Braving The Circuit

The View From Rebreather Forum 2.0

by Michael Menduno

Key West, Florida&endash;Thirty three feet beneath the surface of the lagoon, Andy Sikes was peddling just as fast as he could to maintain the 50-watt setting on the stationary bike, but he still wasn't feeling right. With only one and half minutes remaining in the test cycle, the experienced divemaster knew he could tough it out. The "air hunger" had subsided several minutes earlier after he had flushed his counterlung, and his back-lit wrist display, showed a PO2 of 0.98 bar. The display clock continued to tick off the seconds. It wasn't getting better; Sikes yanked on the safety line, as his body began to slide helplessly towards the bottom in slow motion.

Later the support diver, who pulled Sikes to safety, reported that the test diver looked over, and gave him a "10,000 yard stare. That's when I grabbed him." Sikes had all he could do to remain conscious, breathe, and not spit out his mouthpiece during the dream-like ascent.

Back at the lab, engineers were able to duplicate Sikes' experience. A power spike caused the PO2 portion of the display to lock-up, along with the solenoid that injected oxygen into the system. Sikes had gone hypoxic while test diving a rebreather that the press mistakenly reported had gone on sale this Fall.

Hopefully with more testing, (and back-up displays), the future for rebreathers will bode brighter.

In September, two months before Sikes sobering dive, a group of over 100 industry participants, including representatives from the military, scientific, and hyperbaric medicine communities, met for three days in sunny California to discuss the future of rebreathers, and their application to mainstream recreational diving. Dubbed, Rebreather Forum 2.0, after a similar meeting held in 1994, aficionados came from around the world hoping to find a common ground on which to address a long list of issues, lest the technology become a casualty of the revolution that it inspired.

First conceived of in the 17th century by Giovanni Borelli, rebreathers have long been considered revolutionary. Though the technology has been in use since the turn of the century, it wasn't until WW II that, "the exigencies of war brought it into use, and proved its value," wrote Sir Robert Davis in "Deep Diving and Submarine Operations" Davis was referring to the oxygen and semiclosed sets used by combat swimmers, a decade before advent of scuba.

Twenty years later, inventor, Walter Stark introduced the first electronically-controlled closed circuit system, the "Electrolung," to the consumer market. The 1970 cover of Skin Diver magazine read "Computerized Scuba to 300 feet." Within a year, a series of tragic deaths forced Beckman to pull the system from the market.

Rebreathers made a brief foray into the commercial world during the go-go seventies, when 'oilfield diving' was still a glamour industry, but contractors opted for the hose and saturation diving systems. According to then Oceaneering CEO, Lad Handelman, though a handful of top divers were able to handle the equipment, a fatality and several near-misses proved it too dangerous for rank-and-file hardhat divers, and the maintenance was incompatible with the oilfield environment. Handelman ordered his crew to "dump a quarter million dollars of rebreathers into the drink." The industry followed suit.

Rebreathers remained the exclusive province of the military until the late eighties, when a handful of tekkies determined to "go where no one had gone before," were inspired by the promise of their extended gas range, and decompression advantages. Their enthusiasm rekindled the interest in the arcane technology, while fomenting the technical diving revolution.

Since that time, a dozen upstart engineer-divers, have been quietly hoping that their fortunes would stay afloat, while struggling to get working product out the door. Others saw the writing on the wall. In 1996, German manufacturer, Dräger, who supplies rebreathers to the US military and other navies of the world, launched the Atlantis 1, a US$5000 semiclosed system designed specifically for recreational divers. Nissan-affiliate, Grand Bleu had launched a similarly-targeted rebreather to Japan consumers the year earlier.

The re-emergence of consumer rebreathers comes at a good time for military users, who as a result of shrinking budgets, and an aging base of technology, are increasingly seeking off-the-shelf solutions; assuming that the new class of electronic rebreathers make it to the shelf. Purveyors keep promising product release dates that are just around the corner. But is a mass market technology?

The numbers are revealing. Workshop participants learned that the two largest users of rebreathers, the US and British Navy, combined have 240 mixed gas rebreathers in service out of an inventory of approximately 600, along with an army to support them. The sport industry is hoping to pump out ten to twenty times that amount, each year&endash;an order of magnitude increase&endash;ambitious goal by any one's standards.

