Device may switch off snoring

Anyone who has endured the racket caused by a serious snorer should be pleased to hear that relief may be at hand. A team at University College, Dublin, has come up with a device that could switch off snoring for good.

Dr Richard Reilly of the Department of Electronic and Electrical Engineering at UCD has been studying a particular type of snoring, sleep apnoea, for some time. This isn't just your common or garden snoring, it is the noisy, rasping kind punctuated by intermittent halts in the person's breathing followed by gasps for air.

The sound of sleep apnoea is very disconcerting and makes it seem like the sleeper is snoring their last. The noise is linked to what actually takes place during sleep apnoea, Dr Reilly explained.

When we breath in, our expanding chest cavity creates a vacuum that draws in air through the trachea, or windpipe. The trachea is very flexible and loose in people with sleep apnoea. During sleep, in these individuals the vacuum can actually cause the trachea to collapse, cutting off the air flow.

At first it seems that the person has stopped breathing, but the lack of air rouses the person and the windpipe suddenly opens wide, allowing normal breathing to resume.

Sleep apnoea is not just an annoyance for anyone sharing the room. The break in breathing can happen hundreds or even thousands of times a night.

Sufferers tend to have a higher incidence of high blood pressure, heart disease, stroke and irregular heart beat. The sleep disturbance can cause irritability, depression and lack of energy.

A person suspected of having the disorder must be assessed in a "sleep laboratory" Dr Reilly explained, and St Vincent's Hospital has such a lab. The person is hooked up to electrocardiograph machines to monitor heartbeat, air flow monitors and other equipment.

It can take several days to get used to all the equipment before measurements can be taken, he said. "The big problem is trying to book some time in the sleep lab."

This is where Dr Reilly enters the picture. He is a specialist in "signal processing" and is a member of the Digital Signal Processing Laboratory at University College, Dublin. Signal processing involves the analysis of electrical signals and this expertise can be used in many ways. The 20 people in the DSP Lab are deeply involved in high-speed computer communications, data transmission and networked systems, but also has a group looking at biomedical signal analysis.

"In the past four or five years we have been looking at more biomedical aspects of signal processing," he said. Signals of interest are available from electrocardiograph (ECG) machines, which record the electrical signals of the heart, and electroencephalograph (EEC) machines, which detect brain waves.

The team had been looking at EEC data, trying to spot any connection between brain activity and sleep apnoea. It switched to ECG signals after attending a Computers in Cardiology conference and entering a competition to detect sleep apnoea on ECG recordings.

Its approach as signal processors was to first establish a typical wave form for a person at rest and then search for any tiny changes that might be present before, during or just after a sleep apnoea incident. "We were trying to find a mathematical correlation between the ECG and sleep apnoea," Dr Reilly explained.

"We try to use time domain and frequency domain parameters to identify where the pertinent ECG features are," he said, using software to analyse the signal.

Working with colleagues, Dr Conor Heneghan and Dr Philip De Chazal, the team found what it was looking for, a minute variation in the wave form. Its computer software achieved 90 per cent accuracy in detecting the onset of sleep apnoea. "We ended up getting the best automatic score possible," he said.

"We can predict when [sleep apnoea] happens by looking at the ECG. We now know how to predict it in a very simple way," he added, and without the need for all the equipment in the sleep lab.

Their research received a prize this autumn at the Computers in Cardiology conference in Boston. The team is now developing it further as a way to control sleep apnoea. "What we have been experimenting on is giving the person a little tone in the ear."

The approach is to wire up the person to an ECG machine. A computer monitors the ECG signal, watching for the telltale change that marks the onset of sleep apnoea. If detected, the computer triggers a tone in an ear piece worn by the subject.

The tone does not wake the person but disturbs them sufficiently to halt the sleep apnoea. Previous research by others had shown that this slight disturbance refocused brain activity and was sufficient to stop snoring, Dr Reilly said.

If successful Dr Reilly and colleagues could be on to a real winner. There are those who would pay any money to get a quiet night's rest, free from the interruptions of a snorer.