The first recorded use of hyperbaric therapy was by a British clergyman named Henshaw in the 1600s. He built a structure called the domicilium that was pressurised and unpressurised with air using bellows.
The French surgeon Fontaine built a pressurized, mobile operating room in 1879 and Orville Cunningham built an entire hospital in 1928 that was 6 stories high and could be pressurised to 3 atmospheres.
Behnke and Shaw used pressurised chambers to treat patients with decompression sickness in the 1930s.
The first published report of the use of HBOT in an autistic individual was in 1994. In this report, treatment with HBOT resulted in improvements in mood and social interactions in a three year old autistic child.