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Under Pressure:The Science of "The Bends", Three Centuries in the Making



When Sir Robert Boyle stuck a bird inside an air pump, it was one of a vast number of experiments he was conducting at the time. The bird suffocated quickly and Boyle continued his experiments, testing a viper in an air pump next. That time he observed a bubble form in the viper’s eye. He also noted that the viper seemed agitated. The year was 1670: no one had ever spoken of “decompression sickness” before, let alone observed it

in humans. That was what he had observed, though. He had set science and medicine off on a centuries-long dive into this strange and deadly condition.



In 1873, Dr. Andrew Smith was in charge of medical services for construction workers at the Brooklyn Bridge. The workers toiled for long hours inside pressurized chambers. To describe the effect the work had on some of the workers’ physical condition, Dr. Smith used the term “compressed air illness.” At the worksites, there was another term that had become prominent- “the bends.” This was a reference to “the Grecian Bend,” a pose that models of the era had taken to striking for paintings and portraits, itself a reference to similarly posed statues from Ancient Greece. Workers afflicted with the sickness would lurch forward in a manner reminiscent of the posture adopted by the models. While the Grecian Bend’s popularity faded, the term “the bends” remained in wide use.

It was in New York, two decades later, that Ernest William Moir engineered the first airlock chamber, in order to treat the bends-stricken workers at the Hudson River Tunnel. Dying at a rate of approximately one-in-four, the workers were eager to undergo Moir’s experimental recompression treatment. There were deep flaws in his recompression methods, but it was the only solution available at the time. More importantly, Moir had demonstrated that a solution was possible, thus setting the standard that would motivate other engineers in the 20th century.


John Scott Haldane, of Scotland, was the next pioneer. In 1907, he presented to the Royal Navy a chart for determining appropriate decompression rates. Captain Albert Behnke, a US Navy doctor, then contributed to the science in 1932 by describing the differences between decompression sickness and embolisms in the arteries, concluding that recompression should include oxygen treatment.

Next came a revolutionary extension of the work that Haldane and Behnke had done: Swiss physician Albert Bühlmann, collaborating with deep-diving progenitor Hannes Keller, looked further into the combinations of gases that would benefit divers most at extreme pressures. They began their work in 1959, and three years later, Keller set a deep-diving record, plunging a thousand feet into the Pacific. A group of Swiss divers went to 5,400 feet a few years later, two of the eight developing decompression sickness, and Bühlmann tweaked his gas-combination recommendations once again. These tweaks were groundbreaking in that there was no longer decompression sickness at a depth of more than 11,000 feet.

Albert Bühlmann, thanks to joint funding by the US Navy, Royal Dutch Shell, and the Swiss government, published his magnum opus in 1983: Decompression-Decompression Sickness, a comprehensive guide to decompression algorithms. Today, according to researchers at the University of Nebraska and Central Michigan University, there are fewer than three cases of decompression sickness for every 10,000 dives. From Boyle to Bühlmann, diving enthusiasts the world over can rejoice, the science has come a very long way.







All source photos and illustrations used in this article are made available via public domain.