PFO/ DCS question

[Nailer99]

Just doing a little research, here. I'm very new to diving, and just got interested in so called "undeserved" hits- I get the part about how anybody at any time can suffer DCS, even on a consevative dive, well within established NDLs. What I don't quite grasp is why everyone's first question to someone who posts about an undeserved hit here is whether they've been tested for PFO (patent foramen ovali, or some such). A quick side trip to google tells me this is a defect in the heart, which can allow blood to backflow....or bypass the lungs, in certain circumstances.....can this lead to DCS because certain volumes of blood are not able to offgas nitrogen every time they "miss" the lungs? Leading to higher than reasonably anticipated Nitrogen levels? I bet I just answered my own question here, but....it just seems like if that is the mechanism, the person with the PFO would be....well, sickly or something, due to inadequate gas exchange in the course of their normal life....like, they'd get out of breath really easily and what not...If you're not getting enough blood to your lungs to offgas nitrogen on ascent, how can you be getting enough o2 in non-diving life to be in good enough shape to be a diver in the first place? Is there some relationship to pressure at depth I'm not getting, here?

 

[cornfed]

Here is a article on PFOs which might be helpful.

 

[ItsBruce]

Good question and an interesting observation. However, I'm inclined to think that you haven't answered your own question. I've seen stuff that makes me think that PFO with DCS could lead to bigger problems than just DCS... something about gas bubbles not passing to the lungs, but rather going toward the brain. Maybe someone with actual knowledge will check in on this.

 

[Jay Roy]

I think to affect the person's quality of life so to speak, it would have to be a pretty big hole..I've saw ultrasound mpegs where a person had a PFO and you can see the blood squirt into the other chamber, but it doesnt happen on every beat...So most of the blood would get the nutrients that are needed..But if some blood got thru, that was carrying a bubble, it would miss the filters (lungs) and then expand....I dont think you would get really serious life or death DCS from this..Maybe skin bends, or joint pain etc..

 

[jagfish]

I think to affect the person's quality of life so to speak, it would have to be a pretty big hole..I've saw ultrasound mpegs where a person had a PFO and you can see the blood squirt into the other chamber, but it doesnt happen on every beat...So most of the blood would get the nutrients that are needed..But if some blood got thru, that was carrying a bubble, it would miss the filters (lungs) and then expand....I dont think you would get really serious life or death DCS from this..Maybe skin bends, or joint pain etc..

Hi left winger
Nice dive form in your avatar.
Regarding your comment, seems to me that a PFO that was visibly squirting blood across the heart barrier world qualify as a potentially dangerous situation regarding DCS. The whole danger of a PFO is that if any bubbles cross that barrier, next stop is the brain, before the rest of the body.

This increases the risk/ likelihood of type II neural involvement.

 

[Nailer99]

Here is a article on PFOs which might be helpful.

From the article:

"During normal decompression, nitrogen
is outgassed from peripheral tissues
into the bloodstream. The lungs filter out
gas bubbles in blood returning through
the veins before they can reach the brain.
However, if bubbles are able to leak from
the right side of the heart to the left and
thereby enter into the arterial circulation,
they can lodge in the brain, causing
dangerous neurological decompression
sickness “hits.” "

Yep. Thanks, Cornfed!

(edit- key concept here is that the bubbles in question are small enough to pass through the blood into the lungs for normal outgassing, but large enough to be lethal/ and or debillitating if they make it to the brain!)

 

[vondo]

I think to affect the person's quality of life so to speak, it would have to be a pretty big hole..I've saw ultrasound mpegs where a person had a PFO and you can see the blood squirt into the other chamber, but it doesnt happen on every beat...So most of the blood would get the nutrients that are needed..But if some blood got thru, that was carrying a bubble, it would miss the filters (lungs) and then expand....I dont think you would get really serious life or death DCS from this..Maybe skin bends, or joint pain etc..

After reading these threads, I got tested for a PFO last week. Let me just say that this was a very cool experience. It took about 45 minutes for a complete echocardiogram where they image your heart with ultrasound. I could watch on the monitor as my heart valves opened and closed. In fact, the part of the test for the PFO means they get a view of your heart where you can clearly see all four chambers at once. Then they turn on some kind of "doppler" ultrasound where they can tell if blood is moving between the aorti. (The movements are color coded.)

Now here's the only bad part. If they don't see anything in that part of the test (and they probably won't since most people don't have one), they put in an IV and inject saline with a little stream of bubbles and look for bubbles to cross over. As long as needles don't bother you, no problem, and then you get to see the right side of your heart very clearly as the bubbles reflect the ultrasound very well.

As I said, this is a complete test, so they test for lots of other things too (but don't ask me what).

So, very cool. Mine came back negative, which is good. It should be almost completely covered by insurance, but I will be curious to see what the "cost" is.

 

[Dr Deco]

Hello readers:

Echocardiography

This is a test for many factors concerning the efficiency and health of the heart. Measurements are made concerning the thickness of the heart muscle, the competency [= how well they are working] of the heart valves to check for regurgitation [= backflow] and for the pumping capability) = ejection fraction). The test for the PFO is one portion.

PFO

Considerable material has been devoted to this topic over the years on the Ask Dr Deco board. You can search this with the SEARCH function at the top and look und “patent foramen ovale.”

The short of it this. Several factors come into play.

1. The size of the opening.
2. Most of the time, the pressure is greatest on the left atrial side and bubbles will not cross.
3. Bubbles must be present in the diver and this is not always the case.
4. A sufficient number of bubbles must cross for a blockage of the brain arterials to occur. Usually the arterial pressure will push bubbles through the brain capillaries.

Dr Deco :doctor: