Walter:
It always amazes me, the number of people who insist that narcosis has a threshold effect. The pharmacokinetics of anesthetic gases don't work that way. I'm a Martinis rule fan, myself.
Was I Narc'd?
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It always amazes me, the number of people who insist that narcosis has a threshold effect. The pharmacokinetics of anesthetic gases don't work that way. I'm a Martinis rule fan, myself.
I can believe that....I know narcosis effects can vary from person to person and situation to situation.
It's always been the same for me each time I get it. For me, it's like the first couple of breaths in the dentist chair...a warm, pleasant sensation, relaxing, a tiny bit numbing.
There are times in the dentist chair as the effects are coming on that I feel as though I'm falling into the chair, or through the floor while in the chair. This is normally much more into the gas and right before I'm going to sleep (or REALLY out of it)....I've never been that narc'd before, or at least it's never affected me like that. I suppose if I was really deep on air, well past recreational limits, I could feel that....but that would be extremely dangerous.
bleeb
Contributor
You appear to be saying that nitrox will help with narcosis. This is a common belief, but as others have already posted, scientific evidence (maybe not definitive) leans towards nitrox not actually helping with respect to narcosis, and there may be theoretical reasons to believe it could be a little bit worse. See also the Wikipedia entry on nitrox.
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Maybe narced, maybe a little vertigo, maybe crud in the water moving in an unexpected direction, maybe CO2 retention causing anxiety.
It could be a lot of things.
The important part is that you recognized it and looked at your gauge instead of hitting the "up" button.
If you get this again, take notice of your breathing (fast/shallow/rapid causes CO2 retention) or if you feel "off-balance" or see stuff in the water moving "up". (vertigo).
Also, narcosis lightens as you ascend, so you could see if moving up 10' or 20' starts to help.
Terry
biz_nate
Contributor
When I first started diving, my dad and I spent a day diving a mountain lake in Colorado. About halfway through one of our dives, I had a strong feeling that I was positively bouyant. I dumped my BC/drysuit (thought I had, at least), and finned down as hard as I could. Try to imagine me (not realizing that I had a dump valve on the BOTTOM of the BC) switching between head up/dumping BC ad head down/kicking back down to get back to where I was supposed to be. Eventually I kicked down to a rock, and grabbed on to it. I caught my breath, worked the rest of the air out of my system, and proceeded. I doubt this scenario was the result of narcosis; we were in about 40 ft of depth. To this day, I can only guess at what triggered the event, but I do know what sustained it for so long- heavy breathing associated with the effort of trying to dump my system.
Such times are scary, especially when you can't figure out what's going on. I can imagine that feeling as though you're being pulled down is even more so. Narced or not, I've found that in such times, checking my depth gauge so that I have a realistic basis for decision making it reassuring. If you're so narced that you can't register the reading, then you've definitely pushed it too far.
TSandM, it seems fairly common sensical that there's no narcosis threshold in the form of a brick wall, but I'd be surprised to hear that the effects on one's perception are stricly linear. I've not the educational basis to understand how such a thing might be measured quantitavely, but in appealing to your martini rule, I'd bet that if you feel 1 martini at 100 ft, you probably feel 2 or 3 by the time you're at 150, averaging over environment and physiology. Thoughts?
-Ben
Such times are scary, especially when you can't figure out what's going on. I can imagine that feeling as though you're being pulled down is even more so. Narced or not, I've found that in such times, checking my depth gauge so that I have a realistic basis for decision making it reassuring. If you're so narced that you can't register the reading, then you've definitely pushed it too far.
TSandM, it seems fairly common sensical that there's no narcosis threshold in the form of a brick wall, but I'd be surprised to hear that the effects on one's perception are stricly linear. I've not the educational basis to understand how such a thing might be measured quantitavely, but in appealing to your martini rule, I'd bet that if you feel 1 martini at 100 ft, you probably feel 2 or 3 by the time you're at 150, averaging over environment and physiology. Thoughts?
-Ben
Interesting quotes from both of you. Walter...it's true that if you're diving narcosis is present as ppn2 is increased (and increasing with depth) but it doesn't add much to the OP's question. It's like saying whatever problem you post about underwater the answer is you're narced.
Lynne, I haven't seen many posts where people think that narcosis is like a lightswitch. The threshold effect wouldn't be my choice of words however but since you ascribe to the DIR view of things ...Nitrox isn't used below 100 fsw...that's a threshold in effect.
