INTRODUCTION

Hyperbaric literally means “over pressure.” In HBO2 therapy, a patient breathes 100% oxygen while resting in a chamber that’s pressurized to a level greater than atmospheric  ressure.[1]

Hyperbaric chambers vary widely in their construction, but they can be divided into two major categories. A monoplace chamber, which can accommodate one patient at a time, is typically pressurized with 100% oxygen. A multiplace chamber, as the name implies, can hold more than one patient. 

Multiplace chambers are normally pressurized with air, and the patients breathe oxygen through either a head tent or a mask. In either type of chamber, the patient breathes 100% oxygen while subject to increased ambient pressure. 

CONSIDER PHYSIOLOGY 

The alveoli in the lungs are, for all practical purposes, a gas-fluid interface. One of the bene#cial e$ects of HBO2 is that under hyperbaric conditions, oxygen is dissolved into the plasma in quantities high enough to overcome a defficit in tissue microcirculation. Tissue capillaries can be damaged by therapeutic radiation, diabetes, burns, infection, and other insults. Damage to the microcirculation prevents erythrocytes from reaching tissues and delivering oxygen, which may result in tissue hypoxia, tissue breakdown, and impaired healing. Unlike erythrocytes, which are solid, liquid plasma exits the tissue capillaries through normal capillary leakage. Oxygen that’s dissolved in that plasma is carried along with it and can travel much farther from the capillaries under hyperbaric conditions than oxygen carried on the hemoglobin.[2] The goal of HBO2 therapy is to provide a therapeutic level of oxygen while minimizing the risk of adverse reactions; however, some practitioners disagree about what constitutes a therapeutic level of oxygen.[3] Acute illnesses typically require fewer treatments, and the treatment course is terminated when the disorder resolves or improves to a plateau. For example, patients with carbon monoxide poisoning typically receive one to three treatments over a 24 hour period.[1] More chronic disorders require more lengthy courses of treatment, up to 60 treatments in some cases. Treatments for chronic disorders are typically done once daily with breaks on the weekends. Treatments usually last from 90 to 120 minutes.

INDICATIONS AND BENEFITS

The Undersea and Hyperbaric Medical Society, or UHMS, is a consortium of hyperbaric medicine practitioners and researchers who evaluate hyperbaric and diving medical research and make recommendations for the use of HBO2 therapy based on sound scienti#c evidence. Most hospital based hyperbaric facilities follow the recommendations of the UHMS, which has formally approved these 14 indications for HBO2 therapy: [4]

Besides promoting neovascularization, HBO2 has several other beneficial effects.

In cases of CO poisoning, it’s used to help remove CO from hemoglobin, promote normal oxygen levels, and prevent delayed neurologic sequelae.[1] 

HBO2 also helps to fight infection in several ways. It potentiates the action of certain antibiotics, which increases their e$ectiveness.[5] 

In cases of clostridial gas gangrene, HBO2 blocks the production of tissue-necrosing alpha toxin by the clostridial bacteria, which e$ectively neutralizes the bacteria’s ability to break down tissue.[5]

HBO2 therapy also has anti-inflammatory effects. It helps prevent leukocytes from adhering to the vascular endothelium by interfering with the beta-2 integrin protein, which interrupts
the inflammatory cascade.[6]

The reactive oxygen species, or free radicals, produced during hyperbaric hyperoxia e$ectively scavenge nitric oxide, which is an endogenous vasodilator. Decreased levels of circulating nitric oxide result in net vasoconstriction, which reduces both inflammation and edema.[7] 

CONCLUSION 

There are some off-label indications for hyperbaric therapy. They all have a theoretical basis for treatment, but most have not been scientifically proven to be e$ective. Autism, neurologic injury, fibromyalgia, migraine headaches, sleep disorders,