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J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

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CARBON MONOXIDE POISONING:

A REVIEW.

By BREVET LIEUTENANT-COLONEL A. E. RICHMOND, O.B.E., Royal Army Medical Corps.

CARBON monoxide, together with the dioxide, occurs in the combustion of organic matter, and the less there is available the greater the proportion of carbon monoxide produced. It is colourless and odourless, and on these accounts its presence is normally only detectable by the symptoms it causes, which adds much to the risk of poisoning from it. It it also inflammable and in strong may give rise to explosions. It has been recognized as a poison since ancient times, and has assumed special importance within the last half-century owing to the increased amounts of it produced consequent upon the augmented use of gas for by guest. Protected copyright. illuminating, cooking, and heating purposes, and upon the introduction of the internal combustion engine. It is the favourite means of the suicide to encompass his aim, while accidental poisoning with it frequently occurs. From a military point of view carbon monoxide intoxication is a subject which deserves the close attention and study of all military medical officers in these days of intensive mechanization, and unlimited employment of explosives; and the object of the writer is to lay before his readers in as concise and compact a form as possible those details of moment in connexion with the various aspects of this important subject. In endeavouring to attain this object references have been made to certain publications dealing with carbon monoxide poisoning. These references are clearly indicated, so that those desirous of making a more

detailed study of the matter may have available the same assistance as has http://militaryhealth.bmj.com/ been at the disposal of the author and which he most gratefully acknowledges. Carbon monoxide enters the body through the lungs and by no other means. Drinker [1], in his recently published and most valuable book on the subject, quotes observations by Sendroy Liu and Van Slyke which appear to have established the affinity of carbon monoxide for hremoglobin compared with that of oxygen as being in the proportion of 210: 1. This is a sig­ nificant fact, and the ease with which the carbon monoxide is taken up by hremoglobin is the essential feature of the toxic syndrome. The oxygen-carrying capacity of the blood is in this way interfered with to a greater or less degree, and in severe cases of poisoning disastrous and on September 27, 2021 enduring states of anoxremia may arise with all their resultant adverse effects. It will be realized also that this amazing affinity of carbon monoxide for hremoglobin is an obvious explanation of the occurrence of cases of poisoning in individuals exposed to comparatively low of the gas. J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

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The combination of carbon monoxide with hremoglobin is very slowly reversible, and oxygen will displace it when the individual is removed from the poisonous atmosphere. This is due to the mass action of the oxygen in the air, and the process may be accelerated by the administration of pure oxygen in the usual way. Carbon dioxide exerts a benevolent influence, as this gas affects the combination of both oxygen and carbon monoxide with hremoglobin, which is less able to hold these gases as the carbon dioxide increases. Hence the importance of the administration of carbon dioxide in treatment as it acts not only by aiding the dissociation of carbon monoxide from hremoglobin, but also by stimulating the respiratory centre. When non-fatal concentrations of carbon monoxide are present in the air breathed, the partial in the blood gradually reaches a state of equilibrium with that in the air, and so the blood concentration is prevented from reaching a lethal height. As an example of this, with an­ atmospheric percentage of 0·05 the maximum hremoglobin saturation with by guest. Protected copyright. carbon monoxide produced will be 40 per cent, which will be attained in practically four hours. Perhaps of special importance from a military point of view is the effect of the low barometric , which may be found at great heights, on the absorption of carbon monoxide by the blood. Such influence is clearly adverse owing to the reduction in of the oxygen due to the carbon monoxide taken up coupled with that consequent upon the low barometric reading. This will serve to emphasize the danger of subjecting persons to carbon monoxide at high altitudes. It should be noted that mice and small birds die more quickly from carbon monoxide poisoning than men, owing to the fact that their volume of per minute compared with the total volume of their blood is greater than in the case of man, and it is stated that the average man ought

to be able to remain in an atmosphere with a given concentration of carbon http://militaryhealth.bmj.com/ monoxide twenty times as long as a canary~ It appears to have been definitely established that carbon monoxide inhaled in small amounts over periods of time has the power to increase the red cells and the amount of hremoglobin in the individual [2]. The augmentation of the erythrocytes is thought to be due in the early stages to contraction of the spleen, but it would seem that later true -new red cell formation definitely occurs in the bone-marrow. Finally, the fact must not be lost sight of that on cessation of the excretion of carbon monoxide also ceases, and that evidence of it in the blood may be found for months or even years afterwards. on September 27, 2021

