A Portable Chamber and DCS
by E.R. Cross
A Technifacts reader recently wrote asking What can Technifacts tell me about a German designed, portable, telescopic decompression chamber? The only telescopic chambers I know of were the small, lightweight units made by the German Draegerworks. These were in use at least as early as the 1940s. Their major advantages were their small size and light weight. The small internal volume was also an advantage because of the small amount of air required to reach and maintain working (treatment) pressure. The principal disadvantage was their low maximum safe operating pressure. The compact size was also a definite disadvantage to the patient because even a minimum treatment schedule meant a long time in a tiny chamber.
The chamber was in five sections that telescoped into one end for storage. Control gauges, valves and hose fittings were on an outer panel. The chamber was designed to be pressurized with compressed air. However, it was also rigged so the patient could breathe oxygen during treatment. Two threaded rods extended down each side. They were placed in fittings having threaded ends. When the chamber was extended and the rods turned in the proper direction, they forced the segments of the chamber to fit more snugly to better contain initial internal air pressure. After pressure was applied, sections of the chamber remained quite rigid.
Early Dive Training
For nearly 50 years Skin Diver Magazine has provided answers to questions about diving from thousands of readers. Written accounts had suggested, and sometimes dictated, changes in several aspects of diving. Of equal importance were the questions and suggestions about what was needed to enhance future enjoyment and improve safety.
Fifty years ago we were called skin divers. Immediately after WW II there were few organized training programs for civilian divers. Few technical personnel and limited information were available. There were few diving physiologists or medical professionals. For the first decade of that era, diving sciences and skills were taught by selected members of the many diving clubs then being formed.
Two safety standards evolved in these early days; buddy diving and certification. Club members could not dive alone. New club members could not use any type of diving apparatus until they were certified for its use by the club instructor. These early classes saved the lives of many novice divers.
Skin Diver Magazine (SDM) came into being in that era of scarce information. Almost immediately after its inception, SDM recognized the need to publish answers to the numerous questions regularly received from readers. Several informative columns were developed by writers experienced in various aspects of diving. Some of these were discontinued after a few years as their subjects became standard training. Other columns continued to cover different areas of expertise and a few continue to the present.
During the first decade, the greatest number of questions directed to Technifacts were related to spearfishing and diving as a hunter-gatherer sport. As spearfishing became less popular, an interest emerged in medical and physiological problems. Predominantly, the use of scuba triggered a need to know more about decompression and decompression sickness (the bends) and related treatment tables. During the past two decades, environmental problems, marine life and diving equipment related questions also became important.
Diving was originally simple excursions into the parts of our planet covered by water. We must accept that, to some extent, diving will disturb the complex interactions of the Earths principal components. The more complex the dive, the greater amount of diving and support equipment, the greater the impact on these components.
About Planet Earth
It is the third planet from the sun. It is a nonluminous, predominately water covered, rocky, celestial globe.
The hydrosphere is the 1,400 million cubic kilometers of water (including 24 million cubic kilometers of ice) that is the main component of the Earths surface area. Next in abundance is the lithosphere, the surface outer shell of rock. It consists mainly of continental crust and sediment covered oceanic crust. A small amount of igneous rock also exists. The next most abundant constituent is the atmosphere; the surrounding layer of gases that supports most life on earth, including;indirectly;life in the hydrosphere.
Since the earliest beginnings, thousands of forms of life have formed on planet Earth. They have evolved to inhabit the hydrosphere, the lithosphere and a few will be found floating in the air or in ice. They have become a fourth large and rapidly expanding component that forms a complex interaction with all other elements. The net result of the overexpansion has been to produce serious pollution in many sensitive areas.
A study of our rock will indicate that its main constituents have remained fairly stable for billions of years. Fundamentally, they are not renewable resources. They have all been recycled many times. The hydrosphere is (mostly) made up of the same water the dinosaurs sloshed around in millions of years ago. In spite of the action of many earthquakes and volcanoes, the lithosphere is also not a renewable resource. Finally, the total volume of the atmosphere on Earth has remained mostly unchanged. The one component that has changed drastically is the number and kinds of life. The total number of life forms has multiplied. All life forms, but particularly mammals, are inherent polluters. The mammal we call man may be the worst polluter of the lot.
Decompression Sickness;the Ultimate Cause
One cause of the bends is inadequate decompression for the depth and time of the dive. However, there are several factors that may contribute to the decompression being inadequate. These may be related to the dive itself or they may be physiological. The most likely dive related factors are errors in determining maximum depth or in actual dive (bottom) time. Too rapid an ascent and improper depth or time at decompression stops may be factors. Inadequate thermal protection may also contribute to the bends. Physiological aspects may include physical condition of the diver (such as overweight), extreme exertion during dive tasks and possibly stress during the dive. Severe stress may develop owing to environmental factors such as marine conditions.
In relation to the total number of divers, it seems to me the frequency of bends in recreational divers is decreasing. This is probably the result of the expanded and improved training available. Keep in mind that a dive is but a fragment of your life. It is only a moment between two seemingly long periods of time; the past and the future. A safe dive will be influenced by all a diver has previously learned and experienced. It might also influence his or her life that follows. Everybody should go diving very carefully.
What would you like to see illustrated or discussed in Technifacts? Is there a special piece of diving equipment (past, present or future) about which you would like to know more? Or an individual who has been important in diving (past or present) you would like to know better? Marine life you have seen that puzzles you? Send us a photo of the marine life and we will try to identify it. What marine life or environmental conditions are likely to be or likely to become hazardous? Technifacts readers with questions, suggestions or comments about any diving or diving related subjects should write to E.R. Cross, c/o Technifacts, Skin Diver Magazine, 6420 Wilshire Boulevard, Los Angeles, CA 90048-5515. Your thoughts can make a difference.