Hyperbaric oxygen
Hyperbaric oxygen therapy (HBOT) is a medical treatment that involves delivering 100% oxygen to a patient within a pressurized chamber. This environment significantly increases the amount of dissolved oxygen in the bloodstream, enhancing tissue oxygenation. HBOT is primarily used for various infectious diseases, including gas gangrene, necrotizing soft-tissue infections, chronic osteomyelitis, and intracranial abscesses. The therapy works by raising the pressure to between 1.5 and 3.0 atmospheres, which allows for a higher concentration of oxygen to be absorbed by the body.
At these elevated pressures, tissue oxygen levels can increase dramatically, promoting healing and fighting infections. The heightened oxygen levels contribute to the production of reactive oxygen species, which can help combat bacterial infections by damaging their structures and inhibiting their growth. Additionally, HBOT enhances the antimicrobial functions of immune cells, which can be less effective in low oxygen environments. Although research suggests HBOT may improve outcomes for serious infections, further large-scale clinical trials are necessary to establish its best applications and treatment protocols. Overall, HBOT presents a promising approach to addressing certain life-threatening conditions, with ongoing studies aiming to refine its use.
Hyperbaric oxygen
- ALSO KNOWN AS: Hyperbaric medicine, hyperbaric oxygen therapy, hyperbaric oxygenation, hyperbarics
Definition
Hyperbaric oxygen therapy (HBOT) involves the delivery of 100 percent oxygen to a person in a pressurized chamber. The elevated pressure markedly increases the amount of dissolved oxygen in the bloodstream, thereby substantially augmenting tissue oxygenation. Potential infectious disease applications of HBOT include treatment of clostridial myositis and myonecrosis (gas gangrene), necrotizing soft-tissue infections (such as necrotizing fasciitis), chronic osteomyelitis, and intracranial abscesses.
Physiology
At normal atmospheric pressure, most oxygen in the blood is bound to hemoglobin; a small amount exists in solution. During a hyperbaric oxygen treatment session, pressure within the chamber is raised to 1.5 to 3.0 atmospheres absolute (ATA), forcing a high concentration of oxygen into solution. When breathing 100 percent oxygen at 3.0 ATA, the partial pressure of oxygen in the arterial circulation increases from the normobaric level of roughly 100 millimeters of mercury (mmHg) to approximately 2,000 mmHg. The steep partial pressure gradient in oxygen tension between the hyperoxic blood and the tissues leads to diffusion of oxygen into the cells. With 100 percent oxygen at 3.0 ATA, tissue oxygen tension increases roughly tenfold, from 55 mmHg to approximately 500 mmHg.
Inhibitory and Bactericidal Effects
HBOT for infectious disease indications may be included as part of a multimodality treatment approach, typically in combination with surgical debridement and intravenous antimicrobial therapy. Hyperoxia may combat bacterial infections through a variety of complementary mechanisms. High tissue oxygen tension during HBOT markedly increases the production of reactive oxygen species, or free radicals, which may oxidize and denature structural bacterial proteins and exotoxins. Sufficiently elevated tissue oxygen tension may also inhibit replication and metabolism of anaerobic bacteria. During periods of metabolic inactivity, toxin production temporarily slows or stops, potentially limiting further spread of the infection to surrounding tissues.
Enhanced Phagocytic and Antimicrobial Functions
Increased tissue oxygen tension during hyperbaric therapy may augment the antimicrobial and phagocytic functions of polymorphonuclear leukocytes and tissue macrophages. These phagocytes lose effectiveness at the low oxygen tensions that commonly occur in infected body sites. Certain antibiotics that lose efficacy in low oxygen environments may also become more effective with an HBOT-induced increase in tissue oxygen tension at the site of infection.
Impact
The infectious conditions for which HBOT may be indicated are associated with a significant risk of disfigurement, morbidity, and mortality. Research indicates a trend toward a potential role for HBOT in improving outcomes with these conditions. Large-scale, randomized-controlled clinical trials will help determine the most appropriate settings and treatment protocols for the adjuvant use of HBOT for potentially catastrophic bacterial infections.
Bibliography
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Gill, Adrian L., and Chris N. A. Bell. “Hyperbaric Oxygen: Its Uses, Mechanisms of Action, and Outcomes.” QJM: An International Journal of Medicine 97 (2004): 385-395.
Goldman, Robert J. “Hyperbaric Oxygen Therapy for Wound Healing and Limb Salvage: A Systematic Review.” PM&R 1 (2009): 471-489.
"Hyperbaric Oxygen Therapy." Mayo Clinic, 6 Dec. 2024, www.mayoclinic.org/tests-procedures/hyperbaric-oxygen-therapy/about/pac-20394380. Accessed 4 Feb. 2025.
Jain, Kewal K. Textbook of Hyperbaric Medicine. 5th ed. Cambridge, Mass.: Hoegrefe, 2009.
Rabinowitz, R. P., and E. S. Caplan. “Hyperbaric Oxygen.” In Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, edited by Gerald L. Mandell, John F. Bennett, and Raphael Dolin. 7th ed. New York: Churchill Livingstone/Elsevier, 2010.