures in pearl divers in Hawaii, for example, that probably have a considerable degree of self selection in them. (I am speaking of a Darwinian “survival of the fittest” type of diving. It is really brutal.):boom:

Dr Deco :doctor:

 

[The Iceni]

Dr Deco once bubbled...
Dear Zept:

One test was performed with no waiting period before entering the hypobaric chamber (red checks), once with a one-hour interval (tan) and once with a two-hour interval (blue). Dr Deco :doctor:

It was very interesting to see that half this population was quite resistant to bubble formation, Dr Powell. What I find even more intriguing is that in the affected group more bubbles could be measured when they had the longer two-hour interval after exercise before depressurisation.

I read this to mean that there is significant micronuclei and nascent bubble formation in the period following exercise in conditions equivalent to saturation diving (at 1 atmosphere at least). If I am reading this correctly this appears not to be what one would expect, (Laplace pressures etc.)

Have I read this experiment correctly?

By the way, was there control of hydration both prior to the period of exercise and during the post exercise intervals?

I would be interested to learn if there is a recognised marker for reduced surfactant behaviour in blood (which could possibly be worsened by dehydration in at-risk individuals) as this would explain the protective effect of adequate hydration and the increased risks of DCI associated with dehydration.

For example, erythrocyte sedimentation rate and plasma viscocity are used as non-specific markers in disease. Do you know if these are affected by an individual's hydration status?

Once again a liittle knowledge is a dangerous thing! :baby:

 

[rcohn]

Dr Deco once bubbled...

The vertical axis is the amount of Doppler bubbles measured and the horizontal axis is the individual test subject. Each person did the test three times (shown as colored bars). One test was performed with no waiting period before entering the hypobaric chamber (red checks), once with a one-hour interval (tan) and once with a two-hour interval (blue). The number of bubbles that formed during depress reduced with the duration of the rest interval , as we might expect on the basis of the short-lifetime micronuclei hypothesis. It is easy to see that some subjects produced many bubbles on this profile but many (about ½ produced none at all.)

I'm not sure I'm reading the graph correctly. The blue bars are the two hour interval, but generally show the highest bubble volume??

Ralph

 

[The Iceni]

I just thought about this case a bit more.

I wonder whether dehydration played a part in the causation of your DCI, Zept?

I imagine that as each dive causes a short-lasting diuresis, dehydration will play a major part in the increased risks associated with multiple dives over multiple days.

Zept, what efforts did you take to ensure you did not become dehydrated, even if only relatively speaking?

:doctor:

 

[Dr Deco]

Dear Readers:

Oops!

I transposed the legend for the bar graphs. The world is as it should be. I have relabeled the posting above. Blue is “immediate entrance into the deco chamber” and red checks are “two-hour hiatus.”

Other factors

We did not control for hydration. We told the subjects to drink water as they normally do, but we did not make a special effort to either maximize or minimize this. It would be of great interest to repeat something like this, but with hydration modified in a prospective way.

Additionally, we employed only a two-hour rest (adynamic) period. When the test was completed, it appears that five hours would have been better to assure that the subjects did not introduce tissue nuclei from simply walking to the laboratory.

Last, one half did not form bubbles ON THIS PROFILE. It is dependent on decompression. If very mild, no one will bubble. If very severe, everyone will. There were 1/2 of these subjects who never bubbled...... and it was not random.

Dr Deco :doctor: