Undeserved accidents ?

[Genesis]

I admit to having fairly-seriously "blown" a profile before (bad ascent caused by a combination of factors) and paid VERY careful attention to my body afterward for the next day - remaining prepared to grab the emergency O2 kit and head for the nearest chamber if I experienced anything that even SMELLED like DCS.

Oddly enough, my computer didn't complain about it, other than being upset about the ascent rate during the dive, and hitting me with an "extend surface interval" warning (which I heeded.) I DID do a second dive that day after close to two hours, as I was feeling perfectly fine, and on that second dive I did an EXTREMELY slow ascent - 1 minute at the first ATM on the way up, 2 on the second, 10 at 15', and then 2fpm from there to the surface.

My theory on this was that given that I had not (yet) accumulated symptoms, if I was going to go back in the water I had to be VERY sure to decompress on the second dive EXTREMELY slowly, so as to insure that any excess nitrogen was able to come out of solution the "right way" (through my lungs), since there was an enhanced risk that I had latent trouble brewing.

No problems.

Thankfully.

I tend to be much less observant though if I know that I did everything "textbook"; I think we all do, which is potentially where we can get in trouble - its the "undeserved" hits that can be ugly, as people tend to dismiss the first little signs - which is, of course, the wrong thing to do!

 

[Dr Deco]

Dear “ro”:

Undeserved Hits

With almost total certainty, joint-pain DCS (the “bends”) does not result from a PFO allowing gas bubble passage to the arterial circulation. An idea similar to this formed a portion of the original Haldane hypothesis of decompression sickness. Neurological problems, yes, but the not the bends. I studied this extensively in animals for about twenty years; the topic was my first scientific papers in barophysiology. {MR Powell. Leg pain and gas bubbles in the rat following decompression from pressure: monitoring by ultrasound: Aerospace Med., 43, 168-172 (1972); MR Powell. Gas phase separation following decompression in asymptomatic rats: visual and ultrasound monitoring: Aerospace Med., 43, 1240-1244 (1972).

The presence of a PFO has not been found to be a big player in recreational scuba incidences. Dr Fred Bove, among others, has reviewed this in scuba magazines. Where I believe the bigger problem can arise is when a diver has a PFO, many venous gas bubbles, and performs a Valsalva-like maneuver (straining and holding one’s breath when climbing a boat ladder) or when in the water and performing a Valsalva-like maneuver. In both of these cases, the possibility of rebound flow to the right atrium is increased. This means that right atrial preload ( = the volume of blood that enters the right chamber of the heart) is increased because there is a sudden drop in pressure in the thoracic (= chest) cavity.

Being in the water causes a thoracic fluid shift ( = blood is moved toward the chest) and accentuates this Valsalva effect. This has been measured in arterialization in recumbent and supine individuals. {Schwarze JJ; et al. (1999). Methodological parameters influence the detection of right-to-left shunts by contrast transcranial Doppler ultrasonography. Stroke; 30(6): 1234-9}

This problem of arterial gas bubbles is a difficult one. I have looked at this in the laboratory for thirty years and still have no firm conclusion on all of the mechanisms.

Dr Deco :doctor:

 

[Drew Sailbum]

but in 13 months of working as a dive instructor in Cayman I have personally seen 3 cases of DCS. All three occurred in people who were within no-deco limits as set by their computers.

In two cases there were more than one clear contributing factors - rapid ascent, extertion at depth, dehydration, and/or advanced age.

But the third case, nada. At least nothing obvious. Young male got bent on a single 60ft dive for 30 minutes. It was a joint-pain case and easily resolved by recompression, but still left us wanting to point at a specific "cause".

 

[TheDarknessLord]

Recreational Diving is a very safety sport.
Think about this: The market has a lot of table, each one has different No Deco Limit Time... awesome one! The values change from minutes to hours... awesome two!!!

 

[QKRTHNU]

Dr Deco once bubbled...
They go through the litany of Dr Deco’s No-Nos. Among these we have

• climbing back onto the boat with all of your heavy gear,
• lifting heavy gear on the boat,
• climbing ladders or performing strenuous activity on board,
• sleeping during the interdive interval and slowing nitrogen washout,
• being very active on the bottom during nitrogen uptake.

[/font] Dr Deco :doctor:

Please clear this up for me.

