译文专栏|潜水中的梯度系数GF值|163

此篇文章翻译自DiveRite的Blog

原文网址：https://www.diverite.com/articles/gradient-factors/

译者的话

本人金侠是一位IANTD的技术教练（教练编号9936），在一路学习的过程中越发对潜水专业的知识感兴趣，所以逐步开始翻译一些相关文章。此次选择了学员比较感兴趣的GF值作为话题，选择了DR的一篇文章，希望对各位读者有相关参考作用。此次翻译为中英文对照，在相关段落还会加入一些其他参考资料。资料出处会直接标出。此翻译纯粹是译者个人兴趣，无任何商业目的。请所有读者务必不要用作他用，仅供自己阅读。多谢各位。

梯度系数GRANDIENT FACTORS

By Matti Anttila, Ph.D.

Remember your first diving classes and the lesson about bubbling soda bottle and too rapid ascents? No matter how deeply you study the decompression theory, this soda bubble analogy is still valid. However, it’s time to introduce some more fundamentals of the issue. But let’s start from the history:

您还记得第一次参加的潜水课程吗？那节关于汽水瓶不断冒泡和过速升水的课吗？无论你对减压理论有多深的研究，汽水冒泡分析依然成立。然而，是时候来介绍一些与此相关的原理了。就让我们从历史开始：

历史HISTORY

Decompression theory is a relatively old science. Already in late 1800’s, French physiologist Paul Bert (1833-1886) discovered decompression sickness and the need for decompression stops and slow ascend speed. Bert also studied the effects of oxygen to the humans, as he was more interested in the physiological effects of mountaineering and hot air ballooning. He also extended his studies to cover high pressure environments, and found out later about oxygen toxicity. Bert made a conclusion that high oxygen partial pressures affect humans chemically, not mechanically, as he described the causes of Central Nervous System (CNS) oxygen toxicity. When Bert studied air and nitrogen, he correctly determined the cause of the Decompression Sickness (DCS) to be caused by the nitrogen bubbles in the blood and other tissues (mechanical effects). Bert also did experiments on recompression therapy and oxygen administration in DCS cases. The most famous of Bert’s books is “La Pression barometrique” 1 , published in 1878, which dealt with the human physiology in low and high air-pressures.

减压理论是一门相对古老的科学。早在19世纪末期，法国生理学家保罗·伯特（Paul Bert 1833-1886）发现了减压病、减压停留的需求以及上升速度要缓慢。伯特也研究了氧气对于人体的影响，因为他更感兴趣的是登山及乘热气球过程中的生理影响。他还将自己的研究拓展至高压环境，之后发现了氧中毒。伯特在描述中枢神经系统（CNS）氧中毒的原因时得出结论：“高氧分压对于人体的影响是作用于化学层面，而非物理层面”。当伯特研究空气和氮气的时候，他成功的确定了减压病（DCS）是由血液和其他组织中的氮气气泡引起的（物理作用）。伯特最著名的书籍是《气压》（La Pression barometrique，文献参考1），著于1878年，其中涉及到在低气压和高气压下的人体生理学。

While Bert laid the fundamentals to the decompression studies, it was John Scott Haldane (1860-1936), a Scottish physiologist who approached the problem of decompression theory with more scientific approach. In 1905, Haldane was appointed by the Royal Navy to perform research about Navy’s diving operations. His focus was to study the decompression sickness and how it could be avoided. Haldane performed several tests and studied the effects of compressed air at depth, and in 1908 he published the results of his tests in the Journal of Medicine 2. This article also contained his diving tables.

当伯特为减压研究奠定基础时，苏格兰生理学家约翰·斯科特·霍尔丹（John Scott Haldane 1860-1936）用更为科学的方法研究了减压理论的相关问题。1905年, 霍尔丹被皇家海军任命进行海军潜水行动的相关研究。他研究的重点是减压病及如何避免其发生。霍尔丹做了几项实验，研究不同深度下压缩空气对人体的影响，并于1908年，在医学杂志（Journal of Medicine，文献参考2）上发表了实验结果。这篇文章中还包括了他的潜水数据表。

