Which is why discussions like this are synergistic. Its a pity you dont see that.
Roak
Nitrogen and Red Blood Cell Rigidity
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Roak
The Iceni
Medical Moderator
Pescador,
Don't you mean the vast majority of divers know little about medicine and have no wish to learn and the vast majoriy of medicos know little about diving and have no need to learn.
In fact the majority of "diving medicine" is not strictly medicine. Like the subject of this thread it is environmental physiology, which does not loom large in established medical training or practice.
I would like to believe I am in the small minority of both categories and have learned a considerable amount from this forum, if not from many others.
(I know you are acting as devil's advocate, but your post begs the question, in which of my two groups do you fall, pescador?
ut: )
rcohn
Guest
I had forgotten just how long the discussion was until I searched out the links. You have a lot more patience than I have.
Ralph
Howdy Roger:
I don't subscribe to the DIR/Quest list so I can't directly address what you read there. But I can caution you to take what divers repeat about scientific studies with a grain of salt. In my limited experience with such discussions I have found a tendency among some people to take a study that they didn't read and didn't really fully understand when it was explained to them and contort the study until it fits the agenda that they wish to promote.
Yes, you can postulate about the effects of helium in the study you mentioned, but it's one huge giant stride to go from an interesting hypothesis to an established fact on which you are basing recommendations for actions. The study designers did not conclude that the changes that they found with RBC aggregation were caused by increased partial pressures of nitrogen and they did not find that helium helped relieve aggregation. In fact they specifically stated that they felt that the partial pressures of the gases were NOT the cause of the effect seen, and they pointed out that the same effects are found when you spin blood in a centrifuge. They decided this suggests that it was hydrostatic pressure that was causing the increased aggregability- not partial pressures of gases.
Now, some questions about the DIR/Quest discussion. You say that the list mentioned that the aggregability didn't change much after 66', right? And they think that the lack of much change was because the researchers added helium after 66'? Did the writers to the list mention that the researchers pressurized the chamber to only 36' (partial pressure N2=~1.6) on air and then started compressing with helium at that point? Did they mention that the researchers very carefully kept the partial pressure of N2 <1 ATA for the whole study both at and beyond 66fsw (the point where they started taking mesurements)?
You know, you reach a partial pressure of 1 ATA for N2 at about 8.25fsw on air. Were the writers to the list consistent in their arguments and recommend that all dives below 8.25fsw should be made on trimix to keep the END <8.25fsw? If they really believe that this study points out a "danger" of nitrogen then that's what they should be recommending, IMHO.
HTH,
Bill
Howdy pescador775:
Sorry to take so long to get back to you. You bring up several issues that I'd like to address.
I haven't seen where your question has been specifically addressed by any real research so I can only guess based on what information is known, but here's my 2¢. It appears from the best evidence available that the aggregation seen is caused by hydrostatic pressure, not by the partial pressure of any gas. So to the first part of your question I'd say No, it does not appear that N2 causing aggregation is related to headaches. (Since it's not the cause of aggregation.) As far as rigidity of blood cells is concerned, the researchers who did the studies on rigidity originally hypothesized that increased partial pressure of gases would cause blood cells to become rigid and those rigid blood cells would obstruct the capillaries in bone causing osteonecrosis. They focused on bone capillaries and osteonecrosis because the capillaries in bone are particularly small and inflexible and therefore especially susceptible to occlusion by stiff blood cells. While their results might indicate that some blood cells might stiffen somewhat in some divers, they didn't seem to become rigid enough to significantly obstruct bone capillaries. Seems to me that if they don't become rigid enough to really block the tiny bone capillaries, they wouldn't obstruct brain capillaries and cause headaches either. It's an interesting idea that probably merits further study, but so far from the information available it looks like yours is just another one of those "whacky theories" that seem to disturb you.
I can see how to the unperceptive it can seem like "medicos know little about diving". As Dr. Thomas has already pointed out, most doctors don't know much about diving because it simply isn't their area of expertise and it's not a normal part of their training. Blaming your family doctor for not knowing about diving related issues is like faulting your plumber for not knowing how to configure your PC. ("Dang it, he repairs things, doesn't he!?") As for the doctors (MD, PhD, and DDS) that participate on this board, I for one claim no special credentials in diving medicine- never have. But I do try my best to research my answers to reach the highest level of accuracy that I can based on the current diving and medical literature, and I also try to keep my mouth shut on subjects where I am ignorant and don't know or can't find the answer. (Or at least make it clear when I'm just guessing based on available information.) Regarding the other Medical Regulators on this board, I am continually amazed by the depth and breadth of their knowledge on diving matters and am gratified by their willingness to share their wealth of knowledge so freely. It's probably frustrating to the casual reader here when they don't get a specific answer to a specific question, but those are the breaks. There is still quite a lot about diving medicine that just isn't known (by anyone) because the research to find the answers hasn't been funded. And it would be irresponsible for anyone to try to specifically answer questions asking for personal medical advice on an Internet message board where a complete medical history isn't available, a physical examination can't be done, and appropriate diagnostic tests can't be ordered. But hey, we do what we can.