DANGEROUS PERCENTAGES OF CARBON MONOXIDE. In considering this aspect of the subject with which we are dealing, realization of the fact that given concentrations of carbon monoxide in the atmosphere will not affect every individual equally is essential. Not only J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

A. E. Richmond 81 do individuals vary in their reactions to this gas, but other modifying influences in the situation are also frequently present. It is also important to realize that dangerous precentages of carbon monoxide will never be reached in open spaces owing to the rapid of the gas, and that risks from it only arise in enclosed spaces, or in semi­ enclosed in which ventilation is inadequate or stagnation of air exists. Individual susceptibility depends to some extent upon age, and Drinker emphasizes that the very young and very old are at greater risk than others. " The Medical History of the War" [3] states that young men were more susceptible to carbon monoxide than those over 40, due apparently to their greater elasticity of chest wall and deeper inspiration. Although there may be some doubt as to the influence exerted by sex, there appears to be no question that pregnant women are more liable to fall victims to poisoning by carbon monoxide than others. Such abnormal bodily conditions as anffimia, heart disease, , chronic , alcoholism and narcotism have a material and detri­ by guest. Protected copyright. mental effect in carbon monoxide intoxication, while of prime importance is the extent of any bodily activity taken in the poisoned atmosphere. In this connexion Drinker quotes certain experiments by Sayers, Meriwether and Yant, [4] which illustrate the effect of rest and strenuous exercise respectively on carbon monoxide absorption. These investigations showed that persons at rest breathing 0·02 per cent of the gas developed 16 to 20 per cent hffimoglobin saturation with mild subjective symptoms at the end of six hours. On the other hand, an individual exercising strenuously in 0·025 per cent of carbon monoxide had 14 to 16 per cent saturation in one hour with moderate subjective symptoms. These experiments serve to emphasize the consideration we must give to the degree of activity of the soldier or anybody else in an atmosphere containing carbon monoxide, if we are to assess correctly the extent of

the risk. http://militaryhealth.bmj.com/ As regards atmospheric conditions, low barometric pressure is a factor of considerable moment, and the intake of carbon monoxide at the low pressures of great altitudes will have infinitely more rapid and serious results than would be the case at normal heights. Hence the great necessity for efficient safeguards against the inhalation of exhaust gases of aeroplanes while in flight. High and humidities also accelerate the rate of combination of the gas with hffimoglobin. Varying susceptibilities of animals and birds as compared with man must also be given passing thought as they are of importance in the selection of test creatures for experimental and other work. In this connexion Drinker on September 27, 2021 quotes Anson, Barcroft, Mirsky and Oinuma [5] as showing that carbon monoxide has an effect on animals, etc., in the following descending order of potency: Dog, horse, cat, man, fowl, mouse, rat, tortoise, sheep, lizard, frog, and rabbit. Similarly, in the case of smaller -animals and birds Burrell, Seibert and Robertson [6] concluded that the following was the order of J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

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degree of susceptibility: Canary, mouse, chicken, small dog, pigeon, sparrow, guinea-pig, and rabbit. Finally, we must not lose sight of the fact that carbon monoxide varies in its effects according as to whether it is alone or in combination with other gases. For instance, illuminating gas is of higher toxicity than pure carbon monoxide, as also is the from a car using coal distillate. There appears to be little to choose between pure carbon monoxide in air and the ordinary petrol exhaust gas. From a practical point of view we have to deal in averages when we {;onsider the important question of the maximum permissible concentrations of carbon monoxide in an atmosphere and of the effects likely to be produced by concentrations in excess of such a limit. Many investigations have been carried out in these connexions by experts on the. subject, such as Haldane (1897), Henderson (1921-22), Sayers, Meriwether and Yant (1922), Sayers, Yant, Levy and Fulton (1929) [7], and others, but space does not permit of a detailed consideration of the valuable contributions of these workers to the store of information now available. by guest. Protected copyright. On the other hand, it is possible to summarize in a concise form the con­ dusions come to, and from the viewpoint of the practical hygienist, military or otherwise, such a summary is the essential need. First and foremost it was clearly established that a carbon monoxide concentration in the blood equivalent to at least 20 per cent of saturation is necessary before the average adult complains of toxic symptoms, provided he is at rest. Minor symptoms, though, may occur with exercise with blood concentrations of 10 to 20 per cent. Secondly, symptoms may be expected to develop at rates varying with the concentration of the gas in the atmosphere breathed and subsequently in the blood according to the tables given below. It must, however, be borne in mind that, as already stated, individuals

vary in their reactions to carbon monoxide and consequently the table must http://militaryhealth.bmj.com/ be accepted as only giving an indication of the average state of affairs likely to be produced by varying concentrations of the gas for different periods of time.

