200' on air for 5 min bottom time?

[TSandM]

I think one of the reasons I speak out about the inadvisability of deep diving on air is that I believe, from discussions and from personal experience, that many people do not know how affected they are by narcosis when they are, in fact, quite impaired. People expect to feel drunk or giddy or otherwise abnormal, and they expect to recognize it. In my experience, the opposite is the case. We have had a student so impaired at 85 feet that we had to take him in hand and physically turn him around and bring him shallower. A friend of mine did a dive with an instructor the other day, a dive where the proper plan involves following terrain to 120 feet and then back UP to 110 to find a feature. They got sufficiently narced at 120 to get lost and end up at 140; one of them was confused and anxious, but the other was no longer attempting to dive, and had to be towed up to shallower depth to regain function. None of these people recognized the insidious onset of impairment, but in at least one case, had the diver been alone, they would not have survived. And, in fact, we had a local tech diver have exactly that happen . . . he lost function at 200 or so, and "woke up" to find himself virtually out of gas and requiring a precipitous ascent. He then lost control of a gas switch, as I understand it, and ended up on the surface. He was critically ill and remains with major deficits.

And oxygen toxicity on air at depth, though it may be less common than predicted on other gases, does occur. We lost a young man in Monterey Bay a year or two ago at 250 on air, if I remember correctly; reports of the dive were that he appeared to seize.

Especially for someone who has not taken a lot of time to learn his or her own limits with respect to nitrogen and the brain, going to these depths on a highly narcotic gas is so inadvisable as to make a bad outcome virtually certain.

 

[Dsix36]

I think one of the reasons I speak out about the inadvisability of deep diving on air is that I believe, from discussions and from personal experience, that many people do not know how affected they are by narcosis when they are, in fact, quite impaired. People expect to feel drunk or giddy or otherwise abnormal, and they expect to recognize it. In my experience, the opposite is the case. We have had a student so impaired at 85 feet that we had to take him in hand and physically turn him around and bring him shallower. A friend of mine did a dive with an instructor the other day, a dive where the proper plan involves following terrain to 120 feet and then back UP to 110 to find a feature. They got sufficiently narced at 120 to get lost and end up at 140; one of them was confused and anxious, but the other was no longer attempting to dive, and had to be towed up to shallower depth to regain function. None of these people recognized the insidious onset of impairment, but in at least one case, had the diver been alone, they would not have survived. And, in fact, we had a local tech diver have exactly that happen . . . he lost function at 200 or so, and "woke up" to find himself virtually out of gas and requiring a precipitous ascent. He then lost control of a gas switch, as I understand it, and ended up on the surface. He was critically ill and remains with major deficits.

And oxygen toxicity on air at depth, though it may be less common than predicted on other gases, does occur. We lost a young man in Monterey Bay a year or two ago at 250 on air, if I remember correctly; reports of the dive were that he appeared to seize.

Especially for someone who has not taken a lot of time to learn his or her own limits with respect to nitrogen and the brain, going to these depths on a highly narcotic gas is so inadvisable as to make a bad outcome virtually certain.

In my case you are extremely accurate. A 226' dive on air was my most recent example. I felt fine and thought that I was fully in control, but when I wound up my reel and went to untie it from the jump line, I had a great deal of trouble doing so. I remember telling my self that I was not going to die because of a stupid reel and that if I failed 3 times I would just leave it. If not for that reel episode, I would not have believed that I was impaired in any way at all.

 

[MXGratefulDiver]

Jim and I discussed this recently. We both agree that we don't certify anyone to dive unless we feel comfortable in them diving with a member of our family. This use to be the standard that was applied by most Instructors, but today it's a relic of a by-gone era (like me). That doesn't mean that we don't have it right; it's just not a profitable attitude to have in today's Society (where many people seek instant gratification)...

The loved one standard is still in use today by NAUI instructors ...

