johnny sea ranger
Registered
Oxygen Narcosis
© Steven Thair 2014
You dont have to look very far to discover that narcosis in diving is caused by oxygen as well as nitrogen, and the impairment from both gases starts long before 100 feet deep.
Why do teachings on trusted mainstream websites and mags persist in saying that:
a. narcosis wont affect you in less than 100 or 130 feet; and,
b. nitrogen is the culprit? (Oxygen is too).
Bennett & Rostain, Bauer and Way, Hesser and Fagraeus, Petri. This research is 10 years old. Some of the research on the narcotic effect of gases and solubility in lipids (that seems to be the key) is over 40 years old. When are the operators of the main dive websites going to own up? Is it ignorance or some misguided effort not to scare new divers?
The National Ocean and Atmospheric Administration concluded in 2002 that oxygen should be regarded as having the same narcotic potency as nitrogen. This might be an underestimate since the solubility of oxygen in lipids is much higher than it is for nitrogen. ("Mixed-Gas & Oxygen". NOAA Diving Manual, Diving for Science and Technology. 4th. National Oceanic and Atmospheric Administration. 2002. "[16.3.1.2.4]
Likewise, there is the story that nitrox (which is an enriched air mix with a greater percentage of oxygen) reduces the effects of narcosis. Wheres the research that shows that? Anybody? I know where the theory came from: it was based on the (mistaken) belief that it was only nitrogen that caused narcosis. Now we know both nitrogen and oxygen cause narcosis. Show me the evidence that says narcosis is lower with nitrox.
Yes, its true you are usually free from the more intense effects of narcosis in less than 100 feet. But why not give students and webpage readers the context that a diver at even 45 feet has a significant impairment occurring. This isnt fear-mongering, its telling the truth and its useful. For instance, uw photography courses could teach that you should practice, practice, practice with your SLR camera buttons because even at 45 feet, operation of a camera that you havent used for a year can be difficult, even though you did it flawlessly a few times above water, because of narcosis. Do it 30 times above water. Practice interrupting yourself in the task and then picking it up again.
Better yet, practice at depth. Getting stuck or running out of air is more serious at 80 feet than 20 feet, your brain isnt going to cooperate as well at 80 feet either. So why not practice safety procedures where youll really need them? Dive training should practice safety skills at depth.
Likewise, students in search and navigation courses could be told the truth: it is going to be harder to figure out a new course underwater, and harder to handle ropes, distances, and plans, especially plans that have to change while you are underwater.
Narcosis is one of the reasons to plan for contingencies when you are still above the water. Its because you will be stupid. Accept that. Remember this image: rats have more trouble rolling over off their backs at 2 atmospheres. Now if rats have to work harder to roll over on land at 2 atmospheres, how well are you going to do at your tasks underwater, at 3 bar, all geared up?
The research shows you cant develop a physical tolerance for narcosis, but experience helps. And you can develop work-around strategies. For instance, research shows that focusing on a single task is least effected. So plan to KISS (keep it simple, stupid)
Heres another strategy: if youre at 60 feet and having problems switching your nifty little camera from 30 still shots per second to video of 1080 24 fps wide angle, go up to 30 feet, it will clear your head.
Hearing the whole truth might do something for diver self-esteem, too to understand that the anxiety you felt on your last dive, and maybe your less than stellar performance wasnt yours so much as it was caused by the environment. Its yours to be responsible for, but its not you, its just happening to you.
Those professing to have knowledge of dive issues on some websites should do the same go up to a shallower depth and take a clear look at your teaching intention, and the facts.
As you can probably tell from my tone, I am disappointed with some in the profession.
