How does diving affect blood pressure?

[fisherdvm]

If you took a blood pressure cuff down to 100 ft, and used a doppler to check for pulse - will the blood pressure taken on a diver at 100 ft be the same as blood pressure on the surface, or will it be increased by his blood pressure plus 3 ATM?

If there were an increase in blood pressure, will this increase the load on the heart? My gut feeling is that the blood pressure will be the same, and there is no increase work demand on the heart.

 

[Diver Dennis]

Hmmmm. Very interesting question.

 

[h90]

The blood pressure will be of course 3 bar more, else all the "tubes" in your body would collaps. But as just everything is shifted up 3 bar there is not more work.
It is like you lift 1 bottle water 1 meter at the ground floor or at 30 meter high at the 10th floor, it is the same work even it is 30 meter higher.
I hope it is understandable with my bad english......

 

[fisherdvm]

The blood pressure will be of course 3 bar more, else all the "tubes" in your body would collaps. But as just everything is shifted up 3 bar there is not more work.
It is like you lift 1 bottle water 1 meter at the ground floor or at 30 meter high at the 10th floor, it is the same work even it is 30 meter higher.
I hope it is understandable with my bad english......

You are correct to say that the TRUE blood pressure is 3 more bar. However, this can only be measured by a direct arterial pressure gauge.

But, if you used a standard pressure gauge on a regular blood pressure cuff, I believe that it would only detect the difference in pressure between external (zero), and internal pressure. Otherwise, I would imagine that people who lives at high altitude (10000 ft) would have low blood pressure.

 

[miketsp]

..snip..
It is like you lift 1 bottle water 1 meter at the ground floor or at 30 meter high at the 10th floor, it is the same work even it is 30 meter higher.
..snip..

With so many nitpickers on this board you shouldn't make this kind of statement.
At the 10th floor the force of gravity is less than at the ground floor so you will do (marginally) less work to raise the bottle by 1 meter.

 

[Mark_J]

Interesting question, I'm sure there is some exact and probably surprising scientific answer based on physics for it as well. My own guess would be that the body acts as enough of a protective vessel to have the blood pressure remain relatively unchanged.

Reminds me of a myth I saw busted on that show MythBusters. Does a truck full of birds weight less if all the birds are flying inside the truck? The truck weighs the same, the downward thrust of the bird's wings has to equal the exact amount of their own weight or they couldn't achieve lift.

 

[Mountain Dog]

I'm not a doctor (but I did stay at a Holiday Inn Express last night), but it seems to me that if the blood pressure tripled it would just about blow the burst disks in our heart.

If I'm correct in my thinking here, blood pressure measures the force at which the heart is pushing the blood through the body - which would have very little to do with the external pressure being exerted on the body. A blood pressure cuff squeezes your arm, restricting the blood flow to measure the pressure. We don't feel that kind of squeezing effect underwater (no, I don't have a drysuit), so I don't think there is a significant restriction of blood flow to cause an increase in blood pressure.

Flip the situation around. Astronauts on the space station, in zero gravity, would have no blood pressure.

Mountain Dog

 

[MichaelBaranows]

I think my blood pressure is lower cause I become way more relaxed when I am diving.

 

[ClayJar]

Blood pressure is a *gauge* pressure, not an *absolute* pressure. If you were sitting 100 feet down in a diving bell (with the hatch open to the water), and you had your blood pressure measured, you would see basically the same blood pressure as you would at the surface.

There will likely be some effects from the increased pressure, but the change in blood pressure they precipitate should be similar to other stress factors. There absolutely won't be a 3 ata change in blood (gauge) pressure.

 

[trtldvr]

Physics and physiology aside the opportunity to blow bubbles reduces my BP' but if you really need a "law"....The arterial pressure measured on a given subject is inversly proportional to the measuered time said subject has been breathing at depth.

I think I will call this trtldvr's law. (Do you think PADI will revise the Encyclopedi of Diving to include it?)


Trtldvr

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