SDTechDiving

Safe deep diving needs a sound understanding of decompression physiology more than ever. A deep dive nowadays could mean 80-90m plus. Divers have tools for deep diving that can extend depth and time often way beyond the individuals experience. The widespread use of rebreather units allow divers to explore depths way deeper than a scuba set would allow them. With the hardware easily available to exceed common sense, it is glaringly obvious that academic training and practical deep diving experience should be similarly advanced.

As divers explore wrecks and reefs in deep water they are increasingly pushing decompression boundaries to the point that many are injured or killed. Standard classes in deep diving techniques are very antiquated, mostly being written over 20 years ago, by well meaning individuals with a commercial or military background. These techniques have evolved over time but are seldom collated into a lucid text. Many experts in the field of technical diving are simply computer programmers that dive. When two get together in a chat room, become leading gas physiologists and decompression gurus...the non diving kind!

Trimix training courses even the "Advanced levels" prepare the diver for at best...60m diving. To prepare a student to safely to dive as deep as 100m as many agencies offer would take in my opinion at least 20 dives below 60m, not 2-4 dives as typically offered! A customer expects to be able to dive deep unsupervised after training. Technical dive students are becoming less and less capable after spending many hundreds of pounds with their "cross over special" instructors with 10 dives below 40m!

Diving to depths no deeper than 60m and no longer than 25 minutes at this depth are within the realms of safety, but only if the individual is adequately experienced and diving regularly. Trimix training classes typically contain techniques that include gas management protocols like 1.6 po2 for deco and 1.4 po2 for bottom mix, also divers are recommended to stop breathing trimix mixtures as early as possible during the ascent phase and switch to nitrox mixes to speed off gassing. These techniques have been used relatively safely for many years and thousands of dives.

If the diveplan goes beyond 70m to 80m for significant bottom times (25 minutes) then the above techniques are not advisable and should be modified. Trimix gas mixtures with helium values commensurate with the conditions and divers experience need careful consideration. If conditions are not ideal than an END of 30-40m would be appropriate. If the dive takes place in ideal conditions outside of an overhead environments then a higher END would be a better choice (40-50m). Using more helium is not a substitute for experience. Most deeper diving fatalities are directly linked to buoyancy control. If a diver has a runaway ascent because of dry suit complications or problematic marker buoy deployment, the use of helium in the gas mixture will compound the problem exponentially.

Experience solves problems, not sobriety... Experience comes with repetition

Helium is a far less forgiving gas than nitrogen. Helium will bubble during a problem ascent far sooner than nitrogen with more disastrous effects. Helium is a faster gas to decompress from, BUT, only if the ascent goes perfectly. The more helium in the breathing gas, a perfect ascent needs to be guaranteed.

Helium should be the reward for truly experienced deep divers, This new breed of "shallow" or "entry level" or "Triox" trimix divers can expect long term bone damage that their air diving counterparts are less likely to experience. It is truly a scandal how training agencies create courses that let inexperienced divers believe that diving helium shallow is somehow safe. While you may be decompressing efficiently if all things go perfectly, one problem ascent is all it takes to make your skeleton decay ahead of time!

Once the helium values are derived, oxygen values are worthy of deliberation. While 1.4 po2's are common place for bottom mixes, an advanced trimix diver should be thinking about po2's in the 1.2 range. Helium has the abilty to deflate nerve synapses and this must have a negative affect on divers during descents and in the early phase of the bottom time. Rapid descents are associated with deep scuba dives, these are frought with danger. HPNS is a concern for dives below 150m but END's around 50m will help minimise tremors and pain associated with bone space compromise (be assured that the body has plenty of void spaces that, if compressed regularly will get bigger and bigger causing inflammation then decompression complications, then bone necrosis, helium will ensure that this happens in your lifetime). If a diver is not comfortable with 50m END's then the diver has absolutely no place below 50m!

A descent speed of 10m-20m per minute and slower for anchor line descents should be considered. Descending quickly on trimix feels better than air as it ventilates the lungs nicely and lessens c02 build up.

Dry suit’s pose an interesting complication for decompression divers. If you inflate drysuits with mixes containing helium then this will speed diver cooling. The cooling is not due to heat loss because of helium’s presence in the suit solely (a function of its poor insulating properties). As helium de pressurises and expands (Joules Thompson effect) much faster than air or argon, it enters the dry suit much colder and has a noticeable chilling effect. For the non-believers…simply try it! The Trimix will feel much cooler than the argon or air. Simply dropping the supplying first stage intermediate pressure will sort this problem. Many technical divers rant about the use of Argon in their dry suits. Because of Argons relative density it travels slowly into the dry suit, and this feels quite neutral with regard to temperature. A complication with Argon is, as you are unlikely to be breathing it, there is a large pressure gradient between inert gases in both your skin and other tissue. This can cause skin bends minimally, on larger dives.

