Biomedical subjects

I Pyykkö

Publications and source records attributed to I Pyykkö.

At least 181 records · Page 10Linked to original sources

PubMed1987

Circulatory and thermal responses of men with different training status to prolonged physical work in dry and humid heat.

Eight physically trained and eight untrained, unacclimated men walked on a treadmill at 30% of their maximum oxygen consumption up to 3.5 h in a thermoneutral [20 degrees C/40% relative humidity (RH)], a warm humid (30 degrees C/80% RH), and a hot dry (40 degrees C/20% RH) environment while wearing industrial work clothing. Their oxygen consumption, rectal and skin temperatures, sweating, cardiac output, heart rate, stroke volume, and peripheral blood pressure were measured during the tests. Thirteen of the 32 heat stress tests were prematurely stopped due to high rectal temperature, high heart rate, subjective fatigue, or heat syncope. The physiological strain, as indicated by the rectal temperature and heart rate, was not significantly different between the warm humid and hot dry environments (wet bulb globe temperature approximately 28 degrees C). The rectal temperature and heart rate responses of the physically trained and untrained subjects did not differ in any of the environments. In the heat, the heart rate was significantly higher than in the thermoneutral environment, but because of the markedly reduced stroke volume the average cardiac output was not different between the three environments. The impaired work performance in the heat seemed mainly to be related to the circulatory instability accompanying the increased cutaneous circulation.

Adult↗

PubMed1987

Ethanol-induced modulation of hippocampal EEG and cerebral 2-deoxyglucose accumulation in rat lines with differing alcohol sensitivities.

Rat lines (AT, alcohol tolerant, insensitive; ANT, alcohol nontolerant, sensitive) selectively bred for differences in ethanol-induced motor impairment were subjected to studies on neuronal signal processing and cerebral regional glucose uptake as influenced by an acute moderate dose (2 g/kg) of ethanol. The cerebellar membrane GABA receptor complex was also studied with binding experiments using naive AT and ANT rats. Recordings of hippocampal EEG indicated that with and without ethanol administration a rotational stimulus caused EEG synchronization in both rat lines. There was no major difference in the 2-deoxyglucose accumulation into gross brain regions between the lines. Thus, a moderate dose of ethanol does not make these rat lines distinguishable in these tests. The number of muscimol binding sites tended to be higher and that of flunitrazepam binding sites lower in the cerebellum of AT rats. These variations could not be abolished by treating the membranes with a detergent to remove possible endogenous substances bound to the receptors. The functional significance of this small difference is not known, as the relationship between receptor numbers and function is still vague. The present results indicate that the central nervous system factors involved in acute alcohol sensitivity are subtle requiring detailed study at all levels from the membrane molecules to behaving animals.

Alcoholism↗

PubMed1987

Evaluation of optokinetic nystagmus in differentiating between peripheral vestibular and infratentorial lesions.

Optokinetic nystagmus (OKN) was studied in ten patients with vestibular neuritis, and in seventeen patients with unilateral and thirteen patients with bilateral infratentorial lesions and compared with OKN in fifty healthy subjects. Mean and maximum slow phase velocity of OKN was calculated as well as the asymmetry of responses. The efficiency of the different variables in OKN, in discriminating between different lesion sites, was tested in a linear discriminant function analysis. Slow phase velocity of OKN could satisfactorily separate patients with infratentorial lesions from healthy subjects or subjects with vestibular neuritis. Asymmetry of OKN did not contribute further to the correct diagnosis.

Adolescent↗

PubMed1986

Hand-grip force in lumberjacks: two-year follow-up.

Hand-grip force was measured in 63 professional lumberjacks in 1978 and again in 1980. Lumberjacks with vibration-induced white fingers (VWF) had lost 21% of their muscle force during the two years. Lumberjacks with no hand-arm symptoms had lost 5% of their muscle force in the same time period. Lumberjacks with subjectively diminished hand muscle force had a slight increase in muscle force during the follow-up time. These results suggest that long-term exposure to vibration causes a decrease in muscle force.

Adult↗

PubMed1986

Digital vibrogram: a new diagnostic tool for sensory testing in compression neuropathy.

A Békésy audiometer was modified for use in analysis of vibrotactile sensibility of the hand at frequencies ranging from 8 to 500 Hz. In control subjects the "digital vibrogram" has a typical shape, which differs characteristically in patients with carpal tunnel syndrome (CTS). Changes in digital vibrogram usually parallel or precede abnormalities in neurophysiologic tests, and appear long before changes in two-point discrimination (2PD). One-hundred-thirty-two hands of 76 patients diagnosed as having CTS were tested with a vibrometer. Of 113 hands with normal 2PD, the digital vibrogram showed abnormal in 86 cases. Of 19 hands with abnormal 2PD, the digital vibrogram showed abnormal in all but three cases. Twenty-six hands with neurophysiologically normal appearance had abnormal digital vibrogram in 14 cases, while 53 hands neurophysiologically classified as CTS showed abnormal digital vibrogram in 44 cases. It is concluded that the digital vibrogram is a useful tool for early diagnosis of CTS.

