Nitrogen Narcosis and Scuba Diving Part II - How to Avoid or Reduce Narcosis

Ascend. The narcotic properties of nitrogen and other gases are proportional to the partial pressure at which a diver breathes them. The deeper a diver descends, the greater the partial pressure of the gas, and the greater the narcosis. To reduce or eliminate the narcotic effects of nitrogen and other gases, a diver should ascend at a safe rate to a depth at which his thinking clears and he no longer feels the effects of narcosis.

Any factor that alters a diver's mental, physical, or emotional state may increase his susceptibility to narcosis. Here is a brief list of some of the factors that may increase the probability of a diver experiencing narcosis underwater.

• Increased Carbon Dioxide Levels
Carbon dioxide is narcotic, and amplifies the effect of narcosis caused by nitrogen and other gases. Heavy exertion and improper breathing techniques may increase the amount of carbon dioxide in a diver's body. Furthermore, a diver's breathing gas is compressed at depth according to Learn more about carbon dioxide and scuba diving).

• Fast Descent
A very fast descent may temporarily increase the carbon dioxide level in a diver's body as he approaches the bottom. A diver who descends very quickly may feel a strong narcotic "hit" as he reaches his planned depth. This effect is generally temporary, but can be surprising the first time it is experienced. To avoid a narcotic hit during descent, make sure to perform a slow, controlled descent. (Review the six steps to a well-controlled descent).

• Stress/ Excitement
Stress, anxiety, and excitement may cause a diver's body to release adrenaline, which somewhat alters his brain chemistry and central nervous system function. The effects of adrenaline, like the effects of carbon dioxide, amplify narcosis.

• Fatigue
Exhaustion, as most people will agree, affects a person's mental processes. Just as altered emotional states can augment narcosis, so can altered mental states. A diver who is extremely fatigued would do well to alter his dive plan to minimize the possibility of narcosis.

• Alcohol and Other Drugs (Even Prescription Drugs)
Alcohol and other barbiturates depress the central nervous system. The anesthetic properties of nitrogen and other gases at high partial pressures combine with depressants such as alcohol to amplify narcosis. Drugs that stimulate the central nervous system can also alter a diver's mental processes and augment narcosis.

Even some over-the-counter and prescription drugs (such as some antihistamines) alter a diver's brain chemistry sufficiently to increase his susceptibility to narcosis. Never engage in deep diving when using any medication unless cleared to do so by a diving doctor.

Only two methods exist to eliminate the effects of narcosis.

1. Don't Dive Deep
This is pretty obvious. Narcosis is related the the partial pressure at which a diver breathes the narcotic gas. Partial pressure is directly proportional to depth. To avoid narcosis, don't dive to depths where narcosis is experienced. The depth at which a diver will experience narcosis varies among divers, so a certain amount of trial and error (under the watchful eye of a dive professional or experienced buddy) is necessary. A general rule to avoid most narcosis is to keep your dives shallower than 100 feet.

2. Take a Trimix Course and Use Trimix on Deeper Dives
Trimix is a breathing gas composed of nitrogen, oxygen and helium. Helium does not produce narcosis in divers. By replacing some of the nitrogen and oxygen in a diver's breathing gas with helium, a diver can reduce or eliminate narcosis. Furthermore, helium is a very light gas, and helps to reduce the density of the breathing gas, and therefore the work of breathing. By reducing the work of breathing, a diver lowers the partial pressure of carbon dioxide in his system, which helps to further reduce narcosis.

• Do you know . . . What Is the Difference Between Nitrogen Narcosis and Decompression Sickness?

When diving deep on air, every diver will be affected by narcosis. Research has shown that even divers who do not "feel" narced and appear to function normally are still affected by narcosis. When faced with novel situations, problem solving, and tasks requiring manual dexterity on deep air dives, all divers will function more slowly and with less precision. The first step in becoming a wise diver is to accept that on a deep air dive, you will be affected by narcosis, even if you do not notice it. Narcosis is unavoidable. Once a dive accepts this, he can manage narcosis more effectively and be a better diver.

• Over-Learn Basic and Emergency Diving Skills
Narcosis affects a diver's ability to think, as well as his manual dexterity. If a diver has to think through diving skills when performing them, he will not be able to execute the skills efficiently or effectively when he is narced. The trick is to practice both basic and emergency diving skills to the point that a diver can execute them automatically without thinking. A diver must practice skills repeatedly over a long period of time before skills become automatic. This is a good argument for not allowing new/inexperienced divers on deep dives.

Gaining shallow-water experience with specific dive environments (such as caves, shipwrecks, and currents) will help a diver over-learn a dive environment before embarking on a deep dive.

• Make a Clear, Simple Dive Plan and Execute It Slowly and Deliberately
Review your dive plan several times, even the night before the dive. Review the dive plan on the boat and before descending. Be sure that the plan is clear and logical to all divers involved.

Studies have shown that a diver trades accuracy for speed when narced. Plan to execute tasks and handle situations slowly and deliberately and you are less likely to lose accuracy and make a mistake.

• Write Important Information on an Easily Accessible Slate
Narcosis affects a diver's memory. Nothing is worse than realizing halfway through a dive that you don't remember the tank reserve pressure or maximum dive time. At minimum, jot down your no-decompression limit, the maximum depth, the predetermined dive time, and your tank reserve pressure on your slate. Yes, it is possible to program a computer with this information, but it is nice to have it written down just in case your computer magically puts itself on gauge mode. It is also a great idea to sketch a map of the dive site on your slate to help with orientation.

• Determine Your Limits Slowly
Increase your maximum depth slowly over many dives until you start to understand your limits. Do not dive to 140 feet on your first deep dive. Get used to deep diving slowly.

• Avoid Behaviors That Exacerbate Narcosis
Remember that diving in an altered mental state, such as when exhausted, medicated, drunk, stressed, or excited can all augment a diver's narcosis. Plan dives to avoid heavy work and quick descents whenever possible. Do not be afraid to cancel diving plans if you are sick or nervous. Remember the Golden Rule of Scuba Diving: Any diver can cancel the dive at any point for any reason.

No. A diver can gain experience with narcosis, learn how his body functions at depth, and become comfortable with his altered emotional state. Knowing what to expect on deep dives eliminates much of the stress of deep diving, and divers who gain experience may feel less narced on deep dives because of their lower stress level.

However, even a diver who feels comfortable and appears to be in complete control is still affected by narcosis. When faced with new skills, problem solving, and other novel mental and physical tasks, experienced deep air divers behave just as slowly and inappropriately as new deep divers. Over-learning tasks and becoming comfortable on deep dives may lull an experienced diver into a false sense of security. When things really go wrong and a diver has to problem solve underwater, the affects of narcosis become apparent.

Careful, conservative dive plans and an understanding that you will be narced to some extent during deeper dives on air will go a long way in improving a dive's safety.

Would you go to the dentist, breathe some anesthesia, and then joy-ride an airplane home though unfamiliar territory? I hope not! But a diver who dives deep on air and gets narc'd for fun is essentially doing the same thing. He is piloting complicated equipment through an unfamiliar environment in an impaired mental state. This is less than intelligent. Before engaging in deep air dives, seek proper instruction and gain experience slowly. To a certain extent, mild narcosis can be managed with proper preparation and procedures.

Read Narcosis and Scuba Diving Part I - What Is Narcosis and How Does It Feel? >