1. I understand how increased activity on the bottom would increase Nitrogen uptake.

2. I understand how sleeping on the boat would slow down your body and therefore inhibit off-gassing.

3. I don't understand why increased activity on the surface post-dive would be bad. Wouldn't this accomplish the opposite of the first problem? I would think that the increased circulatory & respiration actions associated with activity would aid in off-gassing. Why is this not the case?

Thanks

 

[chiara]

Salut Amanda,

this might be the dumbest thing I ever contributed to this board, but "undeserved accidents" happened to come up during our bi-weekly IDC session yesterday.

In France and in Belgium when a fatalty occurs (last one just about ten days ago in the Netherlands, Belgian diver under CMAS) they very often come up with an "accident immérité" in order to get round insurance issues and allow the family to get some sort of compensation.

Should the accident be classified as "a diving accident" only people insured with DAN might come up with decent money.

LIFRAS automatically insures their members through a "normal" insurance, which will do all that is in its power in order not to pay.

I was wondering whether some of this might have triggered your thread.

If I'm totally off, just tell me!

 

[Diver0001]

chiara once bubbled...
Salut Amanda,

this might be the dumbest thing I ever contributed to this board, but "undeserved accidents" happened to come up during our bi-weekly IDC session yesterday.

In France and in Belgium when a fatalty occurs (last one just about ten days ago in the Netherlands, Belgian diver under CMAS) they very often come up with an "accident immérité" in order to get round insurance issues and allow the family to get some sort of compensation.

Should the accident be classified as "a diving accident" only people insured with DAN might come up with decent money.

LIFRAS automatically insures their members through a "normal" insurance, which will do all that is in its power in order not to pay.

I was wondering whether some of this might have triggered your thread.

If I'm totally off, just tell me!

This is probably going to get a little off topic but what you say interests me. In Holland there is a great deal of speculation as to how it comes that so many incidents in Dutch waters involve Belgian CMAS divers. Why do you think that is?

R..

 

[chiara]

Again a wild guess...

(rant mode on)

CMAS can go much deeper than PADI.

We basically can't go diving in Belgian saltwater, there's nothing to see and there is too much pollution.

So we go to Zeeland.

CMAS is deservedly known to be a macho business.

(rant mode off)

A woman from our club (PADI) has a CMAS boyfriend.

She has roughly 40 dives and is doing her Rescue.

He's doing the same despite being a 3* CMAS already.

They went diving in Zeeland in mid-February.

It was her first drysuit dive in open water.

They went down to 42 metres (he can, she's not supposed to).

She ballooned and came up with severe barotrauma.

She won't be able to dive until summer.

She's very lucky to be alive.

Would I be happy to dive with either of them?

NO WAY.

 

[Dr Deco]

Dear okrthnu:

Exercise and Off Gassing

Certainly it is confusing to think that activity promotes off gas and is good and activity promotes micronuclei formation and is bad.

The answer lies in the degree of activity. Please note those mention in the post above were vigorous and stressful. What one needs to do is mild activity such as sitting and moving the arms and legs. Walking is fine too, since the tables were tested with walking divers in mind. It is lifting heavy objects and the like that are the “killers.”

We are now encountering the interaction between vigorous activities, off gassing, and nuclei formation in our NASA prebreathe studies. It seems to be showing that exercise cannot be too vigorous if the time to the next depress is an hour or less. This is a very initial look at the situation, however.

Dr Deco :doctor:

 

[Genesis]

On the deco side anyway.

Consider a joint. It is full of synovial fluid (the "lubricant" between the two bones) and covered with cartiledge and a tough membrane to keep it all together (and aligned). Tendons provide the "support" structure for many of these joints.

Now, if you create a motion that "stretches" the joint, you have artificially depressed the pressure inside the joint. That is, it is now at less than 1 bar.

If there are gasses in saturation inside that fluid, they are now free to come out of solution and into bubble form! Oh oh. Now you have the start of the cycle of a "joint pain" bend, and once it gets going, the snowball can accelerate since gas bubbles under some conditions pick up more gas and get bigger.

Pre-breathe studies? Dr. Deco, are you referring to someone at normal pressure exercising at some level, then undergoing DE-pressurization (e.g. a spacewalk where ambient pressures are UNDER 1 atm in the suit?)

That would imply that micronuclei formation is the "seed event" and that it can happen at saturation (not just supersaturation!), and would seem to imply that heavy work under saturation conditions (e.g. where that tissue groiup is saturated) at a given depth could be BAD upon decompression (e.g. return to the surface), for the same reason; you've "seeded" the potential growth of free-gas-phase bubbles in that joint.

Am I on the right track here?