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UNDERSTANDING HYPERBARIC OXYGEN THERAPY We can better understand the concepts behind hyperbaric oxygen (HBO) therapy by first gaining an understanding of some basic terms:
 Hyperbaric Oxygen TherapyHyperbaric oxygen therapy describes a person breathing 100 percent oxygen at a pressure greater than sea level for a prescribed amount of timeusually 60 to 90 minutes. Atmospheric Pressure The air we breathe is made up of 21 percent oxygen, 78 percent nitrogen and 1 percent carbon dioxide and all other gases. The air exerts pressure because air has weight and this weight is pulled toward the earth's center of gravity. This pressure is expressed as atmospheric pressure. Atmospheric pressure at sea level is 14.7 pounds per square inch (psi). Hydrostatic Pressure As we climb above sea level the atmospheric pressure decreases because the amount of air above us weighs less. When we dive below sea level the opposite occurs (the pressure increases) because water has weight that is greater than air. Thus, the deeper one descends under water the greater the pressure. This pressure is called hydrostatic pressure. Atmospheres Absolute (ATA) The combination (or the sum) of the atmospheric pressure and the hydrostatic pressure is called atmospheres absolute (ATA). In other words, the ATA or atmospheres absolute is the total weight of the water and air above us. Terms Used to Measure Pressure We use various terms to measure pressure. HBO therapy involves the use of pressure greater than that found at the earth's surface at sea level. This is called hyperbaric pressure. The terms or units used to express hyperbaric pressure include millimeters or inches of mercury (mmHg, inHg), pounds per square inch (psi), feet or meters of sea water (fsw, msw), and atmospheres absolute (ATA). One atmosphere absolute, or 1-ATA, is the average atmospheric pressure exerted at sea level, or 14.7 psi. Two-atmosphere absolute, or 2-ATA, is twice the atmospheric pressure exerted at sea level. If a physician prescribes one hour of HBO treatment at 2-ATA, the patient breathes 100 percent oxygen for one hour while at two times the atmospheric pressure at sea level. More? For a more detailed list of hyperbaric oxygen related terms and their definitions see our Source: Hyperbaric Oxygen Therapy: A Committee Report. Undersea and Hyperbaric Medical Society. 1996 Revision. Telephone: Email: Chico Hyperbaric Center Web Site Developed & Hosted by Access Now 2000. Copyright © 1999-2001. All Rights Reserved. # |
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