Whis is a PFO in Layman's Terms?

Great question!

The short answer (Google PFO) or look it up on the list for LOTS of reading material, is this:

When your a baby, you have a hole in your heart so your mothers blood circulates through your body. When your born, that hole closes creating the 4 chambered heart that now pumps your own blood.

In 30-50% of normal people, that hole does not completely close or is not sealed. No problem for normal life, until you start to dive.

After a dive, your body bubbles Nitrogen out. Small bubbles flow through your body, to your heart, your heart sends it to the lungs where the bubbles are filtered out and exhaled, clean bubble less blood then is pumped back out to your heart, brain, spine, and body.

If you have an unsealed PFO or do something to make the whole bigger or break the seal, a bubble can pass through the heart, skipping the lung filter and get stuck in the heart, brain, spine (Type II DCS hit). This how you get a real bad case of bends "without doing anything wrong in terms of diving or profiles".

Free diving after diving can push a bubble through the lung filter. Your bubbling after a dive, you free dive to 10ft adding pressure and shrink the bubble so it gets past the lung. Then your ascend and the bubble expands on the other side of the heart and gets stuck. Bingo, instant Type II hit.

Let me hit on your next good follow up question?

Why doesn't everyone get tested for PFO?

Because short of opening your heart up and inspecting the hole, there is no way to know it is sealed? All the other tests can tell you IF you HAVE a hole, but a negative result just means they can't FIND the smaller hole that MIGHT still be there.

Scared yet?

Don't be, for most divers doing recreational profiles this is not a concern, there are that many bubbles and these divers are not jumping off the 2nd floor deck during the surface interval.

This is just one of the many things you need to be AWARE of. When you read accident reports or here stories of "mysterious" Voodoo, random bends hits, usually, its a PFO. Especially when the victim didn't do anything "wrong" and they got a really bad Type II hit.

A type I pain hit is not nearly as dangerous. Its like a runner spraining an ankle from too much exertion. Marathon runners worry about that, me going for an hour walk doesn't. I just stretch out and wear good shoes.

This topic is continually repeated so as you read the list it will appear again and again.

If you want to do a good deed, go back to your instructor and educate them on PFO's after you've read a bit more and ask that they tell everyone they teach about them!