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Old 26 February 2019, 16:11
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Zeljko Dujic: Finding his niche in breath-hold research

Fascinating interview with an authority in breath-hold research. The dive medicine guys can address the physiology.

Link here.

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Quote:
Zeljko Dujic
By Frauke Tillmans, Ph.D.
Finding his niche in breath-hold research

At the forefront of the field, Dujic continues to study the body’s physiological responses to breath-hold diving. Both divers and patients with conditions such as sleep apnea and diabetes benefit from his research.

A leading expert in breath-hold diving physiology, Professor Zeljko Dujic, M.D., Ph.D., is head of the department of integrative physiology at the University of Split in Croatia. He graduated from the University of Zagreb School of Medicine in 1983 and received his doctorate from the Medical College of Wisconsin. Over the past few decades Dujic has been a member of several scientific committees in Croatia and has taught physiology at the University of Split School of Medicine full time since 1988. He is also in charge of the university's evidence-based-medicine doctoral study program and coordinates the international doctoral program. He and researchers at his laboratory have published numerous highly esteemed scientific papers on breath-hold diving and scuba diving. To help commemorate Dujic's 30th year at the University of Split, we met with him to discuss his research.

What sparked your interest in dive research?

Split University Hospital used to be a military hospital, and then the main focus was on navy divers and saturation diving in the commercial diving industry, so my research began in those areas. In 1992 the hospital became civilian and was integrated into the University of Split. When the source of funding and the availability of the hyperbaric chamber changed, so did our research questions. At that time, dive research in Europe appeared to be fading: Commercial diving had previously sponsored dive research for many years, but research funding declined along with the industry. To expand our efforts despite these trends, we reached out to some excellent people in the field and started working with a group under Professor Alf Brubakk from Trondheim, Norway. A few doctoral students from Norway worked with us on bubble measurements, taking echocardiographs of scuba divers before and after dives, with and without exercise.

Some of your most cited dive research focuses on exercise physiology, and your team has examined the effects of physical exercise before and after diving. What advancements do you hope to achieve with your findings?

It is still difficult to assess the personal risk of someone developing decompression sickness (DCS) after a dive. We have focused on bubble grades, and it is still commonly accepted that high bubble grades after diving correlate with a higher risk for DCS. We found that high-intensity interval training up to two hours before the dive seems to reduce bubbles after the dive, while exercise after a dive increases bubble grades.

It is important to understand that being a "high bubbler" is one risk, but the personal risk increases if the diver has right-to-left-shunting pathways. The best known of these shunts is a patent foramen ovale (PFO), but we have also shown that people can have lung shunts, also called intrapulmonary arteriovenous anastomoses (IPAVAs). In some divers these IPAVAs open more easily than in others — in some cases with little workload or even while resting. We assume that not only the heart and the lungs have these shunts but also that every organ in the body has a kind of shunting mechanism that allows blood, and therefore bubbles, to pass from the venous to the arterial side. A standard test battery to determine if a diver has a higher risk for postdive bubbles doesn't yet exist, but this might be one step on the way to personalized decompression.

You speak about high and low bubble grades, but in your experiments you found that some divers never bubble and some always do. Can these two cohorts of bubblers and nonbubblers be used as a model to study?

Those two groups are indeed interesting. In our experiments most divers were inconsistent, but 15 percent of the divers never bubbled, and another 10 percent always bubbled. Of the volunteers who dive for us, we can easily isolate a group of all bubblers if we want to test a mechanism, such as exercise, that may reduce bubbles. We cannot currently explain the difference between bubblers and nonbubblers, and this remains a question of great interest in the dive community, as it seems to be multifactorial. It is likely influenced by the condition of the endothelium (which lines the inner walls of the blood vessels), the immune system and genetic predisposition, among other things. Different groups are investigating these factors, and so far the results have been inconclusive.
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