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Biomedical subjects

I Pyykkö

Publications and source records attributed to I Pyykkö.

At least 145 records · Page 8Linked to original sources
PubMed1990

Vibration stress and the autonomic nervous system.

Raynaud's phenomenon has been considered to be due to activation of the central sympathetic vasoconstrictor reflex, and may represent part of a larger dysfunction of higher autonomic centers. Symptoms, such as sweating disturbances, orthostatic hypotension, insomnia and impotence have been reported to be more common among vibration exposed workers. We studied 217 male forest workers and selected samples of this population for electromyographic (N = 80), autonomic nervous system function, controlled breathing, tilting bed and valsalva manoeuvre (N = 88) tests, and a full clinical neurological examination. Mean alcohol consumption was estimated to be 3.0 kg absolute alcohol/year. The total mean vibration exposure time was 14,100 hours. The prevalence of Raynaud's phenomenon was 5%. The variations in heart rate (HRV) at rest and during deep breathing were observed. The traditional indexes of HRV (CV, CVS, MEAN) were computerized and calculated. There was a significant difference (p less than 0.001) between the HRV indexes during the deep breathing test in those with the shortest and the longest exposure to vibration. The values of HRV indexes were age dependent; and in multiple regression analysis, the total exposure time to vibration had an independent negative association to HRV. Also association of sensory neural hearing loss to Raynaud's phenomenon among vibration exposed workers indicates that there is an involvement of the central nervous system in the pathogenesis of vibration syndrome. The question, does vibration cause permanent changes in autonomic centers of the brain or do these centers only mediate vibration stress to end organs, remains unsettled.

Adult↗
PubMed1989

A microcomputer system for clinical signal analysis of vestibular laboratory.

A vestibular laboratory system was implemented for clinical testing and medical examination of patients with balance disorders. Programs for analysis of postural control and eye movements were made for a microcomputer. The microcomputer system can be used by a nurse without technical education. The system has now been used for two years at the laboratory.

Eye Movements↗
PubMed1989

Risk factors in the genesis of sensorineural hearing loss in Finnish forestry workers.

A detailed analysis of risk factors for the development of sensorineural hearing loss (SNHL) was carried out in 199 forest workers. The hearing threshold of both ears at 4000 Hz was measured, and the effect of age, exposure to noise, blood pressure, presence of vibration induced white finger (VWF), tobacco smoking, plasma LDL-cholesterol concentration, and consumption of drugs were evaluated by multiple linear regression analysis. Aging was the major risk factor, followed by exposure to occupational noise and the presence of VWF. Plasma LDL-cholesterol concentration and the use of antihypertensive drugs also correlated significantly with SNHL. These main factors were able to explain about 28% of the SNHL variance. Additional factors in the analysis, including smoking, systolic and diastolic blood pressure, and consumption of salicylates did not significantly contribute to the genesis of SNHL.

Age Factors↗
PubMed1989

Hierarchy of different muscles in postural control.

The effects of muscle spindle activation on different postural muscles were examined in eight volunteers, using a force platform technique. Small electrical vibrators were placed symmetrically over the muscles concerned and the effects of vibration frequencies of 20, 40, 60, 80 and 100 Hz were studied at a constant amplitude of 0.4 mm (peak-to-peak). Significant responses were observed in most muscles. The responses were observed (in maximum response order) from: the neck, triceps surae, gluteus, abdominal, hamstring, quadriceps, lumbar and tibialis anterior muscles. The response direction did not follow anatomical gonistic vis-à-vis antagonistic distribution of the muscles studied, indicating that it is the functional properties of the muscles that determine posture stabilization. The large inter-individual variability in responses, but the consistency in intra-individual muscle responses indicates that the subjects used afferent muscles to a varying extent in postural control. The vibration-induced activation of the muscles was presumably derived by activation of stretch-sensitive secondary endings of muscle spindles that control postural stability.

Adult↗
PubMed1989

Does impulse noise induce vestibular disturbances?

The effect of impulse noise on postural stability was evaluated in 54 subjects from the Finnish army, who were suffering from acute hearing loss caused by exposure to firearms noise. For referents we used 20 non-exposed army recruits and 39 civilian volunteers. The effects of vision, pressoreceptor function and proprioception were stepwise excluded or altered, leaving mainly the vestibular guidance of postural control intact. Since the postural perturbation was fairly smooth during these instances we assume that the condition evaluates mainly the function of the otolith organs in guiding stance. We found no difference in any of the test conditions used, between normal controls, army controls and impulse noise exposed subjects. Furthermore, there was no dose response with body sway and severity of hearing loss. The results indicate that impulse noise may not be the cause of significant functional changes in the vestibular system that can account for noise-induced postural instability.

Adult↗
PubMed1989

Vestibulo-ocular and vestibulo-spinal reflexes in evaluation of vestibular lesions.

