...there is dead space ventilation in the device that seems greater than in the standard snorkel tube. That dead space can cause carbon dioxide buildup." This CO2 buildup could cause a person to become disoriented, or, even lose consciousness.
...she had negative pressure pulmonary edema, which is caused by an upper airway obstruction generating enough pressure to pull fluid from the arteries that take blood to the lungs.
Snorkelling safety: Snorkelling is a simple and fun activity for all the family! Breathing through a snorkel is more physically demanding than regular swimming. If you feel tired, short of breath or dizzy, remove your mask and get out of the water. Do not use this product if you have cardiovascular or respiratory problems (chest infection, angina, asthma, high blood pressure, heart disease, etc.). If in doubt, consult your doctor.
Pietro es un chico de ciudad, Bruno es el último niño de una localidad de montaña olvidada. Con el paso de los años, Bruno se mantiene fiel a su montaña, mientras que Pietro viene y va. Sus experiencias le harán enfrentarse al amor y a la pérdida, recordándoles sus orígenes y abriendo paso al destino.
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.
The subsequent decompression profile that is generated on the ascent should not exceed the tolerated over-pressure value, or M value — a theoretical construct for the theoretical controlling tissue compartment within the body, in order to avoid decompression illness (DCI). As each compartment comes into play and the relevant M value is reached, a decompression stop profile is generated.
Figure 1 represents a very simplistic example involving just one of the fast tissues which will control the primary ascent phase. The M value for this compartment is shown as a straight line. If the diver controls the ascent, the inert gas loading in the compartment will stay on or below the M value line. If they do this, let’s assume they are using 100% of the available M value, which means there’s no extra safety margin for that dive; they are theoretically diving right on the edge of the model.
For a typical bounce dive, Buhlmann standard practice has been to allow a rapid ascent to the first stop to generate a high level of off-gassing. Doing this, the gas loading in the fastest compartment will be on or near saturation at the bottom depth (the slow tissues are only partially saturated). This means that the fastest compartments will control the initial ascent since their gas loadings will be near or on the tolerated over-pressure value (M value). The first stop depth is set when the controlling (fast) compartment is nearest to the M value. The example only shows up to a point where the first stop starts and does not detail the other compartments or the remaining decompression.
Using gradient factor terminology, the M value line is the 100/100 reference. The first 100 describes how close (in percentage) to the M value line the first stop is, and the second 100 describes how close the final stop is. Thus 100/100 has no added safety margin compared to the M value. In the complete picture, each compartments’ M value and each compartments’ internal pressure right through to the end of the dive (not just to the stop as drawn) would be displayed on the graph each with the same 100/100 gradient. The slower compartments would reach their M value during the final decompression phases while the faster compartments control the deeper decompression.
The gradient factor system modifies the M value by taking a percentage of the difference between the M value and the ambient pressure value. As a simple example to illustrate how Gradient factors work, using 80% of the M value as the controlling value (80/80 line) produces a line on the graph (figure 2) below the 100/100 line, having the effect of reducing the compartments allowed over-pressure value and generating a deeper decompression stop.
Again, in the complete picture all the adjusted M values and compartment pressures would be plotted, adding safety to the whole decompression profile.
As most of these early dissolved gas based tables were formulated around relatively shallow water air range dives, they do not suit deep water dives, although historically they have often been extrapolated for use in deep-water. While these tables have a varying solution for different depths they were depth limited.
So what about Pyle stops? Technical diving pioneer, ichthyologist Richard Pyle developed a practical solution that divers could understand for modifying the decompression profile to reduce the excessive over-pressurization of the controlling compartment at the deep stops. He found that by stopping and venting a fish’s swim bladder below the first tabular stop depth, he ‘felt better’ at the end of the decompression. He was in effect allowing the faster compartments’ pressure to reduce before ascending to the tabular first stop and not reach its M value peak.
The downside of this was that other compartments were still on-loading gas, which could generate an additional decompression obligation in shallow water. He was applying a safety factor that only had an effect on the deeper stops. This had the potential to allow the slower compartments to become closer to their M value during the shallow water decompression phase unless additional safety factors were applied.
Gradient factors can further mimic bubble models by using two different gradient factors to control the decompression: one that primarily references the deep stops, and one the shallow.
So a 20/80 gradient factor, which has been commonly used on deeper dives, would allow an over-pressure value of 20% (instead of 100%) of the difference between the ambient pressure and the allowed M value for the controlling compartment of the first or “deep stop” and 80% (instead of 100%) of the M value for the controlling compartments’ pressure difference at the shallow stop. The stops in between are calculated by drawing an over-pressure value line between the two points and plotting the new adjusted M values for each compartment in between. It assumes a linear calculation between the adjusted first and last M values.
In Figure 3 let’s assume that compartment 4 controls the deep stop and compartment 16 the shallow stop. Again, for clarity, the on-going compartment inert gas loading reductions are not shown past the M value point, neither are all the other compartment M values.
The major drawback of gradient factors is that the factors applied need to be adjusted for each depth/time exposure. For example, if you used the same 20/80 gradient factor for an 80 m dive, on a 30 m dive you might have an excess of decompression in shallow water because we know from experience that a gradient factor of close to 100/100 is reliable for this shallow water dive.
