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Deep Diving

© Linda Gettmann

Earthlings are adapted to living in an air environment with an ambient air pressure of about one atmosphere. When we dive into the depths, we are forcing our bodies and senses to adjust to a totally new set of environmental factors, some with detrimental consequences.

Experienced divers learn to compensate for these changes which are magnified by each 33 feet in depth (= one atmosphere) from the surface. A mask restricts divers' vision, as does murky water, and objects appear larger and closer than they actually are due to the water column magnification. Hearing and balance are affected by pressure changes to the ears and the sound of your own breathing through the regulator. Lack of smell and taste result in further sensory depravation. A diver's unfamiliarity with the underwater environment may cause psychological changes, especially at greater depths.

Risks in sport diving beyond 100-130 feet include the increased susceptibility for DCS, nitrogen narcosis, stress reactions including anxiety and panic, vertigo, negative buoyancy, breathing resistance through the regulator, increased air consumption, hypothermia, and high carbon dioxide and nitrogen levels. In addition, the deeper dives increase risk for a rapid ascent and resulting air embolism injuries.

How can you avoid or minimize these risks? Short of not diving, there are prudent actions every diver should take including:
1. Choose conservative no-decompression limits.
2. Reduce bottom time to compensate for risk factors and increase surface interval time.
3. Ascend slowly, 30 feet per minute.
4. Avoid multiple ascents, bounce profiles.
5. Do a 3-5 minute safety stop at 15 feet at the end of every dive.
6. Avoid dives deeper than 100 feet.
7. Avoid excessively long dives at depth.
8. Take a day off during multi-day repetitive diving.
9. Ensure gauges and computers are working properly.
10.Dive to the deepest depth early in the dive and gradually work shallower during the dive.

Nitrogen narcosis may affect divers at relatively shallow depths, however its manifestations at depth have been compared to the effects of alcohol, drugs, and the early stages of general anesthesia. Brain functions such as memory, concentration, reasoning, and judgment are the first affected by narcosis. A sense of euphoria or anxiety may be experienced, leading to errors in judgment. At depths beyond 165 feet, serious impairment, hallucinations, and unconsciousness may occur. Susceptibility to narcosis varies among individuals and from dive to dive and many divers do not realize they are affected ("narc'd").

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