Hyperbaric medicine

Hyperbaric medicine
A Sechrist Monoplace hyperbaric oxygen chamber at the Moose Jaw Union Hospital, Saskatchewan, Canada
Specialty	diving medicine, emergency medicine, neurology, infectious diseases
ICD-9-CM	93.95
MeSH	D006931
OPS-301 code	8-721
MedlinePlus	002375
[edit on Wikidata]

Hyperbaric medicine is a medical treatment in which an increase in barometric pressure over ambient pressure is employed increasing the partial pressures of all gasses present in the compressed air. The immediate effects include reducing the size of gas embolisms and raising the partial pressures of all gasses present according to Henry's law. Currently, there are two types of hyperbaric medicine depending on the gases compressed, hyperbaric air and hyperbaric oxygen.

Hyperbaric air (HBA), consists of compressed room air (79% nitrogen, 21% oxygen, and minor gases) and is FDA-approved for acute mountain sickness. The hyperbaric air environment is created by placing the patient in a portable hyperbaric air chamber and inflating that chamber up to 7.35 psi gauge (1.5 atmospheres absolute) using a foot-operated or electric air pump. Although the mechanisms of hyperbaric air are poorly understood it is thought that it relieves hypoxemia caused by the decreased partial pressure of oxygen resulting from high altitude by increasing the partial pressure of air (including oxygen and nitrogen) simulating a descent in altitude.^{[1] [2] [3]}

Hyperbaric oxygen therapy (HBOT), the medical use of greater than 99% oxygen at an ambient pressure higher than atmospheric pressure, and therapeutic recompression for decompression illness, intended to reduce the injurious effects of systemic gas bubbles by physically reducing their size and providing improved conditions for elimination of bubbles and excess dissolved gas.

The equipment required for hyperbaric oxygen treatment consists of a Pressure vessel for human occupancy, which may be of rigid or flexible construction, and a means of a controlled atmosphere. Operation is performed to a predetermined schedule by trained personnel who monitor the patient and may adjust the schedule as required. HBOT found early use in the treatment of decompression sickness, and has also shown great effectiveness in treating conditions such as gas gangrene and carbon monoxide poisoning. More recent research has examined the possibility that it may also have value for other conditions such as cerebral palsy and multiple sclerosis, but no significant evidence has been found.

A Pressure vessel for human occupancy (PVHO) is an enclosure that is intended to be occupied by one or more persons at a pressure which differs from ambient by at least 2 pounds per square inch (0.14 bar). All chambers made for hyperbaric medicine fall under the jurisdiction of the Federal Food and Drug Agency (FDA). The FDA requires hyperbaric chambers to comply with the American Society of Mechanical Engineers PVHO Codes^[4] and the National Fire Protection Association Standard 99, Health Care Facilities Code. ^[5]

Hyperbaric medicine poses some inherent hazards that are mitigated by FDA-compliant equipment and trained personnel. Serious injury can occur at pressures as low as 2 psig (13.8 kPa) if a person in the PVHO is rapidly decompressed.^[6][7] If oxygen is used in the hyperbaric therapy, this can increase the fire hazard. This is why the FDA requires hyperbaric chambers to meet ASME PVHO and NFPA 99 standards. All chambers that meet FDA standards must have an ASME data plate, and people seeking hyperbaric treatment should check to ensure the equipment and facilities are to proper standards.

Therapeutic recompression is usually also provided in a hyperbaric chamber. It is the definitive treatment for decompression sickness and may also be used to treat arterial gas embolism caused by pulmonary barotrauma of ascent. In emergencies divers may sometimes be treated by in-water recompression (when a chamber is not available) if suitable diving equipment (to reasonably secure the airway) is available.

A number of hyperbaric treatment schedules have been published over the years for both therapeutic recompression and hyperbaric oxygen therapy for other conditions.