3rd Week Not to be sniffed at

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Medical devices

Not to be sniffed at

For those who have no other means of communication, sniffing may provide liberation

Oct 4th 2010

TO SUFFER from locked-in syndrome—to be mentally alert! but physically paralysed—is one of the worst fates imaginable. Noam Sobel of the Weizmann Institute, in Israel, may, however, have come up with a way to make this fate slightly more bearable.

He starts from the observation that even those who are otherwise paralysed can sniff. Sniffing is regulated by the soft palate, a flap of tissue in the back of the throat that directs the flow of air through the mouth and nose. The soft palate is controlled by cranial nerves—in other words, nerves that do not pass through the spinal cord. So spinal damage, a common cause of paralysis, does not affect these nerves. Nor does brain damage, unless to the exact part of the brain that controls the soft palate.

Dr Sobel and his team thus developed a system for measuring changes in air flow caused by sniffing. It consists of a narrow tube that rests on the operator’s nose. This is connected to a sensor that picks up changes in pressure and translates them into electrical signals. These signals can then be used to get machines to do what the operator wants them to do. At least, that is the theory. All that is required is for the operator to work out how to sniff appropriately.

The first test Dr Sobel put the system to was allowing people who suffer from locked-in syndrome to communicate. Dr Sobel’s team has built a device that lets people dictate text onto a computer screen using coded patterns of sniffing. They worked with patients at Levinstein Rehabilitation Hospital in Ra’anana, a suburb of Tel Aviv. Their first volunteer, a 51-year-old woman, had been locked in for seven months. Within three weeks, she was able to write a letter to her family.

The second device to use the system is an electrically powered wheelchair. This could be a boon to many paralysed people. As little as 15 minutes of practice is enough to give an individual complete control of the machine. Two inward sniffs move it forward. Two outward ones put it into reverse. An outward followed by an inward turns it right, and an inward followed by an outward turns it left.

And sniffing may have applications for the healthy, as well as the paralysed. It is, for example, faster than pressing a mouse button. Dr Sobel’s team has therefore built a variation of the device for use in computer games. If that catches on, arcades may soon sound as if everyone in them should be tucked up in bed with a hot toddy.