"Patent Foramen Ovale Influences the Presentation of Decompression Illness in...+

[DocVikingo]

Doc, can you elaborate on this?

Not intelligently ; )

Cheers,

Doc

 

[boulderjohn]

When we talk about the degree to which established tables are able to keep the general diving population safe, we should remember that to the degree that the tables were tested, the general population was used. When PADI did the testing for the RDP, for example, they did not screen out people with PFOs. We should assume that 25% of the test population that determined that those guidelines were safe had PFOs.

 

[danvolker]

When we talk about the degree to which established tables are able to keep the general diving population safe, we should remember that to the degree that the tables were tested, the general population was used. When PADI did the testing for the RDP, for example, they did not screen out people with PFOs. We should assume that 25% of the test population that determined that those guidelines were safe had PFOs.

I don't take issue with this......what I am concerned about, is the BIG push to go TECH that I see in so many shops today....this sort of tied to the big push in Rebreathers as well.
So all these new "prospects" for tech, are from a population that was fine with a PFO--except for the ridiculous notion of some few getting an "undeserved hit"....this would be a tangent rant

The recreational population now becoming tech divers, are at risk for the implications of PFO's suddenly becoming significant under the greater demands of 200 foot and 300 foot deep diving for extended periods.

And as to my tangential rant....if a set of tables was created for EACH diver, for each diver's unique fitness, physiology, in-gassing and off-gassing potential.and the profiles they run...if such tables existed, I don't think "undeserved hits" would even have a name ( because they would be so rare). I think the real problem is that each diver assumes the tables were made for them...when in fact they are not--they are made for a median or an average diver, with an average range of profiles.....this may have very little to do with an individual.

 

[dreamdive]

Concerning Deep Stops, it is worthwhile to note that deep stops on No-Deco dives has little evidence to support the idea that they are helpful or not. On longer decompression dives, there is evidence showing a significant reduction in size/frequency of bubbles if staged stops are started earlier in the profile.

Tom, there is also a lot of evidence that it is not! It's a widely debated topic.---------- Post added August 22nd, 2014 at 11:11 AM -------------------- Post added August 21st, 2014 at 01:53 PM ----------[/COLOR]I think it's worthwhile to note too that an ASD is an absolute contraindication to diving, while asymptomatic PFO is not. Best regards,DDM[/QUOTE]Yes, no doubt. But if you don't know about it, you will dive with it. Many are asymptomatic with an ASD and unless you get a study, you just don't know.

---------- Post added August 22nd, 2014 at 11:20 AM ----------

I don't take issue with this......what I am concerned about, is the BIG push to go TECH that I see in so many shops today....this sort of tied to the big push in Rebreathers as well.So all these new "prospects" for tech, are from a population that was fine with a PFO--except for the ridiculous notion of some few getting an "undeserved hit"....this would be a tangent rant The recreational population now becoming tech divers, are at risk for the implications of PFO's suddenly becoming significant under the greater demands of 200 foot and 300 foot deep diving for extended periods.And as to my tangential rant....if a set of tables was created for EACH diver, for each diver's unique fitness, physiology, in-gassing and off-gassing potential.and the profiles they run...if such tables existed, I don't think "undeserved hits" would even have a name ( because they would be so rare). I think the real problem is that each diver assumes the tables were made for them...when in fact they are not--they are made for a median or an average diver, with an average range of profiles.....this may have very little to do with an individual.

Hey Dan, I hear you. I want to take it even further, the tables would be made not just for each diver but for each dive for that diver, (if that could actually prevent DCS)!One can dive for years the same dive and never have a problem rec or tech and than one bloody day......BAM!No explanation! Some say that he/she "would have gotten bend no matter what profile he/she dove", and it led to my personal conclusion that bubbles alone just don't explain the phenomena of DCS I see. My friend just sustained a very very serious hit on an NDL dive - no explanation! BTW: Pardon my using the phrase "undeserved hit". Maybe I recoin it to "enigma hit".

 

[danvolker]

I remember a study I read a few years back, that dealt with how an aerobic workout an hour or so before diving, or 6 hours before, or a day before, had different effects on the formation of bubble nuclei --if I remember correctly, there was AN OPTIMAL TIME FOR exercise that could be preventing the nuclei from setting you up for to much creation and cascading of bubbles on the ascent from a dive.
If exercise can effect the nuclei, it is quite probable there are other factors that could contribute to a physiological state in which a diver that would normally be able to easily offgass the bubble load at safe levels, would experience more bubble creation than they could off-gas safely...