Carpal Tunnel Syndrome↗

PubMed1986

Finger peripheral resistance during local cold provocation in vasospastic disease.

Finger systolic blood pressure (FSBP), finger arterial inflow (FAI), finger venous opening pressure (FVOP), and finger peripheral resistance (FPR) were evaluated in 56 workers exposed to chain-saw vibration. Twenty-one of the workers were free from vibration-induced white finger (VWF). In 17 subjects VWF had ceased; 12 of the subjects had active VWF; 6 subjects had Raynaud's disease. The subjects were examined in a supine position under thermoneutral conditions with strain-gauge plethysmography. Cold provocation of the finger caused a significant reduction in FSBP in the groups with Raynaud's disease and active VWF. The finger circulation of the subjects with active VWF and that of those with Raynaud's disease showed a significantly reduced FAI when compared with that of the symptom-free referents. Finger cooling produced a gradual reduction in the FVOP and a significantly increased FPR of the subjects with active VWF and in those with Raynaud's disease. FPR was already increased in the Raynaud's disease group at the beginning of the test, whereas it increased in the VWF group as the temperature fell. The results suggest that in Raynaud's disease the fault is in the level of activity of the sympathetic outflow and in VWF it is peripheral mechanisms controlling the vessel tone.

Cold Temperature↗

PubMed1986

Circulatory reaction to heat and cold in vibration-induced white finger with and without sympathetic blockade--an experimental study.

Central nervous, sympathetic mechanisms and local factors influencing the vascular response to cold in the finger skin were studied with plethysmographic and laser-Doppler methods in a chamber with controlled temperatures from 45 to about 5 degrees C, with and without sympathetic finger blockade. Blood flow and pressure were assessed after finger occlusion, together with finger heating and cooling, in workers with vibration-induced white finger (VWF) and in healthy persons not exposed to cold or vibration. Finger blood flow at vasodilatation, as measured by finger arterial inflow (FAI) after occlusion was smaller in the VWF group than in the reference subjects both with and without anesthesia, and capillary flux in the anesthetized finger tended to be smaller. At vasoconstriction, with or without anesthesia, the VWF subjects had lower FAI values than the referents. The studied flow and pressure variables differed considerably between the groups. The peripheral resistance of the VWF subjects was higher than that of the referents. This difference was the most pronounced after finger anesthesia. A possible pathogenetic mechanism in VWF is an increase in peripheral resistance due to a local defect in the vessels, with subsequent reduction in flow and intramural pressure.

Adult↗

PubMed1986

Impulsiveness of vibration as an additional factor in the hazards associated with hand-arm vibration.

Impulsiveness is defined as the difference between peak and root-mean-square signals. As the difference varies in time, the cumulative distribution function has been used to describe the probability of achieving a certain value of impulsiveness. To make numerical comparison of different vibration signals possible, an impulse index has been selected from the cumulative distribution function. Symptoms of vibration-induced white finger were observed and compared to those expected on the basis of measurements taken according to guidelines of the International Organization for Standardization (ISO). Agreement was found for chain-saw vibration. In the case of pedestal grinding, the ISO draft underestimated the hazardous effects of vibration. Stone workers using pneumatic hammers were exposed to highly impulsive but asymmetrical vibration. The corresponding asymmetry was not, however, observed between the symptoms of the left and right hands, a finding which indicates that coupling between the tool and the hand is important for impulse vibration. The results suggest that the impulse character of vibration increases the risk of vibration-induced pathology. The analysis of high-impulse acceleration peaks obtained by the method presented in this study could provide additional data necessary to improve risk assessment.

Fingers↗

PubMed1986

Cold provocation tests in the evaluation of vibration-induced white finger.

Two types of cold provocation tests, a classical test with immersion of the hand in cold water and the evaluation of finger systolic blood pressure (FSBP) during local cooling, were administered to forest workers. Raynaud's phenomenon in the classical test correlated positively with the number of disabled phalanges, recovery time, and frequency of attacks. It did not correlate with the severity of paresthesia of the hands and arms. Repetition of the test enhanced the number of positive results. A significant reduction in the FSBP was observed in 22 and 25% of the subjects with inactive and active forms of vibration-induced white finger (VWF), respectively. In the same groups of subjects the classical cold provocation test yielded positive results in 7 and 25% of the subjects, respectively. A cold provocation test was found to produce a positive result even some years after the cessation of VWF attacks. The rather low severity of VWF among the examined subjects may explain the lack of positive test results. FSBP measurement was not superior to cold provocation by water immersion, but it is recommended because it is easier to standardize and more convenient for the test subject.