... Bob (Grateful Diver)

 

[DCBC]

I think one of the reasons I speak out about the inadvisability of deep diving on air is that I believe, from discussions and from personal experience, that many people do not know how affected they are by narcosis when they are, in fact, quite impaired. People expect to feel drunk or giddy or otherwise abnormal, and they expect to recognize it. In my experience, the opposite is the case. We have had a student so impaired at 85 feet that we had to take him in hand and physically turn him around and bring him shallower...

The effects of NO2 Narcosis can be mitigated to a degree. This is specific to an individual and tolerance of narcosis will change from one day to another. Adaptation has been shown to occur in numerous experimental dives. The research I was involved in took place at DCIEM in the 70's. Tests were administered to various subjects (non-trained divers/science students from the University of Toronto and Navy Divers) and included a series of Reasoning and Mathematic problems. These were taken on the surface and at various depths in the Chamber. The mechanics of narcosis adaptation are not yet understood. Progressively deeper dives over time will in-fact mitigate the symptoms. They can't however be removed.

Everyone regardless of training or experience will experience the effects to varying degrees. It effects different people, in different ways, at different times. A Diver who regularly faces deep exposures, will often exhibit a tolerance that far exceeds a Diver who has not adapted over time. Training in Deep-Air will help the diver identify and monitor his mental condition and assess when the dive should be terminated. It's all about establishing the Diver's safe diving envelope in a meaningful way to him.

Especially for someone who has not taken a lot of time to learn his or her own limits with respect to nitrogen and the brain, going to these depths on a highly narcotic gas is so inadvisable as to make a bad outcome virtually certain.

I agree. You wouldn't go into a Cave without proper training, why would you venture deep an air?

 

[MXGratefulDiver]

... I've seen several threads on ScubaBoard where people argue cave training isn't necessary ... remember Genesis?

... Bob (Grateful Diver)

 

[Peter Guy]

DCBC wrote

This is specific to an individual and tolerance of narcosis will change from one day to another. Adaptation has been shown to occur in numerous experimental dives.

(emphasis added)

Wayne, I really wonder how relevant your experimental data, and commerical diving experience, is to the vast majority of recreational divers and diving.

The following are my concerns as to why:

a. While your experiments found that adaptation occurred, what about "un-adaptation?" Does adaptation occur only if the dives are done within a short time period? And if so, does "un-adaptation" also occur with a lack of "practice?" [I'm making some assumptions here -- one being that your chamber experimental subjects made their chamber "dives" within a relatively short period of time -- that is, doing a series of dives over consecutive days as opposed to a few days, then off for some time, then another few days like the normal recreational diver in real life. Also, the same is true to commercial divers/diving -- that they are making their dives within a realtively short period of time without a number of days off between the dives. Please advise if I'm way off -- or if I'm not.]

b. The difference between "real life" and a chamber ride -- the biggest differences being (again, these are my assumptions) environment and work load. It is my understanding that the environment (in particular light and temperature) appears to have an effect on narcosis with a dark and cold environment being a "worse" environment than a light, warm one. So if the recreational diver felt that his experience of diving in a tropical setting on deep air showed his adaptation he might be in for a nasty surprise in diving back in your waters in Nova Scotia.

Again, the commercial diver/diving is more likely to be diving the same/similar environment on a more regular basis so an adaptation would be more relevant.

OK, now tell me, in your experience, are these concerns totally unwarranted or somewhere in the ball park?

 

[rlynch]

Thanks for calling me a Debbie downer. Whomever, ya you right I just don't like people dying or killing someone else with an avoidable plan.
There are agencies that train deep air, etc... Go to them
I also ran the plan with an al80 as the tank and a "normal" newbie ish SAC rate of .75ish and guess what .... Empty tank at surface with the plan originally proposed.

 

[flots am]

... I've seen several threads on ScubaBoard where people argue cave training isn't necessary ... remember Genesis?

Training is completely unnecessary to dive into a cave.

