During World War II, a group of scientists performed more than 600 breathing experiments on their own to aid divers and submariners.
In the 1940s, diving became popular but still required bulky suits and large helmets. Anyone who goes underwater for long periods of time needs to be tethered to the boat and receive constant air.
Experts have known about the dangers of decompression sickness for decades. When divers surface too quickly after a deep dive, pressure changes can create nitrogen bubbles in the blood. Accumulated bubbles impede blood circulation, even leading to death in some severe cases.
But this is not the only concern regarding the British Navy’s underwater mobility. In 1939, the submarine Thetis sank during a test dive. Only 4 people escaped, while 99 people were trapped on the ship and died of unknown causes. Thus, the breathing support equipment on board is still not enough to save them.
An engineer investigating the tragedy asked John Burdon Sanderson Haldane, an expert at University College London, to find out what happened. As a child, Haldane participated in the experiments of his father, a physiologist, on decompression sickness and inhaled various gases in his home laboratory.
Scientist John Burdon Sanderson Haldane. Image: Smithsonian
Haldane and a number of colleagues quickly began conducting experiments in a high-pressure chamber, turning themselves into “white mice”. They breathed different levels of CO2 and oxygen to see how their bodies responded to different pressure levels. CO2 will cause them headaches, fatigue, and hyperventilation. Excessive CO2 was killing those aboard Thetis, Haldane realized, and future crews would need a way to absorb the gas.
Pure oxygen can also become toxic, causing violent seizures, vomiting and impaired vision. Researchers also saw flashes of color called “flares.” Haldane injured his back during a seizure, while another researcher suffered a dislocated jaw. Another person even nearly drowned while breathing oxygen while submerged underwater.
Besides, breathing normal air, whose main component is nitrogen, in a high-pressure environment also caused the phenomenon of “nitrogen intoxication” in the research team’s tests.
Finally, the team began mixing oxygen and air to find the ideal mixture that would allow divers and submarine crews to breathe without experiencing side effects such as seizures or loss of vision.
Haldane and his colleagues performed a total of more than 600 experiments themselves. The British Navy relied on their data when equipping X-craft submarines, and supplied a mixture of oxygen and air depending on the depth of each dive.
Documents documenting the work done by Haldane’s group were revealed in 2001, when many of them had passed away. Their dangerous experiments not only aided the D-Day campaign in World War II but also contributed to the scientific foundation for modern scuba diving.