Hyperbaric therapy (also known as hyperbaric oxygen therapy or HBOT) is the medical use of oxygen at a pressure higher than normal atmospheric pressure.
The oxygen is delivered to the individual in a pressurised chamber in order to increase oxygen absorption in bodily tissue.
Under these conditions, their lungs can gather more oxygen than would be possible breathing pure oxygen at normal air pressure.
Normal atmospheric pressure is described as 1 atmosphere (1 atm). In hyperbaric therapy the air pressure in the chamber is gradually increased to a higher target level, which is usually between 2.0 and 3.0 atm depending on the treatment.
The air in the chamber may contain a mixture of gasses, with the amount of oxygen varying between 21% to 100% oxygen depending on the treatment and on the type of chamber used.
Each treatment session consists of a compression cycle during which the pressure is increased slowly to allow for equilibration of air pressure in the ears and sinuses, followed by a period where air is delivered at the target pressure, followed by a decompression cycle when the pressure is returned to normal.
Some people have suggested that autistic people do not need very high atmospheric pressure. For example, according to Halepeto et al (2014)
"..., improvements have been observed via treatments with 95 - 100% oxygen and hyperbaric pressures of 1.5 - 2.0 atm for some chronic neurological conditions, including autism. Furthermore, improvements in autism have also been observed with the use of hyperbaric pressures of 1.3 atm and oxygen levels of 21 - 24%."
There are various different types of hyperbaric chamber including