ginti
Contributor
Your ability to give answers that have nothing to do with the posts you are answering is surprisingly good
Next step for longer bottom times on deep dives?
- Thread starter jf3193
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Your ability to give answers that have nothing to do with the posts you are answering is surprisingly good
Scuba Client
Banned
Anaesthetic gases allow the rapid introduction of an agent into arterial blood via the pulmonary circulation as compared to the more circuitous route of venous circulation. I have been made aware that certain individuals with a high VO2 Max may be difficult to sedate. This also applies to individuals under the influence of Methamphetamine. The narcotic effect at depth can be negated provided you have a developed breathing technique.
2006 Manic Person of the Year.
It's not an opinion that narcosis impedes your ability to function. That is fact.
Those of us who where doing a lot of deep air diving prior to the availability of Trimix can attest to this.
As with everything, the level is the issue. The alcohol analogy is a reasonable base line comparison.
Not only is the depth (PON) an issue, but environment, and the individual on the day.
To state this is not a fact is idiotic in he extreme.
Yes we used to attempt to mitigate the issue. Having very good skills that where automatic. Diving the same kit setup. Ensuring you where mentally and physically fit and not tired. Avoiding heavy workloads. Work up dives to increasing narcosis tolerance [1].
But you where always fully aware that you apparent control of the situation was not as good as you believed.
Many of us have done Chamber exercises at 0m, 40m, 50m and 60m on air.
Interestingly, often the score was better at depth. When we looked at this more closely it became e very apparent this was a case of task narrowing. Task narrowing does allow you to complete tasks, but your perception of other issues is significantly hampered, even ignored, as the task becomes the total focus of the individual. Task narrowing was normally the reason for out of air emergencies and dive depth and time overruns.
One of the guys I occasionally dived with where doing a lot of survey dives for new marks. They adopted the policy of taking video cameras on all of these dives. This was well before GoPro's etc. They where constantly sending lights and housing back to the manufacturer for repair after they failed - so it was not an inexpensive policy.
They found on reviewing footage that there where huge sections of the dive they where totally in ignorance off. Including items of specific interest. When Trimix training became available, (although shunned by many of the dive training organisations at the time,) they leaped at the opportunity.
They revisited many of the previous dives, these where all experienced as new un-dived sites.
For myself, deep air diving did result in a number of incidents that I was involved in, both as the rescuer and potential casualty. I well remember having to lift my buddy off a wreck in 50m when he was totally overcome by narcosis. As we went through 30m, he recovered. On discussing it afterwards he remembered being totally overcome by dread, and was certain we where getting deeper as I took him shallower. He also remembers recovering, - it was like switching a light on. Thankfully, having recovered, he (and I ) where able to complete our decompression stops, although he was mighty relieved to get back on the boat.
He was lucky, when narcosis levels are high, expecting your buddy to be fully functional is a bit Darwinian! This is probably one of the reasons that deep air diving often resulted in double fatalities.
Apart from the issues of Narcosis. There is also the issue of Work Of Breathing (WOB). At depth the gas is denser, the ability to ventilate is impeded, and the risk of CO2 build up is increased.
In case you are unaware high levels of CO2 induce narcosis and paranoia - not good at depth.
It has become apparent, that a large number of 'deep air' incidents where probably induced by CO2 due to high WOB.
One of the reasons that there has been a push towards 'Sports Trimix', in the mid depth range, is to reduce WOB, rather than to address narcosis. In the case of Sports Trimix, it's a win / win.
I am not saying I don't occasionally dive deep on air. In some places, O2 and Helium are unavailable, or equipment is not available. This is now an extremely rare activity for me.
Modern dive computers, rebreathers etc all make Trimix diving much less complex than it was when I started. In addition, it is much more available. In addition, diving CCR means Trimix costs are more than reasonable. (Granted, all the expense and inconvenience of buying and maintaining the bailout kit still exists).
[1] -Narcosis tolerance, if it exists, is a very short term tolerance.
In much the same way as consuming large amounts of alcohol regularly, allows an alcoholic to appear to function normally. It was believed/hoped, that regular deep diving allowed you to function when suffering from narcosis.
I do wonder if this was more a mental stress thing. Doing deep diving regularly, meant you where relaxed and calm at depth. Unlike those who where unused too deep complex dives.
Those of us who where doing a lot of deep air diving prior to the availability of Trimix can attest to this.
As with everything, the level is the issue. The alcohol analogy is a reasonable base line comparison.
Not only is the depth (PON) an issue, but environment, and the individual on the day.
To state this is not a fact is idiotic in he extreme.
Yes we used to attempt to mitigate the issue. Having very good skills that where automatic. Diving the same kit setup. Ensuring you where mentally and physically fit and not tired. Avoiding heavy workloads. Work up dives to increasing narcosis tolerance [1].
But you where always fully aware that you apparent control of the situation was not as good as you believed.
Many of us have done Chamber exercises at 0m, 40m, 50m and 60m on air.
