British Gas has renewed the subject of dive data recording with interested groups within the offshore industry and believe that it is possible to improve on current techniques and systems Surface supplied diving began about 1800 with the development of air pumps During the next 100 years or so, an incredible amount of useful work was accomplished underwater by thousands of divers who often were completely without the slightest understanding of the physiological laws they were daily transgressing.
It was generally known that some divers, after ascending, were afflicted with excruciating pains, paralysis and often death, but the cause was ascribed to bad air, weak constitutions or a variety of superstitious beliefs Some Greek divers ate honey by the bucket as a preventative against decompression sickness, and treatments for it ranged from hot baths to cold packs with liberal use of analgesics and morphine. Many men survived years of diving without crippling effects, and even today, we occasionally encounter divers who consistently Ignore the tables and seem to survive.
Boyle observed that bubbles would form in the blood and tissues of test animals after reduction of atmospheric pressure as early as 1670 In 1857, Bucquoy proposed the bubble theory as the principal cause of caisson disease or diver's palsy, and he suggested that the probable prevention of this illness was slow decompression. In 1869 a recommended decompression rate was one minute per metre of depth In 1875, the first recompression chamber was built to treat caisson workers on the Brooklyn Bridge project In 1878, the first compression and decompression schedules were published for caisson workers. These schedules specified a period of 25 minutes to compress a worker to three atmospheres pressure over surface, a work shift of four hours, followed by a decompression time of 40 minutes, with the pressure reduced at a uniform rate
To control the dissolving of the gas in the divers' blood stream, it became necessary to evolve decompression parameters and tables Decompression is the controlled procedure by which ambient pressure is lowered to atmospheric pressure. It must be carried out so that the additional gas dissolved in the diver's body during the period when gas has been breathed at pressure can leave the body tissues without giving rise to decompression sickness Decompression may be carried out in the water, in a surface compression chamber, in a diving bell or in a combination of them in every case, the decompression method will be influenced by the breathing mixture, the depth and the duration of the dive.
Decompression must be carried out according to an accepted method and recognised decompression tables must be used. The instructions relating to the table being used must be rigidly adhered to, unless the diver is injured or ill and the diving supervisor considers treatment for his condition is more Important than the risk of decompression sickness.
In order to carry out decompression safely, the divers maximum depth of dive and his depth at each stage of the decompression procedure and the period of tune spent at each must be known accurately Decompression stops must be carried out with the diver at rest.
