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6.2. SUUNTO REDUCED GRADIENT BUBBLE
MODEL (RGBM)
The Suunto Reduced Gradient Bubble Model (RGBM) is a modern algorithm for
predicting both dissolved and free gas in the tissues and blood of di vers. It was
developed in a co-operation between Suunto and Bruce R. Wienke BSc, MSc.
PhD. It is based on both laboratory e xperiments and diving data, including data
from DAN.
It is a signifi cant advance on the classical Haldane models, which do not predict free
gas (microbubbles). The advantage of Suunto RGBM is additional safety through its
ability to adapt to a wide variety of situations. Suunto RGBM addresses a number of
diving circumstances outside the range of just dissolved gas models by:
- Monitoring continuous multiday diving
- Computing closely spaced repetitive diving
- Reacting to a dive deeper than the previous dive
- Adapting for rapid ascents which produce high micro-bubble (silent-bub-
ble) build-up
- Incorporating consistency with real physical laws for gas kinetics.
Suunto RGBM Adaptive decompression
The SUUNTO RGBM algorithm adapts its predictions of both the ef fects of
micro-bubble build-up and adverse dive profi les in the current dive series. It will
also change these calculations according to the personal adjustment you select.
The pattern and speed of decompression at the surf ace is adjusted according to
micro-bubble infl uence.
Also on repetitive dives adjustment may be applied to the maximum allo wable
nitrogen overpressure in each theoretical tissue group.
Depending on circumstances Suunto RGBM will adapt the decompression obliga-
tions by doing any or all of the following:
· Reducing no-decompression stop dive times
· Adding Mandatory Safety Stops
· Increasing decompression stop times
· Advising an extended surface interval (Diver Attention symbol).
Some patterns of di ving cumulatively add a higher risk of DCI, e.g. di ves with
short surface intervals, repetitive dives deeper than earlier ones, multiple ascents,
substantial multiday di ving. When this is detected in addition to adapting the
decompression algorithm the Suunto RGBM model will in some circumstances
also advise, with the Diver Attention Symbol (review chapter 3.6) that the diver
extend the surface interval.
