Weight-bearing patterns on the knees of preterm infants.

In this study we present a method of monitoring the forces under the knees of preterm infants lying in the prone position. Dual force sensing resistor transducers, connected to optically-isolated amplifiers, were used to monitor the forces. A thermistor airflow sensor was used for the parallel monitoring of the respiratory signal. The measurements were made on ten preterm infants. The average forces were 0.51 and 0.50 N for the left and right knees, respectively. In the frequency domain, the basic harmonic of the force traces was 1.27 Hz approximately, corresponding to the respiratory rhythm. Additional, smaller harmonics, were detected in the force traces at 2.54 and 3.81 Hz. A rather notable power signal could also be seen around 0.1 Hz. The results obtained indicate that the system developed is highly sensitive for providing data on the amplitudes, periods and sequences of oscillations and symmetry of load bearing in preterm infants. Knowledge of the normal and abnormal reaction force patterns may assist in the early diagnosis of abnormal neurodevelopment.

Computer-controlled portable stimulator for paraplegic patients.

A six-channel lightweight, portable and computer-controlled stimulator for the functional activation of paraplegic patients is described. To enable programming of the various functions, the stimulator was designed to work in a remote-control mode hosted by an IBM PC or compatible computer, in addition to its normally used local mode. The stimulus parameters, including current intensity, stimulus frequency and pulse width, are individually adjustable and programmable for each channel. The power source is 12 V 500 m Ah-1, from 10 rechargeable nickel cadmium batteries, with a run time of 1.5 h for a load of 200 mA in four channels. Various training programmes for the activation of paraplegics in the sitting, standing and walking positions are described. The final design of the stimulator is based on experience gained from 25 patients, treated and evaluated during the course of development. Ongoing work including clinical, biomechanical and physiological studies is carried out to evaluate performance of the activated patients and to optimize stimulation.