What is Hyperbaric Pressure, Definitions!

Hyperbaric pressure

Hyperbaric Oxygen Therapy is defined as the combination of increased atmospheric pressure and increased inspired oxygen.

This article will focus on pressure, the unsung hero of HBOT (oxygen gets all the fame, but it's pressure that makes the magic happen). 

Atmospheric pressure is due to atmospheric gasses above the surface of the earth and is dependent on planetary mass, the radius of the planet surface, and the amount of the gases at every altitude (e.g. their vertical distribution). Think of pressure as the density of gases in the air around you. The air is less dense as we get further away from the surface of our planet which means that the gas molecules get further and further away from each other the closer you get to the vacuum of space.

Atmospheric pressure at sea level is defined as 1 ATA (1 atmosphere absolute). As we go above sea level (higher altitudes), the pressure and density of the air decrease. As we go below sea level (either above ground like at the Dead Sea or under the water), the pressure and density increase.

Imagine for a moment that you are diving 33 feet below sea level.

Although you don’t feel it, all that water above you is heavy and creates a significant amount of pressure on your body.  The more water above you, the heavier that water is, and the greater its effect on your physiology.

Here are some definitions we use for HBOT. 

1 ATA = 0 feet / 0 meters of seawater

1.3 ATA = 10 feet / 3 meters of seawater

2 ATA = 33 feet / 10 meters of seawater

3 ATA= 66 feet / 20 meters of seawater.

HBOT Pressure

Inside a hyperbaric chamber, we simulate the pressure you feel under a certain amount of seawater. It is this pressure that drives supra-physiologic levels of oxygen into circulation due to Henry's Law, a physics law which states that the more pressure put on the gas (in this case, oxygen), the more of that gas that goes from a gaseous form to a liquid form. 

Typically oxygen is carried on red blood cells but when there is pressure, oxygen can diffuse directly into the plasma of the liquid of our bloodstream in huge amounts, up to 12 times what's possible just on red blood cells. 

This is the key to HBOT.  Without pressure, there would be no oxygen super saturation. This is why a face mask of oxygen is not the same as HBOT. 

Pressure Effects on Physiology

In addition to pressure driving more oxygen into circulation, pressure also has a significant effect on our physiology. This mechanical force, also sometimes called shear stress, is affecting your cells, your blood vessels, your lymphatic system, your CSF (cerebral spinal fluid), and pretty much everywhere else, including inducing the firing of action potential of neurons on the brain. 

Our body naturally pumps blood from our heart to our periphery and back to the heart using high flow vessels (arteries) and low flow vessels with valves (veins). We have lymphatic vessels that are like the garbage superhighway of our body, helping us rid ourselves of cellular waste products. The lymphatic system is where most of our immune system cells are stored as well. There’s also cerebrospinal fluid that is produced in the brain’s ventricles and circulates throughout the brain and spinal cord.

Any pressure induced mechanical force/shear stress is going to enhance flow through these fluids simply by creating more stress on them. BUT,..and this is the interesting part: There is the hypothetical possibility that increasing pressure on vessels actually increases the amount of charged or structured water around vessels. This charged water concept has been proposed by Dr. Gerald Pollock at the University of Washington. With more charged water around fluid filled vessels, the amount of structured water or as Dr. Pollack calls it, EZ water (exclusion zone) water is made. And when there’s more EZ water, water flows faster.

Plus, this shear stress related to pressure activates mitochondria ATP production directly. So you get more energy produced with increased pressure too! 


Pressure has massive effects on physiology and inside a hyperbaric environment, is responsible for the driving of more oxygen into circulation plus the creation of more flow and energy production directly. 

As we say in the hyperbaric business, we are under pressure and we love it! 

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