DISCUSSIONS & RESEARCH
Introduction
Set your computer, roughly plan the dive, and just descend—great. But there’s a lot of science behind all of this: The models we dive by were developed decades ago, but they’ve been continuously modified since then. New insights or further questions about decompression keep emerging. And sometimes a new hype appears, penetrates the tech community and occasionally reaches recreational divers—and then takes a long time to fade away.
Where can you find currently relevant information, how do you evaluate it, and what consequences do you want to draw for your own dives? In this section, we can’t address every discussion, but we’ll show you how to inform yourself further.
Overview: How to Read Research Effectively
Despite all the research, knowledge about decompression is limited. Why? This is partly because DCS is very rare with today’s models. The models themselves have been empirically validated; people suffered symptoms to provide this knowledge about acceptable limits—and the insights gained from this make our dives as safe as they are today. A few more recent studies have also provided some insights into riskier or less risky dive profiles. However, the limits of research are reached when people are intentionally exposed to unacceptable risks.
Today, researchers look for many other factors that can be detected after a dive, rather than focusing solely on the endpoint “DCS.” And in research on such a niche topic, you often only have very few subjects, so you never know whether the results might just be coincidence.
Knowing this makes it clear that strong statements like “Anyone who gets DCS was definitely dehydrated / has a PFO / made the second dive deeper than the first…” simply cannot be substantiated.
How do you recognize whether something is true or not? There’s a warning signal: Loud, simple truths are almost always wrong. There are good reasons why the results of scientific studies are often formulated very cautiously: researchers have found another clue, another piece of the puzzle, not a major breakthrough.
Tips & Reading Recommendations
If you want to know more about a topic, you should rely on sources that are factual and cautiously worded and that support their claims. There are some blogs that meet these criteria. You can look at studies yourself—we explain how to read them in a blog post. And AI has now become a powerful research tool—if you use it correctly.
Blog post: Reading Studies
How can you read scientific texts even without a degree?
Using AI Correctly
Asking ChatGPT is now part of everyday life for many people. Since AI gained access to the current internet, it has made rapid progress and can now offer very good internet research. Nevertheless: Everything an AI outputs must be verified yourself! It happens that sources are simply invented—and when they’re then cited, the forgery is no longer obvious at first glance.
- Use a reasoning model
- Formulate the prompt as specifically as possible
- Set a relevant goal: for a technical article, a presentation…
- Explicitly ask for sources—and check them yourself!
DAN
DAN offers more than just dive insurance; it is primarily an institution that conducts a great deal of relevant research. This research is also accessible to non-members.
The Theoretical Diver
Robert Helling’s blog on decompression models and many truly nerdy questions
Individual Decompression
What if you knew how susceptible you are to DCS and could simply adjust your dive profile accordingly?
A wonderful idea, and this concept is precisely the goal of a whole series of studies dealing with very different factors. What can you measure during and after the dive, and can you learn something about the individually best decompression from it?
What could “individual decompression” mean?
Alessandro Marroni from DAN Europe and several others have a big dream: to receive data about the diver’s physical reactions during the dive and be able to react immediately if decompression threatens to become critical.
What would have sounded completely utopian a few decades ago might become reality in the coming years. But what would be necessary for that?
You would need to find a way to monitor the body underwater. Extremely rapid progress is being made in this area: smartwatches that also work underwater already exist, and bubbles can already be measured in the water.
But you would also need to know what to do with the measurements. Which values are actually an indication that DCS is developing or the risk is extremely increasing? And which are just normal physical reactions to the dive that aren’t particularly dangerous?
While there are well-founded assumptions about these questions, they are currently not sufficient to derive clear, concrete recommendations for individual specific measurements. What’s mainly lacking is this: a sufficient amount of data demonstrating the connection between individual factors and DCS.
We’ll take a brief look here at individual measurements that might possibly be incorporated into such concepts of “individual decompression” in the future. We’ll discuss more general risk factors in the next section.
Bubbles
Bubbles in the venous bloodstream can be measured after diving with relatively little effort using Doppler ultrasound. O’Dive has developed a simple, reliable system for this. But: what exactly bubbles mean for DCS risk is unclear.
Immune Markers
After the dive, it’s detectable in the blood that immune reactions are occurring in the body. Detection is not regularly possible on an individual basis after diving, and the significance of individual markers for DCS risk is unclear.
