Decompression & Dive Safety

Text by Frauke Tillmans, PHD

DECOMPRESSION BUBBLES, CARDIAC HEALTH, AND DIVE SAFETY

In 2021, Peter Buzzacott, PhD, of Curtin University in Perth, Australia, received DAN’s Alfred Bove Research Grant for Cardiac Health in SCUBA Diving. What began with a simple proposal has since evolved into a training network for the next generation of scientists, ultimately leading to a research collaboration between Curtin University and Fiona Stanley Hospital in Western Australia.

Beth Jones and Aren Leishman are PhD candidates working on the project.

BETH JONES

Jones began diving during a family holiday to Egypt and has continued diving recreationally worldwide. She received a Bachelor of Science degree in Sport and Physiological Science from the University of Leeds in England, which developed her interest in extreme environmental physiology and sports biomechanics. She pursued a master’s degree in nutrition at the University of Leeds, with her research project focusing on the interaction between nutrition and exercise.

Her interest in the effects of extreme environments on the human body, combined with a love for diving, led her to move to Perth to pursue a PhD in health science, focusing on decompression bubbles in recreational SCUBA divers.

Beth, what is your PhD about?

My PhD focuses on venous gas emboli (VGE), which are bubbles that can form in the blood after diving. These bubbles often go unnoticed and are considered an indicator of decompression stress.

While not directly related, higher bubble loads have been linked to an increased risk of decompression sickness (DCS). In certain individuals, such as those with a patent foramen ovale (PFO), these formed bubbles can move from the venous circulatory system, where the lungs normally filter them out, to the arterial bloodstream, resulting in bubbles heading to the peripheral tissues.

My research aims to develop a predictive model using real-world recreational dives to estimate bubble load based on nitrogen tissue uptake. My goal is to improve recreational dive safety by informing divers of their potential risk of high bubble loads after a dive.

I’m currently collecting dive profile data and monitoring for VGE using ultrasound to image the heart after recreational dives. Perth has an incredible dive community, which has made recruiting participants one of the easiest parts of my PhD. It has been great to interact with local dive groups and see how my research can help the dive community.

AREN LEISHMAN

Leishman has been a passionate SCUBA diver since he was 16. He became a technical diver while completing his Bachelor of Advanced Science degree in physics at Curtin University. His professional background in software development and embedded electronics, along with his passion for developing electronics for diving, caught Buzzacott’s attention.

Leishman completed an honours project using the modelling and mathematical background from his physics degree to analyze the impacts of high altitude on existing decompression models. He updated the R SCUBA package — a tool for performing theoretical calculations related to SCUBA diving — with the capabilities to model rebreather diving and altitude diving. He is currently pursuing a PhD in health science, with a focus on the cardiac effects of diving.

Aren, what is your PhD about?

My PhD is focused on answering the questions that statistics in several DAN annual dive reports have raised, such as why so many divers die due to cardiac events. Cardiac events are a major contributor to fatalities, and fundamental research on exactly how the strains of diving affect the heart is rare.

I plan to answer this question by exercising recreational divers at a controlled rate in a pool and in a hyperbaric chamber. Placing divers in an environment that closely represents real diving — including immersion, pressure, breathing mix, and workload — we have a unique opportunity to investigate physiological changes as they happen.

Both of you are working with an interdisciplinary network in Perth. Who else is involved in this work, and how does it impact your projects?

Buzzacott, who originally applied for the grant, is a well-regarded dive physiology researcher. His background in the field enabled him to identify the skills required when assembling this highly diverse and interdisciplinary team.

Luke Haseler, PhD, is a professor at Curtin University who focuses on cardiac and muscle imaging and how exercise impacts the heart’s ability to function. His expertise enables us to utilise the cutting-edge technology of cardiac measurement to extract the most data from every session in the hyperbaric chamber.

Kagan Ducker, PhD, an associate professor at Curtin, is a sport, exercise, and health physiologist with a focus on enhancing athletic performance and studying exercise and physical activity in extreme environments. His knowledge of the physiological changes that can occur during extreme environmental exposures, combined with his expertise in collecting data in these types of environments, makes him a valuable asset to this research group.

Anna Scheer, PhD, is a physiotherapist and researcher who has collaborated with Luke on the effects of immersion on cardiac function, specifically exploring its potential as a treatment for cardiovascular disease.

Her experience in cardiac health has helped with the challenges associated with working with study participants while immersed in water.

The work would not be possible without the generous support from Dr. Neil Banham, Dr. Ian Gawthrope, and the incredible team at the Fiona Stanley Hyperbaric Medicine Unit. They have always been willing to do whatever they can to support our research, enable opportunities for data collection, and address any questions.

What do you hope to get from the experiments, and how could they benefit the dive community?

Through cardiac research, we aim to gain a deeper understanding of how diving affects the heart and identify potential risk factors that may contribute to the high number of cardiac fatalities in diving. The goal is to develop more specific pre-dive screening recommendations and determine who may be at a higher risk, enabling them to take appropriate precautions.

Beth, you were an intern at DAN in 2022. How has the DAN internship helped you?

Being a DAN intern was an integral and invaluable experience for my PhD. After moving to Perth in March 2022, I had the opportunity to join the DAN Internship Program that summer. I was one of five interns that year and worked as part of the research team at DAN headquarters in Durham, North Carolina.

I gained hands-on experience collecting data on dive boats and at quarry dive sites, which has proven extremely valuable for my current data collection efforts. The workshops on dive safety, data collection methods, ultrasound techniques, ongoing dive research, and dive equipment maintenance deepened my understanding of the field. The opportunity to visit other research institutes, hyperbaric chambers, and dive companies was also a fantastic experience.

What is your favourite dive or site?

Leishman: My favourite dive is Busselton Jetty, south of Perth. It’s a fantastic dive filled with marine life and underwater sculptures. It’s in a wonderful spot for weather and visibility. You can see everything from stingrays to wobbegong sharks, nudibranchs, cuttlefish, and octopuses. I love going there and just floating, watching the world go by.

Jones: My favorite dives are often the ones with my family or when something unexpected happens (in a good way). One dive that stands out was off the eastern coast of Bali during the offseason. With no crowds around, it was just me and a local divemaster heading out on a small boat to a reef about 3.1 miles (5 kilometers) offshore. I had no expectations other than a relaxing dive filled with marine life.

We descended into crystal-clear waters, where a long, sloping reef appeared, full of beautiful corals and an incredible diversity of fish. We saw bamboo sharks, sea snakes, octopuses, and a lot more.

About 30 minutes into the dive, I heard my divemaster laughing and shouting through his regulator and pointing at something. I turned and saw one of the ugliest and most graceful creatures I have ever seen. It was a Mola mola (ocean sunfish), and my very happy divemaster said they are a rare sight, especially at that time of year.

That’s what I love about diving: always seeing something new and never knowing what the ocean will show you.