GENERAL ARTICLES

AIR MEDICINE

In the battle for altitude the medical laboratory is as vital to victory as aviation's draughting rooms

RAYMOND ARTHUR DAVIES December 15 1942
GENERAL ARTICLES

AIR MEDICINE

In the battle for altitude the medical laboratory is as vital to victory as aviation's draughting rooms

RAYMOND ARTHUR DAVIES December 15 1942

AIR MEDICINE

RAYMOND ARTHUR DAVIES

In the battle for altitude the medical laboratory is as vital to victory as aviation's draughting rooms

IN THE early years of the Great War, a study of British air casualties revealed that of every hundred fliers who met violent death, only two were killed by the enemy, eight died because of mechanical failure of their craft, while ninety deaths were the result of the pilots’ own deficiencies.

This appalling discovery prompted the Royal Flying Corps to establish a special “Care of the Flier Service” and to exercise much greater caution in determining the physical and mental fitness of candidates for flying. Research was begun in the effects of lack of oxygen, altitude and cold. By 1915 British aviation fatalities owing to human failure were reduced to twenty per cent and

to twelve per cent by the summer of 1916.

In this war aviation fatalities owing to physiological failure are very few. The improvement in this respect made between the two wars is due mainly to aviation medicine as well as to the mechanical advances of the aircraft industry.

After the war aviation medicine advanced rapidly. As the size of modern aircraft increased, rate of climb mounted, speed attained 400 and more miles per hour, ceiling rose from 15,000 to

40,000 feet, flying stresses grew steadily and the need for further aviation medical research became pressing. Every radical improvement in the performance of military and civilian aircraft

brought with it new demands upon medicine and the advance of aviation medicine became continuous.

In fact, no other phase of modern warfare owes as much to medicine as military aviation. It is quite probable that, without the assistance of medicine, military aviation could not have developed to its present effectiveness.

In considering the effects of flight upon the human system medicine has been confronted with numerous problems. Consider this one, for example.

One of the worst hazards of flying is altitude sickness (anoxemia) which is due to insufficient oxygen in the body tissues, resulting from the reduced pressure of oxygen in rarefied atmosphere. At 18,000 feet the air has only one half and at

30.000 feet one third of the oxygen pressure present at sea level. This is far too little for the sustenance of life.

Strangely enough, instead of feeling ill, pilots suffering from insufficient oxygen at high altitudes often experience a peculiar feeling of well-being and satisfaction. Pfirst symptoms of oxygen lack, when no artificial oxygen is supplied, generally appear at about 9,000 feet, although they may appear in some individuals at as low as 4,000. At 9,000 feet night vision decreases by fifty per cent. At 12,000 feet, respiration deepens, muscles become difficult to control, sight weakens. At 18,000 feet memory begins to go. The pilot develops irrational ideas, is unable to exercise proper judgment. At

20.000 feet the lungs madly fight for air. Above

20.000 feet the sense of time and space is lost. The pilot laughs without cause, now and then becomes angry, wants to fight. At 25,000 feet unconciousness may come, then death.

And yet the signs of warning are almost imperceptible. They are so small—drowsiness, headache, inattention—that they might easily be attributed to other causes and disregarded.

One of the lessons learned in the present war has been that airplane crews who fail to use their oxygen at proper altitude, according to instructions, become easy prey for enemy aircraft and often bring their own destruction by errors in judgment, fatigue, inattention, lack of responsibility. Most pilots who have been in action insist on taking oxygen at 10,000 feet, although they are not required to do so until 15,000 feet. Tests have shown that unless oxygen is taken at 12,000 feet there is a six toten per cent loss of efficiency which is just about the margin between victory and defeat in battle.

Oxygen Supply Vital

YOU CAN see that had not means been found for supplying oxygen to fliers, and telltale signs of danger had not been pointed out in advance by medicine, modern aerial combat could never

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Air Medicine

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have developed. Regulations now require the use of supplementary oxygen for all flying above 15,000 feet and for long flights above 10,000 feet. Oxygen is generally supplied through masks. Tests are continuing to discover better and better masks which can function automatically at certain heights and which do not inconvenience the pilot in any way. At the same time, experiments are being conducted in the design cf

pressure cabins and pressure suits to provide air at pressure above that of surrounding atmosphere. In such cabins the flier would receive his oxygen directly out of the air inside; he would have no need for wearing a mask; the high pressure in the cabin would be the same or almost the same as at ground level and the air crew could function with greater efficiency.