I can also see why the undiscerning might make a broad statement like, "Divers know little about medicine" about board members here. Actually, if you look closely you'll notice that there are quite a few divers on this board who have comparatively little or even no formal medical training, yet they seem to routinely give very sound general medical explanations and advice here. I could name them for you, but there are enough of them that I would surely leave someone out. These people have taken the time and effort to educate themselves, and most importantly, they understand what they DON'T know and limit their answers to their field of knowledge. But as you say, many divers really don't know much about diving medicine. Fortunately most of them are wise enough to realize that and they limit themselves to asking questions instead of making up answers. There are occasional instances when someone will give some bad medical advice here because of what they thought they once heard, but fortunately it's rare.
There was one glaring exception to this rule that might have clouded your view of our posters if you saw it. There once was a fellow (dev something-or-other I think) who for a while there was regularly posting HORRIBLE medical advice. The poor guy had almost no knowledge of anatomy, physiology, or pathology, and what little he did know it seems he badly misunderstood. But even more importantly he apparently had absolutely no cognizance of his own profound ignorance- and no amount of helpful advice or instruction seemed to enlighten him. He appeared to just make up "whacky theories" as he went along and then tried to disseminate them as established fact. Much of what he said was so far out it was ludicrous. I actually became concerned that someone reading Scubaboard might be gullible enough to believe something he said and at best make a fool of themselves repeating it elsewhere or at worst actually come to harm. I'm thankful that for whatever reason he stopped his preposterous behavior. Hopefully he finally developed a touch of wisdom and came to a realization of how ill informed he actually was. I don't suppose it's likely that he was the one who gave you such a low opinion of the posters here because he stopped posting 2 days before you registered on Scubaboard, but if you go back and review his posts you'll see what I mean. Hey, you might know him! He posted from the same IP address that you do. Better watch your back out there pescador775!
It's interesting that you'd say this. Some diving authorities have recommended in the past that divers take aspirin. The thinking was that aspirin inhibits platelet (blood clotting cell) aggregation, and that increased hydrostatic pressure (like in diving) and bubble formation promote platelet aggregation. The reasoning went that platelet aggregation might contribute to the chance of developing DCS or worsen the course of an episode of DCS if it occurs, and taking aspirin might be beneficial in helping to prevent it. But it turns out that aspirin doesn't really help much (or at all) and it can be harmful.
The recommendation for recreational divers to routinely take aspirin does not seem to be the currently accepted standard among most diving physicians now. DCS is very uncommon in recreational divers. If a diver does develop DCS the anti-clotting effect of aspirin could possibly cause increased bleeding in a hemorrhagic lesion (say in the inner ear, brain, or spinal cord) thus making the effects of the episode of DCS much worse. (Such increased bleeding and worsened injury has been seen in animal models on aspirin.) Also, barotrauma injuries are quite common in recreational divers, and those injuries are often associated with bleeding. Aspirin could make the bleeding in such an injury worse, potentially turning a minor annoyance into a major problem. For these reasons, taking aspirin while diving seems to be at best a wash from a preventative medicine standpoint, and in the typical recreational diver it might actually do more harm than good. I believe that there is a study going on in Australia taking another look at aspirin and diving, but the results aren't available yet to my knowledge. As it stands now, the conventional wisdom is to not recommend routine aspirin use to all recreational divers.
Since you seem quite interested in the quality of medical discussions here, perhaps you'd like to share what particular information you have that would cause you to dispute the current generally accepted medical standard regarding aspirin and recreational diving. And while you're at it, why not tell us about your special training and expertise in diving medicine that qualifies you to give specific medical advice (such as what medicines to take) here?
HTH,
Bill
Sorry to take so long to get back to you. You bring up several issues that I'd like to address.
