{"id":15157,"date":"2019-08-07T21:19:22","date_gmt":"2019-08-07T13:19:22","guid":{"rendered":"http:\/\/scubatechphilippines.com\/scuba_blog\/?p=15157"},"modified":"2023-01-08T22:27:12","modified_gmt":"2023-01-08T14:27:12","slug":"scuba-q-and-a-why-do-decompression-divers-use-nitrox","status":"publish","type":"post","link":"https:\/\/scubatechphilippines.com\/scuba_blog\/scuba-q-and-a-why-do-decompression-divers-use-nitrox\/","title":{"rendered":"Scuba Q&A: Why Do Decompression Divers Use Nitrox?"},"content":{"rendered":"

Scuba Q&A: Why Do Decompression Divers Use Nitrox?<\/h1>\n

Q. Why do decompression<\/a> divers use nitrox<\/a> in the shallower part of their dive? <\/strong><\/p>\n

Answer:\u00a0<\/strong><\/p>\n

A diver absorbs or releases inert gas based on the positive or negative partial pressure<\/a> differential of those gases in their breathing mix and body tissues.<\/p>\n

We only have to consider inert gases (i.e. nitrogen<\/i>), because they aren’t metabolised in the body. Whatever is absorbed, must be released. Oxygen is<\/i> metabolised by the body and, thus, doesn’t contribute to decompression sickness<\/a>.<\/p>\n

When the partial pressure<\/a> of the inert gas being breathed is greater than that gas partial pressure<\/a> inside the body tissues it will be steadily absorbed – until the tissues become saturated (gas partial pressure<\/a> is equal<\/i>).<\/p>\n

\"why<\/p>\n

Likewise, when <\/i>the inert gas’s partial pressure<\/a> dissolved inside body tissues is greater than the partial pressure<\/a> of that same inert gas in the breathing mix, the gas will be released. This positive over-pressure differential is called super-saturation.<\/p>\n

The greater the pressure differential\/level of super-saturation, the faster that inert gas will diffuse out of the body tissues.<\/p>\n

Without changing the gas you breathe, the only means of creating super-saturation and a positive inert gas differential is by ascending to a shallower depth.<\/p>\n

This is why decompression<\/a> divers ascend to a pre-calculated depth (to achieve super-salutation<\/i>) and then stop (to allow inert gas to diffuse out<\/i>).<\/p>\n

Bubbles can form if the super-saturation gets too high – causing decompression sickness<\/a>. Every decompression<\/a> model\/algorithm dictates a maximum amount of safe super-saturation. That is known as the \u201cM-value\u201d (maximum value).<\/i><\/p>\n

The science of decompression<\/a> is to get as shallow as possible to maximise off-gassing, whilst also staying below that threshold of maximum super-saturation.<\/p>\n

There is another way that divers can increase the partial-pressure differential of an inert gas they’ve absorbed. That is to reduce the fraction<\/i><\/b> (or %<\/i>) <\/i><\/b>of the inert gas they’re breathing.<\/p>\n

Divers can switch to a different breathing gas that contains less % of the inert gas – and this increases the partial pressure<\/a> differential – thus speeding up the diffusion of inert gas out of their body tissues.<\/p>\n

Because oxygen is metabolised, it is the natural choice as a replacement for the inert gas in the diver’s \u201cdeco” breathing mix.<\/p>\n

However, oxygen poses problems in regard to CNS toxicity – so we have to maintain a maximum operating depth based on the partial pressure<\/a> of the O2% used. This is why it is only used in the shallower phases of the ascent.<\/p>\n

This process of speeding up the removal of inert gas from the body tissues by manipulating the inert gas % to cause a greater differential at a given depth is called \u201caccelerated decompression\u201d.<\/p>\n\n\n\n\n

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