Although the United States Navy began using Heliox (helium-oxygen-gas mixture) in the early part of the last century, it is actually a matter of late for ordinary divers to come into contact with radon gas. The danger of nitrogen intoxication is now a must-read for all diving courses. In the 1970s and 1980s, divers also sucked in compressed air and stumbled in deep sunken ships, sending them to life. From the late 1980s to the early 1990s, Sheck Exley and others began pushing for the use of helium trimixes in the United States. However, due to the proportion of high decompression sickness in the previous naval gas mixing experiment, many technical divers at the time were skeptical that the decompression table for helium had not been adequately tested and was not intended to be used.
There are many old-school technical divers who believe that nitrogen tolerance can be cultivated. The current leader of the TDI, Bret Gilliam, has publicly stated that "(in 73 meters) you are drunk just because you are afraid of being drunk", IANTD boss Tom Mount et al. also conducted a so-called "control experiment" in which 12 individuals were divided into three groups. To support this point of view (the basic statistical knowledge is omitted here and the Tucao 5,000 words, just by the way mention that there is a sister paper in the water 73 meters underwater to do the right math problem than in the water, it is estimated on the water Can't we all be Americans?) Some technical organizations also provide nitrogen drunk management courses, although there are fewer and fewer classes.
All the students who have studied technical diving courses probably know, according to Meyer-Overton's theory (I must stress it again, this is just one of the many hypotheses, and there is relatively more data support. The next section will be detailed when writing nitrogen.) Explained), the gas-soluble fat of hernia is 1/5 of nitrogen, so its narcosis is only 1/5 of nitrogen; also know how to calculate the proportion of hernia in trimix to reduce the proportion of nitrogen to achieve a given, An equivalent depth of anaesthesia (END) or equivalent air depth (EAD) is usually not more than 40 meters or even less than 30 meters.
The benefit of radon is not just to reduce the anesthetic effect. In the OW diving course, it was stated that gas density increases with pressure, and high density gas makes divers feel breathing difficulties. Difficulties in breathing are not just uncomfortable. It will also make natural breathing a hard work.
At a deep depth, fatigue is a terrible thing, because at this time you will produce a lot of carbon dioxide in your body. As you can see from the above table, carbon dioxide is 20 times more toxic than nitrogen. If you watched Dave Shaw's last video, watching him breathing more and more heavily when he was working at 276 meters, and then returning to a silence, he will know how terrible carbon dioxide is. (I have always wanted to write a series, "About the deep world record of those things", including the death of Dave Shaw, but you do not want too much hope for the pit king ...)
Since I did not breathe air in great depth (I will tell you what the depth is, hahahaha), it does not provide first-hand information on when dyspnea begins. I can only tell you that it is very easy to breathe trimix 10/65 (10% oxygen, 65% helium, 25% nitrogen) at a depth of 100 meters.
However, in the United States Navy's 693-meter saturation diving experiment, although the respiratory trimix contains only 5% of nitrogen, most of which is helium, and the density is far lower than air, the divers must still use the mouth to assist breathing, because 70 At atmospheric pressure, light nose does not suck enough. For a saturated diver who lives in the water for several tens of days, there is a very serious consequence of the mouth being used for breathing - it is impossible to eat ... (you guessed it, there is another series in my head, called " Saturation diving history story, but, cough, you guys know)
Of course, every kind of gas has its disadvantages. For the vast number of sight-seeing technical divers, the biggest disadvantage is the expensive gas. The helium price in the Philippines is about 3 cents a liter. Please calculate the price of an 11 litre double aluminum bottle trimix 12/65 to 200 bar.
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You are not wrong, the answer is 22*200*0.65*0.03 = 85.8 dollars. This is only part of the price of gas that does not exceed 100 meters of diving.
(Hey, I have another article in my mind. The name is "Guide to the efficiency of underwater money-burning...")
However, for those divers who are trying to challenge the limits -
Here's an announcement of public service announcement: Dive doctor Frans Cronje said: When scuba diving exceeds 250 meters, only 10% of people can recover without injury, and the death rate exceeds half (Isn't there a memory of the missing doctor)? What we are worried about is that people who go to great depths may not understand the physical limits they face.
DAN said that this limit is 150 meters. Pascal Bernabe also said that he could clearly feel his physical limits after 150 meters. Almost all of the US Navy's missions that exceed 90 meters are saturated, and the Chinese Navy Medical Research Institute has also stated that they will not test non-saturated diving that exceeds a depth of 120 meters. The major technical diving organizations set the limits of the most advanced decompression courses to 100-120 meters.
How deep do you want to go? this is your choice. Just before choosing, ask yourself, do you know what you are facing?
- For divers who are trying to challenge the limits, there is a terrible consequence of hernia: HPNS (High Pressure Nervous Syndrome). Available data indicate that HPNS may appear at any time beyond a depth of 150 meters. Symptoms may start with uncontrolled trembling, followed by nausea, vomiting, dizziness and other symptoms, and may eventually develop into madness. The episode about HPNS is in the diving film "The Abyss" produced by Cameron.
Having said that, even if you are not mad, it is terrible to control all the diving equipment and perform possible work with a constantly shaking hand.
There are two main approaches to dealing with HPNS. The first is slow pressurization. Large-scale saturated divers usually spend a week adding work pressure, which can greatly reduce HPNS. However, those who are drowning for depth and depth often must reach the bottom and return within a few minutes, and only wish them good luck.
The emergence of another approach is a coincidence of unexpected surprises - U.S. divers found in a deep saturation experiment with helium-oxygen mixtures that drinking alcohol to micro-crucibles can help fight HPNS.
See if you are guessing here, they drink with wine every time?
What do you think? Please go back to the previous gas anesthetic form.
People often compare the feeling of drunkenness with drunkenness, so smart people think, then wouldn't it be helpful if I add some nitrogen gas back to the breathing gas and let the diver get a little nitrogen drunk?
The answer is: Yes.
This is the real reason trimix, that is, the helium, nitrogen and oxygen trimix gas into the diving industry.
As I said before, I have always believed that diving theory should not be called theory, but can only be called hypothesis. Because in this field, there is no so-called theory that has physiologically determined support. From the pressure drop or how bubbles cause decompression sickness, to how gas causes anesthetic effects, to why oxygen is poisonous, and how helium produces HPNS, it's just speculation.
At present, the most popular speculation about how helium produces HPNS is that stress acts directly on the surface of nerve cells, causing an increase in surface tension that causes neurotransmitter disturbances. (Red Bull supplement: There are also literatures that pressurization is equivalent to an increase in entropy, leading to increased intermolecular movements, which in turn cause neurotransmission disorders.) (Red Bull said: In fact, the Red Bull said wrong, he was forced at that time. Gas isothermal compression is actually The reduction in entropy is similar to the reduction in isothermal pressure, the decrease in molecular thermal motion, and the decrease in the efficiency of the chemical reactions that could normally pass signals, but the addition of more “active†nitrogen in the gas will increase the degree of chaos and offset some of the entropy. Reduced effect.)
Of course, in addition to these terrible things, there is also a fun place for hernia: after sucking, the speech will become like a Donald Duck.
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