Reduced gradient bubble model

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The reduced gradient bubble model (RGBM) is an algorithm developed by Dr Bruce Wienke for calculating decompression stops needed for a particular dive profile. It is related to the Varying Permeability Model.[1] but is conceptually beyond that early model.

It is used in several dive computers, particularly those made by Suunto, Mares, HydroSpace Engineering,[1] and Underwater Technologies Center. It is characterised by the following assumptions: blood flow (perfusion) provides a limit for tissue gas penetration by diffusion; an exponential distribution of sizes of bubble seeds is always present, with many more small seeds than large ones; bubbles are permeable to gas transfer across surface boundaries under all pressures; the haldanean tissue compartments range in half time from 1 to 720 minutes, depending on gas mixture.[1]

Manufacturers such as Suunto have also devised approximations of Wienke's model. Suunto uses a modified haldanean nine-compartment model with the assumption of reduced off-gassing caused by bubbles. This implementation offers both a depth ceiling and a depth floor for the decompression stops. The former maximises tissue off-gassing and the latter minimises bubble growth.[2] The model has been correlated and validated In a number of published articles using collected dive profile data.


  1. ^ a b c 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. pp. 7–12. Retrieved 12 January 2010. 
  2. ^ "Suunto Reduced Gradient Bubble Model" (PDF). Suunto. 24 July 2003. Retrieved 24 January 2010. 

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