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PubMed2002

Measurement of static and vibration-induced phase noise in UHF thin-film resonator (TFR) filters.

Measurements of the static phase noise and vibration sensitivity of thin-film resonator (TFR) filters operating at 640 and 2110 MHz have been made. They show that the short-term frequency instability of the filters is small compared with that induced in the oscillator signal by the sustaining stage amplifier PM (phase modulation) noise. In-oscillator measurement of filter performance under vibration indicates that fractional frequency vibration sensitivities (deltafo/fo) are on the order of several parts in 10(-9)/g. Because the percentage bandwidth and order (number of poles) of the filters was fairly constant, so was the product of the center frequency and group delay. Thus, the fractional frequency vibration sensitivity of the filters can be expressed alternatively as carrier signal phase sensitivity to vibration. The tau-omega0 product for the filters that were tested was on the order of 300 rad, so that the equivalent phase sensitivity to vibration was approximately 1 microrad/g.

Equipment Failure Analysis↗
PubMed2007

Numerical analysis of strongly nonlinear extensional vibrations in elastic rods.

In the framework of transduction, nondestructive testing, and nonlinear acoustic characterization, this article presents the analysis of strongly nonlinear vibrations by means of an original numerical algorithm. In acoustic and transducer applications in extreme working conditions, such as the ones induced by the generation of high-power ultrasound, the analysis of nonlinear ultrasonic vibrations is fundamental. Also, the excitation and analysis of nonlinear vibrations is an emergent technique in nonlinear characterization for damage detection. A third-order evolution equation is derived and numerically solved for extensional waves in isotropic dissipative media. A nine-constant theory of elasticity for isotropic solids is constructed, and the nonlinearity parameters corresponding to extensional waves are proposed. The nonlinear differential equation is solved by using a new numerical algorithm working in the time domain. The finite-difference numerical method proposed is implicit and only requires the solution of a linear set of equations at each time step. The model allows the analysis of strongly nonlinear, one-dimensional vibrations and can be used for prediction as well as characterization. Vibration waveforms are calculated at different points, and results are compared for different excitation levels and boundary conditions. Amplitude distributions along the rod axis for every harmonic component also are evaluated. Special attention is given to the study of high-amplitude damping of vibrations by means of several simulations. Simulations are performed for amplitudes ranging from linear to nonlinear and weak shock.

Acoustics↗
PubMed1995

A 3-D finite element analysis of the natural frequencies of vibration of a stapes prosthesis replacement reconstruction of the middle ear.

In this work, the natural frequencies of vibration of two different stapes prosthesis replacement reconstructions have been analysed using the finite element method. Prosthesis 1 was constructed of fine stainless steel wire and a Teflon base, while prosthesis 2 was made entirely of Teflon. The results have indicated that generally, the first natural frequency of vibration falls as the prostheses become larger and more bulky. However, the fall in the first natural for prosthesis 1 was modest when compared with that of the isolated tympanic membrane. An important variable influencing frequencies and mode of vibration of the reconstruction was the tightness of fit of the prostheses within the remaining ossicular chain. The tightness of fit in this work was modelled as a range of spring constants applied at the stapes pseudo footplate, together with a series of joint elements at the incus tip/prosthesis head for the Teflon implant. When these spring constraints were below approximately 10 N/mm, the reconstruction exhibited normal mode 1 vibration behaviour, but at larger spring values, an abnormal mode 1 became established resembling the normal mode 2 vibration characteristics. The formation of new geometries and surfaces following reconstruction, introduces new constraints between umbo and stapes footplate particularly at the natural/artificial interfaces. These unnatural constraints may inhibit and modify the natural movements normally occurring at the stapes footplate leading to abnormal modes of vibration.

Ear Ossicles↗
PubMed2001

Muscle vibration sustains motor unit firing rate during submaximal isometric fatigue in humans.

