The
Admiralty Committee needed to frame definite rules for safe decompression in the shortest possible time for
deep diving, and hence, Haldane was commissioned in 1905 by the UK
Royal Navy for this purpose, to design
decompression tables for divers ascending from deep water. In 1907 Haldane made a
decompression chamber to help make deep-sea divers safer and produced the first decompression tables after extensive experiments with animals. In 1908 Haldane published the first recognized decompression table for the British Admiralty. His tables remained in use by the Royal Navy till 1955. "The Prevention of Compressed Air Illness" was published in 1908 by Haldane, Boycott and Damant recommending
staged decompression. • Experiments continued on goats, and symptoms observed on goats were noted each time on appropriated schedule to record the presence of symptoms not the presence of bubbles: :* Bends, the commonest symptom. The limb, most commonly the fore-leg. :* Temporary paralysis, symptom to general deficiency of oxygen :* Pain, continuous bleating :* Permanent paralysis, usually immediately after decompression :* Illness, impossible to identify any local symptoms, sometimes blind :* Dyspnoea and death :* Mechanical symptoms are not important, if goat suffered ear troubles during compression • Experiments on goats included: :* staged decompression on different pressures, and different decompression times, and included also comparison with uniform decompression. Results showed that a certain minimum pressure is required to give symptoms on goats and that duration of exposure to high pressures with different decompression times had also an influence. :* Experiments compared between different types of animals and their susceptibility to decompression symptoms, and compared influence of size between short and long exposures, and decompression time. :* Experiments on blood mass and volume of goats showed apparently no relation to susceptibility. :* Pathological observations on them post-mortem appearances of goats after decompression, showed practical importance in connection with the size of bubbles found in blood. Pathological changes underlying the chief symptoms were sufficiently noticed, except for bends. The exact cause of bends was not known.
Main results of Haldane’s work This work is published in "The Prevention of Compressed-air Illness" book. Results are published in same book under "Summary" in pages 424 and 425. The main conclusions of his decompression model are: • In page 354, Haldane concluded: "It is clear that the rate of desaturation might be hastened by either (1) increasing the difference in nitrogen pressure between the venous blood and the air in the lungs, or (2) increasing the rate of blood circulation". So, in order to achieve faster desaturation, Haldane concluded that muscular exertion can considerably increase the rate of blood circulation, and thus "there should also be muscular exertion during decompression". • In summary, page 424, Haldane's fifth conclusion is: "Decompression is not safe if the pressure of nitrogen inside the body becomes much more than twice that of the atmospheric nitrogen". Haldane had placed goats in compression chambers under pressure for long hours, to ensure their tissues were fully saturated with nitrogen, then concluded after these experiments that "if absolute pressure is reduced by 50% it will not provoke DCI". • Haldane published his "Decompression Tables"
Table I and
Table II, on pages 442 and 443. For ease of use, convert feet to meters by multiplying by 0.3048, and from psi to
bar by multiplying by 0.0689475729. These tables allow divers to ascend to half of their ambient absolute pressure and remain for a calculated decompression time before ascending further to half of the absolute pressure of the last stage. Haldane divided his schedules into Table I for "ordinary exposures" and Table II for "delay beyond the ordinary limits of time". Currently, when assessed, Table II decompression times were associated with great risk of decompression sickness. • Haldane divided body tissues into different categories, and measured the nitrogen desaturation in each. This led to fast tissues and slow tissues concept, where some tissues fill up with gas and empty it out rapidly; these are the fast tissues. On the other hand, slow tissues are slow filling up and slow emptying out. Haldane portrayed the logarithmic trend of these tissues to fill up and empty out. ==Further developments on Haldane's principles==