During World War II, a group of scientists conducted over 600 breathing experiments on themselves to assist divers and submariners. Diving in the 1940s was popular but required bulky suits and large helmets, with divers needing to be tethered to the boat and supplied with constant air to stay underwater for extended periods of time.
Decompression sickness, also known as the bends, has been a concern for experts for many years. When divers surface too quickly after a deep dive, pressure changes can lead to nitrogen bubbles forming in the blood, impeding circulation and potentially causing death. The dangers of decompression sickness were realized after the sinking of the submarine Thetis in 1939, where 99 people lost their lives due to unknown causes.
In response to this tragedy, engineer John Burdon Sanderson Haldane, along with colleagues, conducted experiments in a high-pressure chamber to investigate the effects of different gas mixtures on the human body. The team transformed themselves into “white mice” by breathing various levels of carbon dioxide and oxygen at different pressures, leading to discoveries about the effects of these gases on the body.
Their experiments uncovered the dangers of excessive carbon dioxide and oxygen, which could lead to seizures, vomiting, impaired vision, and other serious side effects. By mixing oxygen and air in different ratios, Haldane and his team aimed to find an ideal breathing mixture for divers that would minimize these risks and enhance underwater mobility.
Over the course of more than 600 experiments, the British Navy relied on the data collected by Haldane and his team to equip X-craft submarines with the necessary breathing support systems. These experiments, although risky, not only helped during the D-Day campaign in World War II but also laid the groundwork for modern scuba diving techniques and equipment.