Hyperbaric Oxygen Therapy

Hyperbaric oxygen therapy is the administration of 100% oxygen breathing in a pressure vessel at higher than atmospheric pressure and is a well-established treatment for a variety of conditions. ^[1] It consists of using pure oxygen at increased pressure, generally 2 to 3 atmospheres, leading to augmented oxygen levels in the blood and tissue. ^[2]

The increased pressure and oxygen bioavailability are related to a range of effects including antimicrobial, immunomodulatory and angiogenic properties, particularly in hypoxic regions. ^[2] HBOT increases the proportion of dissolved oxygen in the blood five- to twenty-fold, placing the mitochondrion at the epicenter of its effects, and long-term treatment improves mitochondrial activity and decreases reactive oxygen species levels partly by increasing antioxidant defense mechanisms. ^[3] In humans, HBOT-induced oxidative stress reduces concentrations of pro-inflammatory acute phase proteins, interleukins and cytokines and increases growth factors and other pro-angiogenesis cytokines. ^[4]

HBOT is documented to be effective and is approved in 14 medical indications by the Undersea and Hyperbaric Medical Society. ^[1] A meta-analysis found that HBOT increased the healing rate of diabetic foot ulcers, shortened healing time, and reduced the incidence of major amputation. ^[5] For sudden sensorineural hearing loss, a meta-analysis found that HBOT combined with medical therapy was associated with higher odds of hearing recovery than medical therapy alone. ^[6] For the emerging indication of aging and age-related disease, the noninvasive nature and favorable safety profile make HBOT a competitive candidate, and appropriate protocols without exceeding the toxicity threshold have shown promise in pre-clinical and small-scale clinical investigations, though a generally applicable protocol against aging still needs to be defined. ^[7] In recent years HBOT has also been explored to improve cognition and quality of life following brain trauma and stroke and to treat neurodegenerative diseases and mild cognitive impairment, but further investigation is imperative to determine the optimal oxygen pressure, exposure duration, and session frequency. ^{[8] [9]}

The therapeutic targets of HBOT overlap considerably with those of aging and age-related diseases, motivating research interest in the field. ^[7] Because many diseases and conditions are characterized by mitochondrial dysfunction and an imbalance between reactive oxygen species and antioxidant scavengers, HBOT's effects on these pathways suggest potential therapeutic intervention. ^[3]