Diving at Altitude

Excerpt

Increased popularity in recreational scuba diving adds to an ongoing category of diving-related injuries and illnesses. Whether recreational or occupational, scuba, or surfaced supplied air, diving at higher altitudes may compound inherent risks. An individual initiating a dive at altitude is exposed to an atmospheric pressure less than sea level pressure, which is the presumed endpoint for standard decompression tables. However, upon surfacing, the decreased atmospheric pressure in the environment exerts an increased “decompression stress” on the diver. This is often thought of as a relative increase in probabilistic risk for decompression illness in proportion to the diminishment in atmospheric pressure. Under this assumption, the best approximations may translate risk equal to that experienced by the diver surfacing from a depth deeper than actually achieved. These calculations determine a new "equivalent depth" for a diver to record bottom time, duration, decompression stops if needed, surface intervals, and residual nitrogen load for repetitive dives to reduce his or her overall risk for decompression illness. Adjusting a dive profile at altitude to an equivalent depth assumes the diver is at risk equal to a sea-level dive; however, other environmental effects inherent to the altitude may also factor in additional risks.