Coming back out, on the other hand is more difficult.

 

[DCBC]

The following are my concerns as to why:

a. While your experiments found that adaptation occurred, what about "un-adaptation?" Does adaptation occur only if the dives are done within a short time period? And if so, does "un-adaptation" also occur with a lack of "practice?" [I'm making some assumptions here -- one being that your chamber experimental subjects made their chamber "dives" within a relatively short period of time -- that is, doing a series of dives over consecutive days as opposed to a few days, then off for some time, then another few days like the normal recreational diver in real life. Also, the same is true to commercial divers/diving -- that they are making their dives within a realtively short period of time without a number of days off between the dives. Please advise if I'm way off -- or if I'm not.]

Subjects made one dive per week, over a six-month period. Others were tested on multiple dives (3 times per week) for two months and there were several other groups with different schedules. There were Students (8 subjects per group) accompanied by 4 Navy Divers. We undertook the same test with 8 certified divers and 4 Navy Divers in the Wet Chamber at DCIEM. The testing process was repeated with new groups over a two-year period. Navy Divers were also tested at various water temperatures and light conditions; with and without muscle loading.

b. The difference between "real life" and a chamber ride -- the biggest differences being (again, these are my assumptions) environment and work load. It is my understanding that the environment (in particular light and temperature) appears to have an effect on narcosis with a dark and cold environment being a "worse" environment than a light, warm one. So if the recreational diver felt that his experience of diving in a tropical setting on deep air showed his adaptation he might be in for a nasty surprise in diving back in your waters in Nova Scotia.

You're absolutely correct; less light, lower temperature and exercise affected NO2 Narcosis in a negative way. There was also a preliminary indication that state of mind (attitude) and lack of concentration could increase narcosis. Actually, this was a big factor. We were able to obtain results that were very convincing. As I mentioned, no one knows the why, but we do know the results.

Again, the commercial diver/diving is more likely to be diving the same/similar environment on a more regular basis so an adaptation would be more relevant.
OK, now tell me, in your experience, are these concerns totally unwarranted or somewhere in the ball park?

A few years later we did another test group on experienced divers (military and commercial) vs. recreational divers. Again this was done in a Dry and Wet Chamber at various depths. The Navy Divers faired much better. Environment may have been a factor because all Navy Divers were stationed at DCIEM and were familiar with our diving environment and procedures, but it was deep diving experience that was credited with the differences.

Overall, there is no doubt in my mind that adaptation occurs. Personally I've been diving Deep-Air since I was about 16 years of age (my first 150' dive). Although I ended-up thumbing the dive, now a 150 FSW dive wouldn't be a narcosis concern at all. Back in the late 60's, I didn't experience too much depth because my legs weren't strong enough to get me to the surface (no BC). If I went too deep, I would have to drop my weight belt to get to the surface... In thinking about it, it's actually pretty funny...

Adaptation occurred for me after several years of progressively deeper diving on air. This was nothing dramatic, as it was a long road, but I'm glad that I traveled it. Today, Divers are quick to change to Trimix. Back then, it wasn't available, so we adapted to what we had. I can operate at partial pressures of Nitrogen that others just don't usually consider. This has been beneficial for my Trimix use as well. There are those like Bret Gilliam and Tom Mount who are able to dive much deeper on air than I would attempt on my best day. Tom amazed me when diving the Blue Holes of Andros in 72. Like I mentioned, it's individual dependent. Most can adapt, but there has to be a will to do so. Most Divers today just don't have the desire to learn, or the patience...

People that throw stones at Deep-Air tick me off in the same way as those who were down on "Voodoo Gas." They just didn't understand what they were talking about, but vocalized a strong negative opinion anyway. Sometimes this can be a hard world to live in when you know better...

 

[rlynch]

For me the negatives of deep air out way the positives, pretty simple. It can be done yes and it's proven, but there are safer methods to accomplish the same goals.
Why add more risk...
For the answer is I've got kids