The technological challenge facing the sport diving industry was highlighted by retired Navy Capt. Ed Thalmann, MD.., during the first day of the forum, "The scuba regulator is the steam engine of diving gear. It's been around for a long time and they’re incredibly reliable. By comparison, a rebreather is like a space shuttle." Thalmann was responsible for the Navy's life-support testing program for the last fifteen years. "The problems are not academic. If you don't know what you're doing, and don't have people around you that know what the hell they're doing, then you'll end up dead."

A rebreather is a closed life-support system that's designed to extend gas supplies by providing the "right" amount of oxygen to meet the diver's metabolic needs, while conserving the diluent gas in the system, and removing CO2. Closed systems control oxygen levels through a series of electronic sensors; activating an injection switch when they're too low, and an alarm when they're too high. Semiclosed systems perform this function mechanically, by trying to match a preset flow of oxygen-rich gas to the diver's consumption; excess gas is exhausted into the water.

Both types of systems passively remove excess carbon dioxide by passing the gas through a canister of CO2 absorbent material, whose duration can vary significantly even under identical conditions. Also, according to Thalmann, there are few tested decompression tables; simply recalculating the math from open circuit tables doesn't necessarily work.

As a result of this complexity, divers face a number of "insidious" risks not found in open circuit scuba; hypoxia (too little oxygen), hyperoxia, (too much oxygen), and hypercapnia. (too much CO2). The result is usually unconsciousness, and probably drowning in the absence of a full face mask.

"One of the most important things that needs to be done if this type of diving is going to be introduced to the sport divers is to get their attention right off the bat," states Randy Poladian, Chief Warrant Officer at the Navy Experimental Diving Unit. "It's quite a different ball game than scuba diving."

Of keen interest at the workshop, were constant mass flow systems, the oldest and simplest type of semiclosed rebreather. like the Atlantis 1 and the Fieno, which are now being offered to consumers. They have no electronics.

"When used gently, the semiclosed rebreather is a beautiful piece of equipment to dive," explained physiologist Dr. David Elliott, who began his naval career training on a semiclosed UBA as a clearance diver. Never the less, they can be problematic. The Royal Navy affectionately refers to their set as the "Clammy Death." A major concern with these systems is hypoxia.

Mass flow systems deliver a preset flow of nitrox to the diver based upon an assumed oxygen consumption rate. However, actual O2 levels depend on the diver's workload, and are independent of depth. If a diver "out-breathes" the system, i.e. exceeds the range preset by the manufacturer, hypoxia can occur very rapidly, particularly at or near the surface, or during ascent where there is insufficient depth to maintain a safe PO2, and the diver may drown.

Elliott offered data that showed that an oxygen consumption as high as 3.0 liters per minute is achievable in extreme situations, for example, when swimming hard against a current. In fact, military systems are designed to take this into account, according to John Sherwood, Fullerton Sherwood who builds semiclosed sets for the Canadian forces. The problem is that, not all of the sport units can handle this high of a demand.

Presenters offered several solutions to the problem including; designing in adequate flow rates, thorough testing of the rig under extreme conditions, always "flushing" the system before ascent, and incorporating oxygen sensors, as soon as possible.

The relative simplicity and low cost of semiclosed systems, may make them the likely candidate for recreational divers. "It's the KISS principle-&endash;Keep it simple, stupid," says IANTD vice president, Billy Deans. "With a real short checklist, you can go diving." Even so, there's a lot more to diving a semiclosed set than what physiologist, Bill Hamilton, once described as the quintessential rule for open circuit nitrox diving, "breathe in and breathe out."

Maintenance is another area that troubles sport makers. Unlike scuba, rebreathers require a significant amount of ongoing maintenance to function properly including; a hour or two preparation before each dive, an hour or two post dive, and regularly scheduled tune-ups.

"If you’re planning on taking the rig and not doing the proper pre and post dives, we’re going to read about it as a statistic," says former Naval Medical Research Institute test diver, JR Hott. "It’s almost going to have to become a religion to you, if you're going to do it right."

Are retailers ready to embrace the faith?

"The majority of dive stores are just not prepared," says photographer Rod Farb, who has a 140 hours of rebreather experience and consults to Biomarine. "It’s going to take a very special dive store to do it right."

According to military specialists, the dominant factor in the military's success is the extensive infrastructure that's in place to support these systems, which is conspicuously absent in sport circles. The military objective is to eliminate human error, and control usage through written procedures, testing and certifying units before they are released, mandatory checklists, adherence to the buddy system, reliance on dive supervisors, and tracking problems in the field.

