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Aviation History
1919
1919 - 0108.PDF
MEDICAL NOTES THE WEAR AND TEAR OF FLYING By Captain T. S. RIPPON-, R.A.F. Medical Service ONE of the problems the commercial aircraft firms will have to face when passenger work becomes common will be how their pilots are lasting. It is obvious that a pilot who has to fly regularly in all sorts of weather will require a rest periodically. How is one to discover this ? Fortunately one of the great discoveries of the War from a medical standpoint was made by a specialist at the R.A.F. Medical Research Depart ment—Lieut.-Col. Flack—who before the War was associated with Professor Leonard Hill, the well-known physiologist and expert on oxygen. Lieut.-Col. Flack, who is a physiologist, discovered by a series of examinations of successful pilots and of pilots sent back from France for a rest that one of the indications of " stress " was fatigue of the various bodily systems (respira tory, circulatory, and nervous), and he invented a simple and ingenious method of testing this fatigue. A glass IJ-tube containing mercury was connected with a rubber tube fitted with a mouthpiece which the pilot put in his mouth and, after taking a deep breath, blew down it, forcing the column of mercury up the other end of the tube. It was found that the tired pilots could not blow the mercury half as high as the fit ones. A further modification of this test consisted in instructing the pilot to blow the mercury to a certain height, and then to keep it there as long as pos sible—at the same time observations were made of the character of the pulse and length of time the pilot was able to hold the column of mercury at the required height, an indication of the degree of fatigue in this way was confirmed. It has been admitted that the British methods of examina tion of pilots are second to none—and one of the chief points of the examination is this fatigue test. By these and other methods, therefore, we are in a position to assure the passengers, before they put their lives in the hands of a pilot, that he is fit and not suffering from fatigue. Methods in Use by French Doctors in Examining Pilots There are two points about the French system which differ from ours :— (t) Examination for self-control and ability to keep cool in moments of danger (Reactions emotivites).—This is done by means of a pneumograph which is fixed round the thorax of the candidate : and to one of his hands is fixed a Hallion and Comte finge. apparatus, the pneumatic pocket of which measures the variations in the peripheral circulation of the blood by which the action of emotions on the circulations is recorded, under the influences of the vaso-motor nerves. A Verdin recorder which registers trembling is placed in the candidate's other hand. These three apparatus are connected by pneumatic tubes, each having a drum which is placed opposite the cylinder of a Marey recorder. This gives graphs of the respiratory system, vaso-motor system and trembling. Unknown to the candidate the examiner fires off a revolver near the candidate and according to the extent of the oscilla tions of the graph, 30 the candidate is regarded as fit or unfit. Value of Test for British Candidates Self-control is usually a marked characteristic of the average British candidate and consequently not so necessary to test as is the more emotional Latin type. There is, how ever, an instinct which the active service pilot needs, viz. the instinct of pugnacity which might with advantage be tested. " Anger " as a Test of the Fighting Type The aggressive type is quickly provoked to anger, and he is the most useful on active service. Anger can be provoked by threatening to oppose the wishes of the candidate, making disparaging remarks about him, or in numerous ways. A brief psycho-analysis would give the key to the method of stimulating the candidate's anger, and a prompt response would be considered satisfactory. Examination of Reflex Reaction Time By a reflex action we mean the movement of a muscle through the nerves coming from the brain and spinal cord, caused by a stimulation of afferent nerve fibres (e.g. visual, auditory or tactile). The total time between the application of the stimulus and the beginning of the response can be determined by special apparatus. The reaction time varies with the conditions of the nerve centres, being lengthened by fatigue, lack of oxygen, alcohol. morphia and other conditions that depress the irritability of the nerve cells. In pilots suffering from the results of concussion and stress of service the time shows marked variations, being alternately rapid and very slow. The efficient pilot is the man who, rapidly informed by his senses, performs the necessary action as quickly as pos sible, that is, the man in whom, in the language of psycholo gists, psychomotor reactions take place in the minimum time. The value of the test is so well known that it is not necessary to emphasise it. Recently however, it has increased in value, as it is a valuable indication of impairment of efficiency at heights. The difficulty at present is the supply of recording apparatus which will measure in hundredths of seconds, this however it is hoped to overcome by producing a simple instrument which will be available for all medical officers engaged in examination of pilots and candidates. Changes in Reaction Time at Heights As the result of a series of experiments with the decom pression chamber it has been demonstrated that (i) the reaction time is prolonged at heights; (ii) that pilots suffering from " stress " show an unusually long and sometimes erratic response at heights. This result is impoitant because with a continuous supply of oxygen the aviator can keep himself practically normal. Italian Methods. The points which [the Italians lay stress upon are as follows :— (1) Good mental constitution. (2) Healthy physical constitution. (3) Normal nervous system. They state that the pilot should have a physical con stitution such as will enable him to take in rapidly all that is going on around him with quick reflexes following the stimuli and leading to movement of the levers of the machine which he is piloting. It is also necessary for him to have good capacity for concentrating his attention and that his attention should be able to extend over a large area. It is also ncces6ary that he should be gifted with accurate and quick powers of observation. Besides having these aptitudes the pilot should be as little emotional as possible, so that no great alteration in his respiration and circulation should take place. These are the physical reactions of psychical phenomena, and they show a more or less emotional psychical constitution. Besides this an examination of the respiratory organs and circulation must show that the influence of the rapidity with which variations of altitude occur and the influence of altitude itself does not exceed a normal average. Psychical Examination Attention, powers of observation, and capacity of perception of certain things are tested by the mental tests empkyed bv Rossolino. " Each subject had to undergo the whole series of cor responding tests (the description of which it is not necessary to give again here) and the result of this series of investiga tions was expressed in figures and graphs. The power of attention (its degree of concentration and extension) the power of accurate perception of certain things and particulars (the Mehrfatingkeir of the German psychologists) and.the powers of observation, etc." Value of Psychological Tests for Mental Fatigue They notice a great mental exhaustion in aviators"after even the shortest flights. The method employed to measure the time of the reaction to sensory stimuli (measured before and after flight) proved that even after flights of very few minutes' duration the times of the reaction became consider ably greater, as also was the divergences frcm the average. In de.ault of suitable apparatus, Gemelli proved by counting and comparing the number of disconnected syllables which the pilots were able to remember before and after flying that they made a great namb-r of mistakes, the evident result of considerable mental fatigue, and that this fatigue was not proportioned to the effort expended Reaction Time Exarmnatrr. theFnmch meth°d aPPears to *» more detailed:than Besides subdividing tactile responses into sensory, muscular and mixed reactions, they state that each individual has his own mode of reacting to sensory stimuli peculiar to 10$
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