Chapter 4- Diving Physiology Diving Physiology 117 ger in extreme cold. Near drowning causes serious injury to your brain, heart, and lungs; and recovery may not be complete. First Aid: Start artificial respiration, if necessary, while still in the water. Once out of the water start CPR, if necessary. The pulse of a cold, unconscious diver is difficult to detect. Check for pulse thoroughly before beginning chest compressions. Begin CPR in all cases of pulselessness. People have revived after more than 40 minutes submerged in cold water. Give oxygen. Transport immediately to a medical facility. Near drowning survivors require continued medical observation in a hospital setting, even if they seem fine at first. Secondary drowning can occur hours after the initial incident. Prevention: Have good training and preparation for your dives. Check weather and water conditions before each dive. Keep your swimming skills at a high level. Exercise regularly for good physical fitness. Don’t mix any water sports and alcohol - alcohol is a major factor in drowning deaths. Don’t hyperventilate excessively before free diving. When scuba diving, monitor your air supply to avoid out of air situations. Keep your backup procedures well-practiced. Keep rescue and resuscitation equipment ready. Have a personal flotation device (PFD), other than dive equipment, for unexpected immersions for each person on the dive boat. Practice your rescue skills often. Supervise children waiting around dive sites and onboard dive boats, at all times. Nitrogen Narcosis Nitrogen narcosis is a general, stuporous condition from breathing nitrogen gas under pressure. Nitrogen narcosis is poorly understood. Part of the mechanism is that nitrogen dissolves in the protein coverings of your nerves, depressing nerve excitability. There are other factors involved, of course, in this complex phenomenon. Effects: Great individual variability exists in narcosis. Some divers may be seriously affected by 30 to 40 m (100 to 130 ft). Others show less impairment. Narcosis is often compared to feelings of alcohol intoxication. However, although it is sometimes called Rapture of the Lungs Air Space Body Fluids FIGURE 4-7. SECONDARY DROWNING. Deep, effects are not always rapturous or intoxicating. They are anesthetizing. In cold conditions, narcosis can be unpleasant to some, and in limited visibility, can be frightening and claustrophobic to divers predisposed to those feelings. In general, narcosis reduces mental and motor ability, reducing diving safety. Narcosis impairs judgment and orientation, making it difficult to monitor time, depth, air supply, and location of buddy. Dive plan information may not be recalled during a dive. You may not know up from down, or care. A key problem is that impaired people are too impaired to know that they are impaired. First Aid: Narcosis rapidly reverses with ascent. Prevention: Avoid factors that increase susceptibility, including carbon dioxide excess (explained earlier), alcohol, hangovers, fatigue, anxiety, cold, and medications or recreational drugs that might cause drowsiness or reduce alertness. Severity of impairment increases with depth. The hazards of narcosis are one reason why recreational diving guidelines limit depth to 40 m or 130 ft. Diving skills become more automatic with experience, creating the guideline for novice divers to limit dives to 18 m or 60 ft.
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