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Mild Hyperbarics Physics Overview

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Diffusion is the movement of one or more gases down a concentration gradient. In other words... things move from greater concentration to lesser concentration. When working with gases, if more than one gas makes up an atmospheric environment, the partial pressure of any particular gas would be equal to the percentage of the gas multiplied by the total pressure.

Example #5: Normal ambient breathing air is about 21% oxygen. At sea level (1 ata), oxygen would have a partial pressure (ppO2) = 0.21 ata. If we increase the oxygen levels to 42%, the partial pressure of oxygen (ppO2) would be = 0.42 ata
Example #6: 21% oxygen at 2 ata gives a ppO2 = 0.42 ata. Note: We received the same partial pressure of a lower atmospheric pressure with a higher oxygen concentration as demonstrated in example #5.

Let's look at two more just to be sure we fully understand this component...

Example #7: 21% ambient air at 1.5 ata gives a ppO2 = 0.31 ata
Example #8: 50% oxygen mixture at 1.3 ata gives a ppO2 = 0.65 ata. Note: A lower pressure with a higher oxygen concentration can actually exert a greater partial pressure than a higher pressure with a lower oxygen concentration.

What we need to understand from these examples is that the pressure and the gas mixture work together to create a partial pressure differential, resulting in a concentration gradient and the occurrence of diffusion. If you are still confused, don't worry! You still don't have the complete picture as to how all this works and what these numbers mean.

When we talk about concentration gradients in respect to hyperbaric medicine we are speaking of the difference between tissue (don't forget that blood is considered a tissue), and the external atmospheric pressure. Of course, there is always a concentration gradient in the lungs. If there weren't, respiration wouldn't take place. The reason why there is always a concentration gradient in the lungs is due to the fact that venous blood is virtually void of oxygen. The cycle is pretty simple; blood from the body returns to the heart from the tissues via the venous system. This blood is high in carbon dioxide and virtually absent of oxygen. The right ventricle pumps this blood to the lungs where the ppO2 (partial pressure of oxygen) is much higher and carbon dioxide is much lower. As a result of this strong gradient, oxygen dissolves in the plasma and becomes bound to hemoglobin; further, carbon dioxide diffuses out of the blood and is exhaled form the body. This oxygenated blood then travels back to the left side of the heart where it is pumped to the tissues before returning once again. If you haven't figured out where the difference in pressure plays a role... it's in the lungs!

The greater the pressure and the greater the oxygen concentration, the greater the partial pressure of oxygen in a given environment. Diffusion says, "greater concentration to lesser concentration", it could also be stated, "greater partial pressure to lesser partial pressure". After all, we are just talking about concentrations of gases in one environment (inside your body) vs. another environment (outside your body). So, the greater the pressure and oxygen concentration in relation to an individuals normobaric environment (normal everyday atmospheric pressure); the more oxygen that will become dissolved into the bloodstream and secondarily the rest of the tissues of the body.

To calculate the amount of additional oxygen that could potentially become dissolved in the tissues we simply need to know the difference between the partial pressure of oxygen in ones normobaric environment vs. the applied hyperbaric environment.

Example #9: If one were to do a hyperbaric treatment at 1.3 ata with ambient air (21% O2) at sea level (1 ata), then there would be a 0.3 ata differential between the normobaric and hyperbaric environments. A 0.3 ata increase is a 3/10 of an atmosphere increase, thus a 30% increase in the amount of molecules of oxygen that need to diffuse in order to equalize pressure. If we actually do the partial pressure mathematics, it looks like this... 1 ata x 21% O2 = ppO2 = 0.21 ata. 1.3 ata x 21% O2 = ppO2 = 0.273 ata. The difference between 0.273 ata and 0.21 ata is 0.063 ata; exactly 30% of 0.21 ata.

So, if the oxygen concentration is a constant and the treatment is being applied at sea level, with only the pressure changing; the potential increase in oxygen saturation is easily calculated by subtracting one from the treatment pressure (ata) and then converting that number to a percentage.

