permeates insulating material in the diver's dress. Development 

 is proceeding with electrically heated underwear worn beneath a 

 conventional wet suit. Another approach is to improve the insulat- 

 ing qualities of the suit material. Developments thus far^ such as 

 filling the voids of the suit material with microspheres, have re- 

 stricted diver mobility. Other deficiency areas are communica- 

 tionsj visibility, tools, gas monitoring and control, and diver 

 transport and navigation. Extensive development is necessary in 

 these areas before divers can perform useful work at pressures up 

 to limits imposed by physiological considerations. 



Bio-Medical Development 



Coincident with diver equipment development must be bio- 

 medical research to determine the physiological and psychological 

 aspects of working in an environment of high pressure, cold, and 

 darkness. Advances are required in treatment of decompression 

 sickness, determination of optimum gas mixtures, toxicological 

 and microbiological control, and hyperbaric medical treatment. 

 In addition, the physiological aspects of audio- visual aids, thermal 

 protection, and communication must be fully understood and made 

 available to designers of diver equipment. 



Man's physiologic depth limitations have not yet been deter- 

 mined. During a recent experiment at Duke University, divers 

 completed a very successful simulated dive in a pressure chamber 

 where they stayed at a pressure equivalent to 1000 feet of water 

 for 78 hours. Projections of man's eventual depth capability 

 breathing mixed gases range from about 1, 500 feet to as high as 

 3, 000 feet. Hydrogen, and other inert gases, are being evaluated 

 as a replacement gas for helium at depths beyond the limit im- 

 posed by helium narcosis. For extreme depths, perhaps as great 

 as 12, 000 feet, liquid breathing is a promising development. Ex- 

 periments with animals have proved that mammals can live under 

 pressure equivalent to several thousand feet of water while breath- 

 ing an isotonic saline solution which has been charged with dis- 

 solved oxygen. The critical unresolved limitation in breathing an 

 oxygenated liquid is elimination of carbon dioxide. The removal 

 of carbon dioxide from the lungs by liquid breathing would require 

 a greater respiratory rate than that required by air breathing; but 

 since water is about 40 times more viscous than air, the lungs 

 can only exchange water at about 2. 5% of the rate at which air can 

 be exchanged. Until this problem can be solved, the idea of divers 

 working beyond the continental margin is rather fanciful. Principal 



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