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Biomedical subjects

S Rebersek

Publications and source records attributed to S Rebersek.

10 recordsLinked to original sources
PubMed2001

A reliable method of determining wound healing rate.

Several wound healing rate measures have been introduced with the main goal of enabling quantification of the effects of various therapeutic modalities on the healing of open wounds. Different definitions of wound healing rate render comparison of clinical results difficult. The goal of the present study was to propose a measure of wound healing rate that is independent of initial wound extent and to present a method of wound healing rate prediction. Comparisons were made of wound healing rate defined as absolute area healed per day, percentage of initial area healed per day and advance of the wound margin towards the wound centre per day. Analysis was performed on 300 wound cases. A disadvantage of wound healing measures that either use absolute area healed per day or percentage of initial area healed per day is their very limited use for comparing healing rates of wounds with different initial sizes. This disadvantage was overcome by incorporating a wound perimeter; thus obtaining a measure of the advance of the wound margin towards the wound centre. A definition of healing rate expressed as the greatest average wound margin distance from the wound centre divided by the time to complete wound closure is proposed. Because not all wounds are closed in the observation period, the time to complete wound closure has to be predicted. A method of wound healing rate prediction is presented based on a delayed exponential model the parameters of which are obtained from at least five weekly wound area measurements. Paired t-tests between actual time needed to complete wound closure and the predicted time resulted in p = 0.062 after four, 0.484 after five and 0.900 after six weeks of observation.

Chronic Disease↗
PubMed2001

Prognostic factors in the prediction of chronic wound healing by electrical stimulation.

The aim of the study is to determine the effects of wound, patient and treatment attributes on the wound healing rate and to propose a system for wound healing rate prediction. Predicting the wound healing rate from the initial wound, patient and treatment data collected in a database of 300 chronic wounds is not possible. After considering weekly follow-ups, it was determined that the best prognostic factors are weekly follow-ups of the wound healing process, which alone were found to predict accurately the wound healing rate after a minimum follow-up period of four weeks (at least five measurements of wound area). After combining the follow-ups with wound, patient and treatment attributes, the minimum follow-up period was reduced to two weeks (at least three measurements of wound area). After a follow-up period of two weeks, it was possible to predict the wound healing rate of an independent test set of chronic wounds with a relative squared error of 0.347, and after three weeks, with a relative squared error of 0.181 (using regression trees with linear equations in its leaves). Regression trees with a relative squared error close to 0 produce better prediction than with an error closer to 1. Results show that the type of treatment is just one of many prognostic factors. Arranged in order of decreasing prediction capability, prognostic factors are: wound size, patient's age, elapsed time from wound appearance to the beginning of the treatment, width-to-length ratio, location and type of treatment. The data collected support former findings that the biphasic- and direct-current stimulation contributes to faster healing of chronic wounds. The model of wound healing dynamics aids the prediction of chronic wound healing rate, and hence helps with the formulation of appropriate treatment decisions.

Adult↗
PubMed2000

Modelling of chronic wound healing dynamics.

Following chronic wound area over time can give a general overview of wound healing dynamics. Decrease or increase in wound area over time has been modelled using either exponential or linear models, which are two-parameter mathematical models. In many cases of chronic wound healing, a delay of healing process was noticed. Such dynamics cannot be described solely with two parameters. The reported study deals with two-, three-, and four-parameter models. Assessment of the models was based on weekly measurements of 226 chronic wounds of various aetiologies. Several quantitative fitting criteria, i.e. goodness of fit, handling missing data and prediction capability, and qualitative criteria, i.e. number of parameters and their biophysical meaning were considered. The median of goodness of fit of three- and four-parameter models was between 0.937 and 0.958, and the median of two-parameter models was 0.821 to 0.883. Two-parameter models fitted wound area over time significantly (p = 0.01) worse than three- and four-parameter models. The criterion handling missing data provided similar results, with no significant difference between three- and four-parameter models. Median prediction error of two-parameter models was between 111 and 746; three-parameter models resulted in an error of 64 to 128, and finally four-parameter models resulted in the highest prediction error of 407 and 238. Based on the values of quantitative fitting criteria obtained, three parameters were chosen as the most appropriate. Based on qualitative criteria, the delayed exponential model was selected as the most general three-parameter model. It was found to have good prediction capability and in this capacity it could be used to help physicians choose the most appropriate treatment for patients with chronic wounds after an initial three-week observation period, when the median error increase of fitting is 74%.

