by Reilly Fogarty
Header image courtesy of DAN
It’s no secret that hyperbaric medicine is a niche field of researchers driven by interest and passion rather than funding. Take away the wound care applications (and with it the majority of the funding) and the field grows even smaller. Today’s cutting edge data analysis tools haven’t yet been brought to bear in the search for a definitive understanding of decompression sickness (DCS), and the result is reliance on models that are fairly good but fail to account for numerous unknown factors. Our current models are inconclusive not because of any shortcomings of those in the field but due to a lack of statistically significant data.
More than one study of divers has called a group of 25 or 40 divers “large,” and many of the foundational studies for current decompression theory have been based on data taken from just a handful of participants. The results aren’t quite anecdotal but lack the impact of modern big data studies made possible by advancements in database analysis and statistical wizardry. The analysis of huge sample sets with consideration of relevance and risk factor probability and incidence reveal not only the flaws in earlier data but entirely new avenues of study that just can’t be correlated with smaller sample sizes. The issue for divers is that databases of this size are expensive and logistically challenging to manage and their analysis even more so. Neither the resources nor the data on divers has been available — until now.
Recently, researchers at DAN Europe published Dive Risk Factors, Gas Bubble Formation, and Decompression Illness in Recreational SCUBA Diving: Analysis of DAN Europe DSL Data Base. What the title lacks in punch the paper makes up for in creativity and execution. Here’s a look at what’s come out of the first big-data project on DCS.
With a project of this scale, establishing the scope and aim can be an undertaking in itself. At its core this paper is an analysis of nearly 40,000 open-circuit recreational dives collected from European divers beginning in 1994. The project aimed to understand the risk factors that contribute to DCS, reveal trends among real-world DCS cases and look at how hypothesized factors including body type, age, gender, workload and environmental conditions contribute to bubble formation and DCS evolution.
Using diver questionnaires submitted with dive profiles, researchers focused on the statistical analysis of 2,629 divers (2,189 men and 440 women). These divers were an average of 37 years old and recorded 39,099 open-circuit dives on air (37,261 dives) and nitrox (1,838 dives) to depths from 5 to 104 meters. Dives using trimix or rebreathers were excluded from the study. The body mass index (BMI) of each diver was calculated, as was the maximum gradient factor associated with each dive. Researchers calculated gradient factors for 16 theoretical tissue compartments for each dive and grouped them into three categories: fast, medium and slow. Additionally, 970 dives involved post-dive Doppler bubble counts. These scores were graded and statistically compared to known and possible risk factors. The sample set included 320 dives that resulted in DCS symptoms, and these were similarly reviewed as an additional dataset. Though daunting in scale, the data is relatively straightforward. It’s in the analysis of this data and the deluge of possible avenues for future research that complexity arises.
What We’ve Learned
The beauty of big data is its ability to resemble the reality of a messy and unpredictable world. As sample sizes grow, the results approach reality, and data sets should begin to resemble known quantities. By the numbers the bulk of our community is recreational divers who perform relatively benign dives, and this is what the DAN researchers’ analysis showed. Most of these dives involved reasonably safe exposures, with an average depth of 27.1 m, run time of 46.4 minutes and maximum gradient factor of 0.66. The average ascent rate was significantly slower than the maximum recommended 10m/min, and very few omissions of decompression obligations occurred. Bubble data confirmed prior study results, showing bubble formation peaking between 30 and 45 minutes post-dive.
What’s most interesting is not the confirmation of diver conservatism or bubble formation but the number of theorized risk factors that appear to be experimentally confirmed and the number of unknowns left to study. There’s a lot to unpack, so here’s what we know (raw data can be found in the paper for those interested in chewing the numbers themselves).
Age and BMI
Correlating risk factors and bubble counts (or bubble counts and DCS symptoms, for that matter) has been historically tricky, but BMI and increased age both appeared to contribute directly to increased bubble formation. Height and weight could not be linked individually to increased bubble formation but their combined value in BMI did correlate with higher bubble counts. Analysis of diver fat mass confirmed this connection and correlated BMI and bubble counts even more closely in the analysis of dives that resulted in DCS symptoms.