Maximum % Period of exposure in hours required to reach certain Cnncentra- saturation of percentage saturations tion in h",moglohin air that will be attained 10% 20% 30% 40% 50% 60% 70% 80% 90%

% % 0'01 14'3 2 on September 27, 2021 0'05 45'5 t 1;t 2 4 0'1 62'5 1/3 ~ 11 2 3 5 0'2 77'0 1/6 1/3 2/3 1 It 21 t 3 0·5 89'3 1/8 1/5 1/3 3/8 ! 5/8 4' l~ 1'0 94'3 1/12 1/8 1/5 i 1/3 3/8 t i !! 5'0 98'8 1/100 1/60 1/16 1/12 1/9 1/7 1/6 3/8 4 J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

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, :~"J\' "'" ~ , .. ;:," SYMPTOMS LIKELY TO OCCUR AT VARYING PERCEN¥AGlll, SATURATIONS OF TH~I\LOOD. '''~' ," " '. "'",', ' (Taken with slight modifications from Review o/d~~i~"if<1!:£()noxide "PoisoJt'{ng, United States Public Health Servicd;1930.}~·;~'~~-;: :',:~: % . , :;~: . " 0-10 .. None. 10-20 Possibly slight headache with dilatation of the cutaneous vessels and tightness across the forehead. Shortness of hreath on exertion. 20-30 Headache. Throbbing in temples. Muscular weakness. , 30-40 Severe headache, weakness, dizziness, confusion of mind, lack of concentra­ tion, dimness of vision, nausea, , collapse. 40-50 As above but greater possibility of collapse and syncope; increased respiration. 50-60 Syncope. Increased respiration. with intermittent convulsions. Cheyne­ Stokes respiration. 60-70 Coma with intermittent convulsions, depressed heart action and respiration. Possibly death. . 70-80 Weak pulse and slowed respiration. Respiratory failure and death.

Thirdly, certain general findings emerged from the work done which by guest. Protected copyright. may be tabulated as follows [8] :- (1) The combination of carbon monoxide with hremoglobin takes place slowly when the subject is exposed to low concentrations and remains at rest, many hours being required before equilibrium is reached. (2) The rate of combination of carbon monoxide with hremoglobin is much more rapid during the first hour of exposure than during any succeeding hour with the subject remaining at rest. (3) Strenuous exercise causes more rapid combination of carbon monoxide with hremoglobin than when the subject remains at rest, the symptoms of poisoning therefore being emphasized by exercise. This accelerated com­ bination is due partly to the raised body and partly to increased respiration. (4) High temperature and humidity with a given concentration of carbon monoxide cause more rapid combination of the gas with hremoglobin http://militaryhealth.bmj.com/ than under normal conditions. Finally, as regards the question of the maximum permissible limit of carbon monoxide in an atmosphere, Drinker's dictum to the effect that in houses, garages, or manufacturing establishments where there is prolonged exposure to carbon monoxide, concentrations above 0·01 per cent should not be permitted, may be accepted as adequate to the need. On the other hand, in special circumstances and where the period of exposure is strictly limited, a higher limit might be permitted. This was done in the case of the Holland vehicular in New York where a limit of 0·04 per cent of on September 27, 2021 carbon monoxide was imposed [9]. With this concentration, a driver of a car after one hour would have less than a 20 per cent saturation rate and, apart from this, the margin of safety was a large one inasmuch as the trip through the tunnel would normally be only ten to twelve minutes in duration, although exceptionally the period of time occupied might be forty minutes. J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

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SOURCES OF CARBON MONOXIDE AND ITS CONCENTRATION IN THE ATMOSPHERE IN CERTAIN. CONDITIONS. The more common sources of this gas will be well known to many readers. The ordinary coal gas is a mixture of gases of which carbon monoxide forms a large proportion. Illuminating gas is usually a combination of coal and water gas, and the average carbon monoxide content is some 15 per cent. Water gas contains as much as 30 per cent. It would appear at present unnecessary to discuss this aspect of the matter further as it is clear that carbon monoxide in the atmosphere due to illuminating gas will vary enormously as regards the proportion present, and that this may be very small indeed in the case of smali leaks, or very high when the gas is used for purposes of suicide. It will be necessary, however, to go into the question in rather greater detail in connexion with preventive measures. Carbon monoxide is produced whenever incomplete combustion of carbon­

