Mecanismos de Diseño

Because decompression tables are based on predictable mathematical models of physio-logic parameters, decompression can be computed with portable dedicated micro-processor computers. These dive computers monitor pressure and time; they then provide information that can guide the diver through a proper decompression. Divers have many choices of designs and algorithms with this technology. These choices are not unlike those available to the personal computer owner, who is faced with the fact that devices that are bought today are likely to be soon Figure 3–10. Upper graph shows the percentage of reduction in performance in cold water. Numbers to the right indicate the conditions of measurement described in the lower graph. (See text for

interpretation.)

Figure 3–11. A trilaminate “shell” dry suit that permits several types of undergarments to be used for thermal insulation. (Photograph courtesy of Diving Unlimited International, San Diego.)

outmoded. Device characteristics vary widely, and many of these computers have far more functions than most divers need. Dive com-puters may be independently mounted as stand-alone devices, or they may be integrated into consoles with tank pressure, remaining airtime, and other functions (Fig. 3–12).

The choice of a personal dive computer should be based on a careful review of func-tions and specificafunc-tions. Reading the owner’s manual should provide a better understand-ing of the nature of the calculated risks and the design assumptions that are inherent in each device. This understanding will mini-mize, but not guarantee, diver safety. Signi-ficant databases of comparative information are available on the Internet and in diving-related consumer reports.⁵

Because the dive computer constantly monitors depth and time, it provides infor-mation (based on the assumptions made in its design) that enable the diver to make immediate informed decisions regarding the conduct of the dive. Computers are not risk-free. They are tools that provide the diver with information but do not guarantee that following the advice will result in a safe dive.

A review of several manuals for decompres-sion computers revealed multiple warnings and 40 to 100 pages of instructions. Warnings include avoiding decompression dives, car-rying a set of printed dive tables as a back-up source for decompression schedules, and maintaining the prescribed ascent rate.

Other decompression computer manuals suggest avoiding high-altitude diving without special training, avoiding air flights for 24 hours after diving or until the computer indicates it is safe, diving with a partner, and limiting sport diving to 60 ft. Manuals warn that the risk of decompression sickness is

increased if the recommended decompres-sion schedule is ignored.

These examples, which are representa-tive of statements found in most current instruction manuals, indicate the concern and uncertainty associated with the current trend toward the widespread use of dive computers. Current dive tables and dive computers are not perfect, but they have demonstrated safety and efficacy in millions of uneventful dives. Responsible divers use all of the diving safety tools at hand to minimize the hazards associated with diving and rarely have problems they cannot resolve with their tools. Adequate knowledge and training can result in a real-istic calculated risk. This “informed con-sent” is fundamental to the acceptance of the calculated risks involved in any inher-ently risky activity. Because there are no

“safe” tables or “safe” dive computers, every diver must accept some risk when diving for sport or occupation. Experience to date with the dive computers is some-what mixed. The largest single cause of decompression sickness while using com-puters appears to be diver error associated with a lack of understanding of the limita-tions of the devices. The causes of the prob-lems associated with the misuse of the dive computer are probably little different than those associated with the misuse of printed dive tables. Carelessness, lack of under-standing regarding the limitations of the logic, and failure to recognize personal limi-tations account for the greatest number of decompression incidents.

Fundamental advice on the use of dive computers and tables remains as it has been since they were developed. Dive computers are tools that can help divers understand their dive profiles. Dive computers cannot guarantee that their use will prevent decom-pression sickness. Properly used, these devices should reduce the risk under normal circumstances.

The proliferation of diving equipment has complicated the diver’s quest for compara-tive information, which can be used to make informed choices. Fortunately, the Internet has opened information channels that allow for up-to-date information. Virtually all of the training agencies, equipment manufac-turers, dive magazines, and special-interest groups associated with diving offer informa-tion and links to issues involving diving equipment.

Figure 3–12. Device used for comparative testing of dive computers.

References

1. Hardy J: Fins in Review. http://www.scubadiving.

com/gearfinder/main.php/results/view/Fins

2. Professional Scuba Inspectors, Inc., http://www.

psicylinders.com

3. U.S. Navy Bureau of Medicine and Surgery: U.S. Navy Diving Manual. Flagstaff, AZ, Best, 1993.

4. National Oceanographic and Atmospheric Admin-istration. NOAA Diving Manual. Flagstaff, AZ, Best, 2001.

5. Hardy J: Computers for the Masses. Mar 1997 http://www.scubadiving.com/gear/compmasses/ and http://www2.scubadiving.com/gear/computers.

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4 Inert Gas Exchange