Tuesday, August 19, 2008

RGBM: A Brief Overview

[This is a re-post of a blog entry I made on August 1, 2005, over 3 years ago... wow.]

More dive computers are incorporating the Wienke Reduced Gradient Bubble Model (RGBM) Algorithm.  What is it and is it worthwhile for recreational divers? 

New research concerning decompression sickness (DCS) are finding if a diver adds a deep stop and a slow ascent to the traditional 15 feet safety stop, a larger margin of safety is introduced against DCS .

Dr Bruce Weinke, a NAUI Instructor trainer developed the RGBM as the next evolution of diving models based on studies of bubbles and the it's effects under pressure.  He theorize, much like the governing of on ramp to highways with traffic lights, adding a deep stop at half your maximum depth helps bubbles dissolve back into tissue for release out through the lungs at a faster rate than the traditional three minute safety stop at 15 feet.

Counter intuitive, you think?  But yes... according to this theory, staying at depth longer can help reduce nitrogen content faster than traditional diving models.

  • In general, the model suggests the following:
    Stop for one full minute at 1/2 your maximum depth.
  • Execute a slow ascent (30 feet / minute) to 15 feet.
  • Perform 15 feet safety stop as normal.

Obviously, there's much more physics and decompression theory involved to help back these findings, however they aren't addressed here.  You may find more information online or in Dr Wienke's book, Reduced Gradient Bubble Model in Depth.

If wanting to integrate deep stops in your diving profile, one must consider the following:

  • All dives are decompression dives
  • There's a difference between mandatory deco stops and safety stops
  • All diving profiles are models, based on thoery.

So, is it worthwhile?  That's for you to decide. 

As I work through my diving education, I've learned it never hurts to be more informed.

[2008 Update:  We have integrated this as part of our diving training procedures and practices.]