Sniff-detector allows paralysed people to write messages, surf the net and drive a wheelchair

By Ed Yong | July 26, 2010 3:00 pm

In Israel’s Loewenstein Rehabilitation Hospital, the patient known as LI1 is a prisoner of her own body. She is a 51-year-old woman who was paralysed by a stroke several months ago. Suffering from “locked-in syndrome”, she is completely aware but unable to move or speak. She cannot even control the blinks of her eyes. And yet LI1 has recently been able answer questions from her doctors and communicate with her family through written messages. All she has to do is sniff.

LI1 uses a ‘sniff controller’, an incredible new technology that allows paralysed patients to control machines with their noses. It’s the brainchild of Anton Plotkin and Lee Sela at the Weizmann Institute of Science. Whenever a patient sniffs, the device measures the change in pressure inside their noses. It converts these into electrical signals that are passed to a computer via a simple USB connection. With just a sniff, people can move a cursor on a screen, allowing locked-in patients to write messages. Quadriplegics can even use the device to surf the web, or drive a wheelchair.

This technology was developed almost by accident in the lab of Noam Sobel, who studies the way of brains process our sense of smell. The group use a device called an olfactometer, which produces waves of smell to see how sensitive a person’s senses are. For one of their experiments, the team rigged the olfactometer so that volunteers triggered the odour pulse themselves when they sniffed. “We noticed that sniffs are a very good and fast trigger,” says Sobel. “It then simply dawned on us that instead of triggering odor, we could trigger anything: letters in a text writer or turns of a wheelchair.  The rest just flowed (or rather, rushed) from there.” It’s a fantastic example of the useful and unpredictable roads that basic scientific research can lead to.

Steven Laureys, head of the Coma Science Group at the University of Liege, says he had “serious doubts” when he first heard about the device. “But the israeli team clearly proved us wrong,” he says. “It’s a good illustration of creative translational research and how lab-thinking outside the box, combined with a rigorous scientific approach validated in clinical settings, now offers exciting, unexplored tools for locked-in syndrome patients.”

Sniffing may be a simple act but it’s not one to be sniffed at – people have very tight control over the length, intensity, pattern and, obviously, direction of their sniffs. The sniff controller can measure all of these traits, independently of the user’s regular breathing. If the user can breathe on their own, they only need to wear a couple of nasal tubes. If they need the help of a machine to breathe, they have to wear a larger nasal mask.

Plotkin and Sela found that healthy volunteers could use the controller to press a button in a computer game as quickly and accurately as they could with a mouse or joystick. They also developed writing software using the sniff controller. It takes three sniffs to write a character. The first selects one of three blocks containing letters, signs of completed words (much like a predictive text menu). The second selects a line in the chosen block and the third picks a character. A cursor flits between the various options and a sniff chooses the one it highlights. The video below explains how it works.

These trials in healthy volunteers were promising, but LI1 was their first big success. She was so badly paralysed that it took her 19 days to produce a sniff on demand, with 20 minutes of practice a day. But once she gained this ability, she started using the writing software immediately. A few days later, completely of her own accord, she had written her first message to her family – a “very moving” and “unexpected” missive that Sobel is keeping a secret. To this date, the sniff controller is still her only means of expressing herself.

The successes came thick and fast. LI2, a man who had been locked-in for 18 years after a car accident, took to the controller immediately. Within 20 minutes, he had written his own name and he still uses the device. QU1, a quadriplegic woman who can speak with severe difficulty, used the controller to write for the first time in 10 years. After 3 weeks, Plotkin and Sela upgraded her to more advanced software (see video below) that lets her move a cursor by sniffing. She can type on a virtual keyboard, surf the net and even write email. Ten other quadriplegics can do the same.

Writing text is still a long and tedious process. LI1 is one of the quickest users and she only manages around three letters per minute, with one mistake with every six letters. That’s may seem frustrating but the freedom of expression more than makes up for it. As Plotkin and Sela write, “The speed of this self-expression is less important to individuals who, put bluntly, have no other options.” When LI1 and LI2 were asked to suggest improvement to the controller, neither mentioned speed.

Neils Birbaumer, who has worked on communication technologies for paralysed people, thinks that the sniff controller will only work for a small proportion of completely locked-in patients. “Sniffing needs muscular control and a partly intact motor system, but that’s exactly what most patients with ALS or complete locked-in syndrome don’t have,” he explains. Indeed, one patient, LI3, never learned to control his sniffs, even after 2 months of practice. Whether he simply couldn’t muster the right amount of control, or whether he was too severely depressed to learn, the device failed him.

Nonetheless, Sobel is hopeful that the sniff controller will be widely useful. His “pessimistic expectation” is that two-thirds of locked-in patients could use the device. “My optimistic yet not unrealistic expectation would be that nearly all would be able to, at least all those who are locked-in due to stroke or trauma,” he says. “Those with ALS may be worse-off at the end stage.” However, he’ll need to test the device on many more patients first.

There are other possible ways locked-in patients to communicate. “Brain-computer interfaces”, which allow users to control cursors through thought alone, are the most promising avenue yet, but they’re still in their infancy. Other alternatives include machines that track the movements of the tongue, the head or the eyes. The French journalist Jean-Dominique Bauby used blinks to dictate his famous memoirs, The Diving Bell and the Butterfly. A nurse read out a stream of letters while Bauby blinked to select the right one; eye-tracking machines could do the same thing automatically.

But the sniff controller has many advantages over eye-trackers and similar technologies. Sniffing itself can code a lot of information in the length and strength of sniff. It depends on neural networks that are widely spread and harder to knock out entirely. And these networks overlap with those for language production, so writing messages through sniffs may come particularly easily.

The sniff controller is simple and doesn’t involve cumbersome equipment (LI2 rejected eye-trackers because they were too uncomfortable). It works for locked-in patients like LI1, who can’t control their head or eye movements. For those with more movement, sniffing allows them to shift their head or eyes while communicating, without sending the wrong signal. And finally, the sniff controller is potentially very cheap. Plotkin and Sela built the version that controlled the wheelchair for $358. If it was mass-produced, that cost could fall substantially. By contrast, and eye-tracking system can cost up to $20,000.

Sobel thinks that his machine is certainly very competitive without rendering others obsolete. The truth is that disability isn’t a one-size-fits-all problem and a technology that works well with one patient may be terrible for another. As Laureys says, “The more tools, the better.”

For severely disabled patients who aren’t confined to beds, the sniff controller has another use – it can drive an electric wheelchair with a simple two-sniff code. “Two-sniffs-in” send the chair forward; “two-sniffs-out” reverses; “sniff-out-then-in” turns left; and “sniff-in-then-out” turns right. After just 15 minutes of practice, QU2, a man paralysed from the neck down, took only two goes to use this simple code to drive round a complex obstacle course, strewn with right angles.

Unlike the writing software, a driving programme raises obvious safety issues. By measuring the carbon dioxide levels in the users’ breaths, Plotkin and Sela think that the risk of hyperventilating is minimal. They also used double commands to avoid the possibility of crashing the chair by breathing. More complex codes could provide even more safety but the duo doesn’t think this is necessary. With practice, people should be able to drive the chairs without mistakes; certainly, Plotkin and Sobel have learned to use the software themselves and they can talk and drive at the same time without any problems.


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