RBC's & PPN2

[Lost Yooper]

Thanks Bill, I didn't know any of that stuff. I'm still working on finding out who that guy is.

What is actually causing these lesions (is it scar tissue, or some kind of mineral deposit) and why aren't they doing harm?

Mike

 

[BillP]

Hi Mike:

Good questions. And questions without definitive answers. (At least not from me!) The lesions in the retina look consistent with those seen with occlusion of blood vessels. Conventional wisdom has been that microvascular occlusion in diving is caused by gas bubbles. The fact that the changes are most clearly associated with DCI rather than with other potential causes supports (but doesn't prove) the conventional wisdom.

Some other possible causes? Hydrostatic pressure can cause platelets (blood clotting cells) and/or red blood cells to aggregate (clump together) and that could obstruct blood vessels. Blood vessels in the retina will constrict under increased partial pressures of O2 which might lead to occlusion. Changes in plasma lipids (blood fats) might alter the fluidity of blood. Or... white blood cells (probably not red like you'll so often read) might change their structure and occlude blood vessels as they proposed in the DDRC studies. But as I've stated before, the last hypothesis is only one of several possible mechanisms, and while it's an interesting idea, it is not yet confirmed as "fact".

Why aren't the changes doing harm? It doesn't look like the changes found in the studies were bad enough for the diver to notice, I guess. If I suffer an injury and it's so slight that I don't notice it, it's not picked up by routine testing, and it can only be discovered by special studies (like an angiogram or an autopsy) then I'd hardly classify it as a "horror".

More of my 2¢,

Bill

 

[Lost Yooper]

BTW Bill, I'm working on the alien dissertation as well. Anything to keep people from diving deep on air will work.

Thanks for clearing that up.

Mike

 

[Dr Deco]

Dear Mike:

I thank BillP for a very nice analysis of the "RBC question." As he said, there does not appear to be any problem traceable to the alleged “nitrogen situation.” If you do something long enough and often enough, problems will appear if there are any. In diving, we see decompression sickness in various forms and aseptic bone necrosis. There does not appear to be anything else (though we could add oxygen toxicity and nitrogen narcosis).

With all of this, I wonder why we would wish to create another malady. I am however fascinated by the concept that possible subsea aliens from the planet Mongo are giving us narcosis or bone necrosis. :robo:

Or possibly it is the result of survivors from Atlantis. :sheik:

I know that there are people who would definitely believe this if you told them.

Dr Deco :doctor:

 

[neil]

Originally posted by Lost Yooper

George clears in 30mins which is good even among his guys.

Mike

Mike,
All this means is that there are no detectable bubbles after 30 minutes. It in no way indicates that he has completely off-gassed, if that's what you are getting at. The Doppler can detect only bubbles moving in the blood stream, not bubbles that have already formed in tissues. In theory, couldn't you be as bent as Haldane's goat and still show little or no Doppler evidence of bubbles?

Neil

 

[Lost Yooper]

Hey Neil,

Yeah, he is cleared of all detectable bubbles in 30 mins. Based on my discussions with him (and other discussions he's had), he considers himself virtually totally off gassed. He'll turn right around and do another dive in an hour or so and will pretty much ignore the first dive other than the oxygen exposure.

He has told me that after a full day of fairly deep repetitive cave diving in the Bahamas (Abaco, I think), he and Bill Mee took a Sesna plane ride at 10,000' back to Florida (and their shorts were still wet). They're off gassed good enough not to worry about flying after diving, repetitive deco dives, or anything else. I've lost my discussions with him about excercises they have done after their big dives and then doppler and blood tests following. I'm going to ask him about that again, because I want to say that nothing showed up, but I can't remember.

Basically, if you don't have any preconditions, and you follow the micro bubble elimination theories and use helium, you can get away with a lot more. Personnally, I give myself a couple hours as a matter of conservatism (among other things).

Take care.

Mike

PS. To answer your question about getting bent with no bubbles being detected, I don't think so unless you had some sort of precondition that would do it (PFO maybe?). It would seem to me that if the bubbles were suffeciently bad enough to get ya bent, then they would be easily detectable.

 

[BillP]

Not meaning to speak for Dr. Deco, but I think that the kind of "wild" diving and out-of-the-box thinking that George Irvine and WKPP are doing regarding decompression practices is exactly what Dr. Deco was referring to when he was talking about valuable information from "recreational divers".

I think it would be fascinating if the information gleaned from those decompression procedures and doppler bubble tests was actually collected and published for others to review. Anecdotal reports from the field are interesting, but peer-reviewed published articles in scientific journals would be even more valuable and generate even more interest, IMHO.

Bill

 

[scubadoc]

I've been following this discussion with interest as I have had several questions on this subject from divers and have been at somewhat a loss to give a reasoned answer.

One of my consultants (Dr. Ed Kay) has found some information that I feel might be valuable as follows:

"In a paper called "Structural determinants of the rigidity of the red cell membrane", (Nash GB, Gratzer WB) Biorheology. 1993 Sep-Dec;30(5-6):397-407. Review, the authors state "Although the stability and viscoelasticity of the red cell membrane are undoubtedly governed by the membrane's underlying protein skeleton, the mechanism by which this network controls elasticity is uncertain... It appears that elasticity may be regulated not only by the structure of the spectrin network, but also by its interactions with and freedom of motion relative to the lipid bilayer." Related Articles

Dr. Kay believes that the lipid layer is highly sensitive to oxidative stress and in Biochim Biophys Acta 1999 Oct 15;1421(2):306-16 Books, an article entitled "Membrane effects of nitrite-induced oxidation of human red blood cells" (Zavodnik IB, Lapshina EA, Rekawiecka K, Zavodnik LB, Bartosz G, Bryszewska M.) the authors found that an "increase in membrane rigidity have been shown as a result of RBC oxidation". Related Articles

The studies he quoted suggest that Oxidative Stress consisting of Superoxide Radical damage and Lipid Peroxidation cause the dominant membrane effect.

It is not nitrogen that interacts with the lipids of a red blood cell but oxygen. This is the dark side of O2. Nitric oxide on the other hand has been shown to improve the membrane fluidity of erythrocytes. The addition of helium offers you more flexability to keep O2 levels below toxic range for extended exposure diving, but probably not because you have less nitrogen."

An exhaustive survey of Medline fails to bring up anything about the effects of nitrogen under pressure on the RBC.

Regards:
Ern Campbell

 

[Lost Yooper]

Cool Scubadoc,

"increase in membrane rigidity have been shown as a result of RBC oxidation".

Does this RBC oxidation occur only when a person is exposed to high PPO2, or does it happen to people who are on O2 treatment (emphazima patients)? Oxygen treatment has been around for awhile, and I'd assume there would be info about this.

Deep air divers would certainly be subject to higher PPO2, but so would nitrox divers as well as trimix divers who deco with nitrox and O2.

Is there an easy way to find out how much nitric oxide is being produced by the body to combat RBC rigidity? It sounds like this would be a fairly simple experiment -- to a layman anyway . It seems like if you could detect elevated levels of nitric oxide, then chamber tests could be conducted incorporating various gas PP's and measuring the nitric oxide levels.

Thanks.

Mike

 

[BillP]

Thanks for the info, Scubadoc. The papers that you cited show that red blood cell membrane flexibility is variable, and that sodium nitrite is one oxidizer that can increase red blood cell rigidity, but have you found any studies that specifically show that increased partial pressures of O2 like those seen in diving increase RBC rigidity?

TIA,

Bill