What is the effect on gravity underwater?

[Stirling]

"hang up the corpse, put it in a pressurized vessel in air and lop off the top & bottom. Will the blood stay? No, the blood will run right out. It will not be slowed like it would immersed in water."

Oh, I've done that *dozens* of times, but the mess and the fear of getting caught keeps me from making good observations and writing them down. Sorry.

I know gravity works even in the ocean, because that's what keeps me surrounded by water. (If the gravity stopped working, all that water would probably go flying off in every direction, and I'd be left there feeling like a chump for spending all that money on SCUBA gear.) Notwithstanding the effects of gravity, I experience a feeling of weightlessness - pretty much just like an astronaut - and that has consequences for the circulatory system.

Assume a vertical (standing) posture. The heart's ability to pump blood up to my head in air against the effects of gravity requires a certain amount of energy; the blood has weight and needs to be lifted, which requires energy. When I am submerged in saltwater, my body is nearly weightless. Different tissues and parts of my body have different specific gravities, but they are *all* affected by being submerged in water, the energy required to lift *any* of them from the level of my heart up to the level of my head is much reduced, and blood is no exception. The energy required to pump blood from my heart up to my head is considerably reduced. If anybody doubts that the effort required to lift every part of your body is reduced when submerged in water, go to the bottom and do pushups.

And what actually happens in the short term is that the heart keeps pumping like it always did, and one of the results is that slightly more blood gets to the head and other higher points in the body than would occur in air, and the body interprets that as an increase in total blood volume. The body can react (1) mostly by trying to reduce the (perceived increase in) total blood volume by eliminating fluids, and/or (2) depending on how much you are exerting yourself, by reducing the effort exerted by the heart. We know that happens in response to weightlessness, because over long periods of time in a weightless environment, greater than (otherwise) expected dehydration and cardiovascular degeneration have been observed in astronauts.

 

[jonnythan]

Blood IS thicker than water, the buoancy of blood depends on what is DESOLVED in it AND at what depth it is.

Incorrect and misleading. Viscosity (thickness) has nothing to do with density, and the specific gravity (density relative to distilled water) of blood is 1.06, meaning it is negligbly (for this exercise) more dense than water [I accidentally typed blood here].

As stated earlie The body matabilises gas slower in the RESTING position

The body does not metablize nitrogen or helium, so this is irrelevant.

by reversing this pressure you are disturbing the bodies NATURAL function and releasing the micro bubbles to become BIGGER on their way BACK to the heart.

This is certainly true. However, bubbles of arbitrary size can pass through the heart without problems. Blood coming from the legs goes through the large chambers of the heart into the lungs, which are at the same pressure as the heart. I'm not very well versed on what happens after that, but it is my understanding that most bubbles get filtered by the small vessels in the lungs without issue.. the issue would be bubbles getting through, then getting pumped by the heart into the rest of the body, where they may cause problems.

IMO, it is a worthy subject to talk about. I'd like to see some sort of study on whether being vertical or horizontal in the water can increase or decrease bubble formation or affect offgassing in any way.

You can rest assured that if it does affect offgassing, it's because of the absolute pressure differential in the 6 feet between the head and the feet, not because of the blood getting pulled down towards the feet the way it does on land.

If someone can post SCIENTIFIC INFO proving this is wrong , from a reputable source , I'd listen .

I believe this goes for you as well. If you can point me to a single reliable scientific study that concludes offgassing is affected by position in the water, I'm quite certain that the entire ScubaBoard community would listen.

 

[jonnythan]

Another point: the mechanisms the body uses to maintain proper blood flow around the body when you go from lying to standing don't come into play when going from horizontal to vertical in the water. Jim's experiment is perfect proof of this.

 

[Walter]

I don't understand why you don't get it.

Oh, I get it. You think the human body is a compressible ziplock bag. I believe that basic assumption is invalid.

Take two bottles full of fresh, unclotted blood underwater (add a little heparin so it'll stay unclotted for you. Or, you can use water and food coloring - you'll get the same result) Turn one of them upside down. Take the tops off both of them. Watch what happens.
Report back with your findings.

An open bottle is not a human body.

Take two bottles half full of fresh, unclotted blood underwater (add a little heparin so it'll stay unclotted for you. Or, you can use water and food coloring - you'll get the same result) Turn one of them upside down. Watch what happens. Report back with your findings.

 

[jonnythan]

Oh, I get it. You think the human body is a compressible ziplock bag. I believe that basic assumption is invalid.



An open bottle is not a human body.

Take two bottles half full of fresh, unclotted blood underwater (add a little heparin so it'll stay unclotted for you. Or, you can use water and food coloring - you'll get the same result) Turn one of them upside down. Watch what happens. Report back with your findings.

If the circulatory system had large spaces full of air, this would be valid. However, it does not. It's entirely incompressible liquid and is surrounded by incompressible, highly flexible tissue.

The only compressible body space are the open air spaces in the respiratory system.

If you put a pressure gauge inside a leg artery, and another just like it on the outside of your thigh, you will see the pressure on the gauges go up *exactly* the same as you descend in the water.

 

[radinator]

I caught a opossum in my raccoon trap last night but my wife say it is NOT going in the pool. :06:

Having had pet raccoons as a kid, I'm with your wife on this one. :11:

 

[novadiver]

Incorrect and misleading. Viscosity (thickness) has nothing to do with density, and the specific gravity (density relative to distilled water) of blood is 1.06, meaning it is negligbly (for this exercise) more dense than blood.


The body does not metablize nitrogen or helium, so this is irrelevant.


This is certainly true. However, bubbles of arbitrary size can pass through the heart without problems. Blood coming from the legs goes through the large chambers of the heart into the lungs, which are at the same pressure as the heart. I'm not very well versed on what happens after that, but it is my understanding that most bubbles get filtered by the small vessels in the lungs without issue.. the issue would be bubbles getting through, then getting pumped by the heart into the rest of the body, where they may cause problems.

IMO, it is a worthy subject to talk about. I'd like to see some sort of study on whether being vertical or horizontal in the water can increase or decrease bubble formation or affect offgassing in any way.

You can rest assured that if it does affect offgassing, it's because of the absolute pressure differential in the 6 feet between the head and the feet, not because of the blood getting pulled down towards the feet the way it does on land.


I believe this goes for you as well. If you can point me to a single reliable scientific study that concludes offgassing is affected by position in the water, I'm quite certain that the entire ScubaBoard community would listen.

so now the american medical association is not as reputable as your theory. and for all interested. I,ve contacted DAN and so should you.

 

[Lil' Irish Temper]

Picture of Jonnythan & Nova discussing a subject,
Sorry I'm going fftopic:

 

[O2BBubbleFree]

Picture of Jonnythan & Nova discussing a subject, Sorry fftopic:

I gotta say.... Good One!!

BTW, have you seen the new fingerpuppet robots? Kinda like a thumb war. I really want a set.

 

[redacted]

Incorrect and misleading. Viscosity (thickness) has nothing to do with density, and the specific gravity (density relative to distilled water) of blood is 1.06, meaning it is negligbly (for this exercise) more dense than blood.

That's where I'm losing it. I would not have thought it to be negligible in this case.

Maybe I'll get a bottle of milk and experiment. Here kitty, kitty, kitty.