jueves, 26 de noviembre de 2020

Algoritmo RGBM (Reduced Gradient Bubble Model) del Dr. Bruce Wienke

Muy buenas,

Algo de info:

https://en.wikipedia.org/wiki/Reduced_gradient_bubble_model

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 different in that it rejects the gel-bubble model of the varying permeability model.

It is used in several dive computers, particularly those made by Suunto, Aqwary, Mares, HydroSpace Engineering 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.

Some 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.[4] The model has been correlated and validated in a number of published articles using collected dive profile data.

Description
The model is based on the assumption that phase separation during decompression is random, yet highly probable, in body tissue, and that a bubble will continue to grow by acquiring gas from adjacent saturated tissue, at a rate depending on the local free/dissolved concentration gradient. Gas exchange mechanisms are fairly well understood in comparison with nucleation and stabilization mechanisms, which are computationally uncertainly defined. Nevertheless there is an opinion among some decompression researchers that the existing practices and studies on bubbles and nuclei provide useful information on bubble growth and elimination processes and the time scales involved. Wienke considers that the consistency between these practices and the underlying physical principles suggest directions for decompression modelling for algorithms beyond parameter fitting and extrapolation. He considers that the RGBM implements the theoretical model in these aspects and also supports the efficacy of recently developed safe diving practice due to its dual phase mechanics. These include:
-reduced no-stop time limits;
-safety stops in the 10-20 fsw depth zone;
-ascent rates not exceeding 30 fsw per minute;
-restricted repetitive exposures, particularly beyond 100 fsw,
-restricted reverse profile and deep spike diving;
-restricted multi day activity;
-smooth coalescence of bounce and saturation limit points;
-consistent diving protocols for altitude;
-deep stops for decompression, extended range, and mixed gas diving with overall shorter decompression times, particularly in the shallow zone;
-use of helium rich mixtures for technical diving, with shallower isobaric switches to nitrox than suggested by Haldanian strategies;
-use of pure oxygen in the shallow zone to efficiently eliminate both dissolved and bubble phase inert gases.

https://www.suunto.com/Support/Suunto-rgbm-dive-algorithms/

Suunto RGBM Dive Algorithms

The Suunto RGBM Heritage
At the heart of every Suunto dive computer is an algorithm – the reduced gradient bubble model (RGBM) – that calculates decompression for a dive. Relentlessly pursuing ever best models for divers of all types, Suunto continues to push for RGBM perfection. Suunto has been developing RGBM algorithms together with Dr. Bruce Wienke for well over a decade. A rich history full of science, development, and underwater experience lies within every Suunto dive computer.

Suunto RGBM
Our pioneering algorithm for managing dissolved and free gas in blood and tissue. Used in Suunto Vyper Air, Vyper, Cobra, Cobra3, Zoop, D4i, and D6i, this adaptable algorithm provides an accurate picture of what’s happening in the body throughout a dive.
-First on the market to implement leading scientific research in decompression modeling.
-Reliability proven by millions of successful dives.
-A pioneering effort reflected in many other dive computers on the market.

Suunto Technical RGBM
An advanced algorithm that provides flexibility and safety during ascent through continuous decompression. Created especially to meet the needs of technical divers, it eliminates the need to constantly monitor depth, time, and when to switch gases, and means all critical data can be provided through a single device. Used in Suunto HelO2 and D9tx computers.
-Founded on the proven Suunto RGBM.
-Developed together with Dr. Bruce Wienke.
-First to include helium in breathing mixes and supports dives down to 120 m.
-Thoroughly tested with over 700 field dives by Suunto test diving team and validated by comprehensive laboratory test dives.

Suunto Fused™ RGBM, Suunto Fused™ RGBM 2
The Suunto Fused™ RGBM algorithm seamlessly combines the benefits of the Suunto Technical RGBM with the latest full RGBM for deep dives. It has rebreather capability and supports dives down to 150 m.

