Acceleration of fetal head induced by vibration of maternal abdominal wall in sheep.

OBJECTIVE: The human body is often exposed to significant vibration stress in the workplace, at home, and during recreational activities. The current study was designed to evaluate whether low- to midfrequency vibrations present at the extraabdominal wall would be attenuated across this wall and what the levels of exposure would be once these vibrations reached the fetal head. STUDY DESIGN: Four pregnant sheep were instrumented with acceleration transducers to obtain acceleration levels at the extraabdominal and intraabdominal walls and at the fetal head. Sine-wave vibration stimulation was applied over a frequency range of 3 to 150 Hz at a constant acceleration level of 2.5 m/sec2 (root-mean-square). RESULTS: Vibration of the extraabdominal wall resulted in a frequency-dependent rise in vibration levels at the intraabdominal wall, from 4% to 140% of the input level. At the fetal head a broad peak in response was noted between 6 and 12 Hz, but the overall levels never exceeded 4% of the input level. CONCLUSION: Fetal exposure to localized vibratory stimulation of the maternal abdomen is maximal in the range of 6 to 12 Hz.

Vibration exposure and prevention in the United States.

There are over one million workers exposed to hand-arm vibration in the United States. Cases of hand-arm vibration syndrome have been reported in the U.S. since 1918. Typical hand-arm vibration exposure conditions are given in this presentation. Vibration control methods are discussed; these include vibration damping and isolation, use of antivibration (A/V) tool and gloves, and the application work practices and hand-arm vibration standards in the workplace.

Lessons from hand-arm vibration syndrome research.

This paper addresses many of the salient issues and difficulties encountered in performing Hand-Arm Vibration Syndrome research since its discovery in the early 1900's by Alice Hamilton. The areas discussed and the resulting lessons learned include the medical, epidemiological, and control aspects of HAVS. The authors conclude with a plea to health professionals to be ever vigilant and responsive to the HAVS problem, or else it will continue unabated into the next century, an overall time span of nearly 100 years.

Raynaud's phenomenon as it relates to hand-tool vibration in the workplace.

The current status of Raynaud's phenomenon of occupational origin as it occurs in various U.S. workplace situations is examined and discussed. Methods of reducing the effects of hand-arm vibration exposure as well as the status of current vibration standards also are discussed. A work practices guide is recommended.

Instrumentation for measurement of sensory loss in the fingertips.

Four aesthesiometers measuring fingertip sensation were fabricated, two for depth-sense perception and two for two-point discrimination. With the use of 20 normal subjects (10 female and 10 male) and seven subjects with vasospastic disturbance (three female and four male) comparisons were made to determine which of each pair of instruments was the more sensitive. The results indicated that instrument A is preferable to B in measuring depth-sense perception, and C is preferable to D in measuring two-point discrimination. Females appear to have more acute sensory perception than males. Female and male patients diagnosed as having "Raynaud's disease" show a loss in fingertip sensory perception.