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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Decompression theory | 17/17 | https://en.wikipedia.org/wiki/Decompression_theory | reference | science, encyclopedia | 2026-05-05T10:06:49.112339+00:00 | kb-cron |
=== Practical effectiveness of models === Bubble models for decompression were popular among technical divers in the early 2000s, although there was little data to support the effectiveness of the models in practice. Since then, several comparative studies have indicated relatively larger numbers of venous gas emboli after decompression based on bubble models, and one study reported a higher rate of decompression sickness. The deeper decompression stops earlier in the ascent appear to be less effective at controlling bubble formation than the hypotheses suggested. This failure may be due to continued ingassing of slower tissues during the extended time at greater depth, resulting in these tissues being more supersaturated at shallower depths. The optimal decompression strategy for deep bounce dives remains unknown (2016). The practical efficacy of gas switches from helium-based diluent to nitrox for accelerating decompression has not been demonstrated convincingly. These switches increase risk of inner ear decompression sickness due to counterdiffusion effects. Besides the basic dive profile and gas mixes, and the residual gas load from previous dives, three groups of factors are considered likely to have significant influence on decompression stress, the evolution of bubbles in the diver, and development of symptoms. These are exercise, before, during and after the dive, Thermal status, during and after the dive, including the effects on perfusion distribution and changes during the dive, and the set of factors grouped under the label "predisposition", such as the state of hydration, physical fitness, age, biological health, and other characteristics which could affect the uptake and release of gases in the diver. Currently these factors cannot be used to make reproducible predictions about decompression risk, and some cannot be numerically evaluated in real time.
== Teaching of decompression theory ==
Decompression is an area where you discover that, the more you learn, the more you know that you really don't know what is going on. For behind the "black-and-white" exactness of table entries, the second-by-second countdowns of dive computers, and beneath the mathematical purity of decompression models, lurks a dark and mysterious physiological jungle that has barely been explored. — Karl E. Huggins, 1992
Exposure to the various theories, models, tables and algorithms is needed to allow the diver to make educated and knowledgeable decisions regarding their personal decompression needs. Basic decompression theory and use of decompression tables is part of the theory component of training for commercial divers, and dive planning based on decompression tables, and the practice and field management of decompression is a significant part of the work of the diving supervisor. Recreational divers are trained in the theory and practice of decompression to the extent that the certifying agency specifies in the training standard for each certification. This may vary from a rudimentary overview sufficient to allow the diver to avoid decompression obligation for entry level divers, to competence in the use of several decompression algorithms by way of personal dive computers, decompression software, and tables for advanced technical divers. The detailed understanding of decompression theory is not generally required of either commercial or recreational divers.
== See also == Decompression (diving) – Pressure reduction and its effects during ascent from depth Decompression practice – Techniques and procedures for safe decompression of divers Decompression sickness – Disorder caused by dissolved gases forming bubbles in tissues Dive computer – Instrument to calculate decompression status in real time Equivalent air depth – Method of comparing decompression requirements for air and a given nitrox mix Equivalent narcotic depth – Method for comparing the narcotic effects of a mixed diving gas with air History of decompression research and development Hyperbaric treatment schedules – Planned hyperbaric exposure using a specified breathing gas as medical treatment Oxygen window – Difference between the partial pressures of oxygen in arterial blood and body tissues Physiology of decompression – Physiological basis for decompression theory and practice Decompression models: Bühlmann decompression algorithm – Mathematical model of tissue inert gas uptake and release with pressure change Haldane's decompression model – Decompression model developed by John Scott Haldane Reduced gradient bubble model – Decompression algorithm Thalmann algorithm – Mathematical model for diver decompression Thermodynamic model of decompression – Early diving decompression model Varying Permeability Model – Decompression model and algorithm based on bubble physics
== Notes ==
- ^a autochthonous: formed or originating in the place where found
== References ==
=== Sources === Hamilton, Robert W.; Thalmann, Edward D. (2003). "10.2: Decompression Practice". In Brubakk, Alf O.; Neuman, Tom S. (eds.). Bennett and Elliott's physiology and medicine of diving (5th Revised ed.). United States: Saunders. pp. 455–500. ISBN 978-0-7020-2571-6. OCLC 51607923. Huggins, Karl E. (1992). Dynamics of decompression workshop. Course Taught at the University of Michigan (Report). Thalmann, E.D. (1984). Phase II testing of decompression algorithms for use in the U.S. Navy underwater decompression computer. Navy Exp. Diving Unit Res. Report (Report). Vol. 1–84. Thalmann, E.D. (1985). Development of a Decompression Algorithm for Constant Oxygen Partial Pressure in Helium Diving. Navy Experimental Diving Unit Research Report (Report). Vol. 1–85. US Navy (2008). US Navy Diving Manual, 6th revision. United States: US Naval Sea Systems Command. Retrieved 15 June 2008. Wienke, Bruce R.; O'Leary, Timothy R. (13 February 2002). "Reduced gradient bubble model: Diving algorithm, basis and comparisons" (PDF). Tampa, Florida: NAUI Technical Diving Operations. Retrieved 25 January 2012. Yount, D.E. (1991). Hans-Jurgen, K.; Harper Jr, D.E. (eds.). "Gelatin, bubbles, and the bends". International Pacifica Scientific Diving..., (Proceedings of the American Academy of Underwater Sciences Eleventh Annual Scientific Diving Symposium Held 25–30 September 1991. University of Hawaii, Honolulu, Hawaii).
== Further reading == Ball, R; Himm, J; Homer, LD; Thalmann, ED (1995). "Does the time course of bubble evolution explain decompression sickness risk?". Undersea and Hyperbaric Medicine. 22 (3): 263–280. ISSN 1066-2936. PMID 7580767. Gerth, Wayne A; Doolette, David J. (2007). "VVal-18 and VVal-18M Thalmann Algorithm – Air Decompression Tables and Procedures". Navy Experimental Diving Unit, TA 01-07, NEDU TR 07-09. Gribble, M. de G. (1960); A comparison of the High-Altitude and High-Pressure syndromes of decompression sickness, Br. J. Ind. Med., 1960, 17, 181. Hills. B. (1966); A thermodynamic and kinetic approach to decompression sickness. Thesis Lippmann, John; Mitchell, Simon (2005). Deeper into Diving (2nd ed.). Melbourne, Australia: J L Publications. ISBN 0-9752290-1-X. Parker, E. C.; S.S. Survanshi; P.K. Weathersby & E.D. Thalmann (1992). "Statistically Based Decompression Tables VIII: Linear Exponential Kinetics". Naval Medical Research Institute Report. 92–73. Salama, Asser (2018). Deep into Deco. Florida: Best Pub. ISBN 978-1-947239-09-8. Powell, Mark (2008). Deco for Divers. Southend-on-Sea: Aquapress. ISBN 978-1-905492-07-7.