Perhaps the first recorded diver, who was not a free diver, was Alexander the Great. He was said to have been lowered in to the Bosporus strait in a glass barrel in 320BC. Not much had improved by 1620, when Drebbel developed a diving bell which must have been severely limited as air was only replenished at one atmosphere. It was Henshaw, an English clergyman, who possibly constructed the first pressurized chamber for people on land in 1662. He called it the ‘domicilium’ and it was large enough to contain a piano and smoking room. Clearly this was before current theories on sound waves and bombs. At the very least, the denser air at pressure have altered the pitch and made the pipes burn much quicker! Sir Edmund Halley, of comet fame, probably developed the first useful diving bell, in which people remained underwater in the Thames for an hour and a half in 1691. Barrels of air were brought down to them which would have flushed out the carbon dioxide and replenished the oxygen. Perhaps also the first open circuit! The earliest recorded attempt at protecting a diver in rigid armour was made by John Lethbridge of Devonshire, England in 1715. The oak suit had a viewing port and holes for the diver’s arms and water was kept out of the suit by means of greased leather cuffs. The device was reported to have made many working dives to 60ft/18m. In 1774 Freminet, a French Scientist, reached a depth of 50ft and stayed there for an hour, using a helmet with compressed air pumped through a pipe from the surface.
Pressure vessel technology really only developed in the early to mid-1800s with the construction of bridges and tunnels. Triger developed open caissons in France, but water leak was a major problem and in 1830 Admiral Lord Thomas Cochrane patented the technique of using compressed air to exclude water. This technique was successful but was soon followed by reports of decompression illness in the workers. In 1854, Pol and Watelle reported that relief was obtained by workers who went back into the tunnels and Paul Bert showed that bubbles in the tissues during decompression consisted mainly of nitrogen in 1871. But it was only after the building of the New York tunnels under the Hudson and East rivers in 1889 and 1893 that the benefits were fully established. Early chambers at tunnelling sites were nothing more than boilers mounted horizontally with an airtight door at one end.
While Scheele discovered oxygen first in 1772, Priestly published first in 1775 and Lavoisier correctly described combustion in 1775. For hyperbaric oxygen, it was Drager in Germany who first realised the potential benefits of oxygen under pressure and devised a system for the treatment of decompression illness in 1917, but it was Benke and Shaw who first finally used hyperbaric oxygen to treat decompression illness in 1937. Official regulation and standards for hyperbaric oxygen therapy came together with The Undersea Medical Society, which was formed in the United States in 1967, and added, hyperbaric to its name in 1986. Diving chambers are now used for more than just recompression and there is a whole speciality called hyperbaric medicine. The Undersea and Hyperbaric Medicine Society publishes a complete list of indications for hyperbaric oxygen at http://membership.uhms.org/?page=indications
Question 1: Why is decompression illness also known as the Bends?
In the USA, the ‘Grecian bend’ was part of popular fashion at the time of building the Brooklyn Bridge, having been introduced into America as a dance move in the mid-1850s. This replicated the position adopted by the workers, presumably with severe girdle pain decompression illness and probably gave ‘the bends’ its name. One can imagine that the association with female attire provoked much joking amongst the men and contributed to the long history of divers making light of the pains of decompression illness.
Question 2: What does the word hyperbaric mean?
Hyper- comes from the Greek word ‘hyper’, meaning over or above and -baric refers to pressure, as in barometer and has its origin in the Greek word ‘baros’, meaning weight. In current scientific language, hyperbaric is an adjective used to describe an environment that is at pressure greater than atmospheric.
Question 3: What is the Paul Bert effect?
Central nervous system oxygen toxicity was first described by Paul Bert and is sometimes referred to as the “Paul Bert effect”. He showed that oxygen was toxic to insects, arachnids, myriapods, molluscs, earthworms, fungi, germinating seeds, birds, and other animals. In humans this occurs as result of breathing increased partial pressures of oxygen and is the reason for limiting pO2 to 1.4 bar while diving. There is an initial syndrome of anxiety, twitching and nausea which develops into seizures which can easily be fatal underwater.
Question 4: What type of chambers exist today?
Hyperbaric chambers are classified into monoplace and multiplace chambers. Monoplace chambers are generally pressurised with oxygen and take one, or occasionally 2 people. There is therefore no need to where a mask, but the oxygen requirements are high as there is continuous flushing of the chamber. Multiplace chambers are more appropriate for emergencies as there is more room and allows for a chamber attendant and better monitoring. These chambers are pressurised with air and therefore require the patient to wear a mask or hood to breath oxygen at the correct pressure. Other features of multiplace chambers include size, entrance locks, and medical locks.
Question 5: Why did the British Navy use goats to research diving tables?
Haldane and the British Navy produced the first theory and set of tables determining ‘safe’ decompression schedules in 1906. While these contained fundamental flaws, the rates of decompression illness were reduced. It is said that goats were used instead of divers in the research because they are of similar size to humans, stamp their feet when in pain from decompression illness and have useful handles (horns) for getting them in and out of chambers. The unfortunate flock of goats was only been disbanded in Portsmouth about 20 yrs. ago, citing huge vets bills. No wonder!