Non-profile-related risk factors such as current and effort at depth have been on the table as possible risk factors for a long time, and that’s where they’ll stay for now. Researchers could not find a statistically relevant connection between these and DCS risk, but they did theorize that these could increase stress in divers, which could increase risk. More on that below.
Hormones, Stress and Sex
While conditions couldn’t be correlated with risk factors, researchers theorized that stress and hormone release could affect bubble formation. This is the subject of a follow-up study — one that links to another interesting connection. Some data has shown that women may be at greater risk for DCS despite few physiological differences between the sexes, and some data has connected menstrual cycle peaks with higher DCS risk and the use of oral contraceptives with decreased risk. The confluence of all this is an interesting foray into the connection between hormones (naturally produced and exogenous) and DCS.
Big data shines in revealing unexpected results, and the effect of visibility on bubble formation is a great example of this. Analysis of the DAN database seems to show that DCS prevalence has an inverse relationship with visibility. This plays into the study on stress and hormone release mentioned above, but it’s interesting to see that workload and current couldn’t be correlated to DCS risk while researchers thought visibility warranted further consideration.
Putting It Together
Research has a way of pulling you in and leaving you hanging without a life-changing conclusion, and this study is no different. This work produced fascinating results, remarkable progress in understanding many of the prevalent DCS risk factors and several unexplored future possibilities. But we haven’t quite solved the mystery of DCS yet. Analysis of the 320 cases of DCS showed that the majority (73.7 percent) occurred with gradient factors (GF) between 0.7 and 0.9 (note that the M-value is 1.0 on this scale), which indicates that an acceptable amount of decompression was performed by most divers.
Only eight cases showed a gradient factor of greater than 1, meaning that a full 97.5 percent of these symptomatic DCS cases would be considered “undeserved” as understood by just our models. The takeaway? We know more — a lot more — about what factors affect DCS risk, but we don’t know everything yet. Keep an eye on the follow-up research from this study; this database is being enlarged to include technical and freedivers, and researchers hope to eventually apply artificial intelligence to search for more undiscovered insights in the data.
Reilly Fogarty is a team leader for risk mitigation initiatives at Divers Alert Network (DAN). When not working on safety programs for DAN, he can be found running technical charters and teaching rebreather diving in Gloucester, MA. Reilly is a USCG licensed captain whose professional background includes surgical and wilderness emergency medicine as well as dive shop management.
Why I Became a GUE Instructor
Jon Kieren had been an experienced tech diver and instructor for years when, curious, he took a Global Underwater Explorers’ Fundamentals class, a prerequisite to GUE’s technical and cave training. Soon, he didn’t just want to be a GUE diver. He wanted to be a GUE instructor. Kieren writes about the draw of GUE and why he started over with a new agency.
by Jon Kieren. Photos courtesy of SJ Alice Bennett.
I’ve had the pleasure of working in pretty much every aspect of the diving industry over the past 15 years or so. I’ve been an instructor and boat captain in the Caribbean, worked in the training department of a large training agency, served as a consultant for equipment manufacturers, and traveled all over the world teaching as a full-time cave and technical instructor trainer. Many would have said I’d reached the highest levels in the diving industry.
So when I decided to start all over from scratch to become a Global Underwater Explorers (GUE) instructor, many of my friends, peers, and students scratched their head a bit and wondered why I would want to invest so much time, energy, and money to teach things I had been capable of teaching for years with other agencies. The answer was I wanted to commit to excellence. “Can’t you do that by teaching for other agencies?” they would ask. Not really.
Over the years, I had become quite frustrated with almost every aspect of the dive industry. Low-quality instruction, lack of accountability from agencies in accidents and quality assurance, manufacturers releasing equipment that created more problems than it solved, and dive shops and instructors at all levels racing to the bottom in terms of quality — all of it was making my blood boil. When I “saw the light,” it was refreshing, inspirational, and a huge relief. I finally found an answer to many of the issues I had been banging my head against the wall trying to solve for years. Here’s how it went down.
In 2016, I left my job in the training department of a large agency after five years of frustration. I realized I could make a larger impact on the industry working with one or two students or instructor candidates at a time. I moved from south Florida to north Florida’s “cave country” to teach full-time as an independent instructor. It was a bit scary to not have a guaranteed paycheck, but I was determined to make it work. I was hungry to improve as an instructor and knew I could do better. The problem was, after working at the highest levels with some of the biggest names in the industry, I didn’t really know where to turn.