I haven't seen where your question has been specifically addressed by any real research so I can only guess based on what information is known, but here's my 2¢. It appears from the best evidence available that the aggregation seen is caused by hydrostatic pressure, not by the partial pressure of any gas. So to the first part of your question I'd say No, it does not appear that N2 causing aggregation is related to headaches. (Since it's not the cause of aggregation.) As far as rigidity of blood cells is concerned, the researchers who did the studies on rigidity originally hypothesized that increased partial pressure of gases would cause blood cells to become rigid and those rigid blood cells would obstruct the capillaries in bone causing osteonecrosis. They focused on bone capillaries and osteonecrosis because the capillaries in bone are particularly small and inflexible and therefore especially susceptible to occlusion by stiff blood cells. While their results might indicate that some blood cells might stiffen somewhat in some divers, they didn't seem to become rigid enough to significantly obstruct bone capillaries. Seems to me that if they don't become rigid enough to really block the tiny bone capillaries, they wouldn't obstruct brain capillaries and cause headaches either. It's an interesting idea that probably merits further study, but so far from the information available it looks like yours is just another one of those "whacky theories" that seem to disturb you.
I can see how to the unperceptive it can seem like "medicos know little about diving". As Dr. Thomas has already pointed out, most doctors don't know much about diving because it simply isn't their area of expertise and it's not a normal part of their training. Blaming your family doctor for not knowing about diving related issues is like faulting your plumber for not knowing how to configure your PC. ("Dang it, he repairs things, doesn't he!?") As for the doctors (MD, PhD, and DDS) that participate on this board, I for one claim no special credentials in diving medicine- never have. But I do try my best to research my answers to reach the highest level of accuracy that I can based on the current diving and medical literature, and I also try to keep my mouth shut on subjects where I am ignorant and don't know or can't find the answer. (Or at least make it clear when I'm just guessing based on available information.) Regarding the other Medical Regulators on this board, I am continually amazed by the depth and breadth of their knowledge on diving matters and am gratified by their willingness to share their wealth of knowledge so freely. It's probably frustrating to the casual reader here when they don't get a specific answer to a specific question, but those are the breaks. There is still quite a lot about diving medicine that just isn't known (by anyone) because the research to find the answers hasn't been funded. And it would be irresponsible for anyone to try to specifically answer questions asking for personal medical advice on an Internet message board where a complete medical history isn't available, a physical examination can't be done, and appropriate diagnostic tests can't be ordered. But hey, we do what we can.
I can also see why the undiscerning might make a broad statement like, "Divers know little about medicine" about board members here. Actually, if you look closely you'll notice that there are quite a few divers on this board who have comparatively little or even no formal medical training, yet they seem to routinely give very sound general medical explanations and advice here. I could name them for you, but there are enough of them that I would surely leave someone out. These people have taken the time and effort to educate themselves, and most importantly, they understand what they DON'T know and limit their answers to their field of knowledge. But as you say, many divers really don't know much about diving medicine. Fortunately most of them are wise enough to realize that and they limit themselves to asking questions instead of making up answers. There are occasional instances when someone will give some bad medical advice here because of what they thought they once heard, but fortunately it's rare.
There was one glaring exception to this rule that might have clouded your view of our posters if you saw it. There once was a fellow (dev something-or-other I think) who for a while there was regularly posting HORRIBLE medical advice. The poor guy had almost no knowledge of anatomy, physiology, or pathology, and what little he did know it seems he badly misunderstood. But even more importantly he apparently had absolutely no cognizance of his own profound ignorance- and no amount of helpful advice or instruction seemed to enlighten him. He appeared to just make up "whacky theories" as he went along and then tried to disseminate them as established fact. Much of what he said was so far out it was ludicrous. I actually became concerned that someone reading Scubaboard might be gullible enough to believe something he said and at best make a fool of themselves repeating it elsewhere or at worst actually come to harm. I'm thankful that for whatever reason he stopped his preposterous behavior. Hopefully he finally developed a touch of wisdom and came to a realization of how ill informed he actually was. I don't suppose it's likely that he was the one who gave you such a low opinion of the posters here because he stopped posting 2 days before you registered on Scubaboard, but if you go back and review his posts you'll see what I mean. Hey, you might know him! He posted from the same IP address that you do. Better watch your back out there pescador775!
