When we think of those who have contributed to the evolution of diving, Jacques Cousteau stands head and shoulders above the rest. Cousteau was, of course, a larger-than-life figure. Yet many other relatively unknown men and women had a significant and lasting impact on diving. One such person is John Scott Haldane.
John Scott Haldane
John Scott Haldane was born in Edinburgh, Scotland in 1860. He grew up in the affluent new town, and was an inquisitive child. Excellence at school earned him entrance into both the University of Edinburgh and Friedrich Shiller University in Jena, Germany. Haldane eventually followed in his uncle’s footsteps and studied medicine, graduating from Edinburgh University medical school in 1884.
As a physiologist he was interested in respiration, specifically the effects of poisonous gases on respiration. He studied the effects of toxic gases on miners. He also helped develop methods to deal with gas attacks in World War I trenches. Haldane also delved into the effects of breathing at high altitude. His contributions in all of these areas are considered ground-breaking. But his experiments into the effects of breathing gases under pressure created a legacy for divers.
Increasing Diving Safety
In 1907, the Royal Navy tasked him to investigate how to increase diving safety. Many hard-hat navy divers of the time suffered from Decompression Sickness (DCS) as a result of their work underwater. Haldane applied the scientific method to the problem. This meant formulating a theory about how to reduce the likelihood of producing DCS, and then testing through experiment. He accomplished this by building a decompression chamber to subject animals and humans to increased atmospheric pressures for varying amounts of time. He then reduced the pressure — sometimes slowly, sometimes quickly — and observed the subjects for any signs of DCS.
What’s fantastic/interesting/scary about Haldane’s work is that he wasn’t afraid to experiment on himself or his family members, including his wife and son. His animal of choice to put in the decompression chamber was a goat as, although pigs have the most similar tissue characteristics to humans, goats were in more plentiful supply and their body-mass to cardiac-output ratio is similar to a lean man.
French physiologist Paul Bert had already discovered that nitrogen coming out of solution in bodily tissues caused decompression sickness. Haldane was trying to determine how divers could sufficiently reduce or prevent this phenomenon during a dive. He realized that different body tissues retain and release nitrogen at different rates. So he developed tables that modeled five theoretical tissue compartments that would become saturated with gas at different rates.
By setting maximum dive times for different depths, the tables allowed a diver to reduce the likelihood that symptomatic bubbles would form in any of those tissues during a dive. John Scott Haldane surmised that a diver could stay indefinitely at 32 feet (10 m) and ascend without any ill effects. Although this has since been revised, it was pretty insightful at the time. He also recommended a maximum ascent rate of 29 feet (9 m) per minute, which is commonly accepted to this day.
There are numerous stories of his experimental exploits. For instance, he didn’t just use a decompression chamber, he also conducted real dives from a ship off the coast of Scotland, the HMS Spanker. He conducted one such dive himself, donning a diver’s helmet and suit weighing 155 pounds (70 kg). Maybe he was so preoccupied with the weight of all that equipment that he forgot he’d never learned how to swim. On another occasion, he sent his 13-year-old son, J.B.S. Haldane, overboard to prove that the tables worked on untrained people. The suit was so big on him that it flooded, which meant he spent 30 minutes at the bottom of the ocean off the coast of Scotland. On surfacing, the crew warmed him back up with blankets and whiskey.
When the Royal Navy published tables in 1908, cases of DCS fell drastically among Navy divers. The tables also became the foundation for subsequent decompression research. It’s hard to overstate the tables’ importance. Jacques Cousteau used dive tables that were heavily influenced by Haldane’s tables. The No-Decompression Limit (NDL) on your computer is a more complicated and advanced version of them as well. In essence, John Scott Haldane’s work paved the way for all of us to go diving, so offer up a silent thanks next time you dip beneath the waves.