1. In keeping with the 'muscular wisdom hypothesis', many studies have documented that the firing rate of the majority of motor units decreased during fatiguing isometric contractions. The present study investigated whether the application of periodic muscle vibration, which strongly activates muscle spindles, would alter the modulation of motor unit firing rate during submaximal fatiguing isometric contractions. 2. Thirty-three motor units from the lateral head of the triceps brachii muscle were recorded from 10 subjects during a sustained isometric 20 % maximal voluntary contraction (MVC) of the elbow extensors. Vibration was interposed on the contraction for 2 s every 10 s. Twenty-two motor units were recorded from the beginning of the fatigue task. The discharge rate of the majority of motor units remained constant (12/22) or increased (4/22) with fatigue. Six motor units demonstrated a reduction in discharge rate that later returned toward initial values; these motor units had higher initial discharge rates than the other 16 motor units. 3. In a second series of experiments, four subjects held a sustained isometric 20 % MVC for 2 min and then vibration was applied as above for the remainder of the contraction. In this case, motor units initially demonstrated a decrease in firing rate that increased after the vibration was applied. Thus muscle spindle disfacilitation of the motoneurone pool may be associated with the decline of motor unit discharge rate observed during the first 2 min of the contraction. 4. In a third set of experiments, seven subjects performed the main experiment on one occasion and repeated the fatigue task without vibration on a second occasion. Neither the endurance time of the fatiguing contraction nor the MVC torque following fatigue was affected by the application of vibration. This finding calls into question the applicability of the muscular wisdom hypothesis to submaximal contractions.

Adult↗
PubMed1996

Reduction of Saccharomyces cell adhesion by liquid mechanical vibration.

The effect of liquid mechanical vibration on the adhesion of Saccharomyces cerevisiae cells to the internal glass surface of a pipette was studied using a 25 Hz vibration source. The maximum vibration amplitude was 1.06 mm (peak to peak) along the pipette direction. Relative movements between the pipette and yeast suspension in it were produced by vibration and reduced the cell adhesion. The reduction in adhesion was affected by both vibration amplitude and suspension pH. Analysis showed that in routine cell counts, cell adhesion to the pipette wall was a significant error source. The construction of a vibration device for routine cell count work appears feasible.

Cell Adhesion↗
PubMed1997

Vibration assessment for thrombus formation in the centrifugal pump.

To clarify the correlation of vibration and thrombus formation inside a rotary blood pump, 40 preliminary vibration studies were performed on pivot bearing centrifugal pumps. No such studies were found in the literature. The primary data acquisition equipment included an accelerometer (Isotron PE accelerometer, ENDEVCO, San Juan Capistrano, CA, U.S.A.), digitizing oscilloscope (TDS 420, Tektronix Inc., Pittsfield, MA, U.S.A.), and pivot bearing centrifugal pumps. The pump impeller was coupled magnetically to the driver magnet. The accelerometer was mounted on the top of the pump casing to sense radial and axial accelerations. To simulate the 3 common areas of thrombus formation, a piece of silicone rubber was attached to each of the following 3 locations as described: a circular shape on the center bottom of the impeller (CI), an eccentric shape on the bottom of the impeller (EI), and a circular shape on the center bottom casing (CC). A fast Fourier transform (FFT) method at 5 L/min against 100 mm Hg, with a pump rotating speed of 1,600 rpm was used. The frequency response of the vibration sensors used spans of 40 Hz to 2 kHz. The frequency domain was already integrated into the oscilloscope, allowing for comparison of the vibration results. The area of frequency domain at a radial direction was 206 +/- 12.7 mVHz in CI, 239.5 +/- 12.1 mVHz in EI, 365 +/- 12.9 mVHz in CC, and 163 +/- 7.9 mVHz in the control (control vs. CI p = 0.07, control vs. EI p < 0.001, control vs. CC p < 0.001, EI vs. CC p < 0.001, CI vs. CC p < 0.001). Three types of imitation thrombus formations were roughly distinguishable. These results suggested the possibility of detecting thrombus formation using vibration signals, and these studies revealed the usefulness of vibration monitoring to detect thrombus formation in a centrifugal pump.

Analysis of Variance↗
PubMed1977

Oxygen consumption and contractile force during vibrations of cat soleus muscle.

The influence of longitudinal vibrations (50 Hz, 0.4 mm) on isometric twitch force development (4 Hz), blood flow and oxygen consumption was studied in the acutely denervated soleus muscle of the anesthetized cat. It was found that the sinusoidal vibrations reduced the twitch amplitude by 60 per cent whereas oxygen consumption and blood flow were lowered by 15 per cent only. Similar reduction in twitch force was also obtained by lowering the nerve stimulation intensity (4 Hz). This was associated with a diminution in oxygen consumption, the degree of which was linearly related to the attenuation of active force, i.e. the number of activated motor units. The results are in agreement with previous observations as to the mechanical effect of vibrations on active force in smooth and striated muscle. They demonstrate that vibrations prevent the contractile response with maintained high oxygen consumption which adds further support to the hypothesis forwarded by Joyce et al. (1969) that vibrations cause increased rate of detachment of actin-myosin cross-links. In addition it appears possible that vibrations to some extent prevent formation of such cross-links.

