The Iceni
Medical Moderator
Dr Deco once bubbled...
Oops!
I transposed the legend for the bar graphs.
Do Rcohn and I get gold stars (or honorary regulator status) for being observant and attentive students?
No observations on ESR and PV?
Bent... but why?
- Thread starter Zept
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Do Rcohn and I get gold stars (or honorary regulator status) for being observant and attentive students?
No observations on ESR and PV?
I don't think dehydration was a factor. I've been living in Singapore for 18 months now and I've got used to drinking copious quantities of water, all the time. When I'm diving, I drink even more... my surface intervals consist mostly of trips to the water cooler (and also to the toilet!). The volume of urine I'm passing suggests I'm more than adequately hydrated.
It is ironic that this thread has come back to life just after I started diving again. With one thing and another, I was out of the water for two months. Got back in on Sunday for two dives to 10-12m (30-40ft). No problems, other than being rusty... not that I would expect problems at that depth.
The more interesting test comes at the end of September, when I'm doing a three-day liveaboard trip. I expect I'll end up doing fewer dives than some of my buddies.
Zept
The Iceni
Medical Moderator
I think you are sensible not to repeat this schedule. Remembering that the time to total desaturation from nitrogen is more than two and a half days, four solid days of diving is "pushing it a bit". I think this is evidence that the commonly used tables are not very accurate over extended periods. I always have a break from diving every third day.
I think it was docVikingo who recently advised to keep drinking until your urine is colourless. That is the only clue we have to adequate hydration. In humid tropical climes insensible perspiration does predispose to a relative dehydration in any case when you are still acclimatising, but after 18 months I have no doubt you are now fully acclimatised.
Sounds like you're sorted. I hope your liveboard trip goes well.
Dr Deco
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Dear Dr T and rcohn:
Hydration
I believe that I have shown this data before, but, against the possibility that I have not, the graph is in the ATTACHMENT . It is some data from a group of Canadian researchers during WW II, and it was published in Fultons 1952 book Decompression Sickness .
It illustrates the decrease in decompression sickness on a given profile with a depress to altitude when water intake has increased. (The incidence of DCS is much greater in these profiles than decompressions from depth and differences are more easily observed.) I believe that the effect is largely founded on changes in surface tension of the body fluids.
This data is interesting because it pointedly illustrates the decrease in incidence in a quantitative fashion. We often hear anecdotal stories about water intake but there is little objective data to support it. Possibly it simply seemed like a good idea and thus becomes imbedded in the mainstream of thought. It is diving physiologys version of the Urban Legend.
Thanks
Indeed you fellows get gold stars for noting the mislabeling. Actually I did that to see who was paying attention (Yeah, sure).
Dr Deco :doctor:
Hydration
I believe that I have shown this data before, but, against the possibility that I have not, the graph is in the ATTACHMENT . It is some data from a group of Canadian researchers during WW II, and it was published in Fultons 1952 book Decompression Sickness .
It illustrates the decrease in decompression sickness on a given profile with a depress to altitude when water intake has increased. (The incidence of DCS is much greater in these profiles than decompressions from depth and differences are more easily observed.) I believe that the effect is largely founded on changes in surface tension of the body fluids.
This data is interesting because it pointedly illustrates the decrease in incidence in a quantitative fashion. We often hear anecdotal stories about water intake but there is little objective data to support it. Possibly it simply seemed like a good idea and thus becomes imbedded in the mainstream of thought. It is diving physiologys version of the Urban Legend.
Thanks
Indeed you fellows get gold stars for noting the mislabeling. Actually I did that to see who was paying attention (Yeah, sure).
Dr Deco :doctor:
Dr Deco
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Dear Readers:
Hydration and Its Effects
I was asked about the reasons for the effect of hydration as illustrated in the Attachment in the preceding post. One sees here that increasing the intake of water reduced the incidence of altitude decompression sickness. The study was performed during WW II and was not a rigidly controlled one. The responders indicated in a questionnaire the number of glass of water drank that day. I will guess that they were standard 8-ounce glasses. Thus there was some degree of leeway since it was simply water intake as remembered by the participants. Nevertheless, the general picture is there even if it could be off by a glass or so here and there.
It is my guess that the effect is based on a change in surface tension of the body fluids. (That was not suggested by the experiments themselves at that time.)
Dr Dennis Walder
For his Doctor of Medicine thesis, Dennis Walder studied the effect changes in surface tension and hypobaric depressurization (Walder, D. N. (1948). Serum surface tension and decompression sickness. J. Physiol. 107. 43P.) The results, shown in the ATTACHMENT, illustrate that small changes in surface tension translated into considerable changes in the incidence of DCS. The problem with this is that no one has since been able to repeat it during the past fifty years. Why the discrepancy? This has not yet been resolved.