Suunto Fused RGBM automatically switches between the two models to effectively manage the risks of decompression sickness. The Fused RGBM is available in Suunto EON Core and Suunto EON Steel (software versions up to 1.6.5) and Suunto DX.
-Helps maximize bottom time while minimizing ascent time; novice divers can use the same Suunto dive computer including Suunto Fused RGBM as they advance in their hobby.
-Provides a slow continuous ascent from depth so technical and deep divers have shorter total decompression time.
-Thoroughly tested with over 1,000 field dives by Suunto test diving team and validated by comprehensive laboratory test dives.

Based on customer feedback, Suunto has adjusted Suunto Fused™ RGBM to a less conservative direction. The adjusted algorithm – Suunto Fused™ RGBM 2 – allows shorter ascent times on deep air dives and on repetitive dives. On repetitive dives, the change primarily affects Air/Nitrox dives.

In addition, the Suunto Fused™ RGBM 2 doesn’t require your body to be completely free of residual gases when calculating no-fly times for a normal airline pressurized up to 3000 meters. The change reduces the required time between your last dive and flying while maintaining your safety. The updated algorithm Fused™ RBGM 2 is introduced in the Suunto D5.

Read more about the Suunto Fused™ RGBM:
http://ns.suunto.com/pdf/Suunto_Dive_Fused_RGBM_brochure_EN.pdf

DR. Bruce Wienke:
“RGBM is the most realistic model in science. The parameters are correlated with real data of thousands of dives which makes it good physics, and the data is validated and correlated. I have been working with Suunto since the 90’s and Suunto’s progression from Suunto RGBM to Technical RGBM and now to Suunto Fused™ RGBM is a very natural one. The new algorithm is a supermodel that covers all types of diving.”

See Dr. Wienke talk about his algorithms on our YouTube channel:
http://www.youtube.com/playlist?list=PL8tpHUu2BPH_urQUhTpZ56yaYQxWtK6dg 

http://ns.suunto.com/pdf/Suunto_Dive_Fused_RGBM_brochure_EN.pdf

Videos:

https://www.youtube.com/playlist?list=PL8tpHUu2BPH_urQUhTpZ56yaYQxWtK6dg









http://www.advanceddivermagazine.com/articles/deeprgbm/deeprgbm.html

 

Actualización a 17/05/2021: Más cositas:



Actualización a 10/12/2022: Tendré que pensar en algo después de que se me haya inundado el Helo2 (https://viviendoapesardelacrisis.blogspot.com/2014/11/cambio-de-pila-ordenadores-de-buceo.html) durante la última Ruta Sur del Mar Rojo:

https://viviendoapesardelacrisis.blogspot.com/2014/06/buceo-en-el-mar-rojo-egipto.html 

https://viviendoapesardelacrisis.blogspot.com/2022/11/buceo-con-tiburones.html 

P.D: Según veo, lo compré el 25/12/2015. A ver qué hacemos porque el algoritmo Tech RGBM nos venía MUY bien para rascar decos (https://viviendoapesardelacrisis.blogspot.com/2019/10/inmersiones-con-descompresion.html) frente al de mi hermano.

Edit: El EON Steel Black:

https://www.suunto.com/es-es/Productos/Ordenadores-e-instrumentos-de-buceo/suunto-eon-steel-black/suunto-eon-steel-black/ 

Este ordenador dispone de dos algoritmos de buceo: Suunto Fused™ RGBM 2 y Bühlmann 16 GF, además de perfiles de ascenso configurables. Tú decides el perfil de descompresión para la inmersión de hoy.

https://www.suunto.com/es-es/Asistencia/Algoritmos-Suunto/ 

https://ns.suunto.com/pdf/Suunto_Dive_Fused_RGBM_brochure_EN.pdf 

 

Actualización a 03/05/2023: Ya veo más claro el tema de los algoritmos (que ya no recordaba):

http://ns.suunto.com/pdf/Suunto_Dive_Fused_RGBM_brochure_EN.pdf 

Página 12:

A ver si consigo que me respondan al tema de la fiabilidad:

https://viviendoapesardelacrisis.blogspot.com/2023/03/problema-con-sensores-de-presion.html 