Another effect of high altitude

flying is aeroembolism better known as "the bends” or caisson disease. It has been known for a long time to deep sea divers and tunnel workers. This condition is believed to be caused by the liberation (in the form of bubbles) of nitrogen contained in the blood.

These bubbles first appear at about 18,000 feet, in the spinal fluid, and at 25,000 feet, in the blood. The cause lies in the lack of air pressure at high altitude. Ordinarily air pressure at or near sea level is great enough to keep gases contained in the human blood in solution. But when pressure lessens these gases begin to bubble out. An attack of aeroembolism is usually accompanied by excrutiating pain in the joints, itching and tingling of the skin, the sensation of heat or cold, fn extreme cases it may result in paralysis, visual disturbances and finally, unconsciousness and death.

Medicine believes that, at present, consciousness cannot be retained above 47,000 feet even with the administration of pure oxygen without a pressure raising device. At that height there is not enough pressure of air outside of the body to keep the liquid contents of the body inside the blood vessels, and skin.

At 63,000 feet, should that height ever be reached, man would face another danger. At that height the fluids of the body would "boil” and failure of the pressure cabin would mean instant death. We can understand this phenomenon better if we recall that water boils at a lower temperature on a high mountain than at sea level.

For years medicine has been concerned with aeroembolism, which, incidentally, does not affect all fliers to the same degree. Some men develop symptoms at 25,000 feet, while others remain immune at 40,000 feet. This has led to test for high altitude fliers who are selected from among those least subject to this affliction.

One method against aeroembolism is to have fliers before flight inhale oxygen or a helium-oxygen mixture for a period of from 45 minutes to 5 hours depending on the length of the journey to be undertaken. Inhalation of oxygen and helium drives out excess nitrogen in the blood in this way lessening the danger of aeroembolism.

Rapid Temperature Change

ANOTHER enemy of the alti• tude flier is cold.

An airplane crew may leave the sun-baked ground in mid-summer with the temperature at 105 At 35,000 feet, the temperature will he 67 below zero. The time elapsed may he only a few minutes, yet the temperature change is 172 degrees.

Clothing fully satisfactory for high altitude flying in open cockpit planes has not yet been developed except in Buck Rogers comic strips, although considerable experimental testing has brought about appreciable improvement, especially in electrically heated clothing. However, at present, to provide adequate warmth, cumbersome hulkiness is required. This restricts movement and has a bad psychological effect. The best

solution is the closed, heated airplane. But although most passenger planes are closed, a fully satisfactory method of heating combat planes has not yet appeared.

Perhaps one of the most spectacular phenomena engaging the attention of aviation medicine is the so-called "blackout” in which the pilot pulling out of a power dive suffers a momentary loss of vision or loses consciousness for a few seconds. This may he just long enough to come into line of enemy fire. Blood and other fluids are forced out of the pilot’s hrain, jam the abdomen and swell the intestinal veins. One result of frequent diving is known in the U.S.A. as "flier’s belly”—excessive appetite, nausea and nervous restlessness. Blackout is due to the terrific effect of centrifugal forces upon a flier in a dive. Imagine the plane sweeping down at perhaps 500 miles per hour. Suddenly the stick is drawn back the plane straightens out and then zooms up again. The effect multiplied many times is like that of a fast elevator stopped suddenly. Except that in the dive bomber at the moment of levelling out pressure may be five times gravity, “5 G” the pilots call it.

Methods of minimizing the tendency to blackout have been devised such as having fliers lie on their backs or sit hunched up, knees near chins in diving, but as yet no fully effective solution has been discovered.

Canada has contributed a great deal to the struggle against the effects of the blackout. Because of their military importance, the results of the work must remain secret until after the war. Research into the effects of and the struggle against the blackout was being carried on by Sir Frederick Banting when he met his untimely death. Many prominent Canadian men of medicine are now engaged in furthering his work.

These are some of the problems confronting medicine in dealing with the members of air crews in the air. Equally important is the medical care of the fliers on the ground.

