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Rebreather Forum 4 Yields CCR Market Data and Consensus Statements
By Ashley Stewart and Michael Menduno. Images by Jason Brown, BARDOPhotograhic unless noted. Header image: Professor Timmy Gambin discussing their shipwreck documentation efforts.
The latest Rebreather Forum produced the most comprehensive data analysis of the rebreather market to date, and a series of consensus statements to improve safety in closed-circuit rebreather (CCR) diving.
The three-day meeting from 20-22 April in Malta gathered 294 rebreather diving experts to advance and consolidate the diving community’s knowledge of rebreather technology and its use by technical, government and scientific divers, with the goal of improving rebreather diving safety and performance.

What is the Rebreather Forum?
The forum is an industry workshop and scientific meeting with a focus on improving CCR safety. Unlike dive trade shows or conferences, the purpose of the Rebreather Forum is to advance research and develop industry consensus on important topics.
Rebreather Forum is similar to dive-industry workshops like the 1992 Enriched Air Nitrox workshop that gathered diving experts to determine guidelines related to nitrox use, or the Flying-After-Diving workshops in 1989 and 2002 which came up with guidelines for surface intervals in between flying and diving.

RF4 Consensus Statements
The forum produced 28 consensus statements intended to reflect widely supported opinions of RF4 participants. The statements include thematic areas designated “safety,” “research,” “operational issues,” “education and training,” and “engineering.” Authors Simon J. Mitchell and Neal W. Pollock published the statements in full on InDEPTH.
Such consensus statements drive change in the industry. Rebreather Forum 3 attendees, for example, reached a consensus regarding pre-dive checklists, specifically recommending “rebreather manufacturers produce carefully designed checklists” and “training agencies and their instructors embrace the crucial leadership role in fostering a safety culture in which the use of checklists by rebreather divers becomes second nature.”
Since then, pre-dive checklists have been widely adopted. In a pre-RF4 survey, 73% of attendees indicated they “always” use checklists. (There’s still progress to be made. RF4 included a checklist-related consensus statement to strongly advocate for specific critical safety items.)

Rebreather Divers Are Dying At A Rate Of Two to Four Deaths per 100,000 Dives
In addition to consensus statements, RF4 produced the most comprehensive data analysis of the rebreather market to date, thanks to research from Dr. Frauke Tillmans and her team who compiled the data that shows the industry needs to do more to improve safety. “Analysis of contemporary rebreather accident data indicates a continued need for integrated effort to reduce the rates of injury, morbidity, and mortality associated with rebreather diving,” as one consent statement reads.
Tillmans, Divers Alert Network (DAN) research director, revealed insights from an analysis of data from DAN, public surveys, and information supplied by CCR manufacturers to give attendees the best look yet at market, demographic and safety data. Frauke’s research is further explored in this InDEPTH article.
Tillmans estimates that rebreather divers are dying at a rate of 2-4 deaths/100,000 dives, which is not substantially different from the analysis made by Dr. Andrew Fock at RF3.
Tillmans reported that at least 241 rebreather divers have died since RF3 (2012). She estimates that rebreather divers are dying at a rate of 2-4 deaths /100,000 dives, which is not substantially different from the analysis made by Dr. Andrew Fock at RF3. Fock estimated that the risk of dying on a rebreather was 5-10X the risk of open-circuit scuba. (Fock AW Analysis of recreational closed-circuit rebreather deaths. 1998-2010. Diving Hyperb Med 2013 Jun;43(2):78-85). Note by comparison, skydiving deaths ranged from 0.28-0.45 deaths per 100,000 jumps for the period 2018-2021 according to the United States Parachute Association (USPA), making rebreather diving 10x as risky as skydiving.
By comparison, skydiving deaths ranged from 0.28-0.45 deaths per 100,000 jumps for the period 2018-2021, making rebreather diving 10x as risky as skydiving.
Using data from the DAN hotline, RF4 participants, and a related survey, Tillmans estimated the mean age of CCR divers is 42-46 years, the CCR diving population is between 84% and 95% male, and certified for an average of six years.
In addition to summarizing the number of reported fatalities, Tillmans calculated the approximate installed base of sport rebreathers in the field, based on information from 20 of 24 sport CCR manufacturers. She estimates between 25,000 to 35,000 rebreather units are on the market today. According to our Pre-RF4 survey, rebreather divers own 1.7 eCCRs on average, so we might estimate that there are 15,000-20,000 rebreather divers up from a very rough estimate of 10,000-15,000 from RF3.
In parallel to Tillman’s data gathering in an effort spearheaded by Brian Carney, president, TDI, a group of training agencies agreed to submit their CCR training data from RF3 (2012) to 2022, to DEMA’s market research firm DP Research Solutions to consolidate and anonymize the agencies’ rebreather training data.
The analysis from DP Research found agency rebreather certifications issued annually ranged from about 3,500 to 5,200 per year between 2012 and 2022, with 2022 being the strongest year for certifications. The data includes certifications from entry-level to advanced, submitted by training agencies BSAC, GUE, SDI/TDI, FFESSM, SSI, PADI, IANTD, and Dive RAID.
More data is needed to understand and make improvements to rebreather safety. For this reason, one product of RF4 was a consensus statement advocating “self-reporting of diving mishaps and near-misses, and reporting of fatalities, to the DAN diving incident reporting system.”
RF4 Overview
RF4 included 22 presentations from experts including Dr. Richard “Harry” Harris, who this year completed the first reported CCR dive with hydrogen as a diluent, and prominent dive-science researchers.
David Doolette of the U.S. Navy Experimental Diving Unit, for example, presented on advances in decompression theory and practice, including the role of biomonitoring for venous gas emboli and heart rate variability in decompression planning. Pollock gave a presentation on hazards of CCR diving and Mitchell gave a presentation about developments in carbon dioxide monitoring, calling for the development of so-called end-tidal CO2 monitoring to detect levels in the diver. Full videos of the presentations will be available later this year.