Adult↗

PubMed1986

Pathophysiological and hygienic aspects of hand-arm vibration.

A review of current knowledge on the pathophysiological and hygienic aspects of the hand-arm vibration syndrome is given. Hemodynamic measurements indicate that the primary factor in vibration-induced white finger is an increase in the peripheral resistance of finger circulation that is present after local and general cooling. The reason for this increase is not known, but it is postulated that an excessive affinity of vasoactive substances for the efferent receptors exists, this affinity being potentiated during local cooling of the digits. So far, the hygienic rating of hazardous vibration in individual work phases is of limited value in diagnosing possible cases, but this rating does provide guidelines for general risk assessment. A consideration of several factors, eg, intermittency of the work, duration of daily exposure, impact of vibration, individual physiological responses, climate, etc, might improve the accuracy of the rating, but the influence of these factors on the development of the vibration syndrome is still poorly understood. Of various preventive measures, only those that significantly reduce vibration will be beneficial in the long run.

Fingers↗

PubMed1986

Vibration syndrome among Finnish forest workers, a follow-up from 1972 to 1983.

A longitudinal survey on the prevalence of vibration syndrome among professional forest workers was conducted from 1972 (118 workers) to 1983 (206 workers). The prevalence of vibration-induced white finger (VWF) was 40% among the workers in 1972; it gradually declined to 5% in 1983. Three new workers developed VWF symptoms during the follow-up period. They had only used saws equipped with antivibration handles. The prevalence of VWF has decreased mainly due to the reduction of chain-saw vibration. The prevalence of paresthesias of the hands and arms declined from 78% in 1972 to 37% in 1976, and then increased to 51% in 1983. The recent increase was thought to be due to static muscle load and the ageing of the workers. No correlation was found between the severity of VWF and peripheral nerve symptoms. No significant changes in muscle fatigue occurred during the follow-up period; it was present in about 10-15% of the workers. The forest workers subjectively assessed musculoskeletal load and strain as being more harmful than the symptoms of vibration syndrome. The preventive measures aimed at reducing chain-saw vibration, implemented since 1970, have been beneficial and explain the decreased prevalence of VWF.

Cross-Sectional Studies↗

PubMed1986

Vasomotor oscillation in vibration-induced white finger.

Vasomotor oscillation at different ambient temperatures, with and without anesthesia of the finger nerves, was studied in six persons with vibration-induced white finger (VWF) and in 10 referents. The power spectral density (PSD) of the Fourier transform of the laser-Doppler flowmeter signal from the finger pad vessels was analyzed. In both groups, the PSD of the vasomotor oscillation in the frequency range of 0.05-0.25 Hz was more pronounced in a cold than in a hot environment. Without finger nerve anesthesia, the oscillations of the referents were significantly greater (p less than 0.01) than those of the VWF subjects (PSD -34.4 dB and -41.6 dB, respectively). With anesthesia of the finger vasomotor nerves, the PSD was reduced in both groups. In the anesthetized finger there was no statistically significant group difference. Thus the myogenic component of the vasomotor activity was the same in the referents as in the VWF subjects. The results show that the autonomic neural influence on vasomotor oscillation in skin of the finger pad is weaker in persons with VWF. This weakness may be a sign of peripheral neuropathy, which may lead to a denervation syndrome causing hypersensitivity of the adrenoceptors to cold.

Adult↗

PubMed1986

Clinical aspects of the hand-arm vibration syndrome. A review.

At present it seems likely that the different components of the hand-arm vibration syndrome, eg, vibration-induced white finger (VWF), numbing of the hands and arms, muscular fatigue, and occasionally prevalent bone degeneration, may arise independently, and therefore they should be evaluated separately. Evidence of changes caused in the autonomic nervous functions of the body by local vibration is not conclusive. The vascular history should be confirmed objectively with a cold provocation test under laboratory conditions. In individual diagnostics it is useful to record (with modern plethysmographic techniques) the recovery of digital temperature, digital blood pressure, and flow after local cooling. Vibrotactile perception measurement seems to be suitable for group diagnosis. Much of the diagnostic weight for VWF can be obtained from accurate case histories, although, for early changes, the history may be atypical. The lack of simple objective tests for evaluating the hand-arm vibration syndrome makes it difficult to, eg, confirm the history of its different components objectively and estimate the extent of the disability it causes.