Our military aircraft are now so advanced that very often they exceed in performance the capacity of the crew. The need to watch scores of instruments on the panel board, to command the crew, to listen to constant radio dispatches and to deal with the new problems in a split second often causes staleness and fatigue after 200 operational 'hours of intensive combat flying. After this fliers are removed from operational flying for a period of approximately six months.

Fatigue is shown not in a lesser capacity to work but in a reduced will to work. Fliers who are stale and fatigued are tired, their alertness is affected, their precision flying is poor, their morale is low.

Fatigue may he due to many factors. Partly it is derived from physical factors accompanying combat flying—noise, vibration, glare, cold, lack of oxygen. Lack of exercise, poor selection of food, excessive use of tobacco and alcohol also tend to produce increased susceptibility to fatigue. But more important are psychological factors— emotional stresses, both on and

off the job, regime of life and habits. There is no single reliable test for fatigue and the medical officer must learn to recognize its general symptoms long before fatigue itself has firmly set in, often incapacitating an excellent flier for long periods of time.

The M.O.’s Job

R.C.A.F. medical officers recognize that fliers may go stale as the result of constant tension, anxiety and frustration on the ground, as readily as in the air. Thus, one of their most important functions is in the field of psychology. They must have a thorough knowledge of all stresses, both physical and emotional, to which the pilot is subjected. They must know their men and must he acquainted intimately with their private and domestic problems, since these have a complete bearing upon flying efficiency. The M.O.must know the personality of every man in his charge and should he able to recognize incipient trouble before it reaches the surface. The M.O. is encouraged to fly so that he may experience the effects of the occupants of aircraft.

A successful M.O. (there are more than 500 in the R.C.A.F.) conveys and invites confidence, is trusted and liked. His field is all inclusive. Within his province are duties connected with night patrols, search parties, fogs, accidents, fatigue, flying stresses of every kind. Every new type of plane brings new problems which must he solved by the M.Obefore a single man can take to the air with complete security.

Medical officers capable of coping with these duties receive special training at the R.C.A.F. School of Aviation Medicine in Toronto. Their practical work and further education is done at the schools and stations to which they are assigned. Laboratory and research work in aviation medicine is being conducted at the R.C.A.F.Clinical Investigation Units, the Banting Institute, and under the direction of the Committee on Aviation Medical Research of the National Research Council in Ottawa and in scientific institutions connected with various universities.

Obviously men for the R.C.A.F. must he picked with care. Failures are expensive. The cost of training is high. The flying student who fails has had, on the average, two months of training with twenty-five hours’ flying time.

In general, in the rigid physical and psychological examinations (the latter are really a review of the applicant’s whole life) all those are rejected whose stamina is low, whose constitution is not rugged and who cannot he expected to "last.”

In the field of selection, however, both the Germans and the Russians have much to teach us. In these countries hundreds of thousands of young men are trained from early childhood to develop flying reflexes Consequently both Germany and Russia have become nations of fliers. The preflight training programs have permitted the natural selection of pilots and air crew members in general, and the result has been that the men, so to speak,

“select themselves.” That is, by the time they reach the age of enlistment the capacity of each is well determined and the chances of misplacement in the air force is smaller than they would be, say, under conditions similar to our own.

The development of air education on a mass scale such as is envisaged in our Air Cadet program, in aerodynamics, meteorology, aircraft recognition, gliding, etc., among youngsters, should create a tremendous semi-trained and partially selected reserve for the R.C.A.F. in a relatively short period of time.

Since the beginning of air training in Canada it has been discovered that boundaries of acceptability are much wider than had previously been believed. A series of tests has been developed to select men for specific services. For example, high altitude

fliers are tested for resistance to 1 cold and oxygen deficiency, and for resistance to the “bends”; pilots of interceptor planes and dive bomb¡ ers are tested for reactions for ac' celeration and centrifugal forces and pilots required to do night flying are tested for visual efficiency at low levels of illumination.

This is a tough war. Aviation medicine has made an enormous contribution toward a Canadian air force second to none. The medical officer is Canada’s insurance that everything possible is being done to make flying safer and to make our men better able to withstand the stresses of air combat.

And after the war the experience ! amassed by aviation medicine will stand in good stead in developing our civilian aviation as well as the general well-being of our population.