Scuba Conversational - Issue #62: Scuba Science
Science and Scuba Diving 1
(A note before I begin: there’s a lot of material here - perhaps too much to digest in one go. If so, you can always bookmark the Substack posts page and go back to it again from time to time.)
The theme of this issue has been in my mind for a while and two things reminded me recently that I really should get around to it.
The first was a conversation concerning scuba diving and narcosis that I had on the dive boat heading out to the outer rim of the enormous lagoon surrounding the islands of Chuuk (Truk) - where the beautiful image at the head of this newsletter was taken.
The second was the arrival of a new book that has just been published which shed light on an important aspect of diving history.
The theme is the serious application of science to what we do.
The importance and rarity of this is what drew me to The Science of Diving, the book that summarised the results of a project seeking to answer some of the unanswered questions about what happens to our bodies when we dive. I found it excellent but hard to follow in places as it was designed and written by scientists for scientists. So I contacted the editors and asked for permission to reformat and re-edit the book to make it more accessible for divers who didn’t have PhDs.
Fortunately, they agreed. And that’s how The Science of Diving became Scuba Physiological.
Here is a short excerpt from an article I wrote for DiveLog Australasia based on the chapter on narcosis in Scuba Physiological. This was what we were talking about on the boat in Truk Lagoon in the conversation that prompted the topic for this newsletter.
Remember, these opinions are not mine. I am just a layperson. These are the conclusions drawn by the scientists who conducted the experiments. I just turned what they wrote into text that was easier to understand.
For years, divers have been taught that higher levels of carbon dioxide (CO2) in the bloodstream, generated by working hard or swimming fast underwater, contribute to nitrogen narcosis. Other factors that are supposed to increase nitrogen narcosis include alcohol use, being hungover, fatigue, anxiety, the effects of motion sickness medication, rate of descent, task loading and time pressure stress.
From a scientific point of view, there is little evidence for most of this. Claims that something makes narcosis worse have often been based on guesswork at best.
Historically, the effects of nitrogen narcosis have been measured by assessing the performance of tasks such as mental arithmetic, memory, reaction time and manual dexterity, while a diver is “at depth” in a hyperbaric chamber. Unfortunately, this method is unreliable, as it has been shown that a diver’s motivation and experience can influence the results.
A more reliable method is to monitor changes in the brain using electroencephalography (EEG), which involves placing electrodes on the scalp. Recently this was used for the first time to measure the effects of nitrogen narcosis during an entire dive AND for a period of time after the diver surfaced.
Diver training manuals have always advised divers that, in order to make the effects of nitrogen narcosis disappear, all they have to do is ascend to a shallower depth. One of the most remarkable findings of these recent EEG studies was that, in fact, not only does nitrogen narcosis not go away when you ascend, but it actually persists for at least 30 minutes after you surface.
The EEG studies also showed clearly that the only factors that affect nitrogen narcosis are the surrounding pressure and the gas being breathed. The other factors mentioned earlier seem to have little or no impact.
Can divers adapt?
The diving community generally believes that divers can adapt to nitrogen narcosis. However, scientific tests have generally been unable to confirm any habituation and researchers have concluded that sport divers do not actually develop tolerance to nitrogen narcosis.
It is more likely the case that divers who perform the same tasks over and over again will gradually find them easier to do. This may make them think that they are adapting to narcosis but, in fact, they are just learning to cope with it. It is like habitual drunks, who learn to cope with the effects of alcohol by, for instance, talking slowly or moving carefully. Of course, this may help them deal with things better, but they are still just as drunk.
The key messages from the work that ended up in Scuba Physiological have been finding their way into magazine articles over the years. Here is another that appeared in DiveLog. Click on the image for the link.
Science and Scuba Diving 2
Our sport is a niche activity and there are many more important matters that occupy the world’s best minds, but, fortunately, some highly capable people think that diving is worthy of serious scientific study, they are the ones that drive our knowledge of scuba diving forward and it is to them that this issue of Scuba Conversational is dedicated.
The other thing that persuaded me that now was the time to focus on diving science was the publication of Chamber Divers, an excellent new book by Rachel Lance, which tells the story of a time when understanding matters such as decompression, narcosis, and the effect of oxygen and carbon dioxide on divers was so crucial that it led to outstanding scientists and other people risking and even losing their lives.
We still follow many of the techniques and procedures that these scientists developed during the 1940s when the world was at war.
Here’s the Amazon description.
The previously classified story of the eccentric researchers who invented cutting-edge underwater science to lead the Allies to D-Day victory
In August 1942, more than 7,000 Allied troops rushed the beaches of Normandy, France, in an all but-forgotten landing. Only a small fraction survived unscathed. It was two summers before D-Day, and the Allies realized that they were in dire need of underwater intelligence if they wanted to stand a chance of launching another beach invasion and of winning the war.
