Blood Pressure Under Water

[RobPNW]

Why doesn’t your blood pressure go through the roof when you’re at depth and have 3-5 atmospheres of back pressure applied to your skin’s entire surface area?

 

[Endler's]

Liquids typically can't be compressed much because there isn't any space between molecules, and we are bags of water (over 50%).

 

[RobPNW]

If the surrounding pressure is applied to the surface of the skin I don’t see why that wouldn’t cause back pressure on the heart.

 

[johndiver999]

It is pressure differential, not actual pressure that you are concerned with.

 

[Duke Dive Medicine]

If the surrounding pressure is applied to the surface of the skin I don’t see why that wouldn’t cause back pressure on the heart.

Blood pressure is affected by immersion, but not for that reason. The pressure in the body is at equilibrium with the ambient pressure and evenly distributed throughout the body so there's no pressure vector from a particular source that will make the BP increase. That would only happen in whole body squeeze, e.g. if a surface-supplied diver suddenly has the umbilical severed on the surface and the check valve malfunctions.

Best regards,
DDM

 

[Learner Diver]

Blood pressure is affected by immersion, but not for that reason. The pressure in the body is at equilibrium with the ambient pressure and evenly distributed throughout the body so there's no pressure vector from a particular source that will make the BP increase. That would only happen in whole body squeeze, e.g. if a surface-supplied diver suddenly has the umbilical severed on the surface and the check valve malfunctions.

Best regards,
DDM

What is the common reason for divers having heart seizures underwater?

 

[happy-diver]

Too many steaks and not enough vegetables above water

whole body squeeze, e.g. if a surface-supplied diver suddenly has the umbilical severed on the surface and the check valve malfunctions.

Hard for me to understand if this is a squeeze, unsqueeze or squeeze followed by unsqueeze or crush, uncrush

But that's probably just me

 

[boulderjohn]

What is the common reason for divers having heart seizures underwater?

I am not sure what you mean by a heart seizure. As Happy-diver suggests, heart attacks are most commonly caused by the same thing that would cause it while you are playing golf, bowling, or eating breakfast. Seizures while diving are most commonly associated with breathing too high a percentage of oxygen for too long, although a recent case of a seizure with a well-known diver was evidently caused by a seizure disorder and would have happened if he had been on land. A severe cardiac arrythmia can cause symptoms that look like a seizure, and that, too, would not be caused by anything on the dive.

 

[MidOH]

Might be thinking of an air embolism? Which gets lumped in with "heart attacks".

Which is caused because they were stupid.

Maybe open water classes need to touch on open airways more often. I know mine taught it in class. But maybe it should be mentioned in the briefing of every training dive.

Typical Diver death:
-something happens
-Diver holds their breath and races to the surface
-air enters blood stream too fast or too much
-Diver makes it to the surface. Waves.
-Diver sinks back to the bottom and dies.


Dozens like that on my AO. Same script. Maybe old. Maybe rebreather. Maybe freeflow.

 

[boulderjohn]

Typical Diver death:
-something happens
-Diver holds their breath and races to the surface
-air enters blood stream too fast or too much
-Diver makes it to the surface. Waves.
-Diver sinks back to the bottom and dies.

Although a joint PADI/DAN study did suggest that a rapid, panicked, breath-holding ascent to the surface is the most action-related cause of death while diving, you have misidentified the reason. It has nothing to do with air entering the blood stream.

The problem is that the air in the lungs expands rapidly in accordance to Boyle's Law. Air in a flexible container (like the lungs) at 33 FSW will double in volume when it reaches the surface. The last 1-15 feet is when the greatest expansion occurs. This can cause a number of different lung overexpansion injuries, the most dangerous is an embolism, a bubble in the blood stream that acts as a clot would. It can cause a very quick death.