Decompression tables

The U.S. Navy Standard Air Decompression Tables (USN) have been, and continue to be, used extensively to guide human decompression procedures throughout much of the world. These tables (ref. 408), as well as the French Navy decompression table (FN) and the Japanese Department of Labor standard decompression table (Japan), are all based on the Haldane-ratio principle (ref. 409,410). However, other tables have been developed that do not employ the Haldane-ratio principle to guide decompression, and several of these tables appear to be considerably safer (ref. 411-413). 

The Royal Naval Physiological Laboratory (RNPL) has also found reason to doubt the Haldane concept of bubble formation and has developed its own decompression schedule (ref. 411). The RNPL table and the decompression table used by the French Ministry of Labor (FL) are based on diffusion theory (ref. 411). The most characteristic feature of these tables is the deeper first stop during decompression after diving, with the result that the total decompression time is prolonged to approximately 3 times the... 

In a related experimental study, the relative effectiveness of all the above-mentioned decompression tables in reducing bubble formation within aqueous gels was evaluated quantitatively under rigorously controlled conditions specifically, visual counts were conducted of the bubbles formed in highly purified agarose gels (ref. 49,139) subjected to the different decompression schedules. 

The separate decompression tables of the French Navy, the U.S. Navy, and the Japanese Department of Labor, which are all based on the Haldane-ratio principle (ref. 408-410), require total decompression times for the test dive which are much shorter than those required by other military and commercial tables (Table 8.1). The first stop during decompression with either the FN, USN, or Japan tables occurred at a 10-ft depth, and the mean bubble counts ( S.E.M.) within the 0.27-ml agarose samples just prior to termination of this first (and only) stop were 127.25 9.39, 111.88 17.64, and 98.75 10.72, respectively. Of these three Haldane-ratio-principle tables, the FN table required the shortest total decompression time and the Japan table the longest time, so that the mean bubble number at the 10-ft depth was inversely related to the total decompression time. (In these three cases, the total decompression time essentially represented the sum of the initial... 

Y. Mano, M. Shibayama, K. Ida, T. Miyamoto, H. Matzunaga, K. Ohgushi, A. Kashikura and H. Maeda, Comparative study of today s different decompression tables, Japn. J. Hyperbaric Med. 12(1977) 14. 

The principal manifestation of the bends is a deep boring ache or pain in the bones of muscles around the joints. The intensity of the pain can vary. This symptom may be accompanied by neurocirculatory collapse. The cause of the pain is thought to be due to excitation of mechanoreceptors as a result of tissue distortion by the expanding bubbles, or to ischemic excitation due to interference with vascular flow. The role of humoral agents in the production of pain should not be overlooked (K9). Even following the standard U. S. Navy Decompression Tables the incidence of bends may be as high as 4%, depending on age, physical condition, etc. 

Decompression Table No. 1 indicates in the body of the table the total decompression time in minutes for various combinations of working chamber pressure and exposure time. 

Example No. 1 4 hours working period at 20 pounds gauge. Decompression Table No. 1 20 pounds for 4 hours, total decompress time. 43... 

Example No. 2 5-hour working period at 24 pounds gage. Decompression Table No. 1 24 pounds for 5 hours, total decompression time Decompression Table No. 2 Stage 1 Reduce pressure from 24 pounds to 8 pounds at the uniform rate of 5 pounds per minute. Elapsed time stage 1 16/5. .. 117 3... 

Decompression table A profile or set of profiles of depth-time relationships for ascent rates and breathing mixtures to be followed after a specific depth-time exposure or exposures. 

Investigate and evaluate each incident of decompression sickness based on the recorded information, consideration of the past performance of decompression table used, and individual susceptibility ... 

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