译者备注：经过查阅资料（比如2010年出版的，梁前进主编，《遗传学-生命科学辅导丛书。名师点拨系列》，），law of Haldane应该正式翻译叫霍尔丹理论。

Haldane is considered to be the father of modern decompression theory. In his research, he made an important conclusion that a diver could surface from an indefinitely long 10m/33ft dive without DCS. From this result, he determined that human body could tolerate pressure change with a factor of 2:1 (the pressure in 10m/33ft is 2 ATA, while on surface it is 1 ATA). Later this number was refined to be 1.58:1 by Robert Workman. Workman was an M.D. and decompression researcher in U.S. Navy during 1960’s. He studied systematically the decompression model that was used in the U.S. Navy and which was then based on Haldane’s research. In addition to refining the tissue pressure ratio, Workman found out that the ratio varied by tissue type (hence the term “tissue compartment” or TC, representing different half-times, e.g. speed of gas dissolving) and depth.

霍尔丹被誉为现代减压理论之父。在其研究中，他得出了一个重要结论：潜水员可以在10米深度进行无限时长的潜水，升水后也不会得减压病。根据这一结果，他确定人体可以承受2:1的压力变化（10米/33英尺处的压力是2 ATA，水面的压力是1 ATA）。后来这个数值被罗伯特·沃克曼（Robert Workman）改进为1.58:1 。沃克曼是医学博士，在60年代任职美国海军减压病研究员。他系统的研究了美国海军所使用的、基于霍尔丹研究的减压模型。除了改进了组织压力比率以外，沃克曼发现这个比率还基于不同的组织类型和深度而变化（术语“组织隔腔Tissue Compartment”或TC，代表不同的半时，即半饱和时间，例如气体溶解的速度）

译者备注：Tissue Compartment直接翻译是组织间隔，但是本人沿用老师以前上课时候使用的组织隔腔作为翻译，感觉更为容易理解。这里所谓的组织，是人为定义出来的，与人体实际的组织不同。

Dr. Albert A. Bühlmann (1923-1994) from Zürich developed decompression theory further. During his long research career, he extended the number of tissue compartments to 16, which was the basis of his ZH-L16 decompression model (“ZH” as Zürich, “L” as Linear and “16” for the number of TCs). The first set of ZH-L16 tables was published in 1990 (previous tables 3, published earlier, contained smaller amount of TCs).

来自苏黎世的阿尔伯特.波曼(Albert A. Bühlmann 1923-1994)博士进一步发展了减压理论。在他漫长的研究生涯中，他把组织隔腔的数量扩充到了16个，这也是ZH-L16减压模型的基础。（ZH表示苏黎世，L表示线性，16表示16个组织隔腔。第一套ZH-L16数据表出版于1990年。（出版较早的表3包括的组织隔腔比较少）

译者备注：十分抱歉，我在网络上没有找到Albert A. Bühlmann博士的中文译名，从专业角度不敢随便乱写，自己音译为阿尔伯特.波曼。如果有更为精确的翻译请随时告诉我。曾经我看过Erik C. Baker一篇文章，名字叫《Understanding M-values》，也就是本文的文献4，其中对于L的解释是Limit而非本文的Linear，本人目前在网上没有搜索到Bühlmann模型最初的相关文献，所以这个问题希望有人可以给出解答。如果想看《Understanding M-values》这篇文章可以在百度学术中免费查阅。还有就是提到的table3，我根据上下文无法确定是什么，如果有人知道也麻烦告诉我。

减压原理 DECOMPRESSION BASICS

Let’s start from basics: A diver goes down and breathes compressed air from his/her cylinder. Air contains nitrogen, which, as an inert gas, dissolves into the diver’s tissues. When the diver starts ascending, the ambient pressure decreases and dissolved nitrogen transfers from other tissues to the blood, from there to the lungs and finally leaves the body with each exhale cycle. Simple as that, is it?

来让我们从原理开始讲：一个潜水员开始下潜并从气瓶中的呼吸压缩空气。空气中含有氮，氮是一种惰性气体，会溶解在潜水员的组织中。当潜水员开始上升时，环境压力降低，溶解的氮从其他组织转移到血液中，接着到达肺部，最终随着呼气循环排出体外。就这么简单，是吧？

In recreational diving, no decompression dives are being conducted. Divers are told to stay within their no-decompression limits (NDL) of bottom time. This NDL is shown in diving tables, and besides that, divers must stay within certain ascent speed. This information is generally enough for most divers, but what is the case when we exceed the NDL and start accumulating decompression time?

