The US Navy has used several decompression models from which their published decompression tables and authorized diving computer algorithms have been derived. The original C&R tables used a classic multiple independent parallel compartment model based on the work of J.S.Haldane in England in the early 20th century, using a critical ratio exponential ingassing and outgassing model. Later they were modified by O.D. Yarborough and published in 1937. A version developed by Des Granges was published in 1956. Further developments by M.W. Goodman and Robert D. Workman using a critical supersaturation approach to incorporate M-values, and expressed as an algorithm suitable for programming were published in 1965, and later again a significantly different model, the VVAL 18 exponential/linear model was developed by Edward D. Thalmann, using an exponential ingassing model and a combined exponential and linear outgassing model, which was further developed by Gerth and Doolette and published in Revision 6 of the US Navy Diving Manual as the 2008 tables.
Besides the air and heliox tables for open circuit bounce dives, the US Navy has published a variety of hyperbaric treatment schedules, decompression tables for open and closed circuit heliox and nitrox, tables incorporating surface decompression on oxygen, a system for modifying tables for use at high altitudes (Cross corrections), and saturation tables for various breathing gas mixtures. Many of these tables have been tested on human subjects, frequently with an end result of symptomatic decompression sickness, and for this reason their test results are considered some of the most reliable available.
US Navy tables have generally been freely available for use by the general public, and have often been modified to further reduce risk, as commercial and recreational divers do not always fit the physical requirements for military divers, may not have a recompression chamber on site to manage decompression sickness on those occasions when it does occur, and may prefer to operate at a lower risk than military personnel. Several recreational diving tables were originally based on US Navy diving tables.
In 1912, Chief Gunner George D. Stillson of the United States Navy created a program to test and refine Haldane's tables. This program ultimately led to the first publication of the United States Navy Diving Manual and the establishment of a Navy Diving School in Newport, Rhode Island. Diver training programs were later cut at the end of World War I.
The first decompression tables produced for the U.S. Navy were developed by the Bureau of Construction and Repair and published in 1915, and were consequently known as the C&R tables. They were derived from a Haldanean model, with oxygen decompression, to depths up to 300 ft on air, and were successfully used to depths of slightly over 300 ft: 3–1
In 1939, after the recovery of USS Squalus, tables were published for surface supplied Heliox diving.: 1–17
See also: Hyperbaric treatment schedules
Although recompression and slow decompression were the accepted treatment, there was not yet a standard for either the recompression pressure or the rate of decompression. This changed when the first standard table for recompression treatment with air was published in the US Navy Diving Manual in 1924. These tables were not entirely successful - there was a 50% relapse rate, and the treatment, though fairly effective for mild cases, was less effective in serious cases.
In 1965,[clarification needed] M.W. Goodman and Robert D. Workman introduced recompression tables using oxygen to accelerate elimination of inert gas.
It is important that any theory be validated by carefully controlled testing procedures. As testing procedures and equipment become more sophisticated, researchers learn more about the effects of decompression on the body. Initial research focused on producing dives that were free of recognizable symptoms of decompression sickness (DCS). With the later use of Doppler ultrasound testing, it was realized that bubbles were forming within the body even on dives where no DCI signs or symptoms were encountered. This phenomenon has become known as "silent bubbles". The presence of venous gas emboli is considered a low specificity predictor of decompression sickness, but their absence is recognised to be a sensitive indicator of low risk decompression, therefore the quantitative detection of VGE is thought to be useful as an indicator of decompression stress when comparing decompression strategies, or assessing the efficiency of procedures.
The US Navy 1956 tables were based on limits determined by external DCS signs and symptoms. Later researchers were able to improve on this work by adjusting the limitations based on Doppler testing. However the US Navy CCR tables based on the Thalmann algorithm also used only recognisable DCS symptoms as the test criteria. Since the testing procedures are lengthy and costly, and there are ethical limitations on experimental work on human subjects with injury as an endpoint, it is common practice for researchers to make initial validations of new models based on experimental results from earlier trials. This has some implications when comparing models.: Ch10
See also: Altitude diving