Animals↗
PubMed1984

Relationship between sine random vibrations, resonance and drug content uniformity.

The effect of sine random vibrations on the segregation tendency of 3 ordered power mixes was studied. Ordered mixes containing either Emdex, Dipac or recrystallized lactose carrier particles mixed with 0.5% fine-particle potassium chloride were prepared. It was found that the coefficients of variation of drug content in samples removed from the ordered mixes following random vibration were, in general, lower than those derived from vibration at equivalent single frequencies. Ordered mixes vibrated at low centre-frequencies were found to be most prone to slight demixing and under these conditions, a vibration bandwidth of 30 Hz produced more de-mixing than a 10 Hz bandwidth. Most ordered mixes were considered to be segregation free following random vibration.

Drug Compounding↗
PubMed1973

Evidence from the use of vibration during procaine nerve block that the spindle group II fibres contribute excitation to the tonic stretch reflex of the decerebrate cat.

1. Experiments have been performed to test the hypothesis that the group II fibres from the secondary endings of the muscle spindle provide an excitatory contribution to the tonic stretch reflex of the decerebrate cat. They have consisted of studying the effect of fusimotor paralysis by procaine, applied to the muscle nerve, on the reflex response to the combined stimuli of stretch (5-9 mm at 5 mm/sec) and of high-frequency vibration (100-150 Hz, 150 mum).2. The reflex response to the combined stimuli was found to be paralysed in two distinct stages which paralleled those of the ordinary stretch reflex described earlier. The two phases of paralysis may be attributed to an early paralysis of the gamma efferents followed by a later paralysis of the Ia afferents and alpha motor fibres. However, the Ia discharges elicited by the combined stimuli, unlike those elicited by simple stretch, should have remained unchanged on gamma efferent paralysis since the Ia firing frequency may be presumed to have been clamped at the vibration frequency by the occurrence of one-to-one ;driving'. The early reduction of the response to the combined stimuli may thus be attributed to the removal of a stretchevoked autogenetic excitatory input other than that long known to be provided by the Ia pathway. This supports the view that the spindle group II fibres have such an action, since their firing will be appropriately reduced on gamma efferent paralysis by removal of their pre-existing fusimotor bias; there is no evidence for the existence of any other group of fibres with the right properties.3. Recording of compound action potentials and of single units confirmed the great sensitivity of the gamma efferents to procaine but showed that the group II fibres were nearly as resistant as the Ia fibres and alpha motor fibres.4. The reliability of one-to-one driving of the Ia discharges by the vibration was tested in control experiments in which the reflex was elicited by an asymmetrical vibratory waveform with a rapid rising phase (1.5 or 1.9 msec at 140 Hz) and a slower falling phase. Recordings from single units showed that the use of this wave form greatly diminished any tendency to double driving (2 spikes/cycle of vibration) during the dynamic phase of stretch and never elicited it during the static phase of stretch when the reflex measurements were made. These ;pulsed' vibrations elicited reflex contractions which were of the same general size and which were paralysed in the same two phases by procaine as those elicited by sinusoidal vibrations. This eliminates the possibility that the early phase of paralysis might have been due to conversion of the pattern of Ia firing from double to single driving on gamma efferent paralysis.5. Wedensky inhibition of the afferent fibres could not be held responsible for the early phase of paralysis.6. The results are taken to strengthen the hypothesis that the spindle group II fibres contribute excitation rather than inhibition to the stretch reflex. The particular support derived from the present experiments is that all measurements of the size of the reflex at various times were made with the muscle at the same length so that the findings cannot be attributed to the tension-length properties of muscle. The detailed mechanism of the excitation, however, remains to be established and certain of the present findings suggest that it may not be a direct one.

Action Potentials↗
PubMed1987

Phase coherence in vibration-induced responses of tactile fibres associated with Pacinian corpuscle receptors in the cat.