What does this mean? First, it is not necessarily appropriate to apply one gradient factor to a range of dive depths. What works deep may not work shallow. Secondly, it means just applying gradient factors in the first place may be too coarse a solution. Just drawing a straight line between the M value points and assuming the mid-water decompression follows this linear approach may not work. So how do we generate a refinement?
Stochastic modelling has been around in diving for some time. Decompression tables are generated based on statistical dive data of incidents; basically, points are plotted on a graph and an algorithm generated. So how could we use this to improve gradient factor modelling? Assuming the 100/100 factor is OK for a certain shallow dive and the 20/80 is OK for a particular deep dive, would it not be best to have a varying gradient factor depending on depth/time exposure and other factors? If we can be fairly certain of key decompression times for a range of depth/time exposures that are ‘safe’ and generate reasonable decompressions, we could use them to generate a gradient factor that varies accordingly. My term for this approach is a Variable Gradient Model (VGM).
A better alternative to fooling the decompression algorithm is to limit the severity of the exposure while fully informing the model. This brings us back to gradient factors, which are defined by two values: The first number of the pair (“GF low”) represents the percentage of the M-value that establishes the first stop during ascent; the second number (“GF high”) is the percentage of the M-value that should not be exceeded at any point during surfacing. The dive computer effectively draws a straight line between the two, creating the ascent slope.
De cara a personalizar el modo Recreativo, cambiar los límites de alertas de presión de botella y sustituir alguna de la info por defecto por otra más relevante.
Actualización a 29/05/2023: Pos, por ahora, simplemente he cambiado del Layout Big al Normal.
Version 17 includes the following changes: -Fixes issue where under some conditions units may not shutoff when left on charger. -Fixed issue where surface interval was logged and displayed incorrectly when greater -than 45 days. -O2 % threshold for considering a gas a “deco gas” now 40% O2 (previously 50%). -SAC calculations for display in dive log modified slightly to match the Perdix AI. -Adds “EN250” information to dive mode start screen for some models.
Version 18 includes the following changes: -Fixes issue that could cause a Watchdog Reset error in certain circumstances. -Fixed error where in CC/BO the dive log gas lists were swapped. -O2 % threshold for considering a gas a “deco gas” now 40% O2 (previously 50%). -Fixed display error in menu where in Gauge mode the GTR/SAC option value displayed as “Off (Gauge) Off” instead of just “Off (Gauge)”.
Version 19 on the Teric includes the following changes: -Up to 4 wireless air integration (AI) tanks are now supported -A sidemount mode has been added -AI tanks can now be renamed. Only 2 characters available per tank -Gas density display is now available -Additional power management options have been added.
Version 21 includes the following change: -This version addresses a minor bug where the Swift AI Tank Pressure Transmitter will occasionally send a false and unwarranted low battery warning. This change suppresses AI transmitter low battery warnings until four (4) have been received consecutively.
Version 23 includes the following change: -Fixed display issue with Air Integration (AI) info row when the only AI Transmitter enabled was T4, the T3 transmitter would erroneously display instead. -Fixed issue where the AI serial number was saved with wrong byte ordering in the dive log.
Imagine having a tool that would give you a numerical percentage value of the decompression stress you would encounter if you were to instantaneously ascend to the surface. Not all dives are created equal. You might be keeping your dives within the NDL, doing your safety stops, but the fact is that different NDL dives will give you different degrees of DCS stress depending on your dive profile. When we launched the Teric we included in it a new feature we called Surface GF (SurfGF). In this blog post we'll discuss SurfGF and how it can help you manage your decompression stress.
...
Setting your conservatism levels in this mode can be as simple as selecting from 3 settings: Low, Medium or High. There is a fourth setting called Custom. We recommend that divers refrain from tweaking the custom settings until the diver is familiarized with Gradient Factors (GF). Once you have grown to be knowledgeable about GF, then you can access conservatism levels that range from 10 to 99 in GF Low (90 settings) and from 30 to 99 in GF High (70 settings).
...
What is GF? Erik Baker developed gradient factors as a conservatism strategy. It is often used in conjunction with the Buhlmann ZHL-16 algorithm. This conservatism strategy provides divers with a good amount of flexibility that allows us to fine tune our dive profiles and how we address DCS risk during a dive. One of its virtues is that it allows users to implement varying degrees of deep stops – how deep do you want to start your stops – through the GF Low parameter. At the same time, by adjusting the GF High parameter you decide how long your shallower stops will be. Both the Buhlmann ZHL- 16 and the Gradient Factors conservatism strategy are open source and readily available to divers for in depth study in relation to their individual responses to decompression stress. This is one of the reasons that has made it so popular with divers, which in turn has yielded a good amount of empirical validation for divers and earned their trust.
...
facing a forced ascent when your SurfGF says 73% is a much different scenario than facing a SurfGF of 187%. The higher the percentage, the more likely you are to getting bent. Any percentage above 100% carries a risk higher than surfacing at the Bulhmann M-value itself (GF 100% = M-Value).
...