It's interesting that you'd say this. Some diving authorities have recommended in the past that divers take aspirin. The thinking was that aspirin inhibits platelet (blood clotting cell) aggregation, and that increased hydrostatic pressure (like in diving) and bubble formation promote platelet aggregation. The reasoning went that platelet aggregation might contribute to the chance of developing DCS or worsen the course of an episode of DCS if it occurs, and taking aspirin might be beneficial in helping to prevent it. But it turns out that aspirin doesn't really help much (or at all) and it can be harmful.
The recommendation for recreational divers to routinely take aspirin does not seem to be the currently accepted standard among most diving physicians now. DCS is very uncommon in recreational divers. If a diver does develop DCS the anti-clotting effect of aspirin could possibly cause increased bleeding in a hemorrhagic lesion (say in the inner ear, brain, or spinal cord) thus making the effects of the episode of DCS much worse. (Such increased bleeding and worsened injury has been seen in animal models on aspirin.) Also, barotrauma injuries are quite common in recreational divers, and those injuries are often associated with bleeding. Aspirin could make the bleeding in such an injury worse, potentially turning a minor annoyance into a major problem. For these reasons, taking aspirin while diving seems to be at best a wash from a preventative medicine standpoint, and in the typical recreational diver it might actually do more harm than good. I believe that there is a study going on in Australia taking another look at aspirin and diving, but the results aren't available yet to my knowledge. As it stands now, the conventional wisdom is to not recommend routine aspirin use to all recreational divers.
Since you seem quite interested in the quality of medical discussions here, perhaps you'd like to share what particular information you have that would cause you to dispute the current generally accepted medical standard regarding aspirin and recreational diving. And while you're at it, why not tell us about your special training and expertise in diving medicine that qualifies you to give specific medical advice (such as what medicines to take) here?
HTH,
Bill
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The Iceni
Medical Moderator
I hope I never cross swords with you, Bill!
Interesting VERY interesting.
Dr Deco
Contributor
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Dear Bill and Readers:
Wow!
I seldom reply to these comments impugning the intelligence of others, but was pleased that someone did.
The fact is that most physicians do not know a great deal about diving, because it is not taught in medical school. My only medical acquaintance with it is in the chapter on Special Environments in Guytons Textbook of Physiology. I am always surprised that readers would believe that their local physician would be an expert on scuba diving; it is a very narrow speciality.
Answers
The answers provided by me are best attempts at answers to many subjects. I certainly am not a specialist in everything hyperbaric. Some of my replies are really quite short in comparison to other writers and indicate (in reality) that I have little to add of substance.
Many of my answers are, in addition, controversial in the hyperbaric community, although they are gaining acceptance. Certainly, the idea that slow tissues can be loaded by physical activity is controversial. Similarly with the idea of a spectrum of preformed micronuclei that can be enlarged by musculoskeletal activity.
I try (though not on every occasion) to point out where these are my opinions derived from my research at NASA. They are not necessarily believed by everyone, even among my colleagues here.
I do believe that they are correct, have experimental data to back them, and are based on sound biophysics and physical chemistry in in vitro models.
Thanks
I do appreciate the comments of BillP on this, and my thanks to the other individuals who offer their comments from time to time on all of the topics.
Dr Deco :doctor:
Wow!
I seldom reply to these comments impugning the intelligence of others, but was pleased that someone did.
The fact is that most physicians do not know a great deal about diving, because it is not taught in medical school. My only medical acquaintance with it is in the chapter on Special Environments in Guytons Textbook of Physiology. I am always surprised that readers would believe that their local physician would be an expert on scuba diving; it is a very narrow speciality.
Answers
The answers provided by me are best attempts at answers to many subjects. I certainly am not a specialist in everything hyperbaric. Some of my replies are really quite short in comparison to other writers and indicate (in reality) that I have little to add of substance.
Many of my answers are, in addition, controversial in the hyperbaric community, although they are gaining acceptance. Certainly, the idea that slow tissues can be loaded by physical activity is controversial. Similarly with the idea of a spectrum of preformed micronuclei that can be enlarged by musculoskeletal activity.
I try (though not on every occasion) to point out where these are my opinions derived from my research at NASA. They are not necessarily believed by everyone, even among my colleagues here.
I do believe that they are correct, have experimental data to back them, and are based on sound biophysics and physical chemistry in in vitro models.
Thanks
I do appreciate the comments of BillP on this, and my thanks to the other individuals who offer their comments from time to time on all of the topics.
Dr Deco :doctor:
100days-a-year
Contributor
For what it's worth fellas,none of the medical regulators or docs who dive need ever explain themselves here to me or anyone.I truly appreciate all the help,references and explanations given.
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