Are we there yet? Rebreather technology for recreational divers by Dr Petar Denoble
“In the future, you’ll simply jump into your car, turn on the Internet, turn on a movie and sit back and relax and turn on the automatic pilot, and the car will drive itself,” says Michiko Kaku in his book Physics of the Future. “Unlike a human driver, it doesn’t get drunk, it doesn’t get distracted and certainly does not have road rage.”
Even though driverless cars are not yet commercially available, driving a car is a simple process with all of the complex technology hidden from the user. Today’s rebreather technology is a few steps behind, but it may be catching up.
Sixteen years ago diving scientists, manufacturers, divers, training agencies and regulators met for three days at Rebreather Forum 2.0 (RF2.0), in Redondo Beach, Calif., to discuss the future of “sport rebreather diving.” At the time, at least one dozen rebreather models had appeared on the market, some of which were there to stay. The market was minuscule, and training opportunities were practically nonexistent. The consumer base consisted of about 100 brave, knowledgeable divers who recognized they could achieve more in their respective fields using rebreathers but at the cost of more work, money and risk than average divers were ready to commit.
RF2.0 reviewed the physiology of rebreather diving and the enabling technology, including the risks and needed enhancements if sport rebreather diving became popular. The findings and recommendations of RF2.0 emphasized the complexity of closed-circuit rebreathers (CCR), a need for technical support and better control of insidious risks including hypoxia, hyperoxia and hypercapnia. Additional safety issues were also noted such as a “caustic cocktail,” an unanticipated variation in the partial pressure of nitrogen, thermal considerations and mechanical or electronic failures. Some technological advances were explicitly required, like full-face masks to prevent drowning in case of unconsciousness and an on-board carbon dioxide monitor to prevent carbon dioxide poisoning. Third party pre-marketing testing was advised, but standards were not proposed.
When compared to open-circuit scuba, rebreathers required significant ongoing maintenance and support to function properly; the consensus among the forum attendees was that rebreathers were suited for the technically savvy rather than the average diver. Military divers have successfully managed the risks of using rebreathers with resources not available in sport diving, including the use of a large supporting infrastructure, a high degree of discipline and extensive formal training.
Dr. Richard Pyle describes the experience of a self-taught rebreather diver best: “After my first 10 hours on a rebreather, I was a real expert. Another 40 hours of dive time later, I considered myself a novice. When I had completed about 100 hours of rebreather diving, I realized I was only just a beginner.”
He did, however, provide a few survival tips for new rebreather divers:
- Know your partial pressure of oxygen (PO2) at all times; do not trust “fail-safe electronics.”
- Learn, in depth, diving physics and physiology.
- Training should emphasize failure detection, manual control and bailout procedures.
- Cover your ass (have a back-up).
The experiences and tips of Dr. Pyle and his peers became the basis for development of formal training for technical rebreather divers.
But there were additional challenges for the trainers. According to Karl Shreeves, technical development executive for PADI worldwide, before the training agency could consider the instructional system, it was necessary to determine who the customers would be and how they would use rebreathers. PADI considered rebreather diving a niche not of interest to mainstream recreational divers at the time, but recognized the trend could change at any point. Indeed, a lot has changed; rebreather technology has improved, some training agencies have started offering instruction and the number of users has increased from hundreds to tens of thousands.
The fatalities have also risen accordingly to more than 20 per year, or more than 190 in the sixteen years since RF2.0. Not all of these fatalities were rebreather-specific, but all analyses indicate operator-machine interaction played a major role in it. It’s an interaction that must be acknowledged, understood and made as safe as possible. Dietmar Luchtenberg of Europe’s Rebreather Advisory Board said, “We can’t get rid of safety issues in rebreather diving by [only] increasing technology standards.” He emphasized the need and challenge of eliminating the factor of human error to enhance diver safety. After RF2.0, there was also a consensus about the significance of the human factor in the safety of rebreathers; the suggested approach seemed to be to develop a reasonably safe device and shift the residual risk to the users.
The full article is available here at AlertDiverOnline, the magazine for Divers Alert Network