Why don't elephants get embolisms?

[Kim]

I don't think - I know. Just like you say, the vascular system is an open circuit (only the artery side).

It works like a pressurized column of water. Low at the head, high at the ankle. The venous system is almost an open system, with the exception of simple flap valves along the way.

That explains why older folks or those with bad genes gets varicose veins. Puncture one of those, and blood will be spurting out for hours, unless you get a pressure bandage on it.

You are welcomed to check the blood pressure on your ankle. You will need a doppler device or someone with a sensitive finger to check for your pedal pulses. Compare that to your heart height, and it simply is a column of water (blood, actually).

Actually I don't think you do "know". Last summer I had an aortal/illiac bypass. I had many blood pressure checks both before and after...at all points of my body...arms...ankles..
After the operation when full circulation was restored to my lower body, the pressure in my ankles was still slightly lower than in my arms, (although nowhere near the less than half it had been to start with). According to my surgeon/doctor, that's perfectly normal. He was very happy at the success of the op...as I was. It seems that the heart needs to have the highest pressure to force blood out to the extremities (simple pneumatics I believe)....the further away from the heart...the lower the pressure.

I'm no doctor though, just saying what I was told.....

 

[fisherdvm]

Actually I don't think you do "know". Last summer I had an aortal/illiac bypass. I had many blood pressure checks both before and after...at all points of my body...arms...ankles..
After the operation when full circulation was restored to my lower body, the pressure in my ankles was still slightly lower than in my arms, (although nowhere near the less than half it had been to start with). According to my surgeon/doctor, that's perfectly normal. He was very happy at the success of the op...as I was. It seems that the heart needs to have the highest pressure to force blood out to the extremities (simple pneumatics I believe)....the further away from the heart...the lower the pressure.

I'm no doctor though, just saying what I was told.....

Your blood pressure was measured while you were laying down... And the fact that you had peripheral arterial disease, you are lucky to have good pressure down by your ankle.

If you do not have arterial disease, the pressure in your ankle should be the same as your heart - assuming both are at the same height.

I am sorry to hear you went through so much..... But lower pressure in the ankle implies that you still have restrictive areas in your arteries. Kinda like living in an old house with old plumbing... Water pressure is alot lower than a new house with new plumbing, due to increased resistance...

 

[fisherdvm]

The amount of arterial disease you have is measured by the ABI. It is measured while you are lying down on a flat table. The ankle pressure is slightly lower than the arm, due to the slight height difference, and the slight resistance along the way.

The Ankle Brachial Pressure Index (ABPI) is a measure of the fall in blood pressure in the arteries supplying the legs and as such is used to detect evidence of blockages (peripheral vascular disease). It is calculated by dividing the systolic blood pressure in the ankle by the higher of the two systolic blood pressures in the arms.

The pressures in the posterior tibial artery and dorsalis pedis artery in the feet and the brachial artery at the elbow are estimated. A Doppler probe is used, through a device called the Pulse Volume Recorder (some variances may apply depending on the physician), to monitor the pulse while a sphygmomanometer(blood pressure) cuff is inflated above the artery. The cuff is deflated and the pressure at which the pulse returns is recorded.

In a normal subject the pressure at the ankle pulses is slightly higher than at the elbow (there is reflection of the pulse pressure from the vascular bed of the feet, whereas at the elbow the artery continues on some distance to the wrist). The ABPI is the ratio of the ankle to arm pressure and an ABPI of greater than 0.9 is considered normal, suggesting that there is no significant peripheral vascular disease affecting the vessels of the legs. A reduced ABPI (less than 0.9) is consistent with peripheral artery occlusive disease (PAOD), with values below 0.8 indicating moderate diseased and below 0.5 severe disease.

However, a value greater than 1.3 is considered abnormal, and suggests calcification of the walls of the arteries and noncompressible vessels, reflecting severe peripheral vascular disease.

 

[fisherdvm]

I am sorry I did not take in consideration of the viscosity of blood, and the resistance generated by the small blood vessels in the leg. But if you assume that the vascular system is static, and not dynamic, then the assumption that blood pressure should be instantanously equalized, and varied only by height - is correct.

But since it is dynamic and affected by viscosity and resistance, it will be different at the distal extremeties than at the heart.

 

[Kim]

Hmmm...is this all your knowledge or Google paste?

Anyway.....it doesn't really matter. I was trying to cause people to think about the huge differences in pressure in the first few meters of water. It's the area that you need to take the most care...both descending, and ascending.

For the record......elephants have much thicker blood vessel walls than humans do.....hence they can handle the higher pressure differences involved. That's according to the National Geographic program I watched anyway. As I said...it seemed interesting and prompted this thread!

 

[fisherdvm]

No it is not my knowledge. I clipped the ABI information from winkepedia, as it is not fresh in my mind. I used to work in a wound care clinic, taking care of people with both arterial and venous diseases.

We had to calculate ABI on a regular basis to determine how much venous disease or arterial disease a patient had.

Too much arterial disease, and you can not use compression... Compression is needed to heal venous disease. Despite my user name, I am also a physician.

 

[Rick Murchison]

Fact: Elephants can swim and breathe while swimming.
Therefore: (1) An elephant's lung's vascular system can withstand the pressure differential between the inspired gas and the blood pressure in the lung's capillaries while the elephant's swimming, and that is why the elephant doesn't get a "reverse embolism."
Whether a human's lungs can withstand the same pressure differential doesn't really bear on the question.
(2) An elephant's diaphragm and intercostals are strong enough to inflate the elephant's lungs while the elephant is swimming.
Whether a human's inspiratory musculature is capable of creating the same vacuum doesn't bear on the question.
Rick

 

[fisherdvm]

On a more serious side, Kim, have you asked your vascular surgeon if the additional water pressure from scuba diving can compromise the blood flow to your feet? I know that when I wear a tight glove, my fingers get numb at depth due to to squeeze caused by the neoprene.

 

[Kim]

On a more serious side, Kim, have you asked your vascular surgeon if the additional water pressure from scuba diving can compromise the blood flow to your feet? I know that when I wear a tight glove, my fingers get numb at depth due to to squeeze caused by the neoprene.

Yes. I'm good to dive, although I didn't yet since the op. As I was diving until a few weeks before the op with little problem, although walking a hundred meters or up a flight of stairs was hard work due to the claudication, diving would certainly appear to demand far less effort.
My doctor has no problem with me diving now. Basically, fluid can't compress so there is no reason why blood vessels should constrict as far as I know.

 

[Spongebobscubasteve]

Oh come on...be serious! How far do you think an elephant would get on an AL80? :no

Touche', I now bow gracefully out! This was getting to serious anyway! It's almost the weekend!!!!!!!!!!!!