PubMed Health⌕ Search

Biomedical subjects

K H Kohn

Publications and source records attributed to K H Kohn.

12 recordsLinked to original sources
PubMed2000

Stochastically-modulated stimulation to slow down muscle fatigue at stimulated sites in paraplegics using functional electrical stimulation for leg extension.

This short communication is a preliminary report on a study concerning slowing down the rate of muscle fatigue when FES (Functional Electrical Stimulation) is applied for standing and walking by complete (traumatic) thoracic-level paraplegics. It is shown that randomly modulating the inter-pulse interval between FES pulses (which serve to trigger action potentials in the peripheral nerves concerned) results in a significantly lower rate of muscle fatigue, as tested in a series of leg extensions, when FES was applied at the quadriceps. Specifically, we report that the best results (longest durations of leg extension prior to onset of muscle-fatigue) were achieved with a +/- 5 msec uniformly-distributed (pseudo-) white-noise modulation at a 42 msec inter-pulse interval (24 pulses per sec). These resulted in an average increase in duration of leg extension of approximately 37% in this pilot study, as compared with unmodulated (fixed-rate) trains of FES pulses. This significant increase, even in a very preliminary study appears to merit careful further examination, since it may allow a possibly significant increase in standing duration and in walking range of paraplegics using FES for ambulation.

Electric Stimulation Therapy↗
PubMed1998

Functional neuromuscular stimulator for short-distance ambulation by certain thoracic-level spinal-cord-injured paraplegics.

BACKGROUND: Functional Neuromuscular Stimulation (FNS) for unbraced short-distance ambulation by traumatic complete/near-complete T4 to T12 paraplegics is based on work by Graupe et al (1982), Kralj et al (1980), Liberson et al (1961), and others. This paper discusses methodology, performance, training, admissibility criteria, and medical observations for FNS-ambulation using the Parastep-I system, which is the first and only such system to have received FDA approval (1994) and which emanated from these previous works. METHOD: The Parastep system is a transcutaneous non-invasive and microcomputerized electrical stimulation system built into a Walkman-size unit powered by eight AA batteries that is controlled by finger-touch buttons located on a walker's handbars for manual selection of stimulation menus. The microcomputer shapes, controls, and distributes trains of stimulation signals that trigger action potentials in selected peripheral nerves. Walker support is used for balance. The patient can don the system in under 10 minutes. At least 32 training sessions are required. RESULTS: Approximately 400 patients have used the Parastep system, essentially all achieving standing and at least 30 feet of ambulation, with a few reaching as much as 1 mile at a time. Recent literature presents data on the medical benefits of using the Parastep system-beyond the exercise benefits of short distance ambulation at will-such as increased blood flow to the lower extremities, lower HR at subpeak work intensities, increased peak work capability, reduced spasticity, and psychological benefits. CONCLUSIONS: We believe that the Parastep FNS system, which is presently commercially available by prescription, is easily usable for independent short-distance ambulation. We believe that its exercise benefits and its other medical and psychological benefits, as discussed, make it an important option for thoracic-level traumatic paraplegics.

Blood Pressure↗
PubMed1997

Transcutaneous functional neuromuscular stimulation of certain traumatic complete thoracic paraplegics for independent short-distance ambulation.

The paper describes a system for transcutaneous functional neuromuscular stimulation (FNS) of certain traumatic thoracic-level complete paraplegics for independent unbraced short distance ambulation. The system described has been approved by the FDA in 1994 for that purpose. Its design, control, operation principles and parameters are described. Patient acceptance criteria and contraindications are outlined as is patient's training. Ambulation results are discussed and clinical and medical observations are reviewed. Finally general comments are made on the system's shortcomings and on possible improvements.

Adolescent↗
PubMed1988

Above- and below-lesion EMG pattern mapping for controlling electrical stimulation of paraplegics to facilitate unbraced walker-assisted walking.

