Sniff-activated system drives wheelchairs

A new sniff-sensing controller out of Israel may enable the severely paralyzed to navigate wheelchairs, surf the Net, and communicate in writing via controlled inhalations and exhalations.

The system, being developed at the Weizmann Institute of Science in Rehovot, employs a sensor that fits in a nostril's opening and measures changes in air pressure. A pressure transducer translates this information into electrical signals, which are transmitted to a computer, and its specialized software, via USB connection. Patients on respirators use a passive version of the device that diverts airflow to their nostrils.

Researchers tested the system on 96 healthy volunteers and 10 quadriplegics, with promising results. Some users, the team says, were able to navigate an electric wheelchair around a complex path or play a computer game with nearly the speed and accuracy of a mouse or joystick (watch the video below to see a demonstration of the wheelchair in action).

While the system can be made to work with a variety of sniffs (long or short, strong or shallow), researchers employed a simple sniff code for their tests: A "double sniff in" implied "forward;" a "double sniff out" implied backward; a successive "sniff out then in" implied left; and a successive "sniff in then out" implied right.

Using incremental signals (a "left" command turned the chair left, another "left" command turned it farther left) volunteers navigated wheelchairs indoors and outdoors, with the most complicated maneuvers, executed both by healthy and quadriplegic volunteers, being sharp turns.

The scientists were particularly encouraged by tests conducted on three patients with Locked-In-Syndrome, a rare neurological disorder in which cognitive function remains unimpaired, but all voluntary muscles are paralyzed, except for those that control eye movement. The condition was famously portrayed in the 2007 film "The Diving Bell and the Butterfly," which told the true story of a journalist with Locked-In who dictated his memoir through eye blinks alone.

Sniffing is a precise motor skill controlled in part by the soft palate, the flexible divider that moves to direct air in or out through the mouth or nose. Because the soft palate is controlled by nerves that connect to it directly through the braincase, the Weizmann team built on its theory that control over soft palate movement might stay intact even in the most acute cases of paralysis.

Using the sniffing system to control a computer cursor, the Locked-In testers were--after considerable practice--able to communicate with family members, said Noam Sobel, a Weizmann Institute professor of neurobiology who developed the system with electronics engineers Anton Plotkin and Aharon Weissbrod, and research student Lee Sela. "Some wrote poignant messages to their loved ones, sharing with them, for the first time in a very long time, their thoughts and feelings," he said.

In a detailed rundown of their system (PDF), published in the latest issue of the Proceedings of the National Academy of Sciences, the scientists stress that because disabilities are so diverse, each assistive technology has merit of its own.

But while eye tracking is the primary non-brain-computer/brain-machine interface technology available for Locked-In Syndrome patients, they do maintain that sniff control bears some distinct advantages. For example, unlike eye tracking, it does not depend on stable capture, meaning that the bumps of a rugged surface wouldn't limit the sniff controller. Also, eye-tracking systems can devote a user's eyes to generating signals, as "using sniffs for communication allows maintenance of ongoing visual attention."

Then there's cost. The team built a standalone sniff controller for a wheelchair for $358 (far less than the average eye-tracking setup, they say), and estimates that if produced at scale, its controller would cost only a fraction of that amount.

Sniff detection, however, would not make eye tracking obsolete. In cases where eye movements would work and sniffs wouldn't (allergies or the common cold, perhaps?), both technologies could be combined for maximum effect.

July, it turns out, has been an exciting month for disability research. A couple of weeks ago, a New Zealand company unveiled a pair of robotic legs that let wheelchair users stand, walk, and even go up and down stairs. That system goes for $150,000, is currently available for purchase and fitting in New Zealand, and is expected to be available in other countries next year.