Gravity and Man. Part I. Studies on the Effect of Increased Gravitational Force on Man. Part II. The Effects of Other Physiological Stresses on Man's Tolerance to Increased Gravitational Force

Browne, Matthew Kennedy (1959) Gravity and Man. Part I. Studies on the Effect of Increased Gravitational Force on Man. Part II. The Effects of Other Physiological Stresses on Man's Tolerance to Increased Gravitational Force. MD thesis, University of Glasgow.

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Abstract

The first part of this thesis consists of a general consideration of the physiological effects of acceleration. The means of determining human tolerance to this force is by means of threshold determinations. These are discussed in relation to the mechanical variables involved: strength, duration and rate of application of g. The changes in pulse rate, blood pressure, the electrocardiogram vectorcardiogram and electroencephalogram, have all been analysed and compared with the results of previous investigators. It was found that the pulse rate varied directly with g while the blood pressure bears a reciprocal relationship to g. The changes in pulse rate closely followed changes in blood pressure, and both depended not only on the peak g but also on the rate with which it is applied. There were no characteristic changes in the electrocardiogram, the electrical axis shows a clockwise rotation which is partly positional and may also be related to increased autonomic activity. There was only one arrhythmia in q series of two thousand runs, this occurred at 8.0 g. and reverted spontaneously to sinus rhythm on returning to 1.0 g. No evidence of myocardial ischaemia was obtained from any of the records. The vectorcardiogram shows instantaneously any changes in the electrical axis of the heart but otherwise gives no additional information to that obtained from the E.C.G. There are no characteristic changes in the electroencephalogram during positive acceleration. During the early part of the runs there is a fall in the amplitude of the alpha rhythm which reverts to normal after five to ten seconds. Greyout and blackout occur without any corresponding change in electrical activity. The onset of unconsciousness however is accompanied by the appearance of slow, large amplitude waves. Most subjects exhibit convulsions of a major or minor type when consciousness is lost. These similarly are not accompanied by any E.E.G. changes apart from the dslta activity found with unconsciousness. The optimal conditions for threshold determination are outlined and a method is described which fulfils these conditions. The method depends on loss of central vision by the dark adapted eye and is accurately repeatable. The value of g at which the end point occurs can be varied at will, the upper limit being the level of absolute blackout. The variables are capable of precise specification. The type of g run used is based on the results obtained in the earlier part of this study and allows cardiac compensation to develop as the g increases. The second half of the thesis is an investigation into stress summation in flight. It was thought that many other factors might operate to produce a diminished tolerance to acceleration, and even to lead to loss of consciousness. (Abstract shortened by ProQuest.).

Item Type: Thesis (MD)
Qualification Level: Doctoral
Keywords: Medicine, Physiology
Date of Award: 1959
Depositing User: Enlighten Team
Unique ID: glathesis:1959-79302
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Mar 2020 11:00
Last Modified: 05 Mar 2020 11:00
URI: http://theses.gla.ac.uk/id/eprint/79302

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