New Dimensions in Designing Medical Devices

Harvey Mudd College and the CIMIT consortium institutions are a continent apart, but a CIMIT Forum on March 18 demonstrated that creative ideas can develop when innovative minds can be brought together.

The event was held at the Simches Research Center of Massachusetts General Hospital, and one of the featured presenters was Clive Dym, PhD, PE, who is Fletcher Jones Professor of Engineering Design at Harvey Mudd College, based in Claremont, CA.

Dr. Dym’s session was moderated by William Wiesmann, MD, founder, chairman and CEO of BioSTAR Group. Dr. Dym said that he heard dynamic and promising ideas for developing medical devices during the two-hour event.

Dr. Dym described the design experiences of his college's broad-based, general engineering curriculum. A major element of the HMC engineering  program is a three-semester “capstone’ experience in which students work on design or development projects sponsored by industry, national laboratories or government agencies.

Also presenting was Steven Rauch, MD, associate professor of otology and laryngology, at Harvard Medical School, who is with the Massachusetts Eye and Ear Infirmary, where he is director of the MEEI Balance Center.

Moderating this session was Alexander Slocum, PhD, professor of mechanical engineering and MacVicar Faculty Fellow at MIT.

Dr. Rauch noted that falls are the fifth leading cause of death among the elderly, and close to 9 percent of those over 65 have balance problems. In mentioning young patients, he said many veterans of the Iraq war have sustained head injuries, and consequently have sought therapy for challenges in maintaining their balance.

One of his objectives is to develop an Ambulatory Vestibular Monitor (AVM) to record voluntary and reflexive eye movements, and other physiologic parameters. Ultimately, the AVM can be used as an ambulatory tool monitoring the patient to aid in the diagnosis of dizzy patients. It could also be used as a “vestibular lab in a box” data record that can be combined with a test battery to enable general vestibular function testing in remote and underserved areas that do not have access to conventional vestibular diagnostic services.

A post-presentation panel included Drs. Wiesmann, Dym, Slocum, Rauch and Rajiv Gupta, MD, a radiologist at MGH. Participants said that the session had provided many new ideas about how to proceed in improving their research as it relates to developing devices to cope with poor balance and the fear of falling.

Medical Device Case Study: Ambulatory Vestibular Monitoring

Over 90 million U.S. citizens have experienced dizziness and balance problems, and it is estimated that 40 percent of the U.S. population will seek medical care for dizziness at some point.  Nine percent of Americans experience chronic balance problems, and the cost of treating patients with balance problems and balance-related injuries is measured in billions of dollars.  As the U.S. population ages, the need to treat balance problems will only become worse.

The balance, or vestibular, system consists of inputs, a central processing module, and outputs.  The inputs include sensory information from organs in the inner ear, from the visual system, and from nerves associated with touch and proprioreception.  These inputs are processed in the brain, and finally, the brain sends signals to the limbs and to the eyes, telling them how to adjust to motion.  These adjustments are some of the body’s fastest reflexes.             

It is difficult to directly study the central processing that occurs in the brain, but doctors can learn a lot about problems in the vestibular system by measuring the motion of a person’s eyes.  When a person becomes dizzy, he or she usually experiences nystagmus, or rapid motion of the eyes.  Currently, vestibulo-ocular reflexes can only be measured in a specially equipped laboratory.  Unfortunately, the laboratory setting is unnatural, the tests are time-consuming, and the people being tested are often asymptomatic while in the lab. 

An ambulatory vestibular monitoring (AVM) system capable of tracking eye movement outside the laboratory would be very useful to clinicians.  Such a system would enable doctors to test patients anywhere, and it would provide valuable diagnostic information obtained in a natural environment.  The device could conceivably correlate eye movement data with other types of information, such as a person’s electrocardiogram (ECG) waves and respiration rate.  Steven Rauch and collaborators developed an AVM prototype, and they found that they were able to track eye movement with very little noise.  Their device is in an early stage of development, however, and many improvements, from wireless electrodes to detectors of head motion, will hopefully be made in the future.  It will take a lot of effort to bring the device to market, but the demand for the device might be very great.       

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