The meeting gathered 294 attendees including CCR manufacturers, dive science researchers, and training agencies including: 83 vendor representatives, 9 external press representatives, 29 exhibitors, 17 sponsors, and five media partners. There were 111 try-dives held at a local pool in the days leading up to the conference. Units included the Liberty back-mount and side-mount units, Lungfish S. Loop and Alliance, Fathom MK III, XCCR, rEvo / Horizon, and Triton.
The latest forum, Rebreather Forum 4, is the fifth such trade and scientific meeting held by the diving community. The original Rebreather Forum was held in May 1994, in Key West, Florida, followed by RF2 in September 1996 in Redondo Beach, California, and RF3 in May 2012 in Orlando, Florida. A related event, Rebreathers and Scientific Diving, was held in February 2015 on Catalina Island, California.
Because the forum is held only when there is a need, it does not follow a specific schedule like an annual conference might. Rebreather Forum 5 is expected in the late 2020s.
RF4 would like to thank all of its sponsors and exhibitors, and our volunteers! Thank you!

DIVE DEEPER
Scubanomics: Expectations For Rebreather Forum 4 & A Glimpse Into The State of Rebreather Diving. The survey was conducted in March & April of 2023 among Rebreather Forum 4 attendees, presenters, exhibitors & sponsors.
DAN Europe blog: Highlights from the first day of Rebreather Forum 4 by Tim Blomëke
DAN Europe blog: What You Missed from Day Two of Rebreather Forum 4 by Tim Blomëke
DAN Europe blog: Insights and Breakthroughs: A Recap of Day Three at Rebreather Forum 4 by Tim Blomëke

InDepth Managing Editor Ashley Stewart is a Seattle-based journalist and tech diver. Ashley started diving with Global Underwater Explorers and writing for InDepth in 2021. She is a GUE Tech 2 and CCR1 diver and on her way to becoming an instructor. In her day job, Ashley is an investigative journalist reporting on technology companies. She can be reached at: ashley@gue.com

Michael Menduno/M2 is InDepth’s editor-in-chief and an award-winning journalist and technologist who has written about diving and diving technology for more than 30 years. He coined the term “technical diving.” His magazine “aquaCORPS: The Journal for Technical Diving” (1990-1996) helped usher tech diving into mainstream sports diving, and he produced the first tek.Conferences and Rebreather Forums 1, 2 and 4. In addition to InDepth, Menduno serves as an editor/reporter for DAN Europe’s Alert Diver magazine, a contributing editor for X-Ray mag, and writes for DeeperBlue.com. He is on the board of the Historical Diving Society (USA), and a member of the Rebreather Training Council.
DCS
Hyperbaric Chambers Are Turning Away Divers. Will There Be One Nearby When You Need It?
Unfortunately, it’s hard to make a business case for treating divers versus wound and burn care victims. As a result, many hyperbaric chambers no longer treat divers, leaving fewer facilities available for divers in need and increasing their post-dive time to treatment. InDEPTH editor Ashley Stewart reports on this growing crisis in the US and what can be done!
By Ashley Stewart

Steven Wells was diving on the scuttled wreck of the USS Oriskany off the coast of Florida in 2016 when a problem with his buoyancy compensator caused a rapid ascent to the surface.
Wells’ dive buddies followed the emergency action plan for the Oriskany listed on the Florida Fish and Wildlife Conservation Commission’s website at the time and brought Wells straight to Naval Air Station Pensacola, the nearest facility with a hyperbaric chamber. The facility turned him away because there was no one there to run it.
Wells was taken 30 minutes away to Baptist Hospital, which also has a chamber capable of treating his injuries, but the hospital had years earlier decided only to use it for wound care. Doctors there decided Wells would be taken by ambulance more than an hour away to Mobile, Alabama, the nearest facility that accepts divers.
By the time Wells arrived at the only chamber that would help him, it was too late.

