Hyperbaric oxygen therapy (HBOT) is the medical administration of 100% oxygen at higher than atmospheric pressures. The treatment, which dates back to the 1660s, was popular across Europe in the 19th century but saw a downturn as medicine became more evidence-based. Its use to treat decompression sickness suffered by divers and tunnel workers took off again during the 20th century. Since then, HBOT's effectiveness in treating a number of other conditions has been demonstrated.
At normal atmospheric pressure, oxygen is mainly transported around the body via the oxygen-biding properties of haemoglobin in red blood cells, with very little carried by the blood plasma. At higher pressures, plasma is able to transport more oxygen. The treatment fights infections by creating a hostile environment for bacteria that thrive and cause infection in the absence of oxygen. There is also evidence to suggest HBOT increases the activity of bone marrow stem cells.
Certainly it has been shown to be effective in the treatment of carbon monoxide toxicity, bone and bladder damage caused by radiation, poorly healing wounds, gas gangrene and severe anaemia. Benefits have been suggested for more than 100 conditions including autism, senile dementia and impotence. However, many such claims have rested on small, uncontrolled studies, which may have been susceptible to placebo effects.
These few well-researched paragraphs pertain more to space travelers than to mountain climbers. Regular visitors may have noticed we're saving a spot for acute mountain sickness (AMS) on our running list of diseases and conditions treated with hyperbaric oxygen therapy. Here's the odd case of an approved indication exclusively reserved for mild HBOT. In fact the inflatable bag chamber was invented by mountain climbers, and AMS remains the only FDA-cleared indication for its clinical use.
[Illustration: Brett Ryder, The Guardian]