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HBOT Terminology: ATA, ATM, PSI, and PSIG

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For us to move forward we must first understand exactly what these terms are referencing. An atmosphere is defined as the normal pressure of air at sea level (normal pressure does not include such factors as barometric pressure). One atmosphere is equal to 14.7 psi (pounds per square inch). To help understand this, if you weighed a column of air, one inch squared, from the sea shore up about 60 miles to the outer atmosphere; it would weigh 14.7 pounds.

An atmosphere as a unit of measurement can be abbreviated (atm). Hence, 1 atm = 14.7 psi and 2 atm = 29.4 psi; hopefully you are seeing the math! When we use the term atmosphere (atm), we aren't necessarily considering the pressure that is already being exerted on the body. To correctly state the total amount of pressure being experienced we use atmospheres absolute (ata). For example, consider a diving scenario in which the diver travels 33 feet under sea water (1 atm). The diver will be at one atmosphere greater pressure and so the total pressure experienced would be 2 atmospheres absolute (2 ATA).

In similar fashion, pounds per square inch gauge (psig), work very much the same. A pressure gauge measures the change between two different environments. No pressure change on a gauge would typically read zero. Should a hyperbaric chamber be pressurized one atmosphere (1 atm), then the gauge would read 14.7 psig (once again, the "g" stands for gauge). To sum things up, the gauge isn't displaying the total amount of pressure inside the chamber; only the difference between inside and outside. In the above scenario (assuming the hyperbaric chamber is located at sea level), the chamber is being pressurized to two atmospheres absolute (2 ata), which would be a total of 29.4 psi. Once again, a gauge would not read 29.4 but rather only the differential of 14.7 psig.

Here are a few more examples... (Assume all chambers are located at Sea Level, 1 ata)

Example #1: Treatment Protocol is 1.5 ata. To calculate the psig we simply multiply 14.7 psi (= to 1 atm) x 0.5 (the diffence between normal atmospheric pressure and treatment pressure) , which = 7.35 psig. So, the gauge would read 7.35 psig if one were doing a treatment of 1.5 ata at sea level.
Example #2: Treatment Protocol is 1.3 ata. Let's just look at the math this time! 14.7 psi x 0.3 = 4.41 psig. So, the gauge would read 4.41 psig if one were doing a treatment of 1.3 ata at sea level.

Okay, so what if you aren't actually at sea level? Then we first need to calculate what the actual atmospheric pressure is in order to figure what your true treatment pressure is. Since altitude and atmospheric pressure are not a constrained equation (more molecules exist at lower elevations, contributing to an exponential increase in pressure as one gets closer to sea level), we won't actually calculate these pressures; Instead I will provide a few examples of various altitudes throughout the United States

Example #3: Chamber pressure is 4.4 psig, located in Boise, Idaho. Boise has an elevation of about 2,800 feet and an atmospheric pressure of roughly 0.9 ata (13.2 psi). By adding the additional 4.4 psig from the chamber to the 13.2 psi atmospheric pressure we get a total treatment pressure of 17.6 psi (1.2 ata).
Example #4: Chamber pressure is 4.4 psig, located in Albuquerque, New Mexico. Albuquergue has an elevation of about 5,300 feet and an atmospheric pressure of roughly 0.8 ata (12.1 psi). By once again adding the additional 4.4 psig from the chamber to the 12.1 psi atmospheric pressure we get a total treatment pressure of 16.5 psi (1.1 ata).

At this point you may be wondering if the mild portable chambers on the market are actually 1.3 ata chambers as advertised? Well, not unless they are operated at sea level. Fact is, most people in the industry aren't familiar with the simple mathematics displayed above and therefore are simply ignorant of the misinformation they are spreading. Basically, a 4.4 psig chamber is not a 1.3 ata chamber... it simply has become acceptable to reference them as such. In the same way, a 7 or 7.35 psig chamber is not a 1.5 ata chamber! To speak in atmospheres absolute you must factor in the elevation of the location where the treatment will be applied.

Does that mean that a chamber which operates at a set pressure (i.e. all mild portable hyperbaric chambers) is less effective at higher altitudes? To answer that question, we will need to first understand how the applied change in pressure affects the body; of which, an understanding of diffusion, partial pressures, and concentration gradients will be necessary.

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Continue to...

Part 3: Diffusion, Partial Pressures, and Concentration Gradients

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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Portable hyperbaric chambers are Class II medical equipment. All consumers must provide a copy of your prescription. As this is class II medical equipment the sale (new or used) and/or rental of such equipment is restricted outside of a physician’s recommendation. Your physician may fax us a copy direct or if you already have a copy you may fax or send us a copy via mail. For businesses purchasing hyperbaric equipment for use in an office setting, we require a copy of of federal Tax ID papers in addition to a signed statement that your intentions of purchasing the equipment are not for personal, rather professional administration.

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The information provided throughout this web site is for educational and informational purposes only and is not intended as medical advice. Hyperbaric Options LLC makes no claims in regards to the effectiveness of "hyperbaric therapies" in the treatment of specific conditions. As "hyperbaric therapies" are considered medical treatment, please consult your physician regarding the benefits and application of such therapies. The term "hyperbaric therapies" includes: hyperbaric oxygen therapy, HBOT, hypberaric therapy, HBT, mild hyperbaric therapy, MHT, mild hyperbaric oxygen therapy, mildHBOT, and any other derivations including the keyword "hyperbaric".

Words of Wisdom

“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.”

–Dr. Albert Szent Gyorgyi