Example #10: Treatment pressure of 2 ata. 2 - 1 = 1.0 Move the decimal two places and you have 100%. To recap, a treatment pressure of 2 ata with 21% oxygen would yield a potential increase in oxygen saturation of 100%
Example #11: Treatment pressure of 2.4 ata. 2.4 - 1 = 1.4. Move the decimal two places and you have a 140% potential oxygen saturation increase.

Okay, examples 10 and 11 make things pretty simple... but the real world is much different. Let's look at what is really going on when pressure and oxygen concentration are changing and the treatment is being applied at elevations other than sea level.

Example #12: Let's take our Boise, Idaho scenario once again with a normobaric atmosphere of 0.9 ata, and a treatment of 4.4 psig inside a mild portable hyperbaric chamber. For the sake of this first example we are going to keep oxygen concentration constant at 21%. To understand this scenario, we will begin by converting the atmospheres absolute into psi; 0.9 ata = 13.2 psi. Next we will add the treatment pressure of 4.4 psig; 13.2 + 4.4 = 17.6 psi. Now let's convert this back to ata! 17.6 psi /14.7 psi = 1.2 ata. Now we can subtract the normobaric from the hyperbaric environment, 1.2 ata - 0.9 ata = 0.3 ata to realize that we still have the same 3/10 of an atmosphere differential. Further, when we actually calculate including the partial pressure of oxygen; the differential is identical to what we saw calculating 4.4 psig at sea level. 1.2 ata x .21 O2 = 0.189 ppO2 and 0.9 ata x .21 O2 = 0.252 pp O2. When you subtract the treatment ppO2 from the normobaric ppO2 you get the same 0.063 ppO2 differential.
Example #13: What if we were in Vail, Colorado at about 8,000 feet, (approximately 0.7 ata). If we convert our atmospheres absolute into psi we get 14.7 x 0.7 = 10.29 psi. Let's now add our 4.4 psi treatment pressure, 10.29 + 4.4 = 14.69 psi. Wow, a mild hyperbaric chamber practically takes you just back to sea level, remember that 14.7 psi = 1 ata. So, considering that our treatment is just about 1 ata, if we subtract our normobaric environment of 0.7 ata we once again receive a pressure differential of 0.3 ata.

What this means is that the treatment (oxygen concentration unchanged), although at a lower atmosphere absolute is just as effective at the higher elevation when we actually consider the differential between the treatment and normobaric atmospheric pressure.

So what happens when we add increased oxygen concentrations into the mixture? Let's take a look at whether oxygen concentration plays a changing role in these same two scenarios.

Example # 14: Continuing on with the Boise elevation and 4.4 psig treatment pressure, let's now introduce more oxygen by changing the breathing mixture to 60% oxygen. Of course in order to properly compare we will also need to factor in the normobaric environment. At sea level, a 4.4 psig chamber yields 1.3 ata x .6 O2 (60% oxygen) for a ppO2 =0.78 ata. Next we can subtract the normobaric ppO2 of 0.21 to get our differenctial. 0.78 ata - 0.21 ata = a differential of 0.57 ata. Now let's look at this in Boise. In Boise, a 4.4 psig chamber yields 1.2 ata x .6 O2 for ppO2 of 0.72 ata. Once again we subtract the normobaric ppO2 of 0.189 ata (0.9 x 0.21) from our treatment ppO2 to get our differential. 0.72 - 0.19 = 0.53 ata.
Example #15: Working with the Vail location and 4.4 psig treatment pressure lets now change the breathing mixture to 60% oxygen. Of course once again we will also need to factor in the normobaric environment. At sea level, a 4.4 psig chamber yields 1.3 ata x .6 O2 (60% oxygen) for a ppO2 = 0.78 ata. Now we can subtract the normobaric ppO2 of 0.21 to get our differenctial. 0.78 ata - 0.21 ata = a differential of 0.57 ata (same math as example 14). Now let's look at this in Vail. In Vail, a 4.4 psig chamber yields 1.0 ata x .6 O2 for ppO2 of 0.6 ata. When we subtract the normobaric ppO2 of 0.147 ata (0.7 x 0.21) from our treatment ppO2 (0.6 ata) we can calculate our differential in Vail. 0.6 - 0.147 = 0.45 ata.