在休闲潜水中，进行的是免减压潜水。潜水员被告知要保持在免减压极限（NDL）的底部时间内。免减压极限可以在潜水表格中查到，除此之外，潜水员需要遵循一定的上升速度。这些信息对于大多数潜水员来说已经足够，但是当我们超过了免减压极限并开始累积减压时间时，情况会怎样呢？

组织饱和以及升限

TISSUE SATURATION AND ASCENT CEILING

When we dive, we always have an invisible ceiling above us. This ceiling is a depth, which we can ascend to without getting DCS symptoms (generally speaking). The ceiling is based on the amount of dissolved inert gas in our tissues.

当我们潜水时，我们的头顶总是有一个看不见的天花板，也就是升限。这个升限指的是一个深度，通常来说我们在上升到达这个深度时不会出现减压病症状。升限是基于我们组织中溶解的惰性气体的数量来设定的。

译者备注：关于ascent ceiling，我查到在航天技术领域可以解释为上升限度，或者简称升限，我认为挺合适的。

Figure 1 represents a typical decompression dive profile with multiple decompression stops. Before the dive, your “ceiling” is in fact negative depth (above surface), meaning that your tissues could tolerate certain overpressure gradient. As the run time increases and diver spends time at the bottom, the ceiling depth goes down and starts limiting the ascent possibilities, generating the need for decompression. In fact, some decompression software indicates the ceiling depth when user types in the desired dive levels. Diving computers indicate the ceiling as the deepest required decompression depth.

图1表示了一个典型的拥有多个减压停留的减压潜水侧面图。在开始潜水之前，你的“升限”实际上是负深度（在水面以上），这意味着你的组织可以承受一定的超压梯度。随着行进时间的增加以及潜水员在底部的耗时累积，升限开始变深，并且开始限制上升的可行性，产生了减压的需求。事实上，当用户输入所期望的潜水级别时，一些减压软件会显示升限的深度。潜水电脑显示的升限代表了需要减压的最大深度。

Figure 1: A typical decompression dive profile with ceiling line visible. Numbers represent different phases (see phases also in Figure 2).

译者备注：图1中数字代表潜水的不同阶段。实线为实际潜水轨迹。虚线代表该阶段的升限。横轴代表行进时间，纵轴代表深度。

When the ascent starts, the diver can not ascend above the ceiling without risking the possibility of decompression sickness. The decompression stops are clearly visible in the dive profile when the line goes below the ceiling depth. The closer one goes to the ceiling, the less margin of safety remains. The ceiling depth does not yet indicate on-gassing or off-gassing. Bühlmann used 16 tissue compartments to model inert gas dissolving in our body. These compartments either take more dissolved gas in (on-gassing) or expel dissolved gas out (off-gassing). The ceiling depth indicates the pressure change from current depth, in which the leading compartment off-gasses so fast, that further increased pressure drop would risk the possibility of DCS.

开始上升时，潜水员无法在上升超过升限深度的情况下，还能避免罹患减压病的风险。在潜水侧面图中，减压停留的深度所显示的线路一直都处于升限下方。越接近升限，意味着安全余量就越小。不过升限深度并不能显示当前状态是在吸气还是排气。波曼一共使用了16个组织隔腔来模拟惰性气体在我们体内的溶解过程。这些隔腔要么吸收更多溶解的气体（吸气），要么排出溶解的气体（排气）。升限深度预示了当前深度压力的变化，可能会导致隔腔排气过快，导致压力进一步下降从而增加减压病的风险。

Figure 2 illustrates these 16 tissue compartments during the dive, presented in Figure 1. A tissue compartment (TC) has reached its saturation point when it is 100% full. During the ascent phase, a TC can go supersaturated (exceed 100%). The key of the decompression is to be supersaturated, but not so much that the dissolved gas would form excess bubbles to our tissues and blood.