containing fuel takes place in the absence of sufficient oxygen. by guest. Protected copyright. Coal, oil, charcoal, coke, wood, etc., may therefore all give rise to this intoxicant, and the circumstances under which it may be produced from such fuels are multifarious, though the basic cause is usually insufficient ventilation. Blocked fiues, for instance, may be the cause of trouble, and it will be remembered that Emile Zola died in 1902 as the result of carbon monoxide poisoning due to a faulty stove. Coke braziers burnt in ill-ventilated rooms are too well known a reason for carbon monoxide poisoning to necessitate further comment, and it will not be difficult for the reader to realize that similar lack of ventilation may occur under certain circumstances in all sorts of stoves, furnaces, and the like. The occurrence of large quantities of carbon monoxide in burning build­ ings is too familiar also to need much emphasis. The more confined and smothered the fire the more dangerous it is, and it is of the greatest impor­

tance that firemen overcome by fumes should be treated as cases of poisoning. http://militaryhealth.bmj.com/ It will be well to interpose at this point some information as to the approximate percentages of carbon monoxide found in certain more common circumstances, and this is given in the table on page 85. The figures given have been obtained from various sources [10], and they should be regarded as average readings only, and that considerable variations from them are quite likely to be found. There are certain sources of carbon monoxide which on Service, and to some extent during the piping times of peace, are likely to be productive of among us as Army medical officers, and it seems essential that a on September 27, 2021 particularly intimate and detailed consideration should be devoted to them. To deal first with the risks to those driving or conveyed in mechanical vehicles of varying description, it has already been stated that the ordinary petrol exhausts contain some 4 to 7 per cent of carbon monoxide. Such gases, if adequate measures of disposal are not employed, may gain entry into closed or partially closed vehicles by various means. Defective J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

A. E. Richmond 85 exhaust disposal may include leaking exhaust pipes or the placing of these in such positions that the gases are not delivered clear of the vehicle, leaky gaskets in exhaust connexions, leaks in mufflers, and leaky piston rings permitting exhaust gases to enter the crank case and be discharged into the vehicle. TABLE. Percentage of carbon monoxide found in common circumstance8. Per cent Illuminating gas 15 Exhaust gases of motor-cars 4-7 Diesel engine exhaust 0'1-0'3 Railway engine smoke 2 Blas~ furnace gases 28 Bessemer furnace gas 25 Coke oven gas 6 Explosion gases-- Dynamite 34 Nitroglycerol 46 Picric acid 61 Miue air­ by guest. Protected copyright. Coal pits 0'104 (maximum) Immediately after dust explosion (experimental) 8 One day after a coal mine explosion 1 Mine fire 1 Seven minutes after blasting with gelatine dynamite 1'2 Air in garages .• 0'05 Air in railway .. 0'01 Air in traffio roads and tunnels .. 0'04 (maximum) The necessity, therefore, for thorough and regular inspections of mechanical vehicles with a view to the elimination of any possible defects of the nature mentioned will be appreciated, as also for the application of similar precautions in the case of motor boats, launches, and the like. Occupants of such vehicles may also be at risk from carbon monoxide poisoning in other ways. There appears, for instance, to be no doubt that a lorry with no through ventilation from front to rear-a state of affairs which http://militaryhealth.bmj.com/ may occur when the" window" in the front of the lorry behind the driver's seat is not kept open-may create a partial in the neighbourhood of the rear portion of the vehicle into which exhaust gases may diffuse and so gain entry into the lorry. Similarly, with a slow-moving vehicle, a follow­ ing wind may at times blow these gases into it. It is also stated by some that poisonous concentrations of carbon monoxide may be found in a vehicle following close behind another in traffic. Similarly aspiration of exhaust gas from below into a closed vehicle may occur owing to the passage of air currents through the upper portions of the vehicle, whether in the ordinary on September 27, 2021 way or possibly due to exhaust ventilators in the roof. In this connexion Henderson and Haggard [11] have stated that a sta­ tionary car with the motor running fills the air behind it at respiratory level with 0·04 to 0·06 per cent of carbon monoxide, and that when running at 10 miles per hour, the occupants of a car 30 feet behind are surrounded by exhaust gases to a concentration of 0·01 to 0·02 per cent. Lehmann gives J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

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somewhat similar figures as regards the carbon monoxide content of air at the back of a motor vehicle-0'04 to 0·05 per cent. Drinker considers that as far as the occupants of following cars are concerned exposure would be very transient and unlikely to cause harm, and points out that no accidents are reported from an experience of this description. The possibilities of untoward occurrences of this sort, however, cannot be altogether dismissed, and they should be regarded as a definite risk in connexion with mechanized formations under certain circumstances. It might well be expected that in narrow city streets full of a conglomera­ tion of motor vehicles or in narrow defiles or cuttings crowded with many vehicles moving very slowly, or perhaps for some reason stationary with engines running, toxic proportions of carbon monoxide might be produced sufficient to cause symptoms in point duty police or even in pedestrians and others.