Chronic Disease↗
PubMed1989

FES and spasticity.

A model of hemiplegic spasticity based on electromyographical and biomechanical parameters measured during passive muscle stretching is presented. Two components of spasticity can be distinguished--phasic and tonic. This classification depends on the pattern of stretch reflex activity which can be either phasic or tonic as well as on the muscle stretch/tension characteristic. Stretch reflex, as a control loop, is in phasic spasticity characterized by increased sensitivity to velocity of stretching. In tonic spasticity, sensitivity to length of stretching is increased. After the injury, phasic spasticity appears first and invokes monosynaptic reflex pathways. The intensity of tonic spasticity increases with the duration of disability and hence causes changes in muscle fiber biomechanical properties. The model mentioned above has been used to evaluate the effects of FES on spasticity. Hemiplegic patients with implanted peroneal nerve stimulator for gait correction were followed up for one year starting a week before implantation. Long-term use of FES resulted in decrease of tonic spasticity in both ankle joint antagonistic muscle groups. In stimulated tibialis anterior muscle, the phasic type of spasticity increased. To obtain the correlation between changes in spasticity and functional abilities of patients, the maximal voluntary isometric contraction of both muscle groups was also measured. An improvement in voluntary strength was also observed. This can be taken as additional evidence that tonic spasticity is of greater physiological and clinical significance than phasic spasticity. It may be concluded that use of FES can decrease tonic spasticity and, if applied early after the injury, can prevent the appearance of tonic spasticity.

Adult↗
PubMed1988

Chronic electrical stimulation for the modification of spasticity in hemiplegic patients.

The effects of long-term electrical stimulation on reflex hyperactivity and voluntary muscle control were studied. Eight hemiplegic patients with implanted peroneal stimulator were included. After six months of functional electrical stimulation (FES) there was a decrease of tonic activity in both tibialis anterior and triceps surae muscles. The phasic stretch reflex activity in the stimulated tibialis anterior muscle increased. The resulting resistance during passive movements decreased due to diminution of tonic activity. The absence of tonic activity also resulted in improvement of voluntary control, particularly in the tibialis anterior muscle.

Adult↗
PubMed1988

Electrical stimulation for control of paralysis and therapy of abnormal movements.

After a short review of the functional aspects of electrical stimulation in rehabilitating paralysed patients, the article describes its effects on spasticity. Three different studies are briefly described. In the first one paraplegic patients' knee extensors and flexors were stimulated with four channel stimulator. In the second one two channel stimulation was applied to the ankle joint flexors and extensors in hemiplegic patients, while in the third, the effects of spinal cord stimulation were studied in multiple sclerosis patients. Although the parameters and sites of stimulation were different in each study, the effects were similar. In approximately 50% of paraplegic and hemiplegic patients stimulation caused decrease of reflex activity which lasted more than half an hour. In M.S. patients measurements were performed only in intervals of day and therefore short term effects were not documented. Two days after interruption of continuous spinal cord stimulation the reflex activity significantly increased in the majority of patients. In addition to this increase the volitional force decreased considerably.

Electric Stimulation Therapy↗
PubMedDate not supplied

Rigidity in parkinsonism: characteristics and influences of passive exercise and electrical nerve stimulation.

Rigidity was measured during sinusoidal passive movements of the ankle joint in 7 patients with parkinsonism. Velocity-dependent changes were observed, less marked than in spasticity and expressed in a different way in flexor and extensor muscles: a mild decrease in resistive torques at faster stretching of dorsal flexors and an increase in resistance on stretching of plantar flexors. Dorsal flexors also frequently showed shortening reactions. Passive exercises and electrical stimulation of the peroneal nerve resulted in decreased electromyographic responses to stretch, smoother passive movements and in improved voluntary contraction.

Aged↗