Posted by John Walker on May 12, 2001 at 17:06:27:
In Reply to: That's a fascinating read, John! posted by BillP on May 12, 2001 at 14:59:58:
Since my plane doesn't leave for a few more hours I am reply to your question.
I posted this to the scuba list after I noticed the intelectually level in which the subject of red blood cell rigidity happened to bring to the California BBS.
I'll try to answer your questions as best I can, although I have a feeling your going to keep creating more and more and more question in order to discredit whoever you can on this issue.
I noticed that you didn't care to credit Bill Mee's explanation on the subject even though he in a biomedical engineer. Im courious as to why not?
But before I start, is it true that you are somekind of surgeon? If so, what type? I am suprised a surgeon would have to look up (and have the time to) information on a recreational scuba list of such biomedical information.
If you noticed in my second paragraph, I stated: The dense meshwork of spectrin forming the skeleton of the flexibility on which the plasma membrane is coupled changes properties UNDER CERTAIN STRAINS. Among them, CHEMICAL and BIOCHEMICAL perturbation, (and others).
This would bring to mind changes that occur during ANY dive, either shallow, long, or deep, technical or not.
One of the issues that I would relate this to for an example is the resistance that Nitrogen mixtures create in our breathing apparatus. This would be due to it molecurlar size and diatomic charactoristics.
N2 14.007 diatomic
He 4.003 monoatomic
O2 15.999 diatomic
The molecular charictoristics are also believed to effect the outcome when each gas perfuses or defuses through tissue(s)
This might also suggest that the lack flushing of Carbon Dioxide from the resiratory system. This in turn would create a back-up of a highly acidic chemical such as carbonic acid, alone create a biochemical change that is going to effect the spectrin.
Nitrogen also creates many biochemical changes simply due to its ability to occupy more space in tissue(s) and its retentive properties. My guess as a none doctor would be the inflamtory processes that take place from pressure gradient and the lack of ability for this nitrogen to leave tissues into circulatory tissue without creating inflamation, and a triggering effect of the auto immune system.
Obviously Oxygen creats biochemical changes as well. The extent of these changes is a mystery that still baffle science. The changes that oxygen occurs once oxygen inters the body. The blood brain barrior issue is just one. As well as the conversion of the superoxide radicals which are created due to the metabolic changes and the interaction with reactive oxygen species.
Several studies have been performed by Florida state university, United States Navy and Hamiltion research just to give a few. Study's were performed on REAL human test subject rather that animal or whatever else one could dream up.
One such study was to look into the reduction of vital capacity of various gas mixtures and profiles. During these tests (which currently still go on) various protein changes were noted. Several of these protiens were in quantity which would indicate an insult to the body. These higher protein changes were noted when breathing gas mixture with higher levels of Nitrogen. These changes where not apparent during higher helium mixture, even when micro bubbling was detected.
Though I know several of the human test subjects in this study, I do not have any of the reports nor do I (or they ) have any evidence, just test conclusions.
Fill in the blank spaces? I never said I had any evidence of anything such as nitrogen causing RBCR and that Helium not causing such an effect.
Suggestions would show to me that helium does not effect the body in the same way nitrogen does, and has less insults during decompression, when done properly. Helium appears to be much easier to regulate gradients than Nitrogen and that is do to the solubility and retentive issues nitrogen hase and helium does not.
I have a mental note of Dr. Julie Bookspans report to a group in which she stated that ALL TISSUES WILL ONGAS AND OFFGAS AT THE SAME RATE,EXCEPT IN FAT. And as we all should know, Nitrogen is highly soluble in FAT and is highly retained. Helium is not, and science suggests that helium will ongass and offgas approximently 2.65X faster than nitrogen. Possible faster to offgas.
This paper I shared with everyone does create a sence of changes due to biochemical changes for one. Though it appear chemically sound, I am not a chemist. Nitrogen seems to have several extended issues that Helium does not. Narcosis is another simple example, but I guess there is no evidence on that subject either.
Do you have any evidence of either you would like to share with us? I would love to see it. Us diver can never get enough.
As a doctor (so I am told) you should be fully aware that medical science if FULL of theory. The only fact is that we live then we die. Hell, I saw a story last night on the news about a group that doesn't even have to eat food. They just require sun and exercise. Hopefully we don't die while enjoying a scuba dive. The best prevention I have found is to learn to evaluate incomming information. And without a big medical background as your, it makes seeking out that information a part time job.
John Walker (now I'm off to mexico)
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