“I got a call from the hospital saying, ‘Your husband is on life support. You need to get here now,’” Rachel Wells said of her late-husband of more than 23 years.
Julio Garcia — the program director of Springhill Medical Center’s wound care and hyperbaric facility where Steven Wells was to be treated — told InDEPTH that while no one can be certain how sooner treatment would have affected the outcome of Wells’ case, it would have given him the best chance for a full recovery.
Each year in the US, there are about 400 serious cases of decompression illness (DCI) — a category including both arterial gas embolism and decompression sickness — in divers, according to one 2020 paper. The Divers Alert Network (DAN) hotline dealt with 587 cases annually over the past five years.
The availability of hyperbaric chambers to treat decompression illness is something many divers take for granted. We try to avoid dive-related injuries through training, but expect treatment to be available when we need it.
The reality — as Steven and Rachel Wells tragically learned — is that only a minority of divers are close to care for diving-related injuries, according to medical professionals in the field. The estimates vary, but it’s generally believed there are about 1,500 hyperbaric medicine facilities in the US and only 67 are currently treating diving accidents, according to DAN.
The estimates vary, but it’s generally believed there are about 1,500 hyperbaric medicine facilities in the US and only 67 are currently treating diving accidents, according to DAN.
“The problem is only getting worse, not better,” Garcia, the Springhill Medical Center program director, said. Garcia has been sounding the alarm about this problem for more than a decade. His hospital takes patients from as far away as Florida cave country and treated 20 DCI cases in 2022. Those patients had an average transportation time of 11.5 hours, according to an InDEPTH analysis of Garcia’s records.
Florida stands out because it’s a popular diving destination, DAN Research Director Frauke Tillmans said, but the situation is not much better across the US. Many of the 1,500 hyperbaric medicine facilities, like Pensacola’s Baptist Hospital, have transitioned to treating wound care only for economic reasons. Emergency hyperbaric services are expensive to train and staff, and come with increased liability.

Time to treatment can be important in DCI cases
Time is of the essence when treating DCI. Divers Alert Network Director of Medical Services Camilo Saraiva told InDEPTH time to treatment is a “pivotal determinant” when it comes to outcomes for DCI patients. “Swift intervention significantly influences the effectiveness of therapeutic recompression,” Saraiva said.
Decompression sickness, for example, results from rapid changes in pressure and can form gas bubbles in body tissues. Initiating recompression therapy minimizes bubble size and number, Saraiva said, enhancing their elimination and reducing the risk of further vascular obstruction and tissue damage.
“The timely provision of hyperbaric oxygen therapy not only aids in bubble resolution but also mitigates the potential for neurological deficits and other severe complications, highlighting the critical role of early treatment in optimizing outcomes for DCI patients,” Saraiva said.
The 2018 paper “In water-recompression” stated delays to recompression in military and experimental diving are typically less than two hours and more than 90% of cases are completely resolved during the first treatment.
Frank K. Butler and Richard E. Moon, hyperbaric medicine experts, wrote in a 2020 letter to the Undersea and Hyperbaric Medicine journal editors suggesting a minority of patients who need life-saving hyperbaric oxygen treatment (HBO2) are close to a major hospital with a 24-hour emergency hyperbaric facility.

“Despite the urgent need for treatment, most hyperbaric chambers will decline to accept emergent patients at present,” Butler and Moon wrote. “Patients may eventually receive HBO2 but after a significant delay and a transfer of several hundred miles. Many never receive indicated HBO2, often resulting in poorer patient outcomes.”
Patients who are delayed treatment, they wrote, face the possibility in some cases of “death, permanent neurological damage, permanent loss of vision, or loss of an extremity, most of which would have been readily preventable had emergent HBO2 been administered.”
Why fewer chambers treat dive injuries
As recently as two decades ago, according to Butler and Moon, the majority of hyperbaric treatment facilities were available 24/7 to treat emergency patients. The percentage of those facilities now treating emergency patients is unclear, but it’s universally agreed the number has fallen significantly.
The reasons for the loss of emergency HBO2 facilities, Butler and Moon suggest, include “a better economic return when chambers focus on wound care patients as opposed to emergencies; the greater legal liability involved with treating high-acuity emergency patients; and the increased training and staffing requirements that would be required to manage critically ill patients — especially diving injuries and iatrogenic gas embolism patients.”
A letter from an administrator at Baptist Hospital — which sent Steve Wells to Springhill Medical Center — viewed by InDEPTH shows the hospital discontinued hyperbaric emergency services in December 2010, citing lack of staffing for specialty trained hyperbaric physicians who can provide 24-hour patient care. Baptist has yet to respond to InDEPTH’s request for comment.

