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Glossary of hyperbaric oxygen therapy terms

Hyperbaric Oxygen Therapy Glossary of Terms

Aeroembolism — Obsolete term for altitude decompression sickness; also used to mean gas embolism.

Aerobic — Requiring air or free oxygen in order to live.

Air — 78% nitrogen, 21% oxygen, 1% carbon dioxide and all other gases.

Ambient — Pertaining to the surrounding environment.

Anaerobic — The ability to grow or thrive in the absence of molecular oxygen.

Angiogenesis — The development of blood vessels. Angiogenesis is a major benefit of HBO therapy.

Ascent — Movement in the direction of reduced pressure, whether simulated or due to actual elevation in water or air.

Atmospheres absolute — The sum of barometric and hydrostatic pressures. This is the most commonly used measurement when dealing with HBO therapy. The abbreviation is ATA.

Atmospheric pressure — The amount of pressure exerted by the weight of the air in our every day environment. At sea level the pressure of the atmosphere is 14.7 pounds per square inch.

Baromedicine — The area of medicine related to physiological processes that occur either from pressure changes or changes in the concentration of inhaled gases.

Barotrauma — The mechanical damage to the tissues caused by unequal pressures.

Bends — An imprecise term denoting any form of Caisson disease or decompression sickness. It is sometimes a fatal disorder that is marked by neuralgic pains (severe pain along a nerve) and paralysis, and dyspnea (difficult breathing); that is caused by the release of gas bubbles in tissue upon too rapid decrease in pressure after a stay in a compressed environment.

Bottom time — The amount of time from getting in the water at the start of a dive until the beginning of the ascent.

Chamber — A vessel designed to withstand differential pressures.

• Double-lock — A chamber with two compartments that can be pressurized independently.

• Hyperbaric — A chamber designed to withstand high internal pressures; used in hyperbaric experimentation, diving simulations, and medical treatment.

• Monoplace — A portable one-person hyperbaric chamber used for therapy in a hospital or clinical setting, and for transport.

• Multiplace — A pressure chamber designed to be used by more than one person at a time.

• Single-lock — A pressure chamber with only one pressurizable compartment.
Decompression sickness — A condition caused by too rapid a reduction in pressure, and having a variety of signs and symptoms. Synonymous with the bends, Caisson disease, or compressed air illness. The abbreviation is DCS.

Decompression — In diving, that phase in which the individual is ascending in the water, or in a chamber when the pressure is being lowered.

Embolism — Air or gas bubbles in the arterial (artery: a vessel conveying blood from the heart) system caused by gas or air passing into the pulmonary (lung) veins after rupture of the alveoli (air cells of the lung).

HBO — Common abbreviation for hyperbaric oxygen. HBO is the use of increased oxygen concentrations under greater than normal atmospheric pressure.

Hydrostatic — Relating to the pressure that liquids exert.

Hyperbaric oxygenation — Also known as hyperbaric oxygen therapy. The use of an oxygen breathing mixture where the ambient pressure is greater than 1 atmosphere. This is abbreviated as HBO or HBO2.

Hyperbaric — Pertaining to pressure greater than one atmosphere.

Hyperbaric pressure — Pressures greater than atmospheric pressure.

Hyperoxia — An excess of oxygen in the body tissues produced by breathing a mixture in which the inspired (inhaled) oxygen pressure is greater than its partial pressure in air.

Hypoxia — Oxygen deficiency.

Ischemia — Local reduction of blood supply due to obstruction of inflow of arterial blood.

Microaerophilic — Requiring free oxygen for growth, but thriving best when the oxygen is less than the amounts in the atmosphere.

Monoplace chamber — A HBO chamber designed to hold one person, usually at a maximum pressure of 3 ATA.

Multiplace chamber — A HBO chamber designed to hold two or more persons, usually with pressures of up to 6 ATA.

Osteomyelitis — Inflammation of the marrow of the bone.

Osteonecrosis — The process of bone cells dying in mass.

• Dysbaric — Changes in structure of bone in which the relative density of the affected bone is increased by sclerosis (hardening). Observed changes are the result of a healing process following insult (trauma). Found in caisson workers and more recently in divers, and probably due to inadequate decompression. Synonymous with aseptic bone necrosis and avascular bone necrosis.

• Juxta-articular — Osteonecrosis occurring near the joint articulation, usually hip or shoulder. May lead to collapse of the joint, together with pain and dysfunction.

• Medullary — Osteonecrosis occurring in the shaft of the bone, usually symptomless and detected by x-ray.

Otitis — Inflammation of the ear, which may be marked by pain, fever, abnormalities of hearing, tinnitus (ringing in one or both ears), and vertigo (dizziness); a very common problem in diving.

Oxygen poisoning — Deleterious (harmful) effects caused by breathing high partial pressures of oxygen. Prolonged exposure can result in effects which become progressively more severe as the inspired partial pressure and/or the duration of exposure increases. Depending on level and length of exposure, may cause lung damage, involvement of the central nervous system causing convulsions, or early death.

Oxygen toxicity — Physical impairment that results from breathing pure oxygen for prolonged periods of time; the time to achieve toxicity is shortened as the pressure in the surrounding environment increases.


• Absolute — The sum of all pressures acting on an object; in diving, the sum of the atmospheric (air) pressure and the hydrostatic (water) pressure acting on a submerged object.

• Ambient — The absolute pressure surrounding an object.

• Atmospheric — Pressure exerted by the earth's atmosphere, which varies with altitude above sea level. At sea level atmospheric pressure is equal to 760 mmHg or 1.03 kg/square centimeter, or 14.7 pounds per square inch.

• Hydrostatic — The pressure of a column of water acting upon a body immersed in the water, equal in all directions at a specific depth.

Pressurize — To increase the internal pressure of a closed vessel.

Treatment depth — The depth or pressure to which a patient is compressed for treatment.