Reduced gradient bubble model

The reduced gradient bubble model, abbreviated RGBM, is an algorithm developed by Bruce Wienke for calculating the decompression stops a diver needs for a particular dive profile. It is related to the varying permeability model but differs conceptually in rejecting that model's gel-bubble picture. It is built on a few stated assumptions: blood flow, or perfusion, limits how far gas can penetrate tissue by diffusion; an exponential distribution of bubble seed sizes is always present, with many more small seeds than large; bubbles are permeable to gas transfer across their surfaces at all pressures; and the Haldanean tissue compartments have half times ranging from 1 to 720 minutes depending on the gas mixture. The model treats phase separation during decompression as random yet highly probable in body tissue, with a bubble growing by taking gas from adjacent saturated tissue at a rate set by the local concentration gradient. Its practical consequences include reduced no-stop limits, safety stops in the 10 to 20 foot seawater zone, ascent rates not above 30 feet per minute, restrictions on repetitive, reverse profile and deep spike diving, and deep stops for decompression and mixed gas diving. Several dive computer makers, notably Suunto, use it or approximations of it, and the source reports that it has been checked against published dive profile data.