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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'.
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