Ponza Rebreather Meeting 2019: Dive, Learn, Eat

Michael Menduno details the highlights of the various presentations given during the sixth biannual international Rebreather Meeting, which took place 1-5 May 2019 on Ponza Island in Italy.

Ponza harbour during twilight

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Michael Menduno is an award-winning reporter and technologist based in California, USA, who has written about diving and diving technology for over 25 years and coined the term “technical diving.”

He was the founder and publisher of aquaCORPS: The Journal for Technical Diving (1990-1996), which helped usher technical diving into the mainstream of sports diving, and organized the first Tek, EUROTek and AsiaTek conferences, as well as Rebreather Forums 1 and 2.

Rebreather Meeting Presenters:
Dott. Pasquale Longobardi, president of SIMSI; Dott. Alessandro Marroni, president of DAN Europe; Dr Simon Mitchell, professor of anesthesiology, University of Auckland, New Zealand; Shearwater founder Bruce Partridge; Edoardo Pavia, owner of Sea Dweller Divers; DAN Europe research supervisor Massimo Pieri; Dr Neal Pollock, research chair in hyperbaric and diving medicine at Université Laval; TDI instructor trainer Mark Powell; Tomasz Stachura, CEO of SANTI

For more information, visit:

1 May 2019 — Nearly three dozen rebreather aficionados made the biannual trek to Ponza, Italy—a picturesque island in the Tyrrhenian Sea about a three-hour journey from Rome—for the sixth International Rebreather Meeting organized by Andrea Donato, owner of Ponza Diving Center, and his partner, Daniela Spaziani. The goal of the four-day meeting—which was sponsored by a number of manufacturers and organizations, including JJ CCR, Shearwater, DAN Europe, Società Italiana Medicina Subacquea ed Iperbarica (SIMSI), and the Italian rebreather users’ association CCR Italia—was to provide the latest research and information to the rebreather community.

“They’re passionate tech divers, hungry for information,” explained Dr Simon Mitchell, a professor of anesthesiology at the University of Auckland, New Zealand, who was one of the presenters. “That’s what I love about these types of meetings. I am happy to be here and share what I know.”

Taking a cue from the hyperbaric medical community, the meeting was organized to appeal to diver sensibilities: diving in the mornings (8:30 a.m.-2:00 p.m.), lectures and discussions in the afternoons (3:00-7:00 p.m.), followed by dinner and drinks (9:00-11:30 p.m.) in the evenings.

Dive right in

Donato and his crew did a masterful job of supporting more than 20 rebreather divers, bearing scooters, cameras and bailout bottles, along with a few open circuit divers, without incident. The operation felt both calm and relaxed, and ran flawlessly and safely, a testament to the team’s skill and experience. They were helped by Ponza Diving’s ubiquitous mascot, an amicable, large, black mastiff named Ugo.

The boat, which was docked just outside of the dive shop, headed out each morning around 8:30 a.m., as divers huddled over strong Italian coffee and fresh bread after prepping their rebreathers. Interestingly, as we were loading up the boat on the first day there, Donato made a point of warning Peter Symes, publisher of X-Ray Mag, and myself to go easy on the espresso. “It can kill you,” he said, citing an American diver who had a heart attack underwater after consuming too many coffees. The boat then made its way to one of the numerous submerged seamounts, covered in soft corals, surrounding the island, where it would anchor for the morning dive.

Our morning dives were typically 165-261ft/50-80m deep, with one- to two-hour run times. Visibility was 50-65ft/15-20m, and water temperature was about 58-60°F/15-16°C. Following each dive, we were treated to a multicourse lunch, which usually included soup, fish, cephalopods, rice, pasta, bread, salad and dessert, along with the requisite pitcher of wine and more espresso. After lunch, the boat headed back to port, where we prepped gear for the next day’s dive.

Where’s the manzo, err... beef?

While rebreather diving in Ponza was clearly the attraction that brought people together, the meat of the meeting was the presentations given by some of the technical diving community’s leading scientists, engineers and practitioners. Our group met in an old stone chapel up the hill from the dive shop. Headphones were available for sequential English and Italian translations.