Actualización a 22/05/2023: Gradient Factors a cuento del nuevo ordenador (https://viviendoapesardelacrisis.blogspot.com/2023/05/shearwater-teric-swift-smart-ai.html):

https://viviendoapesardelacrisis.blogspot.com/2019/04/jill-heinerth-into-planet.html 







Nota: El artículo (David Doolette - Gradient Factors in a Post-Deep Stops World):

https://gue.com/blog/gradient-factors-in-a-post-deep-stops-world/ 

With this information in mind, I set my GF low to roughly counteract the ZH-L16 “b” parameters (I have been using Shearwater dive computers with ZH-L16 GF in conjunction with my tried and true decompression tables for about three years). In ZH-L16, the average of “b” parameters is 0.83. I choose my GF low to be about 83% of the GF high, for instance GF 70/85. Although the algebra is not exact, this roughly counteracts the slope of the “b” values. This approach allows me to believe I have chosen my GF rationally, is not so large a GF low as I am unable to convince my buddies to use it, and satisfies my preference to follow a relatively shallow stops schedule.

Actualización a 27/06/2023: Más:

https://scubatechphilippines.com/scuba_blog/a-simple-guide-to-dive-computer-algorithms/ 

The basics of dive computer algorithms
Diving computers use complex mathematical algorithms to calculate your ascent to the surface whilst avoiding (DCS). They rely on sensors to measure depth, time, temperature, and other parameters, and then use these readings to determine things like no-decompression limits, decompression stops, and ascent rates.

How dive computer algorithms differ
Each dive computer algorithm model works differently and has its own unique advantages and disadvantages.
Some algorithms are more conservative and take a more cautious approach to decompression, while others are more liberal and allow for longer deeper dives.
Understanding the differences between these models can help you choose the right diving computer for your specific needs.

Benefits and drawbacks of different dive computer algorithms
Each algorithm model has its own benefits and drawbacks. Those pros and cons can make different dive computer algorithms more or less desirable, depending on the diving you do. For instance, the following parameters can change between algorithms:
-The length of no-stop times (NDL)
-The level of innate conservatism
-Safety for repetitive diving
-The penalty for missing safety stops
-The impact of surface interval time
-Conservatism over multi-day diving
-Reaction to fast ascent warnings
-Decompression efficiency for technical diving
It is essential to understand these differences before choosing a diving computer. With the right knowledge, you can pick a dive computer that has the right algorithm for the type of diving you do.

Decompression theory and dive computer algorithms
The essence of decompression theory is that reducing pressure around a diver will cause the nitrogen they have absorbed to leave their body. However, a too-sudden reduction in surrounding pressure will cause that nitrogen to form harmful bubbles.
The underlying aim of a dive computer algorithm is to get you to the surface with the least amount of nitrogen remaining in your body. At the same time, the algorithm has to ensure that harmful nitrogen bubbles do not form.

The two main types of dive computer algorithms
There are two main types of dive computer algorithms in use: Dissolved Gas and Bubble Model algorithms. Here are some of the key differences between the two:

Dissolved Gas Decompression Algorithms
-Based on early theories by Scottish physiologist John Scott Haldane and further developed in the 1960s by a Swiss physician Dr. Albert A. Bühlmann
-Based on scientific study, including hyperbaric chamber experiments
-Assumes that nitrogen dissolves into body tissues at depth and is released gradually during ascent
-Assigns a variety of nitrogen absorption and release speeds based on hypothetical tissues within the body
-Limits bubble formation based on a maximum value (m-value) of the pressure difference between the dissolved nitrogen and surrounding pressure
-Do not calculate bubble size
-Do not account for micro-bubbles

Bubble Model Decompression Algorithms
-Theories evolved by researchers including; David Yount, Paul Bert, Bruce Wienke, and Erik Baker
-Primarily mathematical hypothesis
-Assumes that tiny bubbles form in the body during ascent
-Assumes that eliminating small bubbles early prevents large bubbles later
-Focuses on predicting the rate of bubble formation and pausing the ascent in time to eliminate small bubbles
-Typically utilizes deep stops to eradicate micro-bubbles
Each type of algorithm has its own strengths and weaknesses, and the choice between the two ultimately depends on the diver´s personal preference and diving style.