		RANDOM PHOTOS

Safe deep diving needs a sound understanding of decompression physiology more than ever. A deep dive nowadays could mean 80-90m plus. Divers have tools for deep diving that can extend depth and time often way beyond the individuals experience. The widespread use of rebreather units allow divers to explore depths way deeper than a scuba set would allow them. With the hardware easily available to exceed common sense, it is glaringly obvious that academic training and practical deep diving experience should be similarly advanced. As divers explore wrecks and reefs in deep water they are increasingly pushing decompression boundaries to the point that many are injured or killed. Standard classes in deep diving techniques are very antiquated, mostly being written over 20 years ago, by well meaning individuals with a commercial or military background. These techniques have evolved over time but are seldom collated into a lucid text. Many experts in the field of technical diving are simply computer programmers that dive. When two get together in a chat room, become leading gas physiologists and decompression gurus...the non diving kind! Trimix training courses even the "Advanced levels" prepare the diver for at best...60m diving. To prepare a student to safely to dive as deep as 100m as many agencies offer would take in my opinion at least 20 dives below 60m, not 2-4 dives as typically offered! A customer expects to be able to dive deep unsupervised after training. Technical dive students are becoming less and less capable after spending many hundreds of pounds with their "cross over special" instructors with 10 dives below 40m! Diving to depths no deeper than 60m and no longer than 25 minutes at this depth are within the realms of safety, but only if the individual is adequately experienced and diving regularly. Trimix training classes typically contain techniques that include gas management protocols like 1.6 po2 for deco and 1.4 po2 for bottom mix, also divers are recommended to stop breathing trimix mixtures as early as possible during the ascent phase and switch to nitrox mixes to speed off gassing. These techniques have been used relatively safely for many years and thousands of dives. If the diveplan goes beyond 70m to 80m for significant bottom times (25 minutes) then the above techniques are not advisable and should be modified. Trimix gas mixtures with helium values commensurate with the conditions and divers experience need careful consideration. If conditions are not ideal than an END of 30-40m would be appropriate. If the dive takes place in ideal conditions outside of an overhead environments then a higher END would be a better choice (40-50m). Using more helium is not a substitute for experience. Most deeper diving fatalities are directly linked to buoyancy control. If a diver has a runaway ascent because of dry suit complications or problematic marker buoy deployment, the use of helium in the gas mixture will compound the problem exponentially. Experience solves problems, not sobriety... Experience comes with repetition Helium is a far less forgiving gas than nitrogen. Helium will bubble during a problem ascent far sooner than nitrogen with more disastrous effects. Helium is a faster gas to decompress from, BUT, only if the ascent goes perfectly. The more helium in the breathing gas, a perfect ascent needs to be guaranteed. Helium should be the reward for truly experienced deep divers, This new breed of "shallow" or "entry level" or "Triox" trimix divers can expect long term bone damage that their air diving counterparts are less likely to experience. It is truly a scandal how training agencies create courses that let inexperienced divers believe that diving helium shallow is somehow safe. While you may be decompressing efficiently if all things go perfectly, one problem ascent is all it takes to make your skeleton decay ahead of time! Once the helium values are derived, oxygen values are worthy of deliberation. While 1.4 po2's are common place for bottom mixes, an advanced trimix diver should be thinking about po2's in the 1.2 range. Helium has the abilty to deflate nerve synapses and this must have a negative affect on divers during descents and in the early phase of the bottom time. Rapid descents are associated with deep scuba dives, these are frought with danger. HPNS is a concern for dives below 150m but END's around 50m will help minimise tremors and pain associated with bone space compromise (be assured that the body has plenty of void spaces that, if compressed regularly will get bigger and bigger causing inflammation then decompression complications, then bone necrosis, helium will ensure that this happens in your lifetime). If a diver is not comfortable with 50m END's then the diver has absolutely no place below 50m! A descent speed of 10m-20m per minute and slower for anchor line descents should be considered. Descending quickly on trimix feels better than air as it ventilates the lungs nicely and lessens c02 build up. Dry suit’s pose an interesting complication for decompression divers. If you inflate drysuits with mixes containing helium then this will speed diver cooling. The cooling is not due to heat loss because of helium’s presence in the suit solely (a function of its poor insulating properties). As helium de pressurises and expands (Joules Thompson effect) much faster than air or argon, it enters the dry suit much colder and has a noticeable chilling effect. For the non-believers…simply try it! The Trimix will feel much cooler than the argon or air. Simply dropping the supplying first stage intermediate pressure will sort this problem. Many technical divers rant about the use of Argon in their dry suits. Because of Argons relative density it travels slowly into the dry suit, and this feels quite neutral with regard to temperature. A complication with Argon is, as you are unlikely to be breathing it, there is a large pressure gradient between inert gases in both your skin and other tissue. This can cause skin bends minimally, on larger dives.
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This article was contributed by Mark Ellyatt, owner of Inspired-Training.com and author of the book Ocean Gladiator and can be contacted through his website or by email. The articles presented here do not necessarily reflect the beliefs and/or opinions of SDTechDiving; they are the sole written opinion/expression of the authors. SDTechDiving is not responsible for content contained within this article, including links which may take the reader to websites outside of our control.