One of the themes that emerged from the meeting was the role of human factors, i.e. the way we process and act on and/or fail to act on information, and its impact on diving safety. This is a deep body of knowledge that was developed in the aviation, healthcare and other fields, and is now being applied to diving largely through the efforts of pioneer Gareth Lock at The Human Diver ( Several of us noted the fact that human factors being discussed in the absence of the seemingly ubiquitous Lock was a sign that this important work was beginning to gain traction. Here are some of the highlights:

Training does not work

Technical Diving International (TDI) Rebreather Instructor, Instructor Trainer and author Mark Powell began with a list of ten improvements in rebreather diving that he would like to see from a community perspective, things like better buoyancy control, the increased use of checklists, more attention to bailout planning, etc. He then asked the question, “Why hasn’t training made a difference?” That is, why hasn’t training produced permanent observable changes in divers’ behavior in these areas? The answer, documented by numerous studies, is that humans aren’t very good at retaining information. The solution: deliberate practice of essential skills.

“People tend to practice things they like and are good at, which is not very helpful,” Powell explained, noting that practicing things that are very difficult to do doesn’t work either. “The sweet spot,” he said, “is practicing things that are challenging.” He recommended that divers practice something on every dive! Sounded very GUE to me.

In-water recompression (IWR)

The use of in-water recompression to treat divers at remote locations has long been controversial, and until recently, the hyperbaric medical community has failed to reach a conclusion regarding its efficacy. But as Dr Simon Mitchell explained, the situation has now changed as a result of a new paper, “In-Water Recompression,” he coauthored with Dr David Doolette, a decompression physiologist at the US Navy Experimental Diving Unit (and GUE diver). The two were able to find evidence not previously reported that answers two key questions:

  • Does early recompression improve outcomes? (i.e. recompressing an injured diver within minutes vs hours)
  • Is shallower, shorter recompression effective? (Note that IWR typically compresses the diver on 100% oxygen to 30ft/9m vs. a USN Table 6 to 60ft/18m.)

Based on US Navy data derived in part from early research on treatment protocols, Mitchell and Doolette were able to answer both questions strongly in the affirmative. The new recommendation: A diver should be treated with IWR if a chamber is more than two hours away and the team is set up to provide IWR (i.e. has proper equipment, e.g. full face mask and training, support, environmental conditions and appropriate patent status).

Defensive dive profiling: Concerns for aging divers

Dr Neal Pollock, research chair in hyperbaric and diving medicine at Université Laval, gave a pair of eye-opening lectures on the potential long-term impacts of decompression stress and what can be done, and the prospects for aging divers. Was he talking about us?

Pollock began by citing studies that found lesions in the brain and spinal cord have been observed with higher frequency in individuals with a history of repeated decompression stress. Bone lesions have also been found in commercial divers. The factors shown to increase the risk of dysbaric osteonecrosis in commercial divers were: a history of inadequate or experimental decompression, diving deeper than 165ft/50m, and a history of decompression sickness (DCS). The conclusion: While dysbaric osteonecrosis has largely been eliminated in commercial diving due to procedural changes, decompression stress poses a potential long-term risk factor for technical divers! Divers need to think about immediate and long-term risk.

As a result, Pollock, who is known for doing extra deco, encouraged divers to do longer shallow decompression, adding, “It can’t hurt. It can only help.” Specifically, he recommended several ways of adding conservatism: using conservative gradient factors, primarily reducing GF-high, buffering the dive by slowing down on the final ascent to the surface following the last high PO2 stop, delaying exercise post-dive, extending surface intervals to add more time for recovery, using appropriate gasses (Yes, “air is for tires!”), choosing appropriate partners with similar risk tolerances and maintaining good physical fitness.

The bottom line for aging divers: There is no upper age limit, though there may come a point where you may need greater support. Be forewarned! Note, there were several post 65-year-old divers making the plunge at Ponza!

Human factors in rebreather diving

Mitchell began by noting that human factors were the most important but also the hardest path to improving safety in rebreather diving. He then posed the question: Is there a safety problem with rebreather diving?

Mitchell began by reviewing what we know about rebreather safety based on the ground-breaking 2012 paper by Dr Andrew Fock, “Analyzing recreational rebreather deaths 1998-2010,” namely: There were approximately 20 deaths per year for 2000-2010 from a population, which was then estimated to be about 18,000 rebreather divers based on agency certifications. That means that the fatality rate for rebreather diving was estimated to be about 133 deaths/100,000 divers/year compared to about 16 deaths/100,000 divers/year for open circuit diving. The conclusion: Rebreather diving was about 10 times more hazardous than open circuit scuba. Note, there is currently a follow-up study underway to determine if things have improved.

Mitchell broke down the causes of rebreather fatalities into three buckets:

  • Hazards of advanced diving
  • Rebreather equipment failures
  • Diver error and violations

Overwhelmingly, most incidents arose from diver errors (i.e. trying to do the right thing but doing the wrong thing) and violations (i.e. knowingly creating unnecessary risk of harm to yourself and others, and expecting to get away with it). “I have made errors and violations in my rebreather diving,” Mitchell offered to the assembled group of divers, “and I bet you have too.”