Led by the controversial biologists J. B. S. Haldane and Dr Helen Spurway, an ingenious team of ragtag scientists worked out of homemade labs during the London Blitz. Beneath a rain of bombs, they pioneered thrilling advances in underwater reconnaissance through tests done on themselves in painful and potentially fatal experiments. Their discoveries led to the safe use of miniature submarines and breathing apparatuses, which ultimately let the Allies take the beaches of Normandy.
The book is very well written and a terrific read. But, beyond that, for those of us who were among the first sport divers to play with mixed gas and oxygen, it offers a fascinating glimpse of the trials that the researchers had to go through to come up with the exposure limits and systems that saved our lives. At the time, all we knew was - this is what you do and how you do it - we didn’t know where the knowledge came from and who the people were who found the right way by doing it all the wrong way first.
Chamber Divers tells the whole story in detail and gives us a vivid picture of the unusual and talented individuals involved and the almost impossible conditions in which they operated.
Paul Haynes gave a presentation about these experiments at Oztek some years ago (thanks Strikey) and a version of that talk is available on YouTube, see below. This is well worth a listen too.
Driving diving forward
New findings appear all the time and it is hard to stay up to date. InDepth magazine, Divernet and Alert Diver are all excellent sources - and you may have noticed that I frequently quote and link to all of these - but sometimes you need to go deeper. Here is a paper on the Frontiers website by a team including Science of Diving editors Costantino Balestra and Peter Germonpré, following up on the PFO research I mentioned earlier.
Frontiers is a terrific resource. There are currently over 300 cutting-edge papers on scientific findings relating to scuba diving, from manta ray behaviour to the effect of cold water immersion on heart rate.
A good way of keeping up with developments in medical research on scuba diving issues in previous years has been technical diving conferences. Unlike standard scuba diving trade shows, the tech conferences focussed on lectures rather than sales. Here is how I describe the birth of these events in Technically Speaking.
Essential forums for information exchange in the early days of technical diving were the conferences. The practice of holding events dedicated only to technical diving, rather than incorporating them into mainstream sport diving expos, was born of necessity
The first conference was the nitrox workshop organised by Menduno around the time of the 1992 DEMA Show, and it only took place because DEMA had banned nitrox purveyors and promoters from the show and the workshop was part of the last-minute deal worked out to persuade DEMA to rescind the ban.
The conference format, with presentations by expert speakers as the primary focus rather than manufacturers selling gear and resorts plugging vacations, bore a strong resemblance not only to the annual conferences held by cave diving associations in the USA and UK but also the NAUI International Conference on Underwater Education (IQ) events, which began in 1969.
The 1992 nitrox workshop was the precursor to tek. conferences which were held side by side with DEMA Shows between 1993 and 1996, although they were never officially a part of them. Whereas the 1992 workshop had fewer than 100 attendees —mostly dive professionals—tek. 95 attracted more than 2,000 visitors, a mix of the committed and the curious. Technical diving remained a niche, but the niche got bigger every year.
The tek. conference’s demise after its final iteration in 1996 coincided with the closure of aquaCORPS, but like the magazine, by then the primary goal had been achieved: technical diving had achieved critical velocity.
The concept lived on, though. The tek. conferences were the template for the rebreather forums, also a Menduno initiative, the IANTD UK conferences run by Kevin and Mandy Gurr in the 1990s, the 1996 Asia.tek spinoff in Singapore organised by Menduno with Rainer Siegel and Barry Lee Brisco of Asian Diver Magazine, and subsequently the Oztek (from 1999), Eurotek (from 2008), Tekdive Asia (from 2012) and Tekdive USA (from 2014) conferences.
All of these events treated technical diving as if, like cave diving, it was a separate sport outside the mainstream, which in the early days is exactly what the traditional scuba hierarchy had wanted it to be. Yet at the same time, over the years, mainstream diving watched the growing popularity of these more extreme and exotic forms of diving, realised that there was revenue to be earned and began making plans for assimilation. Magazines devoted only to technical diving may not have survived the assimilation process, but the tek.conference idea has survived. In fact, there are more such events now than there were then. My shortlist of spinoffs above omits a whole host of smaller or less well-established technical diving conferences in Europe and elsewhere.
The format lives on also in the Rebreather Forum series, the fourth of which was convened in Malta in 2023, although it has its roots in the 1990s - (there was a BIG gap!) I don’t know how long this will continue to be the case but all the presentations from the latest forum are available online here. This is an extremely generous gesture on behalf of the organisers as it offers divers - not just technical and rebreather divers - a whole host of valuable input from a group of expert speakers - free of charge and you don’t have to fly to Malta. “Take advantage” is my recommendation. There is some absolute Gold here - Dr Frauke Tillman’s accident review is unmissable!
As you can see, not all the talks are for technical divers, David Doolette’s being a good example.