HRV, FMD...
Heart Rate Variability (HRV) and Flow Mediated Dilation (FMD) can provide clues. Medical data can be collected after diving using non-invasive methods. Some of this could be monitored during the dive in the future; pulse can already be monitored by some computers today. However, the relevance for DCS risk is not clearly established.
Risk Factors
As soon as individual decompression is discussed, the question of personal risk factors almost inevitably arises. Age, gender, body composition, fitness, sleep, hydration, alcohol consumption—the list is long, familiar, and intuitively plausible. The assumption is that decompression could be significantly improved if only these factors were consistently taken into account.
Looking more closely, however, the picture becomes much less clear. For many of these factors, there are indications, but rarely robust quantitative relationships. BMI is frequently mentioned but says little about body fat percentage or physiologically relevant characteristics. Fitness is considered protective, without it being clear what type of fitness is actually meant or how it specifically affects things.
The data situation remains similarly vague for factors like smoking, alcohol, or sleep deprivation. The physiological mechanisms are plausible, but the empirical evidence is limited and often context-dependent. Even with the use of nitrox, which is often perceived as safer, the effect is trivially explainable: less absorbed inert gas. That doesn’t replace a differentiated consideration of decompression stress.
Organizations like DAN have been pointing out for years that individual risk factors are real but can only be insufficiently quantified. This is precisely where tension arises between the desire for personalized decompression and the actual state of knowledge. The question is therefore less whether individual factors play a role, but how sensibly they can currently be translated into concrete decisions—and where this translation inevitably remains speculative.
Ultimately, there are only a few factors that increase the risk of getting DCS: age and cold during the decompression phase, and exertion during and after the dive can be considered genuine risk factors. A PFO also increases the risk for certain forms of DCS. But since DCS is very rare overall, it’s difficult to say whether it’s “twice as likely” or “three times as likely”—the risk is still very low.
Risk Factors
Blog article – TO BE ADDED!
Practical tip: Trust your gut feeling!
Listening to your body is always good. If you’re cold, don’t feel well, don’t feel like it—you don’t have to do a dive.
Even if “individual factors” can’t be precisely defined—only you know your body and your mind.
The Perfect Gradients
The scientific discussion about Gradient Factors shows an asymmetric picture. For the upper Gradient Factor, there is now relative consensus: lower GF-High values limit maximum supersaturation at shallow depths and thus increase the safety margin at the end of the ascent, albeit at the cost of longer decompression. The question of a “better” or “worse” GF-High is therefore less theoretical—lower is safer for decompression. The decision ultimately depends on how much time you’re willing to invest and what you consider an acceptable residual risk.
The discussion about the lower Gradient Factor is much more open. GF-Low primarily influences the depth of the first stop and the distribution of decompression time. Very low values, which involve early deep stops, are viewed much more critically today than a few years ago. A stable scientific consensus doesn’t exist here; rather, the assessment depends heavily on profile type, gas, exposure duration, and the underlying physiological assumptions. Today there’s a tendency to set GF-Low only slightly below GF-High—but we’re far from a scientific consensus.
Additionally, much research comes from the military—and they rarely dive according to Bühlmann and Gradient Factors. Therefore, there are very few studies with very few participants and no provoked DCS cases that actually examine profiles with Gradient Factors. Accordingly, reliable findings are also thin on the ground.
Which gradient factors are the best?
Blog article about gradient factors and what influences their selection
Supporting Research: Data Collections
We’ve seen how difficult it is to obtain data. Indications of deco stress are collected in small studies, DCS cases are evaluated but are rare. The US Navy occasionally conducts relevant studies, but these are oriented toward their interests and can only be transferred to recreational diving to a very limited extent.
That’s why data collections and reports of incidents that don’t appear in insurance statistics play such an important role. If you can evaluate many dive profiles that are actually dived this way; if you can also capture the mild symptoms that disappear again—then insights could emerge that are truly statistically relevant.
Anyone who would like to contribute to having data from real dives evaluated can upload them to a DAN platform: the Diver Safety Guardian. In addition to the dive profile, some additional data is requested here, and you receive an evaluation of your own dive.
Participating in something like this means supporting relevant research without having to do too much work.
Why is it good to have more data? So that you get the best possible information in the second part of this quiz. Test here again how successfully you can research.
DAN Diver Safety Guardian
A logbook and dive analysis tool from DAN
