Monopolar needle stimulation: safety considerations.

Stimulation of nerves for conduction studies can be performed with a monopolar needle used routinely for electromyographic studies. Although invasive, this technique allows precise localization of stimulation and access to deeply situated nerve trunks, thus providing otherwise unobtainable information regarding peripheral nerve function. The electric current at the needle tip was measured during supramaximal stimulation of the median and peroneal nerves at distal and proximal sites. After measuring the area of uninsulated needle tip, the local current density was calculated. The maximum current during the stimulation of 0.05msec duration was 0.80mA and the resulting current density was 4.1mA/mm2. It is calculated that this current could cause a local maximum temperature rise of 2.5C in the tissue within 0.5mm of the needle tip. This current flow would not be expected to cause either direct electric or heat damage to the tissue.

Ground reaction forces, center of pressure, and duration of stance with and without an ankle-foot orthosis.

We analyzed the effects of an ankle-foot orthosis (AFO) on the ground reaction forces, the position of the center of pressure, and the timing of stance phase events during walking in 18 healthy volunteers between the ages of 19 and 38 years. The magnitude and direction of the ground reaction forces and the locus of the center of pressure were recorded every one-sixtieth of a second during free-speed ambulation. The horizontal force components of the ground reaction force were plotted vectorially, and the vertical force component was displayed by its magnitude expressed in percentage body weight. All this information was superimposed on the subject's footprint and statistically analyzed, comparing right to left, narrow to wide, and ipsilateral to contralateral use of an AFO. The results showed a significant reduction in the mean duration of the stance phase of 4.83% (p less than 0.05) with the AFO. This reduction was due primarily to the significant reduction during midstance of 7% (p less than 0.025), which was more pronounced with the use of the wide AFO. Using an AFO also resulted in a mean increase of 20% (p less than 0.05) in the vertical force magnitude at the end of push-off. With the use of an AFO, there was a shift of the point of impact at heel strike to a more posterior location and a shift of the trajectory of the center of pressure to a more lateral position throughout the stance phase. These changes should be kept in mind when prescribing an ankle-foot orthosis.

Burns in functional electric stimulation: two case reports.

Electric stimulation of nerve and muscle is a widely used procedure for diagnosis and therapy in spinal cord injured patients. Damage from such stimulation can occur in the form of tissue burns. Two cases of burns in spinal cord patients receiving functional electric stimulation are presented. It is concluded that to avoid burning of tissue: a stimulating electrode with a large surface should be used; uniform contact between the electrode and the skin should be insured; a good conducting-material interface between the electrode and skin is required; adequate ventilation for heat dissipation should be provided; sharply cut electrode corners, wire insulation damage, and cuts in lead wires must be avoided.

Integrated communication/environmental controller system for the physically disabled.

A wireless integrated communication/environmental controller system (ICECS) is described, which offers total communication as well as environmental control for the disabled person. The system is flexible and simple enough to be used from the wheelchair by patients with spinal cord injuries. The system has three parts: the mobile unit, the base unit, and a set of remote-control receiver modules. The mobile unit and the base unit are linked together by radio, while the base unit and the remote receiver modules communicate over a power line carrier. The telephone mode allows telephone calls to be placed and received. Different electrical devices are controlled by the environmental control mode. The intercom mode permits two-way communication with an attendant or the nursing station. The modes can be switched simply by pressing a button on the mobile unit. Sixteen soft-touch switches arranged in a 4 X 4 matrix allow operation by hand or mouthstick.

Ground reaction forces during ambulation in parkinsonism: pilot study.

Gait abnormality in parkinsonism is unique and easily recognizable. A pilot study was designed at our Human Gait Laboratory to learn how this gait abnormality is reflected in ground reaction forces of patients with parkinsonism. The system permitted the collection of kinematic and force data from a subject in real time. Analysis showed an abnormality in the vertical force (Fz) component, the second peak being significantly reduced in size, with asymmetry in the duration of the stance phase. These abnormalities were also reflected in the stance phase and in the angular changes in the knee. Similar analyses should be helpful in following the progress of the disease.

Ultrasound therapy: a comparative study of different coupling media.

Four different materials, water, oil, gel, and silicon, were considered for their relative efficiency as coupling media for ultrasonic therapy. The power loss (attenuation) as a function of distance in each medium was experimentally studied. The degree of impedance match (power reflection into the transmitter) between the medium and transducer head was also determined by measuring the standing wave ratio. The results of the study indicated that oil and water have a large degree of attenuation as well as poor impedance match with the sound head. Gel offered a smaller degree of attenuation and better impedance match. Silicon appeared to offer little attenuation but the encasing material has so much impedance mismatch with the sound head that very little power is transmitted into the silicon medium. For future automated clinical applications, the use of encased silicon such as is used for breast implant is proposed, if mismatch is reduced.

Micturition alert device.

The determination of an accurate postvoid residual (PVR) is essential to a successful intermittent catheterization program. A light (40g), simple electronic device that alerts the hospital staff by means of a buzzer or an LED, when a patient is voiding, is described.

Optical logic gates using liquid crystal light valve: implementation and application example.

In this paper, we propose a new method of optically implementing digital logic gates capable of performing all logic operations and give the technique for construction of an array of n-bit parallel adders as a typical application circuit. These gates are implemented using a Hughes liquid crystal light valve operated in the parallel off-state configuration. It is found that all possible functions of two binary variables are realizable with these gates, some as bright-true-logic and some as dark-true-logic. Experimental results will be given using the portions of a single liquid crystal light valve demonstrating the feasibility of AND, NOR, XOR, etc. gate arrays. As an example of implementation of combinatorial circuits, a design for an array of binary adders will also be given.