So, when we consider treatments at higher elevations, the higher the elevation and the higher the oxygen concentration; the greater the difference in comparison to the same psig treatment at sea level! On the other hand, if you were to actually compensate by applying greater pressure inside the chamber to compensate for the lower atmospheric pressure occurring at higher elevations, the treatment at the higher elevation would actually produce greater differentials in partial pressures of oxygen as compared to the same atmospheres absolute treatment performed at sea level (1.3 ata x 60% O2 - 0.7ata x 21% O2 = 0.63 differntial). Compare this 0.63 ata differential to the 0.57 ata differential that is achieved when performing a 1.3 ata treatment at sea level. As you can see, the potential for diffusion when speaking in terms of atmospheres absolute is slightly greater at higher altitudes. My point in this last statement is that although you may read these terms of 1.3 ata, 1.5 ata, 1.75 ata, etc., there are a lot of details that are being left out and the actual treatment probably isn't what you see written on paper. Further, if the treatment truly is executed at the specified pressure at a higher elevation, then it is actually a greater differential treatment as compared to a lower altitude. Point being, despite the industries attempt to portray hyperbaric medicine as an "exact science", it is far from it. Further, don't forget that we haven't even considered barometric pressure which would only continue to complicate matters. We simply need to realize that this is not an all or none, exact science situation and there is no magic ppO2 you must attain; you simply need a differential to occur for the therapy to provide any potential benefit.

Of course it is a lot easier to just say 1.3 ata rather than figure out your elevation and actually calculate your true treatment pressure. Maybe this is why the industry has fallen into the bad habits that it has. More likely is that people just don't know. Sadly, it is just as easy to say you are undergoing treatment at 4.4 psig; unfortunately the industry is hung up on speaking in absolute terms that it doesn't actually represent. Even if you were representing an absolute pressure, the treatment potential would still vary based on elevation.

Last note before moving on:

The reason for using 60% in a number of the examples is because this is about the highest breathing mixture you can attain inside a portable mild hyperbaric chamber. Since these chambers are never filled with 100% oxygen, a patient may wear a mask or cannula to breath the 85-100% O2 which is being delivered to it from an external oxygen device (O2 concentrator or oxygen tank). When setup in this manner, the actual purity of air that reaches the lungs is a mixture of the oxygen being delivered to the mask and the air surrounding the mask. A tight fitting mask and focused breathing will get about 60%, but chances are most people are getting closer to 45-50%.

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Part 4: Effects of Treatment Duration on Tissue Saturation

Part 5: The Importance of Frequency

About the Author: Greg Harris is the founder of Hyperbaric Options LLC and has spoken publicly about health & wellness in various settings over the past eight years. Greg has a passion for human potential and is a firm believer that nearly all of the health problems we face today, from degenerative neurological conditions to the common cold, are preventable and reversible. As a health professional, Greg has a unique ability to connect the dots where others have left them scattered; it is this ability to integrate disciplines and think outside of the box that give his lectures and written materials a fresh point of view.

Disclaimer: The information and advice published or made available throughout this article is not intended to replace the services of a physician, nor does it constitute a doctor-patient relationship. Information contained within the following and/or preceding pages is provided for informational purposes only and is not a substitute for professional medical advice. The author encourages all readers to further research any topics of interest and reminds the reader that the comments and materials being presented do not necessarily constitute scientific fact and may contain opinions, theories, and third party views not widely accepted. You should not use the information contained in this published material for diagnosing or treating a medical or health condition. You should consult a physician in all matters relating to your health, and particularly in respect to any symptoms that may require diagnosis or medical attention. Any action on your part in response to the information provided throughout the material is at the reader's discretion. Readers should consult their own physicians concerning the information in this material. Hyperbaric Options LLC is not liable for any direct or indirect claim, loss or damage resulting from use of this material.

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“The deeper we go into the facets of life, the more mysterious we encounter. Analyzing living systems, we often have to pull them to pieces, decompose complex biological happenings into simple reactions. The smaller and simpler the system we study, the more it will satisfy the rules of physics and chemistry, the more we will understand it, but also the less “alive” it will be. So when we have broken down living systems to molecules and analyzed their behavior, we may kid ourselves into believing that we know what life is, forgetting that molecules have no life at all.”

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