Perhaps it is a "perfect Storm of events"...dehydration, exercise/exertion at the wrong time prior to diving....... wrong foods in past 24 hours( digestive blood concentrations or excess sugar inflamation--A.G.E ).....There has to be some event or series of events that actually "explains" the "un-explained hit"

 

[lowviz]

...//... I prefer to consider the accepted agency tables today ( what PADI, NAUI and most others use), as too full of fudge factor to be something I want to pay undue attention to. ...

...//... There has to be some event or series of events that actually "explains" the "un-explained hit"

Yeah, tables "fudged" to fit me/you personally. Same thing in today's cutting edge medicine, drugs designed for one and only one person, the patient...

 

[dreamdive]

More on the different studies on DCS:

Add Helium Resource Library | Add Helium

Many things have been studied, including (and don't laugh) the use of a vibrating bed!
Unfortunately, most studies employ only a tiny sample size and very few have follow-up studies. I take refuge in the small statistical incidence of DCS even for us helium/deep divers. Nethertheless, even if one does everything "right" such as being fit, eating well, antioxidants, post-hydration, planning and execution, etc......I know that I, too one day may see the inside of a chamber as a patient rather than as a doc.

 

[tomfcrist]

Concerning Deep Stops, it is worthwhile to note that deep stops on No-Deco dives has little evidence to support the idea that they are helpful or not. On longer decompression dives, there is evidence showing a significant reduction in size/frequency of bubbles if staged stops are started earlier in the profile.

Tom, there is also a lot of evidence that it is not! It's a widely debated topic.

On extreme deco dives? You sir are mistaken. If you are going to do a bubble study comparing the effectiveness of pure haldanian deco models VS the
effectiveness of Bubble models like VPM or RGBM, I'll even be your Guinea pig to prove you wrong. The term deep stop may be confusing you, but if you read above, I never put a rigid figure on where that stop should happen. It is well proven that starting deco earlier and deeper leads to an overall shorter deco obligation with fewer and smaller bubbles.
Dan Volker no doubt saw this in action when he was diving with GI3 on the regular basis. George was known for doing extremely short deco(relatively short considering his dive profiles). I don't believe he was diving a haldanian model...I was never a GI3 fan, but that doesn't mean I don't buy in on his conceptual beliefs. I was more of an opponent of his internet persona.

 

[boulderjohn]

On extreme deco dives? You sir are mistaken. If you are going to do a bubble study comparing the effectiveness of pure haldanian deco models VS the
effectiveness of Bubble models like VPM or RGBM, I'll even be your Guinea pig to prove you wrong. The term deep stop may be confusing you, but if you read above, I never put a rigid figure on where that stop should happen. It is well proven that starting deco earlier and deeper leads to an overall shorter deco obligation with fewer and smaller bubbles.
Dan Volker no doubt saw this in action when he was diving with GI3 on the regular basis. George was known for doing extremely short deco(relatively short considering his dive profiles). I don't believe he was diving a haldanian model...I was never a GI3 fan, but that doesn't mean I don't buy in on his conceptual beliefs. I was more of an opponent of his internet persona.

The DAN workshop on deep stops a few years ago did not come up with anything this conclusive, as far as I can see. I did a search of published research a few years ago, with the active help of Gene Hobbes of Rubicon. Gene showed me a draft of a document he was working on. I don't know if he ever published it. My quick summary of it all is there is not a whole lot of evidence supporting any of the competing theories.

BTW, GUE has stated that the key research document support the key element of the GI3 ascent profile (the oxygen window) was faulty, and they no longer use that profile. JJ told me directly that they no longer accept that theory.

 

[danvolker]

The DAN workshop on deep stops a few years ago did not come up with anything this conclusive, as far as I can see. I did a search of published research a few years ago, with the active help of Gene Hobbes of Rubicon. Gene showed me a draft of a document he was working on. I don't know if he ever published it. My quick summary of it all is there is not a whole lot of evidence supporting any of the competing theories.

BTW, GUE has stated that the key research document support the key element of the GI3 ascent profile (the oxygen window) was faulty, and they no longer use that profile. JJ told me directly that they no longer accept that theory.

However, anecdotally, many WKPP'S and several of us, did a great many very extreme exposures, with very short decos, and with no dcs. In all the extreme dives I did with George, with the very short decos we did, I always felt great afterward....point being, if it was "so flawed", why did it work so well" ? Maybe the flaw was that it was too individualized? I will have to ask Bill to chat with JJ about this sometime