DCI: What could have triggered it?

dteubner

The PFO issue is really quite complex.

There is good evidence that divers with a PFO have a risk of DCI which is about 5 times as great as those who don't.

There is absolutely no evidence that closure of the PFO returns this risk to normal- although it would sort of seem to make sense. A lot of things which seem to make sense aren't true though.

Proper testing for PFO carries a (small) risk of significant health problems (including stroke). PFO closure carries much higher risks.

The question is "Do the risks of testing/closure outweigh the risks of DCI?" This can only be anwered on a case by case basis, and, in my opinion the answer is usually NO.

If you have had an episode of DCI and are an active technical diver (whose risk of DCI is higher than normal) then maybe testing and closure is justified.

A recreational diver with a single episode - which is worse, a 1 in 5000 or so risk per dive of DCI or a 1 in 100 or so risk of complications from a procedure - I know which I'd chose.

Screening of asymptomatic divers is even less justified.

Whilst I agree that only a cardiologist can diagnose a PFO, the issues surrounding PFO's and diving lie fair and square in the field that hyperbaric physicians should comment on.

Dave T

Janos

I don't doubt that PFOs are responsible for a significant number of bends. However I don't know how large this number is. I remember a talk a couple of years ago where the 1 in 4 (close enough to 30%) stat. was mentioned. However most of those PFOs are very small, and the percentage of people with large PFOs is much smaller.

Something my chamber operator said to me when I was in the chamber a couple of years back is that PFOs are "Sexy". People in general like to have a reason for things, and so much the better if the reason is not down to them.

The guy said he'd seen quite a few people who had been bent and recompressed and when diagnosed the first thing they asked was whether it was a PFO, despite short surface intervals, sawtooth profiles, and probably dehydration from being out on the pop the previous night.

That's not to say that PFOs don't cause bends. But I think people's perception of PFOs is somewhat warped, but then that's human nature.

Janos

PS - Digressing slightly but there's an interesting paper on people's perception of risk here: <Click me>. It starts off slowly, but there's a few interesting bits about risk there. For example, people are more likely to accept a risk if they perceive themselves to be in control of the situation. Eg you feel safer in a speeding car if you are driving, compared to when you are the passenger.

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Jim

All,

Leave the diagnosis and risk / reward argument to the professionals and divers concerned.

The PFO test carries no risk at all - a simple canular in the arm - and watch the ultrasound to see if your own blood / saline solution passes through an opening that shouldn't be there.

The repair is a heart op via a small inscision in the groin - like all ops you go under for, it carries a small risk.

Having seen the amount of blood (theoretically nitrogenated) passing the wrong way through the heart back into the body, spine, brain etc rather than the lungs - during a simple sniff, valsalvo or slight strain (all of which you do plenty of during and post dive) - I was left with no question as to whether closure was a bloody good idea or not !! As a tech diver there was no option and anybody who wants to carry on at this level is in the same boat - to continue tech dives with a PFO is a lottery with the odds stacked against you (Granted some holes may be too small to worry about - mine was between 1.1 and 1.3cm).

My extremly experienced cardiothoracic physican (of which most on this forum are not) gave me the options of giving up tech diving, diving to no deeper than 20m for 15 mins on nitrox or getting the hole fixed. I took the latter.

What others like to denyor are simply unaware is the possible non dive related complications such as possible stroke due to a clot passing through said hole, migraines with visual disturbance are also commonly associated with PFO, and the heart is not as effective (not quantifiable) during exercise (CO2 rich blood going back round the body rather than to the lungs). Several of the people I have spoken with also had contadictary advice from the 'Chamber Man' - with respect they are in no position to diagnose or advise on PFO - you take their advice on this subject at your peril.

Don't take my opinion, I am no Doctor - but if in doubt get the test done and make up your own mind after proper advice.

Cheers.

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PaulTG2

Hello,

DCI is most definitely NOT random, it simply appears random because it is impossible to directly measure all the elements that went into a specific hit. Believing it is random suggests that we can't control the risks of getting a hit.

Here is one set of research notes on PFOs that certainly suggests that PFOs should be giving consideration for someone who has been hit -- and those wanting to understand risks for themselves.