Interestingly, often the score was better at depth. When we looked at this more closely it became e very apparent this was a case of task narrowing. Task narrowing does allow you to complete tasks, but your perception of other issues is significantly hampered, even ignored, as the task becomes the total focus of the individual. Task narrowing was normally the reason for out of air emergencies and dive depth and time overruns.
One of the guys I occasionally dived with where doing a lot of survey dives for new marks. They adopted the policy of taking video cameras on all of these dives. This was well before GoPro's etc. They where constantly sending lights and housing back to the manufacturer for repair after they failed - so it was not an inexpensive policy.
They found on reviewing footage that there where huge sections of the dive they where totally in ignorance off. Including items of specific interest. When Trimix training became available, (although shunned by many of the dive training organisations at the time,) they leaped at the opportunity.
They revisited many of the previous dives, these where all experienced as new un-dived sites.
For myself, deep air diving did result in a number of incidents that I was involved in, both as the rescuer and potential casualty. I well remember having to lift my buddy off a wreck in 50m when he was totally overcome by narcosis. As we went through 30m, he recovered. On discussing it afterwards he remembered being totally overcome by dread, and was certain we where getting deeper as I took him shallower. He also remembers recovering, - it was like switching a light on. Thankfully, having recovered, he (and I ) where able to complete our decompression stops, although he was mighty relieved to get back on the boat.
He was lucky, when narcosis levels are high, expecting your buddy to be fully functional is a bit Darwinian! This is probably one of the reasons that deep air diving often resulted in double fatalities.
Apart from the issues of Narcosis. There is also the issue of Work Of Breathing (WOB). At depth the gas is denser, the ability to ventilate is impeded, and the risk of CO2 build up is increased.
In case you are unaware high levels of CO2 induce narcosis and paranoia - not good at depth.
It has become apparent, that a large number of 'deep air' incidents where probably induced by CO2 due to high WOB.
One of the reasons that there has been a push towards 'Sports Trimix', in the mid depth range, is to reduce WOB, rather than to address narcosis. In the case of Sports Trimix, it's a win / win.
I am not saying I don't occasionally dive deep on air. In some places, O2 and Helium are unavailable, or equipment is not available. This is now an extremely rare activity for me.
Modern dive computers, rebreathers etc all make Trimix diving much less complex than it was when I started. In addition, it is much more available. In addition, diving CCR means Trimix costs are more than reasonable. (Granted, all the expense and inconvenience of buying and maintaining the bailout kit still exists).
[1] -Narcosis tolerance, if it exists, is a very short term tolerance.
In much the same way as consuming large amounts of alcohol regularly, allows an alcoholic to appear to function normally. It was believed/hoped, that regular deep diving allowed you to function when suffering from narcosis.
I do wonder if this was more a mental stress thing. Doing deep diving regularly, meant you where relaxed and calm at depth. Unlike those who where unused too deep complex dives.
Scuba Client
Banned
I dive air to 65 metres. Would like to go to 70 metres wearing a full-face mask. If I'm successful in poaching abalone, then I probably have the extra cash to pay for Nitrox and use Best Mix. Decompression gas can be whatever the operator has on hand. Either 32/40/50/80/100%. Ask a more specific question and I'll give you a better answer.
@Scuba Client
I have just noticed that you are in Australia. I suspect your diving conditions are better than mine.
3 weeks ago it was pitch black at 15m. Without a torch you couldn't locate your buddy. At 6m, even though there was light, conditions where so bad that if you where 2m apart you couldn't locate your buddy.
2 weeks ago, at 35m, conditions where perfect, no torches required, and a good 6m of horizontal visibility.
Interesting in the UK, if you where recovering Abalone for money you would be 'at work'. So would come under HSE (Health and Safety Executive) legislation, as such it would be illegal to dive air to anything like that depth. That covers all involved, the diver, the boat operator, the dive supervisor and the company (even if it is a one man band).
I have just noticed that you are in Australia. I suspect your diving conditions are better than mine.
3 weeks ago it was pitch black at 15m. Without a torch you couldn't locate your buddy. At 6m, even though there was light, conditions where so bad that if you where 2m apart you couldn't locate your buddy.
2 weeks ago, at 35m, conditions where perfect, no torches required, and a good 6m of horizontal visibility.
Interesting in the UK, if you where recovering Abalone for money you would be 'at work'. So would come under HSE (Health and Safety Executive) legislation, as such it would be illegal to dive air to anything like that depth. That covers all involved, the diver, the boat operator, the dive supervisor and the company (even if it is a one man band).
Scuba Client
Banned
Scuba Client
Banned
Scuba Client
Banned
Blackcrusader
Contributor
Back to the OP who wants to dive from 90 - 130 feet I would have thought the Advanced Nitrox and Decompression course would be most suitable. This is one of two courses I want to do when I get get back to regular diving and I have dive partners that can do those deco dives with me. CCR is not one of the things I plan on doing due to my "advanced age" lol
Blackcrusader
Contributor
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