Dive boards were built from a process of decompression sickness, which became a major problem in the bridge construction and mining industries. Construction workers suffered from Bends disease or decompression sickness if they rose quickly after working under pressure for a long time.
The first person to sense decompression problems was the French engineer Triger, as a result of accidents that occurred among workers working on pneumatic bridge foundation caissons, but he was unable to solve the problem. It would be another compatriot of his, the physiologist Paul Bert (French) in the 19th century, who discovered that the problems that plagued those men were due to the accumulation of nitrogen in the blood, which was released in the form of bubbles, and that it was the cause of the feared embolisms. He published the results of his research in a book titled: Barometric Pressure, in which he laid the foundations for the future decompression technique; Paul Bert recommended slow decompression to prevent the symptoms of Caisson's Disease (decompression), although he was unable to obtain quantitative values.
Haldane's contributions:
The early death of Paul Bert left his work incomplete, until ten years later the Scottish-born researcher John Scott Haldane (1860-1936), interested in the problems of poisoning of miners by CO2 and carbon dioxide, began to deal with the effects of nitrogen on the human organism.
Starting from the work of Paul Bert, he put all his interest in reaching a solution to the problem. Between 1906 and 1908, John Scott Haldane carried out experiments with 85 goats from which he obtained some of the following conclusions: -The symptoms began to occur when the difference in ambient pressure was half, for example for 4 atm (30 meters), at from 2 atm, or less. -The symptoms seen in the goats were problems in the joints of the legs, they limped even without having weight.
With the result of his investigations and the experiences obtained with the British Navy divers, he came to conclusions such as that the divers who had not exceeded 12 meters. deep, even having spent a long time submerged, they did not present symptoms of embolism. As a result of this and other observations, Haldane came to conclusions in which he tried to get the diver to release all of his N2 before reaching the surface.
The principle from which Haldane started to calculate his tables was based on a biophysical model adopted by him in which he considered the difference in time to reach total saturation of the different tissues of the organism, taking into account that the solubility The nitrogen in fatty tissues is approximately five times higher due to their blood supply, which is why both the saturation and desaturation processes are slower. While in those whose blood flow is more intense, the process is faster.
For this reason he called the former << and the latter >>. Based on this principle he devised five type fabrics that applied a certain saturation time. He carried out different tests with times and pressures, observing how it occurred and how the release of the bubbles was carried out, thus managing to establish tabulated values that, although they did not reach the current safety percentages, gave very satisfactory results. . Haldane considered that the absorption and elimination of nitrogen was an exponential process.
A progressive absorption.
While diving the body absorbs nitrogen, which dissolves in the tissues following Henry's Law (the higher the pressure, the greater the amount of gas molecules that dissolve in the liquid).
As this nitrogen ascends, it must be gradually eliminated through respiration without causing illness (nitrogen forms microbubbles that are not harmful to the body). It was determined that if the pressure ratio was 2:1, the gas was eliminated without generating bubbles.
The human body was considered to be made up of different tissues with different saturation/elimination times. In this way, the mathematical models used to create tables emerged. Years later, in 1937, scientists from the U.S. NAVY (USN) North American Navy modified Haldane's tables.
They were the first experimental tables that also did not contemplate successive dives, since the purpose and development was intended only for divers who went down to a certain depth, carried out their work or mission, and later returned to the surface. The U.S. NAVY would study how to build them, since they needed them for the military and professional work they carried out, and logically they wanted to do them with the greatest safety.
They adapted the boards to the classic divers of that time, using them up to 90 meters. (10 atm.), using for the calculation of average time fabrics similar to those used by Haldane, extended to 80 and 120 minutes, although they erred on the side of caution by limiting the ascent speed to 7.5 meters/min. The subsequent evolution of diving and the invention of the aqualung forced us to reconsider these works, as a result of which, in 1958 the tables were revised, and they considered successive dives. These tables included stops of 3 meters at a time, with an ascent speed that was increased to 18 meters/min.
These tables were translated into the decimal metric system by the G.E.R.S. French; Later, the Italian professor Gaspare Aldano would improve them, although his studies were aimed at deep diving. Another Frenchman, Commander Alinat, improved these works, incorporating for the first time in the tables, the box in which he entered the nitrogen saturation coefficient for successive dives.
Nowadays, the demands of diving at great depths and for those cases of extreme exposure dives have forced part-time fabrics of up to 1000 minutes to be considered for the calculation of these tables. Currently, the G.E.R.S. tables are used. and the North American Navy, the latter much more complete, which are those adopted by our Military Navy and by some diving organizations.
Based on the result and obtaining more or less reliable tables for diving, based as previously explained on the absorption of nitrogen in the tissues, some Italian engineers called De Sanctis and Alinaris, invented an ingenious device, the decompression meter, which came to solve and simplify the problems inherent to decompression calculations.
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