From DAN's "Deeper into Diving":

"There is increasing evidence that this (PFO) is a significant issue. In a study at Duke University, the hearts of 30 divers who suffered from DCI were examined by two-dimensional electrocardiography. Eleven of these divers were found to have a patent Foramen Ovale. These 11 divers were amoung the 18 divers who had the more serious, neurological symptoms of decompression illness. A British study detected shunts in 15 of 63 (24%) of control divers with no history of DCI, 41% of 61 divers who had suffered DCI, and 66% of 19 patients who had suffered early onset neurological DCI. More recently, the same research group demonstrated a medium to large PFO in 52% of 100 divers with neurological DCI compared to 12.2% of divers controls who had not suffered DCI. These data strongly suggests that patent foramen ovale, especially a large PFO, may impose a greater risk of serious neurological DCI."

Jim

Paul,

Good to see someone with a common sense approach and data to back it up .... Well done that man !!

Guys, you have to remember that newbies read this site avidly, to discount a serious condition as 'sexy' becuase that's what the 'chamber guy' says is dangerous and irresponsible on our part ... please think long and hard before posting on the medical issues. I put my test off for far too long, who knows what damage I've done?!

Play nicely. Happy New Year.

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Jim Spence

Genesis

A Type II hit without obvious provocation is a CLEAR indication that you need to be checked for a PFO if you intend to continue to dive.

A Type I hit is not that simple. If you think about it, a PFO is going to (most of the time) produce a Type II cerebral hit if its going to produce one at all - this is just a function of where the blood goes and how your circulatory system is built.

MOST PFOs are exercise-provoked and as such exerting yourself after a dive is a REALLY bad idea, since as 1 in 3 people have one (but most are only provoked by exercise and are quite small.)

The profiles posted without more information don't tell us much. As square profiles they show huge amounts of mandatory deco blown off, so obviously they were not. But - were they sawtooth (a known DCS provoker)? If one or more of them was, then that dive should have been treated as a decompression dive and the schedule followed for the max depth and max time. The computer won't pick up on this - you have to do it manually.

How was the diver's ascent profile? My standard OW "no deco" ascent profile looks a lot more like a decompression profile than a standard "3 minutes at 15'" thing. For a 100' dive I will do short (1 minutish) stops at 50 and 40, 2ish minutes at 30, the standard 3 at 15-20 and then a nice slow ascent to the surface (3 minutes or so for the last 15') Is this "mandatory"? No. Does it lower deco stress? Yep.

The standard OW guys teach what is IMHO an inadequate understanding of decompression theory and reality, all in the name of making the classes "faster" and "easier." Most of the time, this works out ok. But when you start getting aggressive in your diving, and this pattern IS reasonably aggressive, you need to be smarter - or you run the risk of something like this happening.

With all that said the only way to completely avoid a hit is to not dive. It CAN happen "without provocation" and sometimes does.

But - most of the time the truth is that you pushed it just a tad too far, whether due to dehydration, post-dive exertion the profile itself or other factors.

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dteubner

Mate,

I must confess to being a bit pissed off at the tone of your comments above about the 'Chamber Man". You confess to not being an expert and then dismiss the opinions of a large group of people who are.

There is no doubt that the best way to diagnose a PFO is a bubble contrast trans-oesophageal echocardiogram, and that that is a test that cardiologists do. It is NOT risk free - no medical procedure is. You describe watching bubbles flow across your heart into the left side of your circulation - this can cause problems. I know of at least one person who has had symptoms of CAGE after such a test - but I'm only a hyperbaric physician and therefore in your expert opinion, unfit to comment on the issue.

The VAST majority of cardiologists have very little understanding of diving physiology and decompression sickness. If you know a hyperbaric cardiologist then great, otherwise you should talk to a number of different people. Sometimes people give contradictory advice because the situation is far from clear, although, as I have said, a technical diver with a PFO and an episode of DCI is an indication for investigation. I have certainly referred such people for investigation.

It's not that difficult to get an understanding of the PFO in diving literature, it's not like there's that much of it.

I say again, for a diver to make a properly informed descsion s/he needs to see people with an understanding of both PFO and DCI. In my town that means seeing two people, as there is one cardiologist who does the procedure and about 5 people with a good understanding of DCI.

Dave T

abowie

Quite.

Your perception of the risks inherent in these procedures is inaccurate.

Similarly the PFO situation is by no means clear. If it was it would be a simple issue, rather than one of considerable debate. What little evidence there is in the literature does not settle the matter and is at times conflicting.

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abowie

Essentially what that means is that if you have a PFO and if you get a bend you are more likely to get a type 2 bend.

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