The respiratory effects of whole body vibration in man

Sharp, Gordon Russell (1972) The respiratory effects of whole body vibration in man. MD thesis, University of Glasgow.

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Advances in military and civil aviation have, given rise to the need for additional information on the human responses to low frequency structure borne vibration. The occupants of certain aircraft may be exposed to whole-body vibration at frequencies of less than 10 Hz and this is of interest in aviation medicine since vibrations of this type may excite hitman body resonances into large amplitude oscillations. The presence of vibration becomes of concern when it reaches such intensity as to disturb the aircraft itself and in particular where it represents a threat to comforts health and efficiency of aircrew. The work which is reported in this thesis concerns the respiratory affects of whole body structure borne vibration in man. In particular two major areas have been studied - one concerning tbe effects of vibration on pulmonary ventilation and gaseous exchange and the other, more specifically, on the effect of whole body vibration on metabolic oxygen consumption in man. The investigations were carried out at the Royal Air Force, Institute of Aviation Medicine, using a mechanical vibrator which applied sinusoidal vibration, at frequencies of 2 - 10 Hz and acceleration amplitudes of up to 1.4 Gz, to the buttocks of a seated subject. The results of this study have shown that whole body vibration at certain frequencies and amplitudes can induce, a marked increase in pulmonary ventilation, which is a true hyperventilation with hypocapnia. With exposure to vibration at high intensities, the magnitude of the hypocapnia was sufficient to produce symptoms in some of the experimental subjects. When the amplitude of displacement of the vibration was held constant the greatest respiratory changes were found at the highest frequencies used in this study (6, 8 and 10 Hz). With this type of vibrations the frequencies and intensities Which gave rise to the greatest degree of hyperventilation and hypocapnia were also those, Which caused the greatest degree of discomfort and pain in the thorax and abdomen of the vibrated subject. The onset of this pain and discomfort during exposure to constant amplitude vibration was advanced as a possible explanation for the observed respiratory changes. By contrast, exposure of the subject to vibration at a constant acceleration induced the greatest respiratory changes at the lower frequencies studied (2 and 4 Hz) and since these were not accompanied by pain or discomfort in the subject, labyrinthine stimulation was tentatively suggested as the causative machanism. The influence of a number of factors in modifying the respiratory changes associated with whole body vibration have been studied. It has been shown that firm restraint of the subject in the vibrating seat and the posture adopted by the subject during vibration had no effect on the hyperventilation and hypocapxiia induced by vibration at various frequencies and intensities. Only by the application of firm external support to the thorax and abdomen of the vibrated subject (by means of a restrainer suit) were the respiratory changes during vibration eliminated or greatly reduced. The practical importance of the finding of hyperventilation and hypocapnia in the subject exposed to whole body vibration have been discussed in terms of the in-flight hazard associated with this condition. The investigations have also shown that whole body vibration causes a marked increase in oxygen consumption at certain frequencies and intensities. The results showed that this was not due to the muscular activity required by the subject to maintain posture in the face of vibration since changes of similar magnitude were found in conditions where the subject was restrained by harness in the vibrating seat and where he was unrestrained in the seat. High speed cinephotography revealed that during whole body vibration there was alternate tensing and relaxation of musculature - possibly as a protective mechanism - and it was believed that this phenomenon could explain the increased metabolic oxygen consumption observed during whole body vibration. The practical importance of the increased metabolic activity during vibration has been discussed in terms of the energy required by aircrew to fly various types of aircraft in a variety of conditions. The findings of this investigation have advanced knowledge of the respiratory and metabolic responses of man to whole body structure borne vibration. The practical implications of the results of this study have been discussed in relation to the possible threat which they might pose to the comfort, safety and wellbeing of the pilot required to operate in conditions of inflight vibration.

Item Type: Thesis (MD)
Qualification Level: Doctoral
Additional Information: Adviser: J Ernsting
Keywords: Occupational safety
Date of Award: 1972
Depositing User: Enlighten Team
Unique ID: glathesis:1972-72883
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 Jun 2019 11:06
Last Modified: 11 Jun 2019 11:06

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