In this connexion investigations carried out by Henderson and Haggard by guest. Protected copyright. in 1923 showed that 0'01 per cent of carbon monoxide was quite commonly present in certain streets in New York City, and that 0·046 per cent was occasionally present for brief periods of time. Wilson, Gates, Owen and Dawson [12] in 1926 examined the blood of fourteen traffic policemen in Philadelphia after an eight-hour tour of duty in crowded parts of the city , and found carbon monoxide blood saturation of from 0 to 30 per cent, six of the men showing values of about 20 to 30 per cent,quite sufficient to cause minor symptoms of poisoning. Other later observers, however, quoted by Drinker-Connolly, Martinek and Aeberly, 1928, and Bloomfield and Isbell, 1928~after extensive investigations found to all intents and purposes negligible concentrations in the streets of Chicago and other cities. Bloomfield and Isbell[13] concluded that the figures for street air when viewed in the light of present-day standards of exposure to carbon monoxide

did not reveal the existence of a health from this source and that http://militaryhealth.bmj.com/ the only individual who might possibly be exposed to risk from inhaling street air containing exhaust gases is the traffic officer. They also pointed out that any potential hazard there might be could be minimized by diminishing the duration of exposure at the most congested traffic stations. Hepple's work [14], too, in 1929 suggests that the risk of carbon monoxide poisoning in crowded streets is largely negligible, and in samples of air taken in traffic blocks of about two minutes' duration in London streets, the large majority showed percentages of considerably less than 0·01. Taking the wide view, we may to a material extent dismiss the possi­ on September 27, 2021 bilities of carbon monoxide intoxication of traffic duty men from our minds. We must, nevertheless, realize that, whether in peace or in war, exceptional circumstances may at times arise in narrow and enclosed streets or roads, and with them an exacerbation of risks of the nature referred to with the, consequent necessity of taking steps to against them. J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

A. E. Richmond 87

It appears pertinent at this point to give brief consideration to the question of the occurrence of carbon monoxide in garages, repair shops and the like. It is in small garages that fatal accidents are peculiarly apt to occur, owing to the fact that while most people realize the dangers of running an engine in a closed space they do not understand how quickly and insidiously acute poisoning may develop. Drinker, in order to emphasize this last point, quotes an experiment by Yant, Jacobs and Berger [15] in 1924, in which they' showed that in a garage of 2,950 cubic feet capacity, a dog was. unconscious in twelve minutes and dead in twenty-five minutes after the engine of a car had been started running at 200 revolutions per minute, and that at the end of twenty-five minutes the garage air contained 1·31 per cent of carbon monoxide. At the end of an hour the figure had risen to 1·97 per cent, and after two hours the engine stopped due to lowered oxygen in the garage air. At this point carbon monoxide content was 3·10 per cent.

Drinker also points out the obvious fallacy of the belief held by many by guest. Protected copyright. that there is no danger as long as the engine will operate. It is clear that in small garages dangerous concentrations of carbon monoxide will develop very rapidly indeed; so much so that the conditions produced would be sufficient to produce unconsciousness in a man in five minutes and death soon after. It must be remembered, also, that such factors in the situation as operating the engine with the carburettor adjusted for a rich mixture, or the performance of muscular work with the consequent more rapid inspiration and absorption of the gas, will tend to render the state of affairs considerably worse. Finally, we should not be slow to realize that fatal poisoning is often assisted by the fact that the gas renders the individual helpless and incapable of moving out into the fresh air, although he may realize the necessity for this.

As far as large garages and repair shops are concerned, the situation is http://militaryhealth.bmj.com/ one of repeated daily exposures to small quantities of carbon monoxide, and it would appear that many garages and repair shops show concentrations. of this g;tS of more than 0·01 per cent. That is to say that there is enough carbon monoxide to cause headache and malaise, if not in all at any rate in some workers after an eight-hour shift, and, as Drinker states, this will