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Biomedical subjects

R Lundström

Publications and source records attributed to R Lundström.

At least 37 records · Page 2Linked to original sources
PubMed1994

Absorption of vibration energy in the human hand and arm.

A possible basis for the risk assessment for hand-transmitted vibration may be to determine the amount of energy absorbed in the human hand and arm. In the present study, the mechanical energy absorption in the hand-arm system was measured within the frequency range of 4 to 1000 Hz. The study was carried out on ten healthy subjects during exposure to sinusoidal vibration. The influence of various experimental conditions, such as vibration direction (Xh, Yh, Zh), grip force (25-75 N), vibration level (8-45 mm/srms), and hand-arm posture were studied. The outcome shows that the energy absorption in the human hand and arm depended mainly on the frequency and direction of the vibration stimulus. Higher vibration levels, as well as firmer handgrips, resulted in higher absorption of energy. Varying hand-arm postures had only a small influence on the amount of absorbed energy, while the constitution of the hand and arm affected the energy absorption to a larger extent.

Arm↗
PubMed1992

Vibrotactile perception threshold measurements for diagnosis of sensory neuropathy. Description of a reference population.

Recognition of the fact that impairment of the tactile sense may occur independently of other disturbances in the vibration syndrome has rekindled an interest in developing a diagnostic method for early detection of vibration-induced neuropathy. There is also evidence suggesting that vibrotactile measurements represent a valuable diagnostic tool in compressive neuropathies, such as the carpal tunnel syndrome. The method may also become useful for diagnosing sensory neuropathies caused by other factors, such as solvents, pesticides, heavy metals, alcoholism, and diabetes. However, before vibrotactile measurement can be accepted and established as a tool for clinical diagnostic purposes, for screening, and in research, the level and the shape of the normal threshold curve have to be specified. With the purpose of assembling normative data, the vibrotactile perception thresholds (8-500 Hz) of the right index fingertip were measured in 171 healthy males (19-75 years) not exposed to vibration. A Békésy audiometer was modified to operate in combination with a vibration exciter, instead of headphones, at frequencies lower than usual (8-500 Hz). The results showed that the perception thresholds increased from about 100 dB to about 140 dB (rel. 10(-6) m/s2rms) as a function of frequency and age. The frequency-dependent changes were not linear, however, but displayed a peak in sensitivity at 125 Hz. Threshold changes due to aging were most pronounced at the highest frequencies. It is of the utmost importance that these natural changes are taken into account when making comparisons between groups or individuals.

Adult↗
PubMed1992

Vibration-induced muscle injury. An experimental model and preliminary findings.

The hind paws of rats were subjected to vibration at a frequency of 80 Hz., an acceleration of 32 m./s.2 rms (i.e. ah.w approximately 6.3 m./s.2 rms) for five hours daily during five consecutive days. Morphological, histochemical and immunohistochemical analyses of the soleus, extensor digitorum longus and the plantar muscles in the vibrated limb and the contralateral control limb were performed. No changes were seen in the soleus or extensor digitorum longus muscles but different degrees of degeneration of the muscle fibres were seen in the plantar muscle sections as well as signs of regeneration. No changes were observed in the contralateral unexposed limb. It is concluded that it is not only nervous tissue but also muscle tissue that can be affected by vibration. The changes seem to be confined to muscles close to the vibration exciter.

Animals↗
PubMed1992

Vibration exposure and conditioning lesion effect in nerves: an experimental study in rats.

The effects of controlled vibrations of defined frequency (80 Hz), acceleration (32 m/s2 root mean square), and duration (5 hours daily, 2 or 5 days) induced to the hind limb of rats on the regeneration potential in the sciatic nerve after a test crush lesion were determined. Exposure to vibration induced a marked and significant increase in outgrowth length of axons from the crush injury as evaluated after 3 and 6 days with the pinch reflex test. This effect was still observed 1 month but not 3 months after exposure to vibration. Even such a short duration of vibration exposure as 2 days induced an increased length of outgrowth. Such a conditioning effect may be due to local changes in the environment of the axons or to changes in the nerve cell bodies in the dorsal root ganglion. The results indicate that an alarm reaction exists in the nerve at a time point where no structural changes are observed in the nerve. By inducing such a conditioning lesion to nerve tissue, vibration represents a trauma corresponding to a crush lesion or transection of the nerve.

Animals↗
PubMed1992

Vibrotactile function of the hand in compression and vibration-induced neuropathy. Sensibility index--a new measure.