There’s also the issue of pay. Garcia, the Springhill program director, said the current rate of pay for doctors who administer hyperbaric treatments regardless of length is around $150. A typical hyperbaric treatment for other conditions is about two hours. Diving treatments are usually six or seven, he said. “What doctor wants to get paid $150 to be up all night for seven hours, at that point making less than the technician?” Garcia said. “The fix is that healthcare payers need to pay more for the supervision of the treatment for diving injuries. Make it something that’s worth a doctor’s time besides the goodness of their hearts.”
Silence from lawmakers
Medical and diving organizations in 2020 sent a letter to the House and Senate, federal government agencies, governors of Florida and California, and the American Hospital Association expressing concerns about the lack of availability of chambers to treat diving injuries.
“There are approximately three million recreational scuba divers in the US,” the letter stated. “In the unlikely event that they suffer a diving-related injury, they trust that the US medical system will provide state-of-the-art care for their injuries, but the steadily- decreasing number of hyperbaric treatment facilities in the US willing to treat them emergently for decompression sickness or arterial gas embolism often places them at much greater risk than they realize.”
Garcia has on his own contacted lawmakers, reporters, medical systems — even private space companies like SpaceX because his facility is also the only one nearby treating altitude decompression sickness from space and air travel.
Little has changed, Garcia said.
Garcia showed InDEPTH a 2014 letter from a Defense Health Agency director who said, while there are three Undersea and Hyperbaric Medicine Society-accredited clinic hyperbaric medicine facilities and two additional facilities that can treat civilian emergencies, they are not staffed 24/7 and not designed for patients with other medical illnesses. Garcia at the time requested the creation of a federal grant to support the expansion of 24/7 hyperbaric services, but the director said that was outside of the agencies’ purview.

Two years after this exchange, Steven Wells was taken to and turned away from one of these facilities — the NAS Pensacola, listed on the Florida Fish and Wildlife Conservation Commission’s (FWC) emergency action plan at the time.
The Florida Fish and Wildlife Conservation Commission website now shows a map of the nearly 4,000 artificial reefs across Florida’s 1,350 miles of coastline. Two chambers, one in Mobile, Alabama, and one is Orlando, cover 500 of those miles densely packed with dive locations, according to Garcia.
The FWC website now shows a map of the nearly 4,000 artificial reefs across Florida’s 1,350 miles of coastline. Two chambers, one in Mobile, Alabama, and one is Orlando, cover 500 of those miles densely packed with dive locations, according to Garcia. A report from the University of West Florida estimated the sinking of the Oriskany, scuttled in 2006, generated nearly $4 million for Pensacola and Escambia County in the next year alone.

An FWC spokesperson said the agency provides diver safety reminders and recommended actions on its website “as a courtesy” and is not intended for emergency response. FWC and Visit Florida did not respond to inquiries about how much Florida’s government spends on advertising the artificial reefs and other diving activities, or whether any effort to expand the availability of hyperbaric facilities to treat the divers who show up as a result.
“My question is what is my husband’s life worth compared to your chambers,” Rachel Wells, Steven Wells’ widow said. “Why did he have to die?”
DIVE DEEPER
DIVER: A Crisis in Emergency Chamber Availability by Dan Orr (April 2022)
Divenewswire: A Crisis Lurking Below the Surface Emergency Hyperbaric Treatment Availability by Dan Orr (August 2021)
Undersea and Hyperbaric Medicine (2020): Emergency hyperbaric oxygen therapy: A service in need of resuscitation – an open letter by Frank K. Butler, MD, and Richard E. Moon, MD
White paper: Access to emergent hyperbaric oxygen (HBO2) therapy: an urgent problem in health care delivery in the United States (2020)
InDEPTH: A New Look at In-Water Recompression (IWR) (2019) by Reilly Fogarty
Diving and Hyperbaric medicine (2018): In-water Recompression, Doolette DJ and Mitchell SJ
aquaCORPS (1993): In-Water recompression As An Emergency Field Treatment for Decompression Illness by Richard L. Pyle and David A. Youngblood

InDepth Managing Editor Ashley Stewart is a Seattle-based journalist and tech diver. Ashley started diving with Global Underwater Explorers and writing for InDepth in 2021. She is a GUE Tech 2 and CCR1 diver and on her way to becoming an instructor. In her day job, Ashley is an investigative journalist reporting on technology companies. She can be reached at: ashley@gue.com.