Enter Mark Messersmith. He’s a GUE board director, instructor evaluator, chief operating officer of dive equipment manufacturer Halcyon, and one of the nicest guys around. I had gotten to know Mark a little bit over the years, and always appreciated his laidback and super supportive demeanor. When I approached him about GUE training, he asked, “Why?” Knowing my background, of course he knew the answer, but I think he wanted to hear it from me.
Fundamentals: Where the Fog First Lifted
I first started down the technical diving path when I was working in the Caribbean as an open water instructor and boat captain, and I came across GUE in my research. I was immediately put off by the standardization and team-diving philosophy, and decided other agencies would be a better fit for me. Of course I didn’t know what I didn’t know, but my thought was, “There can’t be just one way to do EVERYTHING.” Plus, I really enjoyed solo diving at the time. After moving through the ranks over the years and working with hundreds of technical, rebreather, and cave students, I had the opportunity to work with several GUE-trained divers. Most of them had only taken Fundamentals, the prerequisite to GUE’s technical and cave training courses, but two things were consistent with all of those students: The classes were easier to teach, and they were way more fun. We would be able to start cave or tech diving straight out of the gate and not need to spend three or four days on basic skills. I wanted to know what GUE’s secret was to create such solid and consistent divers, and that’s when I approached Mark.
To answer his question, I was honest and told him I wanted to steal as much as I could from the Fundamentals course to incorporate into my classes. He just smiled through his mustache and said, “OK.” We scheduled a class, and I got to work watching all of the skills videos and practicing on my own in order to prepare. To say that I was nervous when class started was an understatement. I think I hid it pretty well, but what if I didn’t meet the highest standard for Fundamentals and get GUE’s coveted tech pass? What would that say about me as an instructor? Mark’s casual style put me at ease as we began, and I was able to focus. When Mark got to the third slide of the first lecture, it was like the fog had lifted and I could see everything clearly for the first time. I knew the trajectory of my career had just shifted and I’d be starting all over. “This is going to be expensive,” I thought.
So what’s on that slide? A simple statement that was the answer to all of my struggles: “End the disconnect between training and passion.” As Mark explained the issues in the dive industry, of which I was all too aware, he also explained how GUE addresses those issues. From the top down, GUE’s board of directors members and instructors are passionate divers and explorers, no exceptions. This changed everything for me. One of my biggest frustrations was recognizing that at the very top of the industry (senior managers of the agencies), almost nobody was an active diver. Presidents and VPs were diving once a year for social media posts to create an illusion they were still active and passionate—many of them with very limited teaching experience and making decisions on standards at the highest levels of technical, cave, and rebreather training when they had only been in a cave once or dove a semi-closed rebreather a couple of times back in the 90s.
This lack of passion filters down through the industry. It’s amazing how many instructors (technical, cave and rebreather included) refuse to get in the water if they aren’t being paid. Even with my limited experience at the time, when I went to work for the agency, I would have my head in my hands thinking, “You have no idea what you’re talking about,” when sitting in on big meetings as industry heads for all of the agencies were in my opinion focused more on how to keep standards low and profits high rather than on safety and quality.
A Commitment to Excellence
But now, staring at this slide, we discussed the ways GUE is focused on keeping quality at the highest level and inspiring divers to be passionate, competent, and capable of incredible conservation and exploration efforts. We discussed the global GUE community and all of the remarkable things they accomplish. It was so clearly the answer to everything.
I didn’t just want to be a Fundamentals diver. I wanted to be a GUE instructor. As I started on the path, I started to really realize why “Commit to Excellence” is printed on the back of our t-shirts. I was pushed harder than I had ever been in the past, with support and encouragement. The goal was always to improve, no matter what we were doing: from parking our cars at the dive sites to be courteous and leave room for others, to maintaining perfect stability in extremely task-loading situations, and developing the best instructional and evaluation techniques. There was never a time in any of my classes where I was told, “Good job.” It was always, “Good job, but here’s how we can make it better.”