Some questioned the relevance of military procedures to the sport market. In response, Thalmann drew a line between the two groups of divers. "They both breathe air, and neither can breathe water. The main difference I can see is that it’s unlikely some one would be shooting at a civilian diver unless they’re some place where they shouldn’t be." Unfortunately, tekkies have a habit of doing that.

At the present time, there are probably less than two dozen US civilians who own and regularly dive a rebreather. Their experience is enlightening. "Almost everybody I know that has a rebreather has had an incident. If they weren’t able to think it out, or there wasn’t a buddy there to help, they would have been in serious trouble," says film-maker John McKinney, one of six brave consumer souls who described their experiences at Forum 2.0.

"One of the most dangerous things about rebreather diving is allowing your confidence level to exceed your ability," offers self-confessed fish-nerd, Richard Pyle, from Bishop Museum, HI. "It takes direct experience to realize how easily you can kill yourself." He urged potential users to go slow.

Why do they take the risk? Film-technician Mark Thurlow wasn't shy. "Diving a rebreather is the most fun that I’ve ever had underwater, to the point where I’ve probably got cobwebs growing on my scuba gear." For a few, they're the only way to get their mission done.

Training is a major hurdle that sport diving industry will have to overcome if rebreather technology is to become a consumer staple. Ask the Royal Navy. Instructor, Lt. Rob Cornack, summarized his military lessons this way, "You’re not teaching them to dive a rebreather; you’re teaching them to survive in a rebreather. It’s a completely different ball game." At an average training cost of £190,000 (US$285,000) the Royal Navy can afford a lot of survival. Will the recreational market be able to foot the tab?

Today, consumer rebreather training is in its infancy. Though many agencies have rudimentary programs in place, there are no common standards. One problem is the lack of hands-on experience within the community. The second is the lack of sufficient rebreathers to enable trainers to get that experience. Is it the chicken or the egg; which comes first?

Workshop presenters agreed that minimally, an instructor should own or have on-demand access to a unit, and should have the minimum experience for competence which may be as many as 100 logged hours, the same as an open circuit instructor. Also manufacturers need to take an active role in the process since, unlike scuba, training is system-specific. "[That's] the problem that I see with the transition to sport diving," cautions Cornack. "You’re going to have a different bunch of divers turning out each weekend, probably on different pieces of equipment. Without a common standard of training amongst your divers, you guys are going to have to be much better at [rebreather diving] than we are."

Or at least comparable (excluding bullets). Though there aren't any distinct liability problems that should keep rebreathers off the market, according to Hruska & Lesser defense attorney, Bill Turbeville, "Regulatory concerns are by far the most significant issue that we're facing right now." During the week prior to the workshop, the US Occupational Health & Safety Administration, which regulates the workplace, declined to grant a recreational exemption for rebreather training. That means that agencies, retailers and instructors, technically, will fall under commercial regulation until the issue can be resolved. If casualties mount, consumer rebreathers may well join Stark's "Electrolung," in the annals of diving history.

What's to be done?

A few basic themes kept re-emerging at the Rebreather Forum. First, all agreed that before a rebreather is released on the market, it should undergo manned and unmanned testing and the results be made available to the public. The good news is that performance standards are readily available from the military. The bad news; they can cut both ways. "If somebody gets hurt, they're going to ask you about your design standards," points out Thalmann. "All their lawyer’s got to do is spend about $100 to get the EDU reports and you’re mincemeat unless you can show that your rig has been designed to a set of standards, you know how it performed, and you can defend it."

Second, the industry needs to take a hard look at incorporating full face masks, and diving with a buddy, "Because when you black out, you’re not going to know it, and the only guy that’s going to save you is a buddy" as NavSea's Ruth was quick to point out. Andy Sikes would agree.

"This was a very important meeting, counsels Dräger pointman Christian Schult. "I got a lot of information and the impression that we are still on the right way. We not only need to go step by step into this market, but we have to fulfill a lot of requirements, and name and document all the problems, so that we can move forward."

And for consumers? "Everyone here has had a certain amount of training, but they are diving to their own standards, says Forum co-chair Tracy Robinette. " And that’s how it’s going to be until there is a standard out there, and some type of organization, and more time."

tec.asia editor, Michael Menduno was the organiser of Rebreather Forum 2.0. A detailed proceedings of the Forum, has been published by DSAT and is available through PADI.