The perception thresholds for vibration stimuli of the hand at seven frequencies (8-500 Hz) were evaluated in 300 patients referred to the Department of Hand Surgery in Malmö during the years 1985-1990 for various types of neuropathy (carpal tunnel syndrome, vibration-induced neuropathy, cervical rhizopathy, brachialgia, ulnar neuropathy, radial tunnel syndrome, and polyneuropathy). A sensibility index was calculated by dividing the integrated area under the obtained vibrogram curve of each object tested (areaT) by that of the corresponding area under a superimposed and age matched reference curve (areaR). Sensibility index of less than 0.8 was regarded as the cut off value. The index and little fingers bilaterally were tested to reflect median and ulnar nerve function. There were considerable variations in patterns of pathology among the various groups of patients. In patients with unilateral carpal tunnel syndrome only 10 patients (23%) had abnormalities limited to one recording, while 21 patients (47%) showed abnormalities in all four recordings. This indicates that an isolated carpal tunnel syndrome may reflect more generalised disease of the peripheral nervous system.

Carpal Tunnel Syndrome↗
PubMed1988

Mechanical energy absorption in human hand-arm exposed to sinusoidal vibration.

A possible basis for risk assessment of human exposure to vibration when using hand-held tools may be to determine the amount of mechanical energy that is absorbed by the hand-arm system. The aim of this investigation was to study the absorption of mechanical energy in the human hand-arm system during exposure to sinusoidal vibration within the frequency range of 20 to 1500 Hz. A handle, specially designed for this type of experiments, was used during the measurements. The influence of various experimental conditions, such as three different hand-arm postures, grip force (25-75 N) and vibration levels (27-53 mm/srms), were studied on eight subjects. The outcome clearly shows that the energy absorption properties of the human hand-arm system are more or less dependent on all of the experimental conditions studied, but mainly to the frequency of the vibration stimuli. Furthermore, the results indicate a non-linear relationship between the energy absorbed and all other variables studies.

Arm↗
PubMed1985

Changes in wakefulness during exposure to whole body vibration.

Thirty subjects were exposed to low frequency sinusoidal and random whole body vibration in the vertical direction, 0.3 m/sec2 (rms). Changes in wakefulness during 15 min vibration were compared to changes occurring during corresponding pauses without exposure. Measurements were made on EEG and ECG. Exposure to whole body vibration was found to be correlated with reduction in wakefulness. This effect, verified by an increase of theta and decrease of alpha activity, was greater during sinusoidal than random vibration.

Adult↗
PubMed1984

Local vibrations--mechanical impedance of the human hand's glabrous skin.

The mechanical point impedance has been studied in ten different areas of the glabrous skin of the human hand on three male and three female subjects within the frequency range of 20-10 000 Hz. For all tested areas the impedance decreased with increasing frequency down to a minimum value, corresponding to the natural frequency of the skin. After that, the mechanical impedance was directly proportional to the frequency. The highest natural frequency, about 200 Hz, was measured in the distal areas of the finger and the lowest, about 80 Hz, in the proximal areas of the palm (thenar). Small differences in internal damping were also showed to exist. A great amount of handheld tools used in industry have their maximum vibrational levels within the natural frequency range of the skin. In order to avoid adverse effects the skin's mechanical properties should therefore carefully be taken into consideration at designing vibrating tools.

Biomechanical Phenomena↗
PubMed1982

Responses of mechanoreceptive afferent units in the glabrous skin of the human hand to sinusoidal skin displacements.

The impulse responses to perpendicular sinusoidal skin displacements were recorded from 4 different types of mechanoreceptive different units innervating the glabrous skin of the human hand. The cycle responses, defined as the number of impulses evoked per sine wave cycle, were studied at a wide range of frequencies (0.5-400 Hz) and amplitudes (0.001-1mm). The rapidly adapting units (RA) were most easily excited at stimulus frequencies between 8 and 64 Hz, whereas the corresponding frequencies for the Pacinian units (PC) were above 64 Hz. However, at high stimulus amplitudes, the RA and the PC units showed quite similar response profiles within the range of frequencies tested. The sensitivities of the slowly adapting unit types (SA I and SA II) were greatest at lower frequencies. A characteristic finding for all 4 types of units was that the higher the amplitude, the lower the frequency at which the cycle response was maximal.

Adult↗
PubMed1982

Sensitivity to edges of mechanoreceptive afferent units innervating the glabrous skin of the human head.

One type of rapidly adapting (RA) and one type of slowly adapting (SA I) mechanoreceptive unit innervating the glabrous skin area of the human hand have small and well defined receptive fields. Their responses to perpendicular sinusoidal skin displacements were measured when the field was completely covered by a flat contact surface and when the edge of the contact surface was placed over the field. It was found that the majority of the RA and SA I units exhibited stronger responses when the edge of the contactor was placed over the receptive field. This edge sensitivity, which was greatest for the SA I units, may be of particular importance in improving the spatial analysis of the edges of objects in contact with the skin during manual manipulation and exploration.

Adult↗
PubMed1980

Case of Legionnaires' disease with deep venous thrombosis.

During the last three years many cases of Legionnaires' disease have been reported. Several cases reported had underlying disorders such as immunity deficiencies, or were undergoing immunosuppressive therapy. In this report we describe a previously healthy young man who acquired Legionnaires' disease and recovered after ampicillin-gentamicin treatment. During recovery he developed a lower leg thrombosis followed by pulmonary embolism.

Adult↗