- Describe the historical event that led to the use of the acronym SCUBA to describe diving.
Caisson's Disease and "The Bends"
In the mid-1800s, the first fully enclosed, waterproof diving rig was developed and a new industry in Great Britain called salvage diving was born. As these salvage divers extended their bottom times, more and more cases of what was erroneously called “rheumatism” were reported. Since this type of diving was relatively new, divers’ physiological problems could only be related to surface maladies. Medical science had no understanding of the effects of water pressure on the human body.
The problem became greater when pumps were designed to maintain air pressure underwater in relatively large spaces. Large, dry chambers called caissons allowed divers to build bridge footings and tunnels underwater.
Workers entered caissons from the surface through air locks, but after extended periods at depth, they showed severe physiological disorders upon surfacing, and many died. This pressure malady was called Caisson's disease, or “the bends” due to the contorted posture the disorder causes in its victims. In the late 1870s, French physiologist Paul Bert studied the effects of gradual decompression and his findings led to the development of the decompression chamber.
In response to the Royal Navy’s Deep Diving Committee request to investigate the possible causes of the bends, British physiologist J.S. Haldane composed a set of diving tables based on stage decompression. The tables were based on the amount of time a diver spent at a certain depth. The greater the depth and the longer the bottom time, the more slowly the diver would have to ascend to remain free of the bends.
Jacques Cousteau and the SCUBA
In 1943, Jacques Cousteau, a young French naval officer, and his partner, Emile Gagnan, developed the demand regulator. The demand regulator enabled a diver to breathe air at the proper pressure for his depth and in the amount that he needed. For the first time, a diver could descend into the undersea world with a complete, independent life support system. This innovation, along with high-pressure compressors and cylinders, was called Self-Contained Underwater Breathing Apparatus, or SCUBA.
In the mid-1900s, primitive, consumer-targeted SCUBA systems appeared on the market, but diving instruction for the recreational diver was non-existent. This was SCUBA’s “Wild West” period when most sport divers were very fit individuals whose strength and sheer determination made up for their SCUBA systems’ lack of safety. The risk of physical injury and even death was viewed as part of the challenge and excitement of SCUBA diving.
Around 1955, the lack of an air gauge was the most significant hazard to SCUBA divers. When their air supply was depleted, divers were forced to ascend rapidly to the surface. Also, the regulators of this era developed greater breathing resistance as depth increased or as cylinder pressure decreased.
- Explain why the pressure on an object increases as it descends underwater and give examples of the effects of this increasing pressure.
Effects of Pressure on the Surface and Underwater
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