The most popular dive computer algorithms
The most popular dive computer algorithms are the RGBM (Reduced Gradient Bubble Model), and Buhlmann ZHL-16, along with several derivative models.
These algorithms are used in a wide variety of modern dive computers and are known for their effectiveness in preventing decompression sickness.
Each algorithm has its own strengths and weaknesses, and divers should understand these differences when selecting a dive computer.

Bühlmann ZHL-16C dive computer algorithm
The Bühlmann ZHL-16C dive algorithm is a dissolved gas model used in recreational diving. It is the most widely tested and studied algorithm currently available.

Bühlmann ZHL-16C algorithm and Gradient Factors
Many dive computers using the Bühlmann ZHL-16C algorithm incorporate Gradient Factor settings as a user-adjustable way to vary conservatism and shape decompression ascent profiles.
Essentially, Gradient Factors determine the maximum pressure difference tolerated between the pressure surrounding the diver and the pressure of nitrogen in their body. A lower pressure difference equals more conservative dive limits. Technical divers also use a separate gradient factor (low) to determine the depth where their decompression stops begin.

Benefits of Bühlmann ZHL-16C:
-Can allow longer stop no-stop times
-Uses Gradient Factors for fine-tuning conservatism-Removes more nitrogen from the diver for a given duration of ascent
-Can be customized for different types of diving
-Very popular with advanced and technical divers

Drawbacks of Bühlmann ZHL-16C:
-Does not account for micro-bubble control and can cause more post-dive fatigue
-Is less responsive than RGBM in adding conservatism for repetitive and multi-day diving.
-Using custom gradient factors be challenging for new or inexperienced divers to understand

Dive computers using Bühlmann ZHL-16C:
-Shearwater
-Garmin
-Mares (some computers)
-Suunto (optional on the Eon Steel model)
-Oceanic (derivative Pelagic Z+ algorithm)
-Scubapro (derivative ZHL8 ADT MB algorithm)

Bühlmann ZHL-16C doesn´t offer the automatic conservatism adjustment offered by the RGMB algorithm. As a result, divers may be exposed to higher DCS risk on very aggressive repetitive deep diving schedules.
Likewise, the algorithm does not adjust limits based on limiting micro-bubbles which can result in post-dive fatigue. Diving aggressively using Bühlmann ZHL-16C demands more knowledge and understanding from the diver.

Derivatives of Bühlmann ZHL-16C
There are several derivative dive computer algorithms that are based upon Bühlmann ZHL-16C:

RGBM dive computer algorithm
RGBM stands for Reduced Gradient Bubble Model and is a widely-used algorithm developed by Bruce Wienke in the late 1990s. It was first implemented in dive computers by Suunto in 2002.The RGBM algorithm focuses on reducing the risk of decompression sickness by tracking the formation and growth of microbubbles in a diver´s tissues. It presumes that eliminating micro-bubbles through deeper stops allows for more aggressive decompression.

Benefits of the RGBM algorithm:
-Deep stops reduce micro-bubbles
-Reducing micro-bubbles can prevent post-dive fatigue
-Automatic increased conservatism if unsafe dive behaviors occur:
    -Fast ascent warnings
    -Incomplete safety stops
    -Surface intervals of less than 1 hour
    -Saw-tooth dive profiles (depth fluctuations)
-Allows longer no-stop time on a single dive

Drawbacks of the RGBM algorithm:
-Very conservative for repetitive and multi-day diving
-Unpredictable behavior on planned decompression dives

Dive computers using RGBM:
-Suunto
-Atomic
-Cressi
-Mares (some models)

The RGBM algorithm is most applicable for inexperienced recreational divers who will benefit from an algorithm that preserves their safety if they make common mistakes.

