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dteubner · 21st April 2007, 09:33

Quote: (Originally Posted by Andre)

Just get out of the decompression chamber in Toulouse France. 8 Hours comex. I was told told by my doc two years ago that my foramen ovale is closed 100%. Now the the doc in duty told my that this can chance any time.

A PFO is present in 30% of the non diving population, therefore presumably present in 30% of the diving population.

The presence of a PFO increases the odds of having serious neurological DCI about 4 fold.

This means that, if you get serious neurological DCI AND you have a PFO then there is about a 75% chance that the PFO contributed to the DCI. YOU CAN NOT SAY THAT THE PFO CAUSED THE BEND, just that it was likely to have.

PFOs do not increase the risk of musculoskeletal, pain only type bends, so if these are the 'minor hits' then they had nothing to do with a PFO.

Size is likely to be important, and small holes that do not shunt blood easily are probably of very little significance.

To look at it another way, in a population of divers about 50% of underserved serious neurological DCI can be ascribed to a PFO, which menas that 50% CAN'T and you can't establish causality in an individual diver. You can, on the other hand ascribe causality to PFO for minor, pain only DCI. It didn't cause it.

There is a line in The Origin of Species where Darwin says that the appearence of particular species is due to "what we may call chance". He means that it's not really due to chance, but there mechanisms involved are so complex that we can never really understand them. Very little in medicine (or indeed life) can be understood in great enough detail to really say this caused that, causality is extremely difficult to establish. Because of this, we use statistics to try to make sense of things. People don't like this approach.

Here are some more things - if every diver who had a PFO had it closed and IF having it closed removed all of the increased risk of DCI then the incidence of serious neurological DCI woul fall by 50%. IT WOULD NOT GO AWAY, it would just halve.

PS - Apologies for the deja-vu.

21st April 2007, 09:33	#48 (permalink)
dteubner Pedant Current Rebreather/s: Sport Kiss Classic Kiss Other Rebreather/s: Join Date: Mar 2005 Location: Adelaide, Australia Posts: 216	Re: Patent Foramen Ovale Quote: (Originally Posted by Andre) Just get out of the decompression chamber in Toulouse France. 8 Hours comex. I was told told by my doc two years ago that my foramen ovale is closed 100%. Now the the doc in duty told my that this can chance any time. A PFO is present in 30% of the non diving population, therefore presumably present in 30% of the diving population. The presence of a PFO increases the odds of having serious neurological DCI about 4 fold. This means that, if you get serious neurological DCI AND you have a PFO then there is about a 75% chance that the PFO contributed to the DCI. YOU CAN NOT SAY THAT THE PFO CAUSED THE BEND, just that it was likely to have. PFOs do not increase the risk of musculoskeletal, pain only type bends, so if these are the 'minor hits' then they had nothing to do with a PFO. Size is likely to be important, and small holes that do not shunt blood easily are probably of very little significance. To look at it another way, in a population of divers about 50% of underserved serious neurological DCI can be ascribed to a PFO, which menas that 50% CAN'T and you can't establish causality in an individual diver. You can, on the other hand ascribe causality to PFO for minor, pain only DCI. It didn't cause it. There is a line in The Origin of Species where Darwin says that the appearence of particular species is due to "what we may call chance". He means that it's not really due to chance, but there mechanisms involved are so complex that we can never really understand them. Very little in medicine (or indeed life) can be understood in great enough detail to really say this caused that, causality is extremely difficult to establish. Because of this, we use statistics to try to make sense of things. People don't like this approach. Here are some more things - if every diver who had a PFO had it closed and IF having it closed removed all of the increased risk of DCI then the incidence of serious neurological DCI woul fall by 50%. IT WOULD NOT GO AWAY, it would just halve. PS - Apologies for the deja-vu. __________________ Dave T Hanlon's Razor - Never attribute to malice that which can be adequately explained by stupidity.
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