What’s to be done?

Mitchell reviewed several fatalities involving violations, like diving with two-year-old oxygen sensors, or using a type of sorb not specified by the manufacturer. He said that we needed to remove the motivation for violations. This involves a culture change: Make safe choices be seen as a strength versus a weakness. Training, mentoring and role modeling are critical in this regard.

Typical errors might include forgetting to analyze one’s gas, forgetting to turn on the rebreather or open the oxygen valve, or leaving out an O-ring on the scrubber. In fact, each of these errors have resulted in multiple fatalities. Mitchell said that pre-dive checklists are the primary means for preventing errors. As a testament to the power, he cited a study analyzing the impact of using checklists in surgical suites: Deaths were reduced by 50 percent after the introduction of checklists and, as Mitchell pointed out, these were among highly trained professionals. He then cited a DAN study of some 2,041 dives examining the impact of pre-dive checklist use on scuba mishaps: Mishaps, including rapid ascents, low or out-of-air situations, etc., were reduced by 36 percent.

Barriers to using checklists

First, misunderstanding about their purpose: Checklists are not meant to replace a manual! Second, arrogance or ignorance: thinking “I can do it from memory,” or “I don’t make mistakes.” Checklists can be supported by training, practice and engineering.

Interestingly, after the meeting, I asked one of the Italian rebreather divers if he used a checklist on our dives. “My instructor taught me to do it by memory,” the diver told me, “So, that is what I do. I haven’t had any problems.” And therein lies the problem!

Bruce Partridge, founder of Shearwater Research, and explorer Edoardo Pavia, owner of Sea Dweller Divers, also gave individual presentations focused on understanding human factors and changing divers’ behaviors. Partridge noted that there were approximately 600 failure modes possible on a rebreather. However, only 40 were equipment-related; the remainder involve diver error.

DCI Research/Telemedicine

Massimo “Max” Pieri, research supervisor for DAN Europe, discussed DAN’s research focusing on preventing decompression illness (DCI) using DAN’s diving database of some 66,000 dives, ranging in depth from 16 to 628ft/5 to 192m, with an average depth of 100ft/30m. Some of the factors DAN’s researchers have considered include: gradient factors, hydration, genetic disposition and hematological parameters. They are also conducting a decompression study with a local (Italian) GUE group with the help of GUE instructor Mario Arena, examining the efficacy of so-called “deep stops” versus shallow decompression profiles (see Dr David Doolette’s post, “Gradient Factors in a Post-Deep Stop World”).

Next, DAN Europe president, Dr Alessandro Marroni, discussed his visionary program dubbed Advanced Virtually Assisted Telemedicine in Adverse Remoteness (AVATAR). The goal is to develop tools and procedures to enable real-time monitoring of divers during their dives—think Fitbits on steroids! Marroni described his vision of a DAN doctor able to assess a diver who is still in the water, and communicate directly with that diver via an underwater communications system. In fact, they have already tried out a prototype.

Dott. Pasquale Longobardi, president of SIMSI, also presented SIMSI’s research examining the biochemical mechanisms involved in decompression stress. He concluded with a set of best practices, namely to run PO2s at 1.3 bar or less, maintain PN2s at 3.16 bar (the equivalent of breathing air at 100ft/30m) or less, and run PHe as high as possible; Longobardi stated that helium in the form of trimix protects divers from oxidative stress (inflammation) compared to diving air (kick those tires again!). A medical colleague in the audience told me he had questions about the supporting data.

Mangia, mangia!

Having gotten our daily dose of brain food, attendees retired to their hotels and apartments to catch up on email, clean up, and later, walk to the ristorante du jour, which had been chosen for that evening. There, we were greeted by our attentive hosts, Andrea and Daniela (accompanied by Ugo), who had arranged for a family-style dinner and wine affair, and would ensure that everyone had enough to eat and drink. If you had trekked to the meeting for the food alone, you would have not been disappointed.

“Mangia,” Dani told me, gesturing emphatically with her hands and pointing to my empty plate, after the second (or was it the third?) course. “Please, you must eat some more,” she insisted, passing me a bowl of mussels. It felt like a family gathering—a small but mighty band of passionate, geeky divers, who were there to celebrate and improve their underwater practice. And, the eating and drinking and sharing of stories continued into the night. ■


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