Back in 1670, when few people ever dreamed that anyone would spend extended periods of time underwater for work – let alone for pleasure! – Robert Boyle built a compression chamber in order to study the effects of increased air pressure on animals.
Although Boyle registered the fact that he’d observed a bubble of nitrogen in the eye of a de-compressed snake – and lent his name to a Law of Physics understood by everyone (?) who dives – it was to be two hundred years before another scientist, Paul Bert, explained the bubble’s significance and it’s relevance to caisson workers and divers.
An air-bath cures all
As a device ahead of its time there was seemingly little practical application for Boyle’s compressed-air chamber – until a contemporary with a flair for business built a pressure chamber of his own, called it an ‘air-bath’, and began selling treatments as a cure-all for whatever ailed people.
The idea rapidly took off. All around Europe, fashionable doctors built large air tanks, some capable of seating seventy or more patients at a time. No matter what the ailment – tuberculosis, asthma, chest deformities, eczema, small-pox and even snake-bites – ‘air-baths’ held promise of a cure.
So popular did the air-baths prove that, by the middle part of the 19th century -when their use in the USA and Canada had become widespread – there were insufficient numbers of licensed physicians to handle patient demand. Lay-people took over the administration of treatments and the claims as to the curative benefits of an ‘air-bath’ escalated to include hypochondria and hysteria!
Early DCS antidotes
Meanwhile, thanks to the extensive use of Siebe’s patented diving helmet and closed flexible dress, diving had progressed in leaps and bounds. Now able to perform meaningful work for long periods of time at hitherto undreamed of depths, divers – and caisson workers – exposed to higher than normal air pressures began to be afflicted by a strange malady; one that could cause crippling injury or death.
Lacking a scientific explanation for its causes, divers devised their own antidotes. These included chewing tobacco and even hot baths.
(With the exception of one far-sighted doctor who, in 1873, saved the life of a caisson-worker employed on the Brooklyn Bridge project by recompressing him in a chamber, nobody apparently considered the use of ‘air-baths’ in treating victims of the little understood, ‘Caisson’s-Disease’)
Prominent among the small handful of scientists researching its causes, Paul Bert became the first person to provide an explanation of the illness. Originally studying the effects of decreased air pressures on balloonists and mountain climbers, he turned his attention to the other extreme of pressure, that encountered by divers.
First published in 1878, his masterwork, ‘La Pression Barometrique’, determined that the excess pressure of nitrogen breathed by divers was the cause of the sickness. He offered two solutions to the problem.
The first was to raise the diver very slowly so that excess nitrogen would gradually be passed out of the body: The second, should symptoms later present themselves on the surface, was to immediately ‘recompress’ the victim back to the depth at which they had been working in a compressed-air chamber. The victim would then be slowly ‘decompressed’ at the rate of 20-minutes of decompression for each atmosphere of pressure.
Now recognised as being integral to diving safety and vital to the work of later scientists – like Haldane, who refined Bert’s original work and devised the first practical decompression tables – the recompression chamber is once again finding favour with the broader medical community who again regard hyperbaric medicine as providing solutions to a variety of non-diving related ailments.