1. In pentobarbitone-anaesthetized cats, responses were recorded in peripheral nerves or cervical dorsal columns from sensory fibres associated with Pacinian corpuscle (P.c.) receptors in the forelimb footpads. Factors affecting the phase of response to cutaneous vibration in individual P.c. fibres, and the extent of phase coherence in the responses of different P.c. fibres were examined when sinusoidal vibratory stimuli at 100-400 Hz were delivered using a 1 mm diameter probe. 2. Increases in vibration amplitude from the absolute to the 1:1 threshold for the P.c. fibre led to phase advances in the response, often of about 60 deg, in over 85% of fibres tested at 200 and 300 Hz, but further increases had little effect. 3. Variations in stimulus position within the receptive field led to unpredictable changes in the response phase that ranged from minimal change to shifts of 180 deg. As the response phase was unrelated to the distance from the point of peak sensitivity it is likely that at high vibration frequencies (greater than or equal to 100 Hz) the recruited population of P.c. fibres will respond over the whole range of phase angles. 4. The calculated phase of spike initiation in different pairs of P.c. fibres that shared coincident points of best sensitivity on the skin ranged from near synchrony to maximum asynchrony indicating that there is little phase coherence even in the subpopulation of somatotopically related P.c. fibres recruited by high-frequency cutaneous vibration. 5. Paired recordings from P.c. fibres within the cervical dorsal columns revealed a broad range of phase discrepancies in the responses of P.c. fibres to vibration at 200 and 300 Hz. 6. Several hypotheses are considered to explain the known presence of phase-locked responses to high-frequency (greater than or equal to 100 Hz) vibration in the central neurones of dorsal column nuclei.

Action Potentials↗
PubMed1987

Temporal patterning in the responses of gracile and cuneate neurones in the cat to cutaneous vibration.

1. Recordings were made in decerebrate cats from gracile and cuneate neurones responding to vibration-induced inputs from Pacinian corpuscle (P.c.) receptors of the hind-limb and forelimb footpads. The two groups of neurones were compared, in particular for their capacities for responding to cutaneous vibration with phase-locked impulse patterns. 2. In both nuclei the P.c. neurones were most sensitive to vibration in the range 80 to greater than 600 Hz. Stimulus-response relations were similar for the two groups, as were measures derived from these relations such as response levels, absolute thresholds and the dynamic range (defined as the vibration amplitude range over which responses were graded). 3. At frequencies up to 300-400 Hz, responses for some neurones in both nuclei remained well phase locked to the vibration; however, quantitative analysis using a factorial analysis of variance indicated that the phase locking was poorer in gracile than cuneate neurones. 4. In both nuclei there was marked variability from neurone to neurone in measures of phase locking which may reflect variations in the extent of convergence of P.c. fibres upon different target neurones. For neurones in either nucleus that had comparatively tight phase locking of responses to vibration it is proposed that their output is functionally dominated by one or a few of their convergent P.c. input fibres.

Action Potentials↗
PubMed1987

Effects of ischaemia upon reflex electromyographic responses evoked by stretch and vibration in human wrist flexor muscles.

1. The reflex electromyographic responses evoked in a wrist flexor muscle, flexor carpi radialis (f.c.r.), by forcible extension of the wrist ('stretch') and by vibration of the flexor tendon have been studied in normal subjects. Reflexes were elicited during the maintenance of a low level of voluntary flexor contraction (5% maximum). Stretch regularly produced a relatively prolonged (ca. 100 ms duration) increase in e.m.g. activity which was usually divisible into short-latency (ca. 25 ms, M1) and long-latency (ca. 50 ms, M2) peaks. Vibration produced a single, phasic peak, at short latency, with no sign of an accompanying long-latency wave comparable to the M2 stretch response. 2. Ischaemia was induced by inflation of a blood-pressure cuff around the upper arm and its effects upon the reflex patterns were studied. During ischaemia M1 stretch responses showed a more rapid and pronounced decline than did M2 responses and were abolished before voluntary power was appreciably affected. Vibration-evoked short-latency peaks changed in an essentially parallel manner to M1 stretch reflexes. During recovery from ischaemia M2 reflexes were restored before short-latency responses. 3. The patterns of reflex reductions in e.m.g. upon withdrawal of stimulation were also studied. Such troughs in activity, under non-ischaemic conditions, regularly commenced at short latency and were of relatively small amplitude. The records of several of the subjects, and particularly ones obtained during ischaemia, suggested that release of stretch (with concomitant stretch of antagonists) could elicit an additive, long-latency decline in e.m.g. The existence of any such separate, delayed component was never observed upon termination of vibration. 4. Measurements of changes in the latencies and durations of reflex components, accompanying the progression of ischaemia, indicated that depression of early reflex activity resulted in part from increases in the latencies of these initial peaks but predominantly reflected simultaneous and separate reductions in their amplitudes. 5. The generation of short-latency reflexes by stretch and vibration, both of which stimuli powerfully excite muscle spindle primary endings, and the marked susceptibility of these responses to ischaemia supports their being mediated by group Ia afferents. The contrasting behaviour of M2 stretch responses, both regarding their absence with vibration and their resistance to ischaemia, suggests that they depend crucially upon a separate group of reflex afferents.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed2004

Biodynamic response of human fingers in a power grip subjected to a random vibration.

BACKGROUND: Knowledge of the biodynamic response (BR) of the human hand-arm system is an important part of the foundation for the measurement and assessment of hand-transmitted vibration exposure. This study investigated the BR of human fingers in a power grip subjected to a random vibration. METHOD: Ten male subjects were used in the experiment. Each subject applied three coupling actions to a simulated tool handle at three different finger grip force levels. RESULTS AND CONCLUSIONS: The BR is practically independent of the hand coupling actions for frequencies at or above 100 Hz. Above 50 Hz, the BR is correlated to finger and hand sizes. Increasing the finger coupling force significantly increases the BR. Therefore, hand forces should be measured and used when assessing hand-transmitted vibration exposure. The results also show that under a constant-velocity vibration, the finger vibration power absorption at frequencies above 200 Hz is approximately twice that at frequencies below 100 Hz. This suggests that the frequency weighting specified in the current ISO 5349-1 (2001) may underestimate the high frequency effect on vibration-induced finger disorders.

Algorithms↗
PubMed1988

Evidence for different types of mechanoreceptors from measurements of the psychophysical threshold for vibrations under different stimulation conditions.

The shape of the psychophysical frequency threshold curve for vibrations presented to the skin in the frequency region 5-1000 Hz is strongly dependent on the static force that the vibrator exerts on the skin and on whether there is a rigid surround around the vibrating contactor (presence of contrast). Where there is no rigid surround, an increase in static force reduces the threshold in the high-frequency region and increases it at low frequencies. When the static forces are sufficiently large, the thresholds reach a minimum value above 30 Hz and a maximum one below 30 Hz, this being the crossover frequency. Under these conditions in the frequency region around 200 Hz, where the threshold is determined by the Pacini receptor system, the vibration sensitivities of finger pad and thenar eminence (glabrous skin) are equal, while the value for the inner side of the forearm (hairy skin) is 12 dB higher. However, when a rigid surround is used, the threshold increases above 30 Hz and decreases below 30 Hz. The latter increase in sensitivity, which is introduced by the presence of contrast cues, amounts to about 20 dB and is sharply tuned at 18 Hz for the glabrous skin of the finger. It is argued that in this case the threshold is determined by the Meissner receptor system. This increase in sensitivity is less pronounced (about 10 dB) and less sharply tuned for the other sites. Finally, when the contact of the vibrating surface to the skin is at a minimum, the vibration threshold has the same displacement value (about 3 microns) over the whole frequency region independent of the site of stimulation and whether or not a rigid surround is present.

Humans↗
PubMed1972

Tonic vibration reflex in spasticity, Parkinson's disease, and normal subjects.

The tonic vibration reflex (TVR) has been studied in the quadriceps and triceps surae muscles of 34 spastic, 15 Parkinsonism, and 10 normal subjects. The TVR of spasticity develops rapidly, reaching a plateau level within 2-4 sec of the onset of vibration. The tonic contraction was often preceded by a phasic spike which appeared to be a vibration-induced equivalent of the tendon jerk. The initial phasic spike was usually followed by a silent period, and induced clonus in some patients. No correlation was found between the shape of the TVR and the site of the lesion in the central nervous system. The TVR of normal subjects and patients with Parkinsonism developed slowly, starting some seconds after the onset of vibration, and reaching a plateau level in 20-60 sec. A phasic spike was recorded occasionally in these subjects, but the subsequent tonic contraction followed the usual time course. Muscle stretch increased the quadriceps TVR of all subjects, including those with spasticity in whom the quadriceps stretch reflex decreased with increasing stretch. It is suggested that this difference between the tonic vibration reflex and the tonic stretch reflex arises from the selective activation of spindle primary endings by vibration, while both the primary and the secondary endings are responsive to muscle stretch. The TVR could be potentiated by reinforcement in some subjects. Potentiation outlasted the reinforcing manoeuvre, and was most apparent at short muscle lengths. As muscle stretch increased, thus producing a larger TVR, the degree of potentiation decreased. It is therefore suggested that the effects of reinforcement result at least partially from the activation of the fusimotor system. Since reinforcement potentiated the TVR of patients with spinal spasticity in whom a prominent clasp-knife phenomenon could be demonstrated, it is suggested that the effects of reinforcement are mediated by a descending pathway that traverses the anterior quadrant of the spinal cord.

Electromyography↗
PubMed1976

Discharge pattern of single motor units in the tonic vibration reflex of human triceps surae.

Using a single fibre EMG electrode the firing pattern of 46 motor units in the triceps surae has been studied during vibration of the Achilles tendon at frequencies of 25--200 Hz. Potentials activated in the tonic vibration reflex (TVR) were phase-locked to the vibration cycle but tended to become somewhat less so with continued vibration. The firing pattern of voluntarily activated motor units became locked to the waveform by the application of the vibrator. The discharges of 21 motor units were studied during low threshold (sub-M wave) tetanic stimulation of the tibial nerve at 25--100 Hz. No evidence was found of synchronization of potentials activated in the resulting tonic contraction. During weak voluntary contractions, stimulation also failed to regularize voluntarily activated motor units. The findings can be reconciled by postulating that, in normal man, vibration activates monosynaptic and polysynaptic pathways, the latter circuit being adequate to generate reflex contraction, while the former merely affects the temporal patterning of the motor outflow.

Action Potentials↗
PubMed2003

The effect of fatigue on abnormal vibration induced illusion of movement in idiopathic focal dystonia.

BACKGROUND: Perception of vibration induced illusionary movement (VIIM) is subnormal in dystonic patients, suggesting abnormal sensory-motor processing in patients with idiopathic focal dystonia. OBJECTIVE: To examine the effects of fatigue on VIIM in patients with idiopathic torticollis. METHODS: An illusionary sensation of arm extension was evoked by an 80 Hz transcutaneous vibratory stimulus applied to the biceps brachii tendon while the arm was restrained. Blindfolded patients attempted to copy the perceived movement of the vibrated arm with the opposite (tracking) arm and the change in elbow angle of the tracking arm was quantified over 45 seconds. The tasks were repeated following volitional fatigue of the vibrated arm. RESULTS: The subnormal perception of VIIM perceived by patients with torticollis, occurring bilaterally and remote from the location of dystonic symptoms, was corrected by fatigue of the vibrated arm compared with prefatigue values (mean (SEM): 19.04 degrees (1.76) degrees v 24.25 degrees (2.41 degrees ); p = 0.01, paired t test). CONCLUSIONS: While a combination of central or peripheral factors may be involved in the correction of abnormal perception of the vibration induced illusion of movement in dystonia, subnormal elasticity of muscle spindles could be implicated in the impaired perception of vibration induced illusionary movement and may predispose an individual towards developing idiopathic focal dystonia.

Adult↗
PubMed1988

Vibration elicited vasoconstrictor reflex in Raynaud's phenomena.

The fingers of seven women with primary Raynaud's phenomenon (PRP), 10 female controls, seven men with vibration induced white finger (VWF), and eight male controls were exposed to vibration and the relative change in finger capillary blood flow was measured by an atraumatic 133xenon washout technique without and during proximal nervous blockade. All four groups showed a vasoconstriction to vibration (p less than or equal to 0.02) which was abolished by proximal nervous blockade. Women with PRP had an augmented response to vibration (p less than 0.01) and men with VWF had a normal response (p greater than 0.10) when compared with that of their respective sex matched controls. The results show the existence of a vibration elicited central sympathetic vasoconstrictor reflex in the normal finger and in fingers affected by PRP and VWF. The results indicate a hyperreactivity of the central sympathetic nervous system in PRP and VWF and a dysfunction of the peripheral sensory nerve fibres in subjects with VWF. The described vibration test may be of guidance in the differentiation of PRP from VWF.

Adult↗