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Perhaps this will provide some grist for the slow-grinding-of-late mill, from Ocean Science News, Volume 35, Number 6, March 26, 1993. There is no copyright notice so I assume it is okay to post. The author is writing for an audience of scientists who may not be divers. The community of "technical diving" addressed at tek.'93 is predominantly made up of divers who do it for fun rather than as their job, but what they do does not fit into the category of "recreational" diving. The latter term as used by agencies who train recreational diving [sic] applies to dives using air, to a depth no greater than 130 feet and requiring no decompression stops. Technical diving is outside this range, but the implication is that some special equipment or techniques are needed. The basic garden variety technical dive is to about 250 feet of sea water for a bottom time of about 20-25 minutes. Breathing mixtures are usually "trimex," [sic - should be trimix] and in this range would be about 17% oxygen with between 25 and 50% helium, and the balance nitrogen. Trimixes effectively reduce narcosis that would result from a dive like this if done on air. Divers wear a backpack of two large, 3,500 liter or 120 cubic foot, tanks of bottom mix, a side-mounted tank of, say, 40% oxygen enriched air used as an intermediate decompression mix, and another "wing" tank of pure oxygen to be breathed at the last couple of stops before surfacing. Another "pony" tank of bottom mix provides redundancy. Decompression takes about 1.5 hours, and may use "custom" decompression tables designed for a specific dive. Much longer dives in caves rely on gas tanks cached in the cave. Energy balance is achieved with dry suits, often inflated with argon when cold stress is significant. One important characteristic in many such dive patterns is that each diver is self sufficient; the "buddy" concept used at shallow depths is not very effective at these depths. While this pattern seems to be working well under favorable conditions, when things go wrong the safety net is thin. Commercial divers for a dive of this magnitude would have a full-face mask with communications, gas supplied by hose from an adequate source and a diver-carried "bailout" tank, a supervisor and standby diver, and a recompression chamber on deck, to mention a few differences. Many aspects of technical diving as currently practiced were thoroughly examined at tek.'93. Among these was the need for an operations team, in particular a topside crew with a standby rescue diver. Another recognized weakness is lack of voice communications, and the use of [a] mouthpiece that can be lost in the event on an oxygen convulsion; appropriate masks and techniques for using them with "comms" were proposed. The extremely limited gas open-circuit supply may in due course give way to rebreathers; a couple of promising units were described in the most popular session of the conference. For more ambitious dives the divers use battery powered "scooters" or diver propulsion vehicles. Not many of these are being manufactured which are suitable for this work, and they often have to be modified to take higher pressure than the manufacturer had in mind. Decompression sickness seems not to be much of a problem when dives are executed according to plan. In addition to several consultants who can provide tables, four different PC-based decompression planning programs selling in the $100 to $400 range were demonstrated at tek.'93; with one of these a technical diver can calculate his own tables. These programs provide a fine teaching and planning tool, but some are skeptical as to whether this much capability might lead to "computer narcosis": over-reliance on the computer and not enough judgement. When decompression sickness does happen, several experts stressed that conventional oxygen treatment procedures are just as appropriate for dives with special gas mixes as for air dives, and Dr. Phillip James of Dundee, Scotland, made a now-familiar case for the use of helium-oxygen mixtures on any tough treatment. The conferenced learned that a remote-site alternative to evacuation to a hyperbaric chamber is treatment in the water with oxygen, a controversial practice but one with a bank of good experience behind it. A better alternative, a type universally endorsed for conditions when a proper chamber is not close by, is a Kevlar one-person evacuation chamber with the trade name Hyperlite. How to handle a problem some divers only have nightmares about was well covered: what to do when the diver surfaces only to find no dive boat in sight. Several "entertainment" speakers stretched beyond technical diving in several directions. Dr. Claes Lundgren of the State Univ. of New York at Buffalo covered both physiology and feats of breathold diving, opening his talk with seven minutes of silence while he help his breath. Jean Pierre Imbert of Comex Services told about the 20Nov92 record-setting chamber simulated dive to 70 bars, 2280 fsw pressure at the Comex laboratory in Marseille. Using a breathing mixture rich in hydrogen, a Comex diver bettered Duke Univ.'s Atlantis III record of 68 bars pressure set in 1981, despite some physiological problems at near maximum pressure. More tantalizing to some aggressive and affluent technical divers was a talk by Phil Nuytten of "hard suits," the one-atmosphere articulated anthropomorphic suits that can take a person to great depths without exposing him to pressure. Nuytten is founder of Can-Dive and inventor of the Newt Suit, among other accomplishments. Another former commercial diver who served as a tek.'93 session chairman was Lad Handleman, a Cal-Dive founder and former CEO of Oceaneering Intl. In what might become a tradition similar to those of other professional groups, the first "tekkie" award was given to Dr. R.W. "Bill" Hamilton. This handsome sculpture of a technical diver by Augie Rodriquez recognized Hamilton's "contribution to the philosophy, development, and art of technical diving," mainly through his work with special breathing gas mixtures and decompression. Hamilton has been an occasional correspondent for OSN. Perhaps the most threatening aspect of technical diving is that it requires considerable experience and special training as well as expensive equipment; it is not for everyone. Several experienced diving educators bemoaned that training for technical diving had to start back at square one, because most recreational divers are inadequately trained in physics, gas chemistry, and physiology. They strongly discouraged quickie tech diving courses for divers lacking adequate preparation. Demographics of the tek.'93 audience showed a varied collection of backgrounds and objectives, with a typical diver about 40 years old, having an income of just under $50,000, and with about $14,000 invested in diving equipment. Some are the subterranean equivalent of Everest climbers, and several are members of the Explorer's Club. Plans are underway for tek.'94, to be held in New Orleans 10-11Jan94. A call for papers will be issued soon. For information contact "AquaCorps" at 1-800/365-2655, or PO Box 4243, Key West FL 33041.
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