Inside a hyperbaric oxygen chamber a medical technician helps a male patient with an individual oxygen mask. The chamber is used to treat various conditions including decompression illness, more commonly known by divers as the bend, carbon monoxide poisoning and smoke inhalation. Hyperbaric medicine, also known as hyperbaric oxygen therapy (HBOT), uses oxygen at a higher than atmospheric pressure. Photographed at St John and St Elizabeth Hospital, London, UK.