hemoglobin guidelines: racers versus FDA

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Ken Roberts
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Postby Ken Roberts » Mon Nov 24, 2008 10:45 am

Don Callander wrote:I also remember some physiologic testing of Himalayan sherpas done at the U. of MN in the early 90's; they presented with Hgb of >20 (Hct >60) with no clotting issues.

I just found a research result which says that native Tibetans have unusually high concentration of Nitric Oxide (NO) in their blood:
http://blog.case.edu/case-news/2007/10/31/tibetstudy

I'm no medical person, but apparently NO tends to dilate blood vessels, and this increases oxygen transport starting with blood flow thru the lungs and finishing with capillaries to the muscle cells -- another reason beyond hematocrit why native Tibetans perform well at high altitude.

I've read that NO also inhibits the adhesion and clumping of platelets, which helps fight against dangerous clots in the blood vessels -- which might explain how they can tolerate high hematocrit with less risk of clotting than non-Tibetans.

Apparently lower atmospheric pressure tends to decrease NO levels in many non-Tibetans, so it might be that this decreases athletic performance at altitude more than just the reduced oxygen pressure would indicate.

A drug known to manipulate NO function is Viagra -- but I sort of heard it operates more selectively, especially in the lungs (and another organ) -- so I guess the native Tibetans are getting their result by some other means.

Of course even enhancing NO function only in the lungs could give a substantial benefit to athletic performance -- but it's not clear how that could help athletes in sea-level performance. Nevertheless it's getting studied . . .
http://www.nytimes.com/2008/11/23/sports/23viagra.html

Ken

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Postby Don Callander » Tue Nov 25, 2008 1:23 pm

Ken Wrote:
I'm no medical person, but apparently NO tends to dilate blood vessels, and this increases oxygen transport starting with blood flow thru the lungs and finishing with capillaries to the muscle cells --

Sorry I can never figure out out to do the quote box.

Back when I worked clincally we would often give Nitric Oxide (NO) to newborns that presented with very high pulmonary pressures; often high enough to impede blood flow. We were trying to prevent a very dangerous, expensive and invasive procedure called ECMO (extracorporeal membrane oxygenation) Often this was sucessful, although I am clueless as to how it would apply to a healthy athlete.

Don

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Postby Biffbradford » Tue Nov 25, 2008 4:27 pm

Nitric Oxide (inhaled) is also used on an investigational basis on adults, particularly those in heart failure with pulmonary hypertension. It dialates the pulmonary vessels. Viagra is often used as the pill form for this purpose. In the ICU where I work, we see this daily. ;)
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Ken Roberts
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Postby Ken Roberts » Wed Dec 03, 2008 12:57 am

Biffbradford wrote:Nitric Oxide (inhaled) is also used on an investigational basis on adults, particularly those in heart failure with pulmonary hypertension. It dialates the pulmonary vessels. Viagra is often used as the pill form for this purpose.

There's also interest in using Viagra / sildenafil for High Altitude Pulmonary Edema (HAPE). One source commented that inhaled Nitric Oxide should work against HAPE, but it's difficult to administer in the setting of a high-altitude mountaineering expedition.

I just found an abstract which suggests that sildenafil might inhibit platelet activation.

I'm guessing (with my very limited medical knowledge) that this might reduce the risk of dangerous blood clots.

Ken


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