11 y/o Surfaces with Convulsions

[GJC]

Have a look at this abstract from a paper we published in DHM in September (by "we" I refer to my role as editor of the journal - I was not an author):

Arterial gas embolism breathing compressed air in 1.2 metres of water - PubMed


Neither statement is correct. If performed quickly enough a CT scan will sometimes pick up intravascular gas in the cerebral vessels, but mostly it does not because (unlike a solid embolus) gas redistributes. Probably because of that redistribution the natural history of CAGE often includes early spontaneous recovery after the initial onset of symptoms (which is often loss of consciousness).

Simon

I stand corrected and am very interested in references for that or your personal experiences. My personal experience is as I stated.

 

[DandyDon]

“Having agencies require affiliated shops and fill stations keep a gas test kit on hand for use in a potential fatality wouldn't be cheap but it would definitely help.”

The agencies and DAN hardly talk about the risk because it's bad for business. I once got to talk with the head guy at DAN and told him I was very disappointed in the corporation.

 

[Biotech Diver]

Have a look at this abstract from a paper we published in DHM in September (by "we" I refer to my role as editor of the journal - I was not an author):

Arterial gas embolism breathing compressed air in 1.2 metres of water - PubMed


Neither statement is correct. If performed quickly enough a CT scan will sometimes pick up intravascular gas in the cerebral vessels, but mostly it does not because (unlike a solid embolus) gas redistributes. Probably because of that redistribution the natural history of CAGE often includes early spontaneous recovery after the initial onset of symptoms (which is often loss of consciousness).

Simon

I don’t doubt it can happen and it’s worth the discussion but one should base their analysis on the rules and not the exceptions. That’s just my opinion based on doing risk assessment for a living. It’s good education to know all the possibilities but it’s better practice to know the rules, IMO. I know a meteor can kill me while I’m driving my car but it’s not likely to happen.

 

[tursiops]

I don’t doubt it can happen and it’s worth the discussion but one should base their analysis on the rules and not the exceptions. That’s just my opinion based on doing risk assessment for a living. It’s good education to know all the possibilities but it’s better practice to know the rules, IMO. I know a meteor can kill me while I’m driving my car but it’s not likely to happen.

What are these "rules" (in diving) that you speak of?

 

[Biotech Diver]

What are these "rules" (in diving) that you speak of?

Rules of probability. In layman’s terms the likelihood of it occurring. It’s insane to make your decisions on the exception. If that’s you the go for it. I’m basing mine on probabilities.

 

[tursiops]

Rules of probability. In layman’s terms the likelihood of it occurring. It’s insane to make your decisions on the exception. If that’s you the go for it. I’m basing mine on probabilities.

I understand the definitions. I'm asking what you think the high-probability causes are (in the context of this thread) since you seem to think an AGE from holding his breath is low probability.

 

[Biotech Diver]

What are these "rules" (in diving) that you speak of?

Figure it out. I know your strategy. Rules as un probabilities. I would win if we were betting in Vegas.

 

[Dr Simon Mitchell]

I don’t doubt it can happen and it’s worth the discussion but one should base their analysis on the rules and not the exceptions. That’s just my opinion based on doing risk assessment for a living. It’s good education to know all the possibilities but it’s better practice to know the rules, IMO. I know a meteor can kill me while I’m driving my car but it’s not likely to happen.

Hello,

Thank you for the diagnostic advice, and the lesson on relative risk.

An 11 year old surfaces from a compressed gas dive, becomes unconscious and convulses. Can you provide me with your list of differential diagnoses that are more probable than cerebral arterial gas embolism in this setting?

Thanks,

Simon M

 

[GJC]

I don’t doubt it can happen and it’s worth the discussion but one should base their analysis on the rules and not the exceptions. That’s just my opinion based on doing risk assessment for a living. It’s good education to know all the possibilities but it’s better practice to know the rules, IMO. I know a meteor can kill me while I’m driving my car but it’s not likely to happen.

It's a case study. Case studies are published to illustrate something unusual, unique, or not usually thought possible.

The incidence of occurrence of the case studie may be unknown and in the conclusion of the case study it may say "further research is indicated" or words to that effect.

Case studies remind us to keep our options open and to think outside the box and may result in additional study that gives us more definitive information.

 

[Dr Simon Mitchell]

It's a case study. Case studies are published to illustrate something unusual, unique, or not usually thought possible.

Hello,

I posted the link to that paper because the shallow depth (6m / 20') of the dive being discussed in this thread had been cited as evidence against a diving related problem. My aim was to show that CAGE can occur in very shallow depths (1 - 2m). However, to be clear, there is nothing "unusual, unique or not usually thought possible" about pulmonary barotrauma and CAGE occurring during ascent from a depth of 6m / 20' (as likely occurred in the case being discussed on this thread).

In relation to your previous question:

...very interested in references for that or your personal experiences. My personal experience is as I stated.

The most comprehensive account of CAGE is Tom Neuman's chapter in the last edition of Bennett and Elliott [1].

In describing the presentation and natural history of CAGE in divers (and comparing it to submarine escape training - SET) he states:

The most frequently observed signs are loss of consciousness and or stupor and confusion. Also frequently seen are seizures, vertigo, visual disturbances and sensory changes (Harker et al 1993). The most important difference between these victims and those who sustain their AGE during SET is that in many of these victims symptoms will resolve in minutes to hours before treatment is initiated. Typically about 50% of those victims who are less severely affected will have their symptoms ameliorate, however even comatose patients may improve....

Table 10.5.4 in his chapter shows presenting signs and symptoms in 74 diving accidents involving CAGE. The three most common presentations were: stupor and confusion (24/74); coma without convulsions (22/74); coma with convulsions 18/74. The doubters on this thread should note the latter. This is not in the improbable realms of a meteor hitting ones car as someone else implied. It seen in 24% of cases in a large case series.

In relation to CT findings, you can search the literature fairly easily. You will find cases where early CT has demonstrated intravascular gas in some cases, but not in others. One of the more interesting cases I treated was a young man who inhaled directly from an unregulated cylinder of high pressure balloon gas (for the helium voice experience) and immediately went unconscious. Early imaging showed multifocal areas of cerebral ischaemia (which is one of the positive diagnostic clues that CT or MRI can sometimes provide - gas goes to many places in the brain whereas a clot typically affects a single territory), but it did not show any gas. We published that case, and you can find the abstract here:

Simon M

Reference:
1. Neuman TS. Arterial gas embolism and pulmonary barotrauma. In: Brubakk AO, Neuman TS. Bennett and Elliot's Physiology and Medicine of Diving (5th ed). Edinburgh; Saunders: 2003. p.557-77.