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Gerard, this is not a WKPP or DIR issue - it is a fact of life. Yes, I do require my divers to get tested, but then I am not an idiot, and do not need to put my hand on the stove to know it is hot. Obvious is good enough for me. You guys argue this while I don't worry about it . Gerard Stainsby wrote: > > Asbestos drysuit on... :-) > > WILLIAM GEARMAN wrote: > > > > Just FYI everyone. > > > > The below was released today. > > Which do you mean, the Reuters article, or the > paper/presentation to which the Reuters article > is referring? (Which you haven't referenced and > presumably didn't attend.) > > > Again, the experts > > have conveniently left out numerous variables. > > Ah, so the Reuters journalist/s who've downgraded > any actual scientific content to the level that > Joe Average reader can understand and that you can > criticise have left out numerous variables, so you > presume that there were none in the source presentation? > > > Even so, it could raise some interesting > > discussions. > > True, but I expect it'll turn into a flame war > like most other opportunities here. > > > It sure would have been nice if > > they had done this study with data with other > > types of gas media and differential subject > > groups such as WKPP. Wonder how many stokes were > > in the study? > > Probably all of 'em. (that is, many or all of the > people studied may have been strokes, not that all > the strokes in the world would have been studied!) :-) > > Partly this will be due to a sampling bias. > > 1. most of the world doesn't do technical diving at > all, let alone DIR technical diving. If you stand on > a street corner and shout out "20 bucks if you're a > diver and will lie still for a brain scan", you'll > get PADI, not WKPP. > > 2. Non-strokes are usually? often? people who have > graduated through strokedom, once they've been exposed > to the light. If a person in their early diving days > gets enough subclinical hits (perhaps because of a PFO) > they're unlikely to progress to technical diving or DIR, > meaning that if you study DIR divers you're more likely > to find non-PFO people. > > 3. If Knauth has studied people who have had a documented > hit, we have another sampling bias: the WKPP won't > conveniently generate enough brain lesions to study, > at least that we know of. > > The sampling method would have been presented by Knauth > in the paper, but it's not really his/her fault that > Reuters hasn't given it in their release. > > Let's face it, if you wanted to make the diving world > safer (saving neurones or lives, whichever) for those > great PADI masses who do air in warm water to 12m > (18m on an adventurous day) there are two approaches: > > - get 'em to do DIR (desirable, but pretty unlikely, and > watch the price of heliox as demand rockets) or > > - get 'em to dive conservatively, and identify divers > at special or increased risk, & devise strategies to > minimise extra risk in these people. > > > BigVon, did you participate? ;-) Might explain > > his attitude and mind set. eeh, George? > > Cheap shot & brown-nosing in two lines. Very economical. > > > > > >"Monday November 29, 2:20 pm Eastern Time > > > > Scuba diving dangerous for heart defect > > sufferers > > > > CHICAGO, Nov 29 (Reuters) - Scuba diving can be > > dangerous for > > the one out of every four people who have a > > common heart defect that > > makes them susceptible to decompression sickness > > and brain lesions, > > researchers said on Monday. > > > > The heart condition, called patent foramen ovale > > (PFO), is an opening > > in the connection between the left and right > > sides of the heart. Those with PFO can have > > relatively harmless skin rashes or develop > > serious neurological problems such as vertigo or > > even paralysis. > > > > During dives, inert gas bubbles that form in the > > bloodstream can bypass the filter in the heart of > > PFO sufferers that would normally send the > > bubbles to the lungs. > > > > The bubbles then travel through the body, causing > > decompression sickness, and into the brain > > where they can create lesions, said Michael > > Knauth, a radiologist at the University of > > Heidelberg Medical School in Germany, who > > presented his findings to the annual meeting of > > the > > Radiological Society of North America in Chicago. > > > > Decompression sickness, which can be fatal, > > occurs when gas bubbles are released into tissue > > after a too rapid decrease in air pressure > > following a stay in a compressed atmosphere -- > > such > > as under water. > > > > In cranial examinations of 88 scuba divers, > > Knauth said four of five divers with PFO were > > found to have several brain lesions each. Brain > > lesions were rare among non-PFO divers. > > > > ``It is unclear whether the brain lesions can > > cause long-term problems, but common sense would > > tell you if you have enough of them and they're > > in the right places, they could cause problems, > > such as memory disturbances or difficulty > > concentrating,'' Knauth said. > > > > In another aspect of the study, 19 out of 24 > > divers who had unexplained diving incidents, > > despite > > following the rules of decompression such as > > descending and ascending slowly, turned out to > > have PFO. Some also had large brain lesions. > > > > ``Divers with PFOs should reduce the depth they > > are descending to, not stay deep too long, > > ascend slowly, increase the time they spend above > > water between dives and avoid several > > descents during one dive,'' Knauth said. > > > > Knauth suggested prospective divers get tested > > for PFO before being certified to dive."< > > Knauth is citing this on traditional investigational > medicine grounds (and presenting to a group of > investigational medicine specialists). > > a) if there's a group at risk (seems to be divers > with PFO) and > b) if there's a test to identify this group then > c) if you do the test you'll identify the group > at risk, and can > d) take steps to reduce the risk. At the very least > you'll have a group of divers who know that they > have an otherwise fairly benign condition which might > influence the way they (should) dive. > > (This may seem very obvious but some of the readership > seems to have/claims to have legal training, and it's > worth noting that (investigational) medicine is a > discipline based on scientific principles and truth > based on observation and logic, rather than law where > the "truth" is based on what you can persuade a jury.) > > > > Duh? That's a no brainer! > > Why? > > The fact that it is probably impracticable on the > basis of cost, compliance, availability of tests > and so on doesn't mean that in principle it's not > a reasonable thing to suggest. > > Since I didn't attend the presentation, I don't know what > test Knauth is proposing. A reasonable test is transthoracic > echocardiography with bubble contrast, looking for > microbubbles in the systemic circulation after an intravenous > injection of agitated saline. Possibly a better test would > be transoesophageal echocardiography, which usually permits > better visualisation of some of the relevant cardiac structures. > It requires fasting beforehand, intravenous sedation, a trained > echocardiologist with an assistant, about half-an-hour and > probably _wouldn't_ fit into the $70 or so (around here) > fee for a standard diving medical. Around here an echo machine > with a TOE probe costs ~ $300K and they're mostly busy doing > tests on actual patients with actual sick hearts. > > If Knauth has a better test he (she?) might be onto something > worthwhile. > > > > > Sincerely, William > > Cheers, > > Gerard Stainsby > (in a funny sort of mood today, sorry, don't know why) > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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