Making a mental note of your SurfGF at the time you arrive at the surface can also provide valuable information. Sometimes after a dive you can feel more tired than usual. Is it DCS stress? It would help if you have a numerical value to associate that feeling with.
...
SurfGF can give you valuable information when facing difficult choices. It is better to be bent than drowned. Sometimes breaking a deco stop is the safer choice. Shearwater won’t lock you out for doing that. SurfGF will give you a number that can influence a tough decision on whether to head to surface during some urgency or do some more deco. When used along with GF99 you can numerically manage your deco stress all throughout the entire dive. GF99 tells you the gradient factor as a percentage for your current depth and time. SurfGF is also useful for dives within the NDL. You can objectively see the effects of doing a 3 minute safety stop and compare it to a 5 minute safety stop or even to having no safety stop at all. If you have a strenuous dive doing heavy kicking while battling a current, you can consciously choose to surface at a SurfGF of 70% instead of your usual 85% just to pad your chances. Now you can apply numerical values to your padding. Please bear in mind that while SurfGF is a powerful tool it is not a replacement for proper dive planning. You can program your Teric to have the SurfGF value to appear in your home screen and always be present during the dive without needing to touch a button. After divers discovered SurfGF on the Teric and the word spread around, we got many requests to add this feature to our other computers. So we did.
Vale, y habla de usar un GF99 de entre 1/3 y 1/2 del GF Hi para maximizar la desaturación:
In contrast, you can use the GF99 display to ascend to a depth that guarantees more efficient nitrogen removal. As a rule-of-thumb, you should aim for anywhere between 1/3 and 1/2 of your preset GFhi. For instance, if your GFhi is set at 85%, aim to conduct your safety stop at a depth that creates a GF99 between 28% and 42%.
Sobre la velocidad de ascenso:
I will always ascend at 9-10m per minute from the bottom to my safety stop. Then, from the safety stop to the surface, I will ascend at a rate of 3m per minute. This strategy works very well for avoiding post-dive fatigue.
Actualización a 04/06/2023: Biosnar:
Actualización a 08/06/2023: Correa en casa y montada:
Definitivamente, tenía que haberla pillado en 22 y no en 20. Me dí cuenta luego. Voy a probarla y decidir si así o como la venden.
Actualización a 10/06/2023: Acabo de personalizar ya que no encontraba el GF Surface durante las inmersiones y tenía que andar cambiando al GF99 para hacerme una idea de cómo tábamos limpiando en los ascensos.
Así:
Actualización a 17/06/2023: Hoy lo he usado en Técnico:
MÁS deco. :P
Actualización a 21/06/2023: Pantalla de Técnico por defecto:
Personalizada:
P.D: Info:
Nota: Todavía no lo he vuelto a cargar.
Actualización a 26/06/2023: Sigo en Técnico y he cambiado la personalización de la pantalla para no tener el NDL duplicado (ya que va en la de Deco) y mostrar el GF Surface (bajo el TTS y pasando el GF99 debajo de la Deco):
Edit: Y acabo de escribir Andy Davis para un par de dudas:
Actualización a 09/07/2023: Estoy ENCANTADO.
P.D: La App del móvil:
Actualización a 22/07/2023: Hoy se me ha olvidado en casa! :(
As it happened, the 20/80 GF soon became a popular “norm,” typically giving a deep stop similar to Pyle’s and the bubble models. ... Many are themselves using Bühlmann, but with the low GF value of 40 or 50 instead of 20. ... For Bühlmann ZHL-16C, GF low settings lower than 55 led to first stops that were considered to be too deep. The study mentioned that a GF Low of 70 was also acceptable, so it explicitly approved of a range of 55-70 but did not specify an upper limit. It also said a GF high of 70 or below was within the preferred US Navy limits.
Actualización a 26/08/2023: Primera carga desde que lo compré y cargué por primera vez (llevamos 7 inmersiones):
En su cuna (conectada al ordenador por USB) y sin quitar la correa NATO.
Actualización a 22/09/2023: A ver...
Actualización a 02/10/2023: Pensando en cambiar los GF ya que ayer me comí una buena deco cuando los demás ni entraron con los Suuntos:
Bien, según tengo leído:
As it happened, the 20/80 GF soon became a popular “norm,” typically giving a deep stop similar to Pyle’s and the bubble models. ... Many are themselves using Bühlmann, but with the low GF value of 40 or 50 instead of 20. ... For Bühlmann ZHL-16C, GF low settings lower than 55 led to first stops that were considered to be too deep. The study mentioned that a GF Low of 70 was also acceptable, so it explicitly approved of a range of 55-70 but did not specify an upper limit. It also said a GF high of 70 or below was within the preferred US Navy limits.
Y:
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.
Bien, si quisiera seguir saliendo a GF High 70 (por defecto en modo técnio), tendría que usar un GF Low de 58,1 (83% de 70) en vez del GF Low 30 por defecto.
Actualización a 03/10/2023: Pues, me cuadra con el 40/85 del Rec:
Voy a empezar a probar, poco a poco, con el GF Low ya que mantengo el High conservador (70 del Tec u 85 del Rec). Es decir:
