Professor Peter Catcheside (L) and PhD student Laura Gell (R)

Research that puts you to sleep
(in a good way)

The building blocks of sleep

If you live to be 90, you’ll spend about 32 years of your life asleep—yet there’s so much we don’t know about sleep. We don’t understand exactly why we sleep. We haven’t worked out the nitty-gritty of how we dream. We also don’t understand all the causes and consequences of sleep disorders like sleep apnoea, which leads people to stop breathing repeatedly throughout the night. Physiologist Professor Peter Catcheside and signals processing engineer and PhD student Laura Gell are working on that exact issue.

It used to be thought that sleep apnoea is simply an airway anatomical problem: a narrow and floppy or collapsible upper airway. Researchers like Professor Peter Catcheside and Laura Gell are moving on from this overly simplistic idea. As Peter explains, ‘In a sleep apnoea patient, the muscles sometimes aren’t engaged enough to stop airway collapse—but, in theory, the muscles are all there and are perfectly capable of keeping the airway open when the patient is still awake.’ Sleep apnoea is typically worst in REM sleep, which makes sense because our muscles are most relaxed in REM sleep. However, there are baffling questions around why and how sleep apnoea gets much less severe in deep sleep, when the person is least likely to wake compared to other stages of sleep.

Peter and Laura, along with others in the team, are investigating the physiological mechanisms in sleep apnoea which, at its extreme, can cause profound disturbances to breathing and sleep—often translating into severe daytime sleepiness and fall-asleep accident risks. Conventional sleep measurements are labour intensive and expensive; they also can’t properly identify underlying physiological problems causing sleep apnoea. So, Peter and Laura are using a brand new technique for very detailed breathing measurements during sleep. They ask patients to swallow an oesophageal catheter with a balloon that sits in the oesophagus inside the chest. It measures how hard the person is trying to suck when they’re breathing in. This involves a small amount of anaesthetic up the nostril, followed by a catheter through the nose and swallowing it down into the oesophagus with sips of water. Once it’s in, they also hook up a few additional pieces of equipment (a mask and airflow sensor and various electrodes for measuring brain, eye movement, heart and muscle activity, including wires under the tongue—since the tongue is one of the main muscles involved in helping to keep the airway open). Then participants are asked to go to sleep; although Peter and Laura are quick to admit it’s not so easy to sleep with all the recording equipment. Once they do, Laura is able to obtain very detailed information around how much airflow each attempt at breathing in actually achieved, versus what it should have achieved. They can then identify when the airway obstruction is occurring, how much breathing is impaired, and how the person’s breathing efforts are changing.

I really want to see our ideas mature into useful outcomes. It’s exciting the work that we’re doing, trying to unravel complex mechanisms in sleep apnoea. We hope it will ultimately translate into useful real world applications.

Professor Peter Catcheside

Every person is different. Sometimes you can look at two different people and their signals are so different, you wouldn’t believe we’re measuring the same thing. Coming from a background in physics, Laura is used to everything being neat and ordered, with a clear solution. She says, ‘The fact that we all can be so different still surprises me, and it creates unique challenges in our research. We need to work out how to take account of all of that information and develop tools that can be used across the board.’ The differences from person-to-person isn’t Laura’s only challenge; because it sits so close to the heart, the new oesophageal balloon device also catches heart rhythms. To separate the two processes, she’s had to record heart activity overnight with an ECG and use signal filtering methods to help distinguish between heart and breathing in her analysis.

Peter and Laura are hoping this research will have a big impact. About 20% of adult males have moderate to severe sleep apnoea—some studies say more. It is as common as diabetes or asthma. For some, they wouldn’t know they have it because the symptoms vary so much between people; they may not notice symptoms and may or may not need treatment depending on severity and daytime impacts. Others can suffer very severe consequences, potentially even death caused by accidents (like falling asleep while driving). In these cases, treatment can be life changing—and potentially life saving.

The main treatment for sleep apnoea is called continuous positive airway pressure (CPAP). Basically, to be effectively treated you wear a mask over your nose—or nose and mouth—all night, every night, which is connected to a machine that blows air and holds the airway open with pressure. It’s a very effective treatment, but, as Peter explains, ‘It’s not exactly convenient or sexy, and around half the people recommended to use it don’t use it at all or enough to be well treated.’ It doesn’t matter how great a treatment is if people won’t use it. While modern machines are very small and quiet, and masks can be comfortable with the right choice for your face, many people still won’t or don’t use CPAP effectively long-term. Peter thinks we can do better. The first step is to better understand how and why sleep apnoea occurs in the first place. He also has some ideas for treatments that might not need a mask and machine to force the airway to stay open.

Fast Facts

This research is funded by a National Health and Medical Research Council grant. The Chief Investigators are Professor Peter Catcheside and Professor Karen Reynolds. The Associate Investigators are Professor Doug McEvoy and Professor Yuanming Luo.
The Adelaide Institute for Sleep Health (AISH) is a Flinders University Centre of Research Excellence within the College of Medicine and Public Health.
AISH has a broad program of clinical and non-clinical sleep related research, including multiple collaborations across the university with the College of Science and Engineering and the College of Education, Psychology and Social Work, along with national and international collaborations and industry projects—such as those with the Cooperative Research Centre for Alertness Safety and Productivity.
Following closure of the Repatriation General Hospital, AISH is relocating to a new sleep research facility at the Sir Mark Oliphant Building in November 2018.

It’s a complex area with so many questions still to answer. I think we’re uniquely set up to do that. The connection between people with deep physiological knowledge, clinical understanding and engineering expertise is vital to our research.

Laura Gell

Since sleep medicine is so new—only about 40 years old—there are plenty of rabbit holes Peter and Laura could find themselves tumbling down. Sleep research has some strong overlaps with other areas in medicine, where breathing is very relevant and where new techniques for assessing breathing could be very useful to others; so it’s understandable for them to get a little distracted and sidetracked. In a side collaboration with Intensive Care Unit (ICU) specialists at Flinders Medical Centre, Peter and Laura’s methods have recently been tested to see if they could be useful for improving the care of patients who need a ventilator to help to them breathe in ICU.

When a patient in the ICU is on a ventilator, the machine is trying to help breathe for the person—but it doesn’t necessarily have all the signals needed to know precisely when, or for how long, the person is trying to breathe. Breathing can be quite variable breath-to-breath and although modern ventilators can track and try to adjust to patient breathing based on flow and pressure sensors in the machine, sometimes they can be out of sync. In partnership with Flinders University Professor Andrew Bersten and his team, they recently completed a ten patient pilot study in the ICU. The team are currently analysing this data that they hope will lead to improvements in ventilator monitoring technology and, ultimately, improve the care of patients requiring breathing assistance in ICU.

For Peter and Laura, working together allows them to problem solve in exciting new ways. Bringing together their expertise has allowed them to invent an entirely new technique for analysing complex physiological data, and put it to use in a developing field of medical research. They hope to soon answer their central questions about how our physiology changes in deep sleep to improve upper airway function. Once that’s achieved, they’ll turn their sights to sleep disorder treatments—all in the hopes of giving people around the world a better night’s sleep.

Professor Peter Catcheside completed undergraduate, honours and PhD degrees at the University of Adelaide, majoring in exercise physiology. He has worked in various clinical and research support roles—including as a respiratory function scientist at the Royal Adelaide Hospital and Women’s and Children’s Hospital—before joining Professor Doug McEvoy at the Repatriation General Hospital as a research assistant in 1997. He joined Flinders University in 2012 as an ARC Future Fellow and now leads a broad program of clinical and basic science research focused on understanding the mechanisms and consequences of disturbed sleep, from respiratory problems or environmental noise exposure.

Laura Gell completed her bachelor’s and master’s degrees in physics at the University of Cambridge. In 2015, she started work at Flinders University as a research assistant in the Medical Device Research Institute and in 2016, she commenced her PhD in biomedical engineering. Gell’s research is focused on understanding the underlying physiological mechanisms of sleep apnoea. She won the 2018 New Investigator Award for this research. She is jointly supervised by Professor Peter Catcheside and Professor Karen Reynolds.