Experienced divers often express frustration at the high level of conservatism that occurs during repetitive and multi-day diving. However, RGBM does allow longer no-stop times when the diver has no residual nitrogen from past dives.

VPM-B dive computer algorithm
The VPM-B algorithm is a bubble model primarily used by technical divers to plan and execute dives. It was initially developed by David Yount and later updated by Erik Baker.

Benefits of VPM-B:
-Favors deep stops
-Micro-bubble control reduces post-dive fatigue
-Allows longer dive times at shallower depths

Drawbacks of VPM-B:
-Divers surface with more nitrogen compared to an equivalent ascent time using Bühlmann ZHL-16
-Generally more conservative for no-stop dives

Dive computers using VPM-B:
The VPM-B algorithm is implemented in various decompression software programs, such as V-Planner and MultiDeco. It can also be selected as an upgrade option in Shearwater dive computers

DSAT dive computer algorithm:
The Diving Science And Technology (DSAT) algorithm was developed by Dr. Raymond Rogers in 1983. It is based on the US Navy tables, but adapted to be more suitable for shorter, repetitive dives conducted by recreational divers.
As a result, the DSAT algorithm allows more repetitive and multi-day diving without excessive conservatism. However, it becomes very conservative if used for decompression diving beyond no-stop limits.
The DSAT algorithm was used to create the PADI Recreational Dive Planner (RDP) tables.

Benefits of DSAT:
-Favors repetitive no-stop dives in a single day
-Longer no-stop times on repetitive dives
-Allows shorter surface intervals between dives

Drawbacks of DSAT:
-Shorter no-stop limits on single dives
-Not favored for technical dives
-Very long deco time compared to other models

Choosing the right dive computer algorithm:
When choosing the right dive computer algorithm, there are several factors to consider. One of the most important is your personal risk tolerance and diving habits.
-Do you tend to push the limits of no-stop limits or are you more conservative in your diving style?
-Do you dive intensively on diving vacations?
-Can you maintain square-profile dives, or do your dive profiles fluctuate significantly in depth?
-Is your buoyancy control consistent and accurate?
-How knowledgeable are you about manually tailoring an optimal ascent profile?
-Do you frequently suffer from post-dive fatigue?
These are important questions to ask yourself when selecting an algorithm model.

While choosing the right dive computer algorithm is a good starting point, it´s important to remember that they are not one-size-fits-all solutions.
Your personal physiology, variable DCS predisposing factors, and overall risk tolerance will all play a role in determining which model is right for you.
That´s why it´s important to personalize your algorithm model by adjusting the conservatism settings to reflect your individual circumstances.

Adjust to a higher level of conservatism if the following factors apply:
-High body fat %
-Older age
-Dehydration
-Insufficient sleep
-Sick or unwell
-Menstruation
-Getting cold during dives
-Raised exertion on dives
-3+ dives per day
-3+ days of diving
-Diving close to NDL
-Previous DCS incident
By doing so, you can ensure that you´re using the algorithm that best fits your needs and helps you minimize the risk of decompression sickness.

Make the most out of dive computer algorithms:
In conclusion, understanding dive computer algorithms is crucial for any scuba diver who wants to ensure their safety and make informed decisions when purchasing a new dive computer.
While decompression theory and complex mathematics are involved in the creation of these algorithms, it is not necessary for divers to have a deep understanding of these subjects to understand how different algorithms work and their benefits and drawbacks.
By knowing the strengths and weaknesses of the different dive computer algorithms, you can choose an option that best fits your need. For that reason, it is important to investigate what algorithms are supplied on dive computers. It should be a high-priority factor when you are shopping for a new computer.

To summarize, here are the key points to remember:
-Dive computer algorithms play an important role in dive safety and should not be discounted as a factor when purchasing a new dive computer.
-Different dive computer algorithms may be better suited for certain types of diving or personal preferences.

Actualización a 17/10/2023: Bühlmann:

https://viviendoapesardelacrisis.blogspot.com/2023/10/algoritmo-buhlmann-decompression.html 


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