DAN PFO study

[lamont]

Saw this posted on another forum, DAN is looking for volunteers for a PFO study, they're looking for divers with PFOs, including divers that have had them closed:

http://www.diversalertnetwork.org/pfostudy

( I'm just passing this info along, I don't have any association with the study, I just thought it would be of interest )

[Scott]

What is PFO?

[loanwolf]

PFO - patent foramen ovale, It is a opening in the heart between chambers from when we are in our mothers womb. On most people they close up but on some they do not. It causes not all the blood to pass though the lungs so it can greatly impede off-gassing and lead to DCS in divers. They can also open back up as we get older in life so it is something that one should get checked for if you dive.

[Scott]

Thanks for the info

[airsix]

This is pretty cool. I just read the linked DAN page and see that the cardiologist conducting this study is a well known re-breather diver. I have a non-PFO shunt and he provided me with an extremely helpful personal consultation last year. Really great guy. He's done a lot of PFO closures including one for a well known member of our local diving community.

-Ben

[spatman]

Are there facilities in the PNW that can test for PFOs?

[lamont]

Are there facilities in the PNW that can test for PFOs?

A transthorasic echocardiogram (TTE) with doppler bubble can be done by any cardiologist. The more conclusive transcranial doppler (TCD) and transesophageal echocardiogram (TEE) i think are a little more specialized, but I know that Spencer Vascular will do them ( http://spencervascular.com/ ).

I don't have migraines, don't have a lot of issues with DCS symptoms post-dive, and I've had a TTE w/bubble (for other reasons) that didn't find an obvious PFO, which is good enough for me, for now at least. YMMV.

[spatman]

thanks, lamont.

[John Rawlings]

After my unexplained DCS Type II "hit" a few years back I was tested for a PFO and they "found" one with an ultrasound. Prior to scheduling surgery they conducted further, more advanced, tests while I was anesthezied to determine the exact location and size of the PFO so that the size of the device and the methods used in the surgical procedure could be planned. Strangely, despite every effort they were completely unable to find it. It was the opinion of several cardiologists that the initial test was flawed and that I do NOT have a PFO. However, I often wonder....

My friend, Kevin Gurr, in the UK told me that he had had similar results, and that it ended up that his PFO was small and would ONLY open under exertion or strain, which makes me wonder if I might have a similar one - not visible when I'm completely relaxed, such as I was under anesthesia.

Again, I often wonder....

I dive a LOT more conservatively than I did back then, partly fostered by those doubts.

- John

[Peter Guy]

Several of us were involved in a PFO study at UCLA last June and it was pretty interesting to be able to "watch" bubbles in one's blood vessels. As I recall, none had a PFO show up but a couple had "some bubbles" during the stress phase which was said to be common.

I wonder if this "stress bubbling" has anything to do the admonition NOT to exert for a while after a dive when off-gassing will be (should be?) maxxed out.

BTW, Doug Ebersole, who is doing the DAN study is a very nice guy and I hope he gets his study going soon.

[Sounder]

Echoing what Peter said, we had a resting "bubble check" and then we had to exert ourselves blowing into a plugged hose up to a specified pressure while having bubbles injected into us. I actually thoroughly enjoyed the testing process and am grateful to have had the opportunity. Airsix/Ben set the whole group for PFO tests before our trip to the Channel Islands last year so the timing worked out beautifully too... and we were AT UCLA when Michael Jackson (along with every media outlet on the west coast) showed up.

[ljjames]

Did they test for other types of shunts? It is my understanding that there are 2 or 3 other types of shunts that can also cause bubbles that are detectable with transcranial doppler, but if they are looking specifically for a PFO that they will not see them. I don't know much more at this juncture other than the Neuro anesthesiologist where i work feels that the transcranial doppler should be considered the gold standard for finding issues that relate to things going from one side of the vascular system to the other (in an improper way) and showering the brain with badness (bubbles, clots, etc...) and he has done extensive studies with TCD during aneurysm, AVM and other big brain surgeries.

His studies are not directly related to 'diving' but he has interest in shunting, blood flow, bubbles, etc... as you can imagine.

After my unexplained DCS Type II "hit" a few years back I was tested for a PFO and they "found" one with an ultrasound. Prior to scheduling surgery they conducted further, more advanced, tests while I was anesthezied to determine the exact location and size of the PFO so that the size of the device and the methods used in the surgical procedure could be planned. Strangely, despite every effort they were completely unable to find it. It was the opinion of several cardiologists that the initial test was flawed and that I do NOT have a PFO. However, I often wonder....

My friend, Kevin Gurr, in the UK told me that he had had similar results, and that it ended up that his PFO was small and would ONLY open under exertion or strain, which makes me wonder if I might have a similar one - not visible when I'm completely relaxed, such as I was under anesthesia.

Again, I often wonder....

I dive a LOT more conservatively than I did back then, partly fostered by those doubts.

- John

[airsix]

What Dr. Doug shared with me is that the TCD is a great diagnostic first step. It can be used to estimate the location of a shunt based on the number of cardio cycles it takes for bubbles to show up on the wrong side of town. An interesting thing he shared: We all have shunts (short circuits bridging the veinous and arterial systems) and that if you watch anyone's TCD for enough cardio cycles you'll see crossover. With regard to DCS, the greater the time before crossover, the lower the risk caused by crossover. A shunt in the heart produces a quicker crossover than a shunt in other organs (I was told).

A positive TCD does not confirm that you have a PFO, it just indicates that you have a shunt somewhere, and gives an indication of how significant it is. Other tests are required to verify location. But, it's a very non-invasive low cost first step that gives 75% of people a definite "no". The other 25% get a "maybe/probably".

[Tangfish]

Are there facilities in the PNW that can test for PFOs?

I had mine done at Virginia Mason. I have a small PFO.

[limeyx]

Did they test for other types of shunts? It is my understanding that there are 2 or 3 other types of shunts that can also cause bubbles that are detectable with transcranial doppler

I had heard the same thing, but I am not sure where.
I was told that the TCD is about 96% as good as the better of the TTE/TEE (I can never remember which is which) but that that was mostly from "operator error" in administering the TCD test, not necessarily inherent in the test itself.

[ArcticDiver]

Using doppler I've heard bubbles in "normal" non-divers. I remember watching a presentation on a doppler study that was done on some divers who were doing some exploration. According to the presentation almost all the divers had bubbles but no detectable DCS symptoms. Does all this mean that there is a threshold value of bubbles that separates "normal" from "bent".

[lamont]

Does all this mean that there is a threshold value of bubbles that separates "normal" from "bent".

Its more the symptoms that separates "normal" from "bent".

An increase in bubbles in correlated to an increase risk of being bent, all other things being equal, but there's no clear line, and there's reason to believe that people with no/less shunts are going to tolerate more bubbles than those with shunts -- so the line can shift from person-to-person, and probably day-to-day or dive-to-dive. Its all fuzzy logic, rather than aristotelian logic.

[ArcticDiver]

Yep, just about what I know, or think I know anyway. Lots of studies and analysis leading to lots of theories but no certain knowledge of what causes DCS.

In no way do I think we ought to stop doing studies on the subject and related theories. One of them might stumble on a true, replicable cause and effect fact. In the meantime we are fortunate that DCS is very rare, or we think it is anyway, and made rarer by a diver being in touch with their body.

It is amazing how many times in how many sports that the final arbiter comes down to the participant being in touch with their body. I guess that just illustrates that we are analog creatures whose statistically minor differences are as important as the similarities.