Why? There are any number of drugs which have essentially linear dose-response curves (and of course, some that don't).
biz_nate
Contributor
My (admittedly, few) experiences with narcosis, along with stories I've heard suggest that it's typically first noticed around 130 ft END, followed by more dramatic changes in perception as one descends further.
I'm arguing not so much from first principles (I understand that many systems are, in fact, linear), but instead from anecdotal evidence. It's not lost on me, though, that the conventional wisdom I was taught in my OW class was that if you start to feel narced, ascend 10 or so feet, and things will clear up quite nicely. If it were indeed strictly linear, wouldn't it be more accurate to say something along the lines of halve your depth and you'll feel halfway better?
You mentioned that there are drugs which exhibit linear dose-response behavior; I'm quite interested to know if you believe that a linear model fits N2/O2 responses specifically.
I think that I'm like a lot of people in that I am not aware that I am having any symptoms of narcosis unless something unusual happens that makes me see that my thinking processes are not operating at full speed. If I were having a routine dive, my impulse would be to say I was not at all narced, even though I were. To refer to TS&M's martini comment, it is like the person who has had a couple of drinks but feels just fine until he has to do something that demonstrates the level of impairment that was always there.
In my most recent example, I was on a dive that was very simple except for the depth, and I was alert from the start for signs of narcosis. At one point in the dive I became aware that I was getting a very minor free flow from my regulator. I played with its adjustment, carefully moving it so that I got the easiest breathing without that slight free flow. I was actually thinking that I was being very alert and "un-narced." At that point my buddy signaled with his light. He wanted to know why I was breathing off my alternate regulator. I had no idea that I was. I looked and saw that my primary was neatly clipped off on my right D-Ring, so I must have made some sort of intentional switch, but I have no idea why. I felt perfectly fine otherwise.
A previous post referenced a 100 foot limit for DIR. I assume the reference is to the policy of using gas mixes that keep an equivalent narcotic depth of 100 feet. The poster suggested that this implies a trigger. It really doesn't--it just assumes that the effects of narcosis are normally manageable at that depth, kind of like the acceptable range for a blood alcohol level. To return to the martini law concept, if we use the 50 foot per martini rule that some people use, a 100 foot limit implies that we should be able to function with the effect of two martinis.
Maybe.
The most clear example of impaired thinking I ever had took place on air at 100 feet.
In my most recent example, I was on a dive that was very simple except for the depth, and I was alert from the start for signs of narcosis. At one point in the dive I became aware that I was getting a very minor free flow from my regulator. I played with its adjustment, carefully moving it so that I got the easiest breathing without that slight free flow. I was actually thinking that I was being very alert and "un-narced." At that point my buddy signaled with his light. He wanted to know why I was breathing off my alternate regulator. I had no idea that I was. I looked and saw that my primary was neatly clipped off on my right D-Ring, so I must have made some sort of intentional switch, but I have no idea why. I felt perfectly fine otherwise.
A previous post referenced a 100 foot limit for DIR. I assume the reference is to the policy of using gas mixes that keep an equivalent narcotic depth of 100 feet. The poster suggested that this implies a trigger. It really doesn't--it just assumes that the effects of narcosis are normally manageable at that depth, kind of like the acceptable range for a blood alcohol level. To return to the martini law concept, if we use the 50 foot per martini rule that some people use, a 100 foot limit implies that we should be able to function with the effect of two martinis.
Maybe.
The most clear example of impaired thinking I ever had took place on air at 100 feet.
I think a lot of people don't think they are impaired, because they don't feel woozy or off balance or unable to accomplish the normal activities of diving. But I think problem-solving is impaired much earlier than most people think. As I sat and looked stupidly at a problem at 95 feet last week, my brain just wasn't absorbing and processing information normally. I mean, I make my LIVING in a high risk environment, where absorbing and correctly processing information is critical. If I couldn't do it, I'd get sued out of existence (or fired). But at 100 feet, I'm (as Doc Intrepid would put it) farm animal stupid. I don't feel drunk or euphoric or anxious or anything . . . I just can't think straight. And this is what the research on narcosis has said -- learned tasks are maintained, but novel situations are not handled as quickly or well under the influence of nitrogen. It's insidious, and if you reach the point where you are really AWARE you are impaired, I think you are VERY impaired.
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