My Tech 1 (and later Tech 2) instructor, Guy Shockey, made a statement that I remember every day. He explained that he chooses to be a GUE instructor because when he wakes up in the morning and gets ready to teach a class, he knows without a doubt that he has the capacity and resources to teach the best class available. So when I’m on my way to the shop or dive site to meet my students in the morning, I keep that in the back of my mind. I have the capacity and resources to teach the best class available. It not only gives me confidence, but keeps me honest. There are no excuses and no room for shortcuts. Commit to excellence.
We are held to that standard of excellence through several mechanisms. We have strict annual renewal requirements to ensure we are actively diving and exploring so that students are learning from someone still passionate about what they are teaching. These requirements go far beyond what is typical in the industry, and we are actually monitored for meeting them.
Staying Current (And Competent)
Most agencies have some form of “currency” recommendation, meaning you’re supposed to teach or assist a class every few years. However, there’s no oversight to ensure instructors are meeting this requirement. There’s loads of instructors out there (tech instructors and instructor trainers included) who haven’t taught a class in five-plus years. There’s nothing stopping these instructors from going out and teaching a class at their highest level. Sure, if something terrible happens, the agency and insurance company will likely drop the instructor, showing that they violated a standard by not remaining current. But at that point, it’s already too late. Students pay the price. Even if there isn’t an accident in training, it’s very likely that students will not have received adequate training and will be more at risk in their post-training diving activities.
GUE instructors need to show dive logs verifying we have conducted at least 25 non-training dives each year, half of which need to be at or above their highest teaching level. This ensures that when you sign up for a GUE class, you can be sure the instructor in front of you is still active, current, and passionate about what they are teaching you.
All GUE instructors, instructor trainers, and instructor examiners are required to be re-evaluated at their highest teaching level every four years. Nobody is exempt from this rule, as it means that we are consistently ensuring everyone is teaching the same things, to the same standards, without drift.
Scuba diving is a physically taxing activity, and the more aggressive the dive, the more physically fit the diver should be. Even on fairly benign dives, you never know when the current or seas might pick up, or when a failure could result in extended decompression times. We believe that having physical fitness requirements that are consistent with diving goals is extremely important. No smoking allowed for any GUE diver or instructor, and we require swim tests at every level of training.
Instructors have to meet pretty stringent fitness requirements each year. We have to be medically evaluated for fitness to dive, maintain a low Body Mass Index (BMI), conduct timed swims and diver tows, stair climbs and equipment carries over long distances, all of which verify our ability to assist our students in emergencies. This is surprisingly absent from other agency’s renewal requirements. There are lines in the renewal agreement about being fit to dive, but there’s no oversight, and they don’t even require a medical exam.
We also have a 100% quality assurance process, meaning every student completes a quality control form. This is not only so our QC director can identify any drift from the standards or issues with our conduct in class, but also to help provide feedback on how we can improve the training we offer. We encourage our students not to just tell us what we did well, but treat us how we treat them in the debriefings and include areas we can better support their growth, because there’s always some room for improvement.
I don’t mention all of the renewal requirements as a flex, but rather to show that it takes a significant investment for GUE instructors to remain in current teaching status. Someone who isn’t committed simply won’t remain current. It was a huge draw for me, as I had seen how the minimal standards typical in the dive industry contribute to the disconnect.
For me, as an instructor, the benefits of GUE go beyond the high-quality training, standardization, and community. The opportunity to work toward ending the disconnect between training and passion as well as the continuous commitment to excellence are what keep me motivated. Not a year has gone by since my Fundamentals course that I haven’t seen significant growth as an instructor, and I don’t see that changing until I hang up my fins.
InDEPTH: The Economics of Being a Tech Diving Instructor by Darcy Kieran
Other stories by Jon Kieren:
InDEPTH: I Trained “Doc Deep” by Jon Kieren
InDEPTH: SUMP POTION #9 by Jon Kieren
InDEPTH: Grokking The FATHOM CCR: My Dive into the Nuts & Bolts with the Inventor by Jon Kieren
Jon Kieren is a cave, technical, and CCR instructor/instructor trainer who has dedicated his 13-year career to improving dive training. As an active TDI, IANTD, NSS-CDS, and GUE Instructor and former training director and training advisory panel member for TDI, he has vast experience working with divers and instructors at all levels, but his main professional focus resides in the caves. In his own personal diving, Jon’s true passions are deep, extended range cave dives, as well as working with photographers to bring back images of his favorite places to share with the world.