The surface tension changes the critical radius of a bubble. When you have a population of these bubbles, that change is probably quite important. The ATTACHMENT also shows number of gas bubbles versus size (in sea water). Similar measurements have not been made in fluids in animals.
Perfusion Changes
The explanation given for hydration is that it is a change in fluid volume and an improvement in perfusion. There may be some truth to this, and exercise has been shown to change the incidence of DCS probably by variations in perfusion. [Loftin KC., J Conkin, MR Powell. Modeling the effects of exercise during 100% oxygen prebreathe on the risk of hypobaric decompression sickness. Aviat. Space and Environ. Med. 68, 199 - 204, (1997); Powell, MR, K Loftin, and J Conkin. An algorithm for the calculation of change of the longest half-times under various metabolic work loads. Undersea and Hyperbaric Medicine, 25, (Suppl), 20, (1998)]
Walder found that by increasing the fluid load, he could change the surface tension of the serum (blood without the red and white cells) in the test subjects. The greater the value of the surface tension (i.e., the nearer it came to that of pure water), the less was the incidence of DCS.
Dr Deco :doctor:
Hydration and Its Effects
I was asked about the reasons for the effect of hydration as illustrated in the Attachment in the preceding post. One sees here that increasing the intake of water reduced the incidence of altitude decompression sickness. The study was performed during WW II and was not a rigidly controlled one. The responders indicated in a questionnaire the number of glass of water drank that day. I will guess that they were standard 8-ounce glasses. Thus there was some degree of leeway since it was simply water intake as remembered by the participants. Nevertheless, the general picture is there even if it could be off by a glass or so here and there.
It is my guess that the effect is based on a change in surface tension of the body fluids. (That was not suggested by the experiments themselves at that time.)
Dr Dennis Walder
For his Doctor of Medicine thesis, Dennis Walder studied the effect changes in surface tension and hypobaric depressurization (Walder, D. N. (1948). Serum surface tension and decompression sickness. J. Physiol. 107. 43P.) The results, shown in the ATTACHMENT, illustrate that small changes in surface tension translated into considerable changes in the incidence of DCS. The problem with this is that no one has since been able to repeat it during the past fifty years. Why the discrepancy? This has not yet been resolved.
The surface tension changes the critical radius of a bubble. When you have a population of these bubbles, that change is probably quite important. The ATTACHMENT also shows number of gas bubbles versus size (in sea water). Similar measurements have not been made in fluids in animals.
Perfusion Changes
The explanation given for hydration is that it is a change in fluid volume and an improvement in perfusion. There may be some truth to this, and exercise has been shown to change the incidence of DCS probably by variations in perfusion. [Loftin KC., J Conkin, MR Powell. Modeling the effects of exercise during 100% oxygen prebreathe on the risk of hypobaric decompression sickness. Aviat. Space and Environ. Med. 68, 199 - 204, (1997); Powell, MR, K Loftin, and J Conkin. An algorithm for the calculation of change of the longest half-times under various metabolic work loads. Undersea and Hyperbaric Medicine, 25, (Suppl), 20, (1998)]
Walder found that by increasing the fluid load, he could change the surface tension of the serum (blood without the red and white cells) in the test subjects. The greater the value of the surface tension (i.e., the nearer it came to that of pure water), the less was the incidence of DCS.
Dr Deco :doctor:
BurBunny
Contributor
Going back a few days here and taking this in a slightly different direction, I too would be curious to know how sed rate might affect DCI risk, and as Dr. Thomas questioned if hydration can affect that rate.
Reason for asking is I have mild SLE (lupus). While I have been cleared to dive, I do often have a moderately elevated sed rate. The information disseminated by DAN does not seem to address this that I have found, and the risk factors for discussed for lupus divers are CV and joint impairment.
So has there been any research that an elevated sed rate could affect DCI risk, and if so, can that sed rate elevation be offset by additional hydration?
Dr Deco
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Dear BurBunny:
"Bends" and Sed Rate
I am not aware of any studies related to DCS risk and sedimentation rate. The rate might be influenced by fluid density and/or viscosity. The later is a factor in some types of hydrodynamic cavitation. Thus, the formation of micronuclei might be influenced by sed rate.
Dr Deco :doctor:
"Bends" and Sed Rate
I am not aware of any studies related to DCS risk and sedimentation rate. The rate might be influenced by fluid density and/or viscosity. The later is a factor in some types of hydrodynamic cavitation. Thus, the formation of micronuclei might be influenced by sed rate.
Dr Deco :doctor:
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