Emerging Issues
A frequent speaker -he was at Rebreather Forum 4 too - and someone who has a gift for presenting complex aspects of diving medicine in straightforward, comprehensible terms is Professor Simon Mitchell. Here he is speaking about decompression theory in South Africa a few years ago.
Clicking on the image will take you to the video.
And here is Mitchell again, speaking about gas density, carbon dioxide and work of breathing.
This is essential stuff for all divers.
Unsurprisingly, Mitchell has had plenty to say recently about the issue of Immersive Pulmonary (O)Edema or IPO/IPE, a phenomenon thought to be behind many unexplained diving and snorkelling accidents.
Here is what he wrote in a recent issue of DiveLog
One can also see why the risk of this occurring might be quite variable because it can be affected by position in the water, water temperature, the health of the heart, the breathing resistance of the regulator or rebreather, the level of exercise, overhydration, possibly some types of drugs, various medical conditions and other things. This helps explain why a diver with many event-free dives may suddenly experience an IPE event out of the blue. Most of the key factors which contribute to the problem are directly related to the effects of immersion, and this helps explain why many cases improve spontaneously once they leave the water.
.One of the fascinating things about IPE is that there seems to be an increasing number of cases. Part of the reason for this may simply be that we are recognising them more…It might also have something to do with the fact that the diving population is ageing, and there may be an associated increase in the prevalence of heart issues. The sorts of issues I refer to can be quite subtle and not noticed by the diver, like an increase in the stiffness of the heart (quite common in people with high blood pressure) or an increase in the pressure in the lung arteries (possible in obese people).
The full article is here.
As Mitchell says, IPO/IPE is not a new phenomenon by any means. It is just that it is being identified and written about more these days. Someone who has been highlighting the issue for a while is Steve Weinman of Divernet, who unearthed a story from 1990 of a diver in the UK who was a victim and lived to tell the tale. This is her story. It’s called “The dive that turned into my fight for life”.
Steve has done a great deal to raise awareness of IPO/IPE through stories in Divernet, flagging up a Snorkel Safety Study carried out in Hawaii. For decades Hawaii’s Department of Health had collected data on drownings and had grown increasingly concerned about the high incidence of snorkel-related incidents occurring among tourists in apparently unchallenging conditions. So they set up an expert committee to produce a report and its findings.
John Lippmann, chairman and CEO of the Australasian Diving Safety Foundation, has produced a report too. They both make sobering reading. Here are a few clips from the Divernet article.
Snorkelling fatalities are most likely to result from pre-existing health conditions, inexperience, ignoring adverse conditions and “going solo”, according to a new Australian report that is cautious about pinning deaths on Immersive Pulmonary Oedema (IPO) – the “drowning from inside” condition blamed for the majority of such fatalities in a 2021 Hawaiian study.
The new statistics-based report, published in the journal Diving & Hyperbaric Medicine, is written by an expert in the field, Dr John Lippmann.
“Increasing age, obesity and associated cardiac disease have become increasingly prevalent in snorkelling deaths,” says Dr Lippmann, calling for better health surveillance and risk-management as well as closer supervision of inexperienced snorkellers.
Snorkelling can increase heart workload and anxiety levels, points out the report, which describes the 91 victims as “predominantly middle-aged males, many of whom had pre-existing medical conditions, which predispose them to an incident while snorkelling.”
“Most of the victims were alone at the time of their incident, whether they had set off solo or become separated from their buddy or group,” says the report.
“Despite repeated advice about the benefits of an effective buddy system, which may enable more rapid recognition of a problem and subsequent assistance, sadly this is often ignored.”
“It’s important to educate folks about the potential pitfalls of snorkelling so they better understand the risks, of which IPO is certainly one. Cardiac issues in the ageing person is a big one, as it is with scuba.”
The full article and associated links can be found here.
Finally, for the diving science topic in this issue of Scuba Conversational anyway, via Divernet, John Lippman and the Australian Diving Safety Foundation - here’s a gift.
Click on this link or the image below to download a copy of the updated ADSF Diving Medicine for Scuba Divers book.
You never know when having this on your phone or laptop may come in very handy!
Last but not least (and on a much lighter note)…
I thought you might like to see a selection of pictures from our visit to Chuuk / Truk Lagoon last month.
We had a ball.
And finally, a picture from a long time ago of Kimiou Aisek - finder of wrecks and founder of Truk diving - and his son Gradvin as they were when I first met them. It was a huge pleasure to meet Gradvin again on this trip after so many years. Neither of us has changed a bit!
Right, that’s it from me for this issue. Chat with you again next month, in Scuba Conversational #63.
Great newsletter this month!! exciting times!
Thanks again Simon! Very much appreciate your efforts-extremely valuable approach that I and my colleagues appreciate. Great to see you at the Blue Lagoon!