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Cerebral Anoxia

Hyperbaric Oxygen Theraphy in Global Cerebral Ischemia/Anoxia and Coma

HBOT Therapy in Global Cerebral Ischemia Anoxia and Coma

 
Paul G. Harch and Richard A. Neubauer

 An entry from K.K. Jain's Textbook Of Hyperbaric Medicine

Hyperbaric oxygen therapy has been used in a number of conditions characterized by global ischemia (as opposed to focal ischemia of stroke), and anoxia, and leading to impairment of consciousness. Conditions such as coma due to brain injury and anoxia associated with drowning and hanging are discussed under the following headings:
 

 

Introduction


For a discussion of the effectiveness of hyperbaric oxygen (HBOT) therapy in global cerebral ischemia/anoxia and coma, we define HBOT as a medical treatment that uses high pressure oxygen as a drug by fully enclosing a person or animal in a pressure vessel and then adjusting the dose of the drug to treat pathophysiologic processes of the diseases. Like all drugs, the dose of HBOT is crucial and should be customized to each patient's response. It is dictated by the pathological target and is determined by the pressure of oxygen, duration of exposure, frequency, total number of treatments, and timing of the dose in the course of the disease. As diseases and their pathologies evolve, different doses of HBOT are required at different times. In addition, patients have individual susceptibility to drugs, manifest side effects and toxicity. Unfortunately, the ideal dose of HBOT in acute or chronic global ischemia/anoxia and coma is unknown. The studies reviewed below suggest higher pressures (2 ATA or higher) and lesser numbers of treatments very early in the disease process whereas lower pressures (2 ATA or lower) and a greater number of treatments have been used as the brain injury matures. While this general trend seems justified, the absolute or effective pressures delivered to the patients in these reports may be slightly less than what is stated since many studies do not specify the HBOT delivery system that was employed. For example, an oxygen pressurized chamber has an effective HBOT pressure equal to the plateau pressure administered during the treatment, whereas an air pressurized chamber in which oxygen is administered by aviators mask can achieve a far lower effective HBOT pressure, depending on the fit of the mask and the amount of its air/oxygen leak. In the later cases, the dose of oxygen is less. This concept is particularly important when analyzing the studies in this chapter performed prior to the late 1980s when the aviator mask dominated delivery systems in multiplace chambers.