In order to evaluate to what extent different diseases causing vertigo can be detected by studying vestibulo-spinal and vestibulo-ocular reflexes, 146 patients were examined. The diagnosis classes were: periodical attacks, position induced attacks, vestibular neuronitis, brain concussion, cerebrovascular disorders and acoustic neurinoma. Dynamic posturography was performed on all the patients, standard bithermal caloric test on 129 and voluntary saccades on 127 patients. The proportion of pathological test results in posturography exceeded that in the caloric test in all but one diagnosis class. In vestibular neuronitis the amount of abnormal test results was low in posturography, probably due to vestibular compensation. Posturography tested with eyes open and with 80 Hz vibration revealed disturbances in equilibrium the most sensitively.

Caloric Tests↗
PubMed1989

Reduction of the time constant in the VOR as a protective mechanism in acute vestibular lesions.

Fourteen patients with vestibular neuritis were examined at onset of symptoms and after one year. Postrotatory time constant and gain in the vestibulo-ocular reflex (VOR) were measured after rotation with a velocity step of 150 deg/s. There was no significant difference in gain towards the healthy side at onset of the disease compared to recordings after one year. The time constant towards the healthy side was significantly shorter at onset compared to measurements after one year. The results reflect the loss of unilateral vestibular function on the velocity storage mechanism, both in the acute situation and after compensation. The findings indicate that reduction of the time constant in the VOR is not only due to unilaterally vestibular impairment but it is also an effect of the generally reduced activity in the vestibular system after a lesion and may act as protective mechanism in acute vertigo.

Acute Disease↗
PubMed1988

Hippocampal rhythmic slow activity in rat lines selected for differences in ethanol-induced motor impairment.

Hippocampal rhythmic slow activity (RSA) was recorded during rotation and vibration stimulation after saline and ethanol (2 g/kg) administration in restrained alcohol-sensitive (ANT) and alcohol-insensitive (AT) rats implanted with chronic bipolar electrodes in the dorsal hippocampus. The saline-treated ANT rats had more high-frequency RSA than the AT rats, especially during the rotational stimulation of the optovestibular mechanisms. The difference was not found during ethanol sessions. Plasma corticosterone levels were significantly higher in the AT than the ANT rats after the recording sessions. This first electrophysiological demonstration of an alcohol-sensitivity difference in the brain between these rat lines is discussed in relation to behavioral tilting plane test used in the development of the lines, to the different innate responses of the lines to acute stress, and to the plausible line differences in brain GABAergic and serotonergic mechanisms that are known to modulate hippocampal EEG in rodents.

Animals↗
PubMed1988

Forestry workers exposed to vibration: a neurological study.

Neurological findings were examined in 186 forestry workers with a mean exposure to chain saw vibration of 16.6 hours. The prevalence of active vibration induced white fingers was 5%, parethaesias of the hands 53%, and muscle weakness 13%. Clinical polyneuropathy was observed in 16 forestry workers in the hands (7.5%) which did not correlate with alcohol consumption. Seventy nine forestry workers of the total population were selected for electromyographic examination. Generalised EMG based polyneuropathy in the hands was observed in only two of the 79 forestry workers (2.5%). The carpal tunnel syndrome was found in 20 of the 79 forestry workers (26%). Headache and vertigo were not linked with exposure to vibration in forestry and a significant part of the numbness reported may be due to the carpal tunnel syndrome. Sensorimotor polyneuropathy is rare among forestry workers. The rise in the vibration detection thresholds was linked to the carpal tunnel syndrome.

Adult↗
PubMed1988

The Otorhinolaryngology Department in Helsinki: organization and otologic research.

The organization and the otologic research in the Otorhinolaryngology Department of the University of Helsinki are described. The department has 4 surgical wards, each with 22 beds, and a new surgical wing with 6 full-sized operating rooms. The ear research is centered on middle ear histopathology and immunology, focusing especially on secretory and chronic otitis media. There is an audiological and vestibular unit, the latter is expanding rapidly. Acoustic neuroma surgery is performed as team work with a neurosurgeon. The department takes part in a cochlear implant and Audiant prosthesis program.

Audiology↗
PubMed1988

Computerized posturography, a development of the measuring system.

A computerized posturography system is composed of a custom made strain gauge force platform and it utilizes commercially available amplifiers. The body sway response signals are digitized for the calculation of the following parameters by a computer: average velocity of body sway, mean value for fore-aft and lateral body sway, and maximal amplitude of body sway. Calf muscles were exposed to vibration to disturb the postural control. The program contains appropriate filters to remove transient and quantification noise.

Humans↗
PubMed1988

Evaluation of factors affecting sensory neural hearing loss.

A detailed analysis of risk factors in the development of sensory-neural hearing loss (SNHL) was carried out in 199 forest workers. The mean hearing threshold of both ears at 4000 Hz was measured and the effect of age, exposure, blood pressure, presence of vibration induced white finger (VWF), tobacco smoking and plasma lipid concentrations on SNHL were evaluated by multiple linear regression analysis. A part of aging the major risk factors were presence of VWF, elevation of LDL-cholesterol level and usage of antihypertensive agents. Additional factors in the analysis, e.g. smoking and diastolic and systolic blood pressure did not significantly contribute to the genesis of SNHL.

Age Factors↗