We describe and evaluate above- and below-lesion EMG control of functional electrical stimulation (FES) in upper motor neuron paraplegics, in order to provide them with a patient-responsive system for walking with a walker support. Control is considered in terms of a combination of above-lesion EMG control and below-lesion response-EMG control. The above-lesion EMG is used to control the activation of limb functions involved in standing up and walking with FES, control being accomplished by analysing raw surface-EMG time-series patterns to discriminate between upper-trunk muscle contraction patterns, which in turn, are correlated with intended lower-limb functions involved in walking, so that natural and instinctive balance changes in paraplegics are controlled by the patient from above the lesion. The below-lesion response-EMG is the EMG produced in response to the FES pulses at the stimulation sites, for adjusting stimulation levels as needed when contractions weaken due to muscle fatigue. Above-lesion EMG is a stochastic (random-like) signal, being a response to unsynchronized motor neuron firings, whereas the below-lesion EMG is a deterministic signal responding to synchronized firings that result solely from the FES pulses. We also discuss the merits and difficulties of EMG control, and evaluate patient performance under such control, noting that FES-activated walking without adequate and patient-responsive control is of very limited use to paraplegics.

Electric Stimulation Therapy↗
PubMed1987

A critical review of EMG-controlled electrical stimulation in paraplegics.

This review presents a description and provides a comparative performance evaluation of EMG control vs. other approaches to controlling functional electrical stimulation (FES) in upper-motor-neuron paraplegics to provide them with a certain degree of walking ability with walker support. EMG control is considered in terms of a combination of above-lesion EMG control and below-lesion response-EMG control. The above-lesion EMG is to control the activation of different limb functions involved in standing up and walking via FES. This control is accomplished by analyzing raw surface EMG time-series patterns to discriminate between upper-trunk muscle contraction patterns which, in turn, are correlated with intended lower-limb functions involved in walking, so that natural and instinctive balance changes of paraplegics are reflected and controlled by the patient only above the lesion. The below-lesion response-EMG is the EMG produced in response to the FES pulses at the stimulation sites, for adjusting stimulation levels as needed when contractions weaken due to muscle fatigue. Above-lesion EMG is a stochastic (random-like) signal, being a response to unsynchronized motor-neuron firings, whereas the below-lesion EMG is a deterministic signal responding to synchronized firings that result solely from the FES pulses. The present review discusses the merits and difficulties of EMG control and attempts to give a critical evaluation of patient performance under such control, contrasted to other methods of control, noting that FES-activated walking without adequate and patient-responsive control is of very limited attraction and use to paraplegics. Of the various control methods, only foot- or hand-switch control comes close in overall performance to above-lesion EMG control. Although one cannot categorically prefer EMG control to foot- or hand-switch control performance-wise, psychologically, EMG control has the advantage in that concentration is not diverted to the patient's fingers, whereas foot switches are inadequate for patients lacking reasonable natural (non-FES) pelvic thrust control. However, for stimulation-level control, below-lesion response-EMG appears to be the clear answer. It is shown that below-lesion EMG control of stimulation levels can be used independent of above-lesion EMG control. Below-lesion EMG control can thus be combined also with hand-switch control or, in case of low level upper-motor-neuron lesions, with pelvis control. Hence, and since FES-activated walking is as good as its control, we conclude that EMG control should be given serious consideration in any FES walking.(ABSTRACT TRUNCATED AT 400 WORDS)

Electric Stimulation Therapy↗
PubMed1982

Multifunctional prosthesis and orthosis control via microcomputer identification of temporal pattern differences in single-site myoelectric signals.

The paper discusses results of on-line tests on amputees and hemiplegics of multifunctional prostheses and orthoses control by identifying the parameters of single-site temporal EMG signal signatures. The results relate to tests on above-elbow amputees, on shoulder-disarticulation amputees (including a congenital disarticulation amputee) and on hemiplegics, varying from 5 to 50 years of age. The system employed is based on an 8-bit Intel 8080 microprocessor, when computation is in double precision, to obtain an effective 16-bit work-length. The system employs a sequential least-squares algorithm to identify a 4-parameter auto-regressive time-series model of the EMG signal, and a Bayesian rule discrimination algorithm.

Adolescent↗