Humans↗

PubMed1985

Combined effects of noise, vibration and visual field stimulation on electrical brain activity and optomotor responses.

Eye movements and electroencephalographs (EEG) were recorded in intact rabbits during an optokinetic test. The animals were exposed to pure tone noise (85 dB at 4000 Hz), impulse noise (159 dB), and vibration directed at the abdomen (amplitude 0.9 mm at frequencies of 40, 80, and 120 Hz). The velocity of optokinetic nystagmus (OKN) significantly increased with these stimuli. The increase seen with vibration was greater than the noise-induced increase. The response was strongest when noise and vibration were combined. The increase in OKN induced by vibration was successive and dependent on frequency. The increase was weakest during exposure to vibration at 40 Hz and strongest at 120 Hz. EEGs of the dorsal hippocampus, amygdaloid complex, midbrain reticular formation, and frontal motor cortex were all activated during noise and vibration exposure, but activation of the hippocampal EEG was the most closely related to the increase in OKN. Combination of the different stimuli indicated that their interaction could not be predicted on the basis of responses to single stimuli, and, in most cases, the result was indifference due to the high alerting effect of vibration alone. The findings can be related to the non-specific dizziness found in aerospace workers exposed to excessive noise and vibration.

Animals↗

PubMed1985

Detection of saccadic eye movements using a non-recursive adaptive digital filter.

Saccadic eye movements provide important information about the neuron system at several levels. In recent years computer analysis of saccades has been adapted for use in clinical work. The most common detection methods do not always function without the user's control and aid. In the present paper a digital filter is described for the detection of saccades. This non-recursive filter unscrambles saccade data which has been collected during the execution of an algorithm. The method is suitable for use with microcomputers. The filter is adaptive. Two concise experiments using the method are described.

Biometry↗

PubMed1985

Vibration-induced neuropathy among forestry workers.

The neurological findings of 217 forestry workers were evaluated during a compulsory annual health examination. Vibration detection thresholds were determined for the left hand and foot. The handgrip forces were measured for both hands. A reduction in the vibration detection threshold or handgrip force was not associated with clinical neuropathy. Polyneuropathy was found in 4% of the lumberjacks whereas neuropathy restricted to the arms was found in 7.5% of the lumberjacks. The neuropathic findings were not linked with alcohol consumption but were associated with a history of numbness in the hands and diminished muscle force. The findings support the concept that local vibration can cause neuropathy in the arms, but the mechanism of vibration-induced neuropathy still remains uncertain.

Adult↗

PubMed1985

The effects of TTS-scopolamine, dimenhydrinate, lidocaine, and tocainide on motion sickness, vertigo, and nystagmus.

The effects of TTS-scopolamine, dimenhydrinate, lidocaine, and tocainide on motion sickness and vertigo and on caloric and postrotatory nystagmus were evaluated in healthy volunteers. TTS-scopolamine was administered transdermally (delivering approximately 10 micrograms X h-1 scopolamine base) and 100 mg dimenhydrinate orally. Lidocaine and tocainide were administered intravenously (average plasma concentration of lidocaine 6 mol X L-1 and of tocainide 20 mol X L-1). TTS-scopolamine and dimenhydrinate significantly reduced vertigo induced by calorization of the ears, nausea provoked with Coriolis maneuvre, and nystagmus in caloric and rotatory tests. During treatment with lidocaine and tocainide no alleviation of vertigo and nausea was observed. Caloric nystagmus was reduced but rotation induced nystagmus was virtually unchanged. Presumably the motion sickness drugs act at the brain stem where TTS-scopolamine and dimenhydrinate have their target cells in the vestibular nuclei. Furthermore, the alleviation of motion sickness was linked to a decline of nystagmus. Lidocaine and tocainide, the action of which in vertigo and nausea in patients is proposed to be on the vestibular end organs and the supratentorial brain structures, consistently failed to alleviate motion sickness.

Administration, Topical↗

PubMed1984

A model of visual-vestibular interaction in cerebellar disorders.

The number of saccades, vestibular gain and visual suppression as a function of smooth pursuit gain were determined in 10 cerebellar cases. Visual suppression increased and the number of saccades decreased with increasing smooth pursuit gain while a high vestibular gain was found in most cases but without relation to the gain of smooth pursuit. An eye-motor model is presented according to which all findings could be related to a disturbance of proper cerebellar processing of optic impulses and of impulses to the vestibular nuclei in the paramedian reticular formation.

Cerebellar Diseases↗