NARCOSIS
WHAT IT IS! WHAT IT IS NOT!


by WALLY BARNES,
Training Director
SCUBA LATINA


We learned in our entry level dive courses about nitrogen narcosis. We were told it is something like a drunken state where every 50’/15 m was equivalent of having one very dry martini on an empty stomach… whatever that is intended to be. For many years, it was labeled as the “rapture of the deep”. This concept is still nursed not only by many recreational instructors, but by many so-called technical instructors who still accept it, believe it and still teach this quasi-fallacy.

It is a quasi-fallacy because at a recreational diver depths (40-130’/ 12-39 m), this is not a common symptom, but at much greater depth, narcosis which is medically defined as incipient or threshold of anesthesia, can be truly be interpreted as a drunken feeling. So maybe by calling it like that, a term everyone is familiar with, maybe even recognize its symptoms, is understandable. But problems could sprout when divers expect to feel drunken symptoms to realize they are “narked”… and because they do not feel them continue forth risking themselves to the point of danger.

Another problem could be for technical instructors NOT informing their students, who are truly going to feel the real signs and symptoms of narcosis, how to cope with them once they are noticed. That’s our real danger and why candidates for technical training should screen their instructors to ensure they get a truly technical instructor not a recreational one who just does technical dives.
Inert gas induced narcosis, and practically ALL gases we breathe have a narcotic potential, at the depths recreational divers frequent will have other much lessened signs and symptoms than “being drunk”. This increases the danger of its effects. What is inert gas narcosis? The short answer is …we don’t know. A longer response would say it is the result of a deterioration of the mental process, neuromuscular control and high order cognitive functions (thinking, understanding, analyzing). The level of the effects can vary from difficulty analyzing a fact (perception), to slowness in thinking, to a slow response to a situation, time distortion, or loss of short-term memory, This makes narcosis more subtle to identify than just descending, feeling drunk and ascending to lower the nitrogen partial pressure and eliminate the narked feeling.

It has been universally shown, without shadow of doubt, that narcosis can be measured at depths as shallow as 60’/ 18 m. This has been done through exercises of coordination and time. Nobody escapes its dangerous tentacles. Of the most clear and sure signals we can name, recalling the dive, what was seen, done or achieved, is the one that shows the failures in our nervous system. Our short-term memory (what just happened) breaks down to the point of not recalling what was seen or done. If asked, what was your pressure at point XX? Your blank look will give you away.

So, how would a recreational diver at 100’/ 30 m on air or Nitrox feel it? A good instructor, recreational or technical, would give mental exercises to do while submerged. Divers would see the number of mistakes done, time taken to completion… assuming they completed the tasks. While studies show that under extreme concentration, a diver could complete a simple task with minimum of errors, when faced with several simultaneous or sequential tasks, the error level jumps sky high. This is certainly NOT the time to realize you are narked, just when you are close to losing your life needlessly. The most common error is… not checking your gas pressure. Why? Because the time function is the first one to get distorted and given something to do at a particular time, we forget. If we learned in the course to compute our gas consumption for the next 15 minutes, we make arithmetic errors, we forget the process sequence or forget the exercise.

What other ways are we affected? Well, imagine a diver at 120’/ 37 m who checks his pressure gauge and reads 500 psig/ 35 bar LESS than what he was supposed to have at that point or time in the dive? A “sober” response would be to take immediate actions like notifying the buddy, cutting the dive short, turn around ahead of time or at a closer point or other measures to ensure gas sufficiency at the ascent time/point. A “narked” response could narrow our choices to thinking slower breathing will do to stretch the remaining gas (?). Note: most readers would understand how this option would endanger the diver and increase the chances of an out of air situation at depth. What many might NOT see is that less breathing can stimulate carbon dioxide retention, which in turn exacerbates narcosis and increases the possibility of decompression sickness (DCS) due to blood acidosis.

How many readers noted the above examples are valid for air or Nitrox? Many people think, not completely wrong, that with less nitrogen, less narcosis. But, other factors enter the narcosis equation here. Some studies indicate the possibility that Nitrox promotes the retention of carbon dioxide. This would amplify the narcosis effect, although lesser due to lower levels of nitrogen, as dilated blood vessels allow more amount of nitrogen into the brain’s neurological system.

Another myth divers have is that they are NOT drunk at whatever depth they have gone. This is so because they are looking for the wrong signs and symptoms ignoring mistakes, overlooked tasks or slower decisions while they are “not drunk”. These are the real signs and symptoms of inert gas narcosis, not what you were given in Scuba 101.

How should I do to dive beyond 80’/ 24 m ? Most universal answer is… obtain proper training. Some agencies now offer Helitrox and Trimix courses to enable divers to reach 200’/ 60m with decompressions. These courses are ideal for divers who are interested in extending their depth limits and/or time limits at depth without completely entering the technical world realm. The uses of helium in the breathing mix eliminate or significantly decrease the effects of narcosis and allow full use of mental capabilities at depth which would otherwise increase our risks to the point of becoming dangerous.

Only when a diver makes a Trimix dive at a particular depth where he has been on air or Nitrox, will he really understand and feel how “narked” he has been and never accepted it. That’s the best proof a diver gets of what nitrogen narcosis really is… or is not.

To contact me, e-mail to :
WALLY BARNES or call (305) 975-1716.***