图2阐释了这16个组织隔腔在图1潜水过程中的变化。一个组织隔腔吸气量到100%时就达到了它的饱和点。在上升阶段，组织隔腔可处于过饱和状态（超过100%）。减压的关键就是达到过饱和，但是又不能超过太多以至于溶解的气体会在我们的组织和血液中形成过多的气泡。

Figure 2: An example of inert gas loading in tissues. Pressure in tissue compartment is indicated as percents, 100% being ambient pressure.

译者备注：图2是16个组织隔腔惰性气体吸收的例子。组织隔腔压力用百分比表示，100%表示环境压力。内外压力一致即100%时表示饱和，过饱和状态会开始排气。

As shown, the amount of dissolved gas, or specifically the partial pressure of the dissolved inert gas in our tissues, tends to follow the ambient pressure in which we are during the dive. The bigger the pressure difference (i.e. pressure gradient), the faster the gas dissolves, in both directions. This leads to an obvious question: Why not just come up? What are the limits of supersaturation, and how are they defined?

如图所示，溶解气体的量，或者确切地说，组织中溶解的惰性气体的分压，在我们潜水过程中会趋向于接近环境压力。压差（压力梯度）越大，气体溶解或析出的速度越快。这就引出了一个明显的问题：为什么不直接上升？过饱和的极限是什么，它们是如何定义的？

M 值 M-VALUES

Back to the history: Robert Workman introduced the term M-value, which means Maximum inert gas pressure in a hypothetical tissue compartment which it can tolerate without DCS. As mentioned, Haldane found out in his research that M-value is 2, and Workman refined it to be 1.58 (this number comes from pressure change from 2 ATA to 1 ATA, and taking into account that air has 79% inert gases, mainly nitrogen).

说回历史: 罗伯特·沃克曼引入了术语 M值,代表一个假想的组织隔腔在不罹患减压病的前提下，能承受的最大惰性气体压力。如上所述，霍尔丹基于自己的研究发现M值是2，沃克曼改进为1.58（这个值来自于压力从2个ATA到1个ATA时，只考虑空气中含有79%的惰性气体，主要是氮气）

Workman determined the M-values using depths (pressure values) instead of ratios of pressure, which he then used to form a linear projection as a function of depth. The slope of the M-value line is called ΔM (delta-M) and it represents the change of M-value with a change in depth (depth pressure).

沃克曼用深度(压力值)来代替压力比来确定M值，然后用它来得出一个关于深度的线性函数。M值函数的斜率称为ΔM,它代表了在深度(深度压力)变化时M值的变化情况。

Bühlmann used the same method than Workman to express the M-values, but instead of using the depth pressure (relative pressure), he used absolute pressure, which is 1 ATA higher at depth. This difference is shown in Figure 3, where Workman’s M-value line goes above Bühlmann’s M-value line.

波曼使用了和沃克曼一样的方法来表达M值，但他使用的不是深度压力（相对压力），而是绝对压力，即压力会比深度大1个ATA。这种差异如图3所示，沃克曼的M值直线位于波曼之上。

Figure 3: Comparison of different M-value lines.

Figure 3 shows a comparison between Workman and Bühlmann M-value lines. A more detailed explanation can be found in literature 4, but it is easy to spot the greatest differences: while Workman M-value line is steeper than Bühlmann M-value line, there is also less margin for safety. Workman M-values also allow higher supersaturation than Bühlmann’s.

图三是沃克曼和波曼的M值直线的比较。更详细的解释可以在文献4中找到，但是图中很容易分辨他们最大的不同：沃克曼的M值直线比波曼的更陡，安全余量也更小。沃克曼的M值相比波曼的允许更高的过饱和度。

To make things a bit more complex, it should be noted that while the M-values vary by tissue compartment, also two sets of M-values are used for each TC; M0-values (of depth pressure, indicating surfacing pressure. M0 is pronounced “M naught”) and M-values of pressure ratio (ΔM, “delta-M” values). Workman defined the relationship of these different M-values as:

再复杂一些的说，值得注意的是：不同的组织隔腔所对应的M值也不同，并且每个组织隔腔都使用2套M值； M0值（深度压力，代表水面压力，读作M naught）和压力比的M值（ΔM, “delta-M” 值）。沃克曼将这些不同M值之间的关系式定义为:

These sets of values are listed in literature 4. However, they concern the same thing: maximum allowed overpressure of the tissue compartments. It is also important to know, that decompression illness does not exactly follow the M-values. More sickness occurs at and above the pressures represented by the M-values, and less sickness occurs when divers stay well below the M-values.

这一系列的M值在文献4有详细列出。然而，它们关注的是同一个事：组织隔腔允许的最大超压。同样我们应该知道，减压病并非完全遵循M值。大多数减压病发生在超过M值的压力下，而当潜水员保持在M值之下时，减压病较少发生。

译者备注：在文献4，即《Understanding M-values》一文中列出了大量M值的相关列表，可以去参考。如果之后有时间，我会把该篇文章重新进行梳理和翻译。

梯度系数 GRADIENT FACTORS

Gradient Factors are meant to offer conservatism settings for Bühlmann’s decompression model. As mentioned in the previous chapter, M-value line sets a limit which is not supposed to be exceeded during ascent and decompression. However, as no decompression model can positively prevent all DCS cases, and because both dives and divers are individual, additional safety margin should be applied.

梯度系数是为了给波曼减压模型提供保守度的设定。如上章节所述，M值直线确定了上升和减压阶段所不能够逾越的极限值。然而，由于没有任何减压模型可以绝对的预防所有的减压病情况，同时每一次的潜水和潜水员都不尽相同，因此应采用更加安全的余量。

As shown in Figure 3, ascent and decompression occurs between the M-value line and Ambient Pressure line. Inert gas pressure in tissue compartments must exceed the ambient pressure to enable off-gassing. On the other hand, we do not want to go too close to the M-value line for safety reasons. Gradient Factors define the conservatism here.

如图3所示，上升和减压发生在在M值线和环境压力线之间。组织腔隔内的惰性气体压力需要超出环境压力才能开始排气。另一方面，出于安全考量，我们不希望过于接近M值直线。梯度系数在这里定义了保守度。

The Gradient Factor defines the amount of inert gas supersaturation in leading tissue compartment. Thus, GF 0% means that there is no supersaturation occurring and inert gas partial pressure equals ambient pressure in leading compartment (Note: The leading TC is not necessarily the fastest TC!). GF 100% means that decompression is being done in a situation where the leading TC is at its Bühlmann’s M-value line and risk for DCS is far greater than using lower GF. (Note: Sometimes, especially in equations and calculations, GF’s may be numbered as 0.00 … 1.00 instead of percentage. However, these are effectively the same thing as 100% = 1)

梯度系数定义了优先组织腔隔中惰性气体过饱和程度。因此，GF值等于0% 表示不存在过饱和现象，优先组织腔隔中的惰性气体分压等于环境分压（注意：优先组织腔隔不一定必须是吸收或排放最快的组织腔隔）。GF值等于100%表示意味着减压是在这样一种情况下进行的: 优先组织腔隔在其波曼的M值直线上，此时罹患减压病的风险要远远高于使用较低的GF值。（注意：有时候，尤其是在方程和计算中，GF值可能表示为0.00 … 1.00，而非使用百分比。然后，他们实际就是相当于100%=1一样。）

Some diver’s did not like the idea of using the same conservatism factor throughout the ascent. Instead of having one GF, there was need to change the safety margin during the ascent. This led to two GF values; “GF Low” and “GF High”. Low Gradient Factor defines the first decompression stop, while High Gradient Factor defines the surfacing value. Using this method, the GF actually changes throughout the ascent. This is illustrated in Figure 4, where GF Low and GF High forms start and end points to a Gradient Factor line. In that graph, decompression starts when the inert gas partial pressure in diver’s TC’s reaches 30% of the of the way between Ambient Pressure line and M-value line. Then the diver spends time in that stop until partial pressure drops in the TC’s enough for enabling ascent to next stop, which again has a bit higher GF. These two GF values are often written as “GF Low-% / High-%”, e.g. GF 30/80, where 30% is GF Low value and 80% GF High value.

一些潜水员不喜欢在整个上升过程中使用相同的保守度设定。为了不只有一个GF值，上升时需要改变安全余量。这导致了2个GF值“GF低”和“GF高”。GF低值定义了第一个减压停留，GF高值定义了升水的值。使用这种方法，GF在整个上升过程中都会不断变化。如图4所示，GF 低值和GF 高值形成了梯度系数直线的起点和终点。在这个图中，减压是从潜水员的组织腔隔中惰性气体分压达到环境压力直线到M值直线之间间距30%时开始。然后潜水员开始在那个深度进行停留，直到组织腔隔的分压下降到允许上升到下一个停留，每一个当前停留深度的GF值会比之前的停留点高一些。两个GF值一般表示为“GF Low- %/ High- %”，例如 GF30/80，其中30%是GF低值, 80%是GF高值。

Figure 4: One-tissue model of decompression. Graph starts from top right and goes left down, staying between the ambient pressure line and Gradient Factor (GF) line. GF line stays below the M-value line and forms the safety margin for the decompression. Pure Bühlmann decompression would follow the M-value line (GF 100/100).

实际运用和安全的潜水习惯

PRACTICAL APPLICATIONS AND SAFE DIVING HABITS

No decompression model can positively prevent divers getting hit. M-values do not represent any hard line between “no DCS symptoms” and “getting hit”. In fact, modern decompression science has proven that there are bubbles present in our tissues even when there are no DCS symptoms after a dive. Therefore, M-values neither represent a bubble-free situation, but tolerable amount of “silent” bubbles in tissues.

没有任何减压模型能够让潜水员完全避罹患免减压病的风险。 M值也不能成为得不得病的安全线。事实上，现代减压科学已经证明，潜水后，即使没有减压病症状，我们的身体组织里也有气泡存在。因此，M值不代表没有气泡，不过是组织中有可承受的“安静”气泡。

Figure 5: Silent bubbles are present in our tissues even when no DCS symptoms are present. It is important to know personal safety margin and individual susceptibility to DCS.

It is important to understand that certain dives and different people may need different safety margins. Therefore it is good to know the practical differences between dive plans where different Gradient Factors are used. Let’s take another example:

需要理解的很重要的一点是，特定的潜水和不同的人可能需要不同的安全余量。因此，了解使用不同梯度系数的潜水计划之间的实际差异是有好处的。来看另一例子：

A diver goes to 50m/165ft for 20 minutes bottom time, using Trimix 18/45 (18% oxygen, 45% helium) as back gas, and oxygen for decompression from 6m (20ft) on. Descent rate is 15m/min (50ft/min) and ascent rate is 10m/min (33ft/min). Decompression algorithm is based on Bühlmann ZH-L16B and the different decompression tables, based on five different GFs, are shown in Table 1.

一潜水员下50米，底部时间为20分钟。使用18/45的三混气作为背气（18%氧气，45%氦气），在6米使用纯氧做减压。下降速率是15米/分钟，上升速率是10米/分钟。减压算法使用波曼ZH-L16B，使用5个不同的GF值算出减压计划表。如表1所示：

Table 1: Decompression tables for 50m (165ft) / 20min using different Gradient Factors

译者备注：相关减压计划表如何使用，以及如何使用Deco Planner计划减压潜水以及其他相关知识，推荐学习IANTD的ART课程（初阶三混气）。这里不再展开。

These GF parameters are commonly used for different types of dives (e.g. rebreather, deep/cold dives, default values in some decompression SW) and GF 100/100 is shown here as a reference, since it is pure Bühlmann table (containing no margin, so it is also not very safe!). As clearly shown in Table 1, low GF Low numbers generate deeper stops. In fact, some divers use GF Low value of 10% to generate “deep stops” 5. Deep stops, also called “Pyle stops”, are a means to reduce micro bubbles during deeper phase of ascent. However, during deep stops, many slower tissues are still on-gassing and thus total decompression time will increase (but again, safety is worth for some added hang-time!).

这些GF参数通常用于不同类型的潜水（例如：循环呼吸器，深潜/冷水潜水,一些减压软件的默认值），表格里面用 GF 100/100作为一个参考，因为它是原始的波曼数据表（没有安全余量，所以不太安全）。如表1所示，更小的GF低值意味着更深的深度停留。事实上，一些潜水员使用10%的GF低值达到“深度停留”（参考文献5）。深度停留，也被称作“派尔停留”（Pyle Stop）是在上升阶段的较深位置减少微小气泡的一种方法。然而，在深度停留阶段，很多较慢组织还在继续吸收气体，因此整个减压时间会变长（但是，再三强调，只要安全，水里多待一会是值得的）。

译者备注：关于Pyle Stop，可以去看文献5《Clearing Up The Confusion About "Deep Stops"》，深度停留的概念和重要性在1996年由Pyle提出，所以也因此命名（Pyle RL. 1996. The importance of deep safety stops: Rethinking ascent patterns from decompression dives. DeepTech. 5:64; Cave Diving Group Newsletter. 121:2-5.）。

Figure 6: Fundamental knowledge about the Gradient Factors is essential for your safe diving. On long decompression dives, safety margins not only contribute to preventing of DCS, but also to gas planning, logistics and equipment considerations. A good diver adapts his/her personal Gradient Factors according to personal fitness, environment and dive type. No matter which diving gear you use, decompression and need for conservatism follows your plan!

It is easy to modify the dive plan even drastically by using different gradient factors. Most modern decompression software provides either conservatism settings (in verbal terms or numbers) or gradient factors. A diver can modify the total dive time easily by even tens of minutes with these settings, not to mention also the decompression gas needed. But this is also a pitfall; consider a situation where decompression software indicates that you need an intermediate decompression mix fill pressure which is just above your cylinder capacity (including margins). Now, an easy but dangerous choice would be altering the gradient factors so that the decompression time decreases, leading to lower decompression gas need.

使用不同的梯度系数是可以很容易的大幅度修改潜水计划。大多数现代减压软件要么提供保守度设置(用文字或数字表达)，要么提供梯度系数。通过这些设置，潜水员可以很容易的修改总潜水时间，甚至是上下几十分钟的差别，更不用说更改使用的减压气体了。但这也是一个陷阱，考虑这样一种情况：减压软件指出，你需要的过渡减压混合气体刚好超过你的气瓶容量(包括备份气体)。现在，一个简单但危险的选择是改变梯度系数，从而减少减压时间，降低对减压气体的需求。

Divers using computers, which have user-configurable gradient factors, should understand how modifying their GF’s will affect to their decompression profiles. Too many divers simply use the default settings or copy their GF parameters from other divers or even from the Internet, no matter what kind of a dive they are doing. Some divers have higher susceptibility to DCS and some dives are physically more demanding than others. Although the gradient factor method provides substantial flexibility in controlling the decompression profiles and thus the dive plan and gas logistics, it just might be worth to hang there a bit longer sometimes.

潜水员使用的潜水电脑，其中有用户可配置的梯度系数，潜水员应了解GF值的修改将如何影响其减压计划。有太多的潜水员只是简单地使用默认设置或从其他潜水员甚至从互联网上复制他们的GF参数，而并不去思考他们究竟在做什么类型的潜水。一些潜水员更容易得减压病，而一些潜水员的生理需求会比他人要高。虽然修改梯度系数方法在控制减压侧面图、潜水计划和气供应方面提供了很大的灵活性，但有时还是值得在水里多停留一会。

As always in diving, it remains YOUR responsibility to choose the gradient factors and conservatism appropriate for you!

为了一直潜下去，选择适合你的梯度系数和保守度是你的责!

文献参考 REFERENCES：

1. Bert, Paul: La Pression barométrique, recherches de physiologie expérimentale, 1878

2. Boycott, A.E., Damant, G.C.C., and Haldane, J.S: The Prevention of Compressed Air Illness, The Journal of Medicine (Journal of Hygiene, Volume 8, (1908), pp. 342-443.)

3. Bühlmann, Albert A.: Decompression – Decompression Sickness. Berlin: Springer-Verlag, 1984.

4. Baker, Erik C.: Understanding M-values

5. Baker, Erik C.: Clearing Up The Confusion About "Deep Stops"

Matti has an M.Sc. in technical physics and Ph.D. in spaceflight instrumentation, so diving science is close to his heart. He got trained as a minehunter diver in the Finnish Navy in 1995 using semi-closed rebreathers, and later pursued for recreational and then technical diving. In late 1990’s he begun teaching technical diving in Finland, and currently he is on the IANTD Board of Advisors. Matti is interested in diving technology, experimental diving and cave diving, but still founds it equally nice to teach open water diving class for beginners or trimix diving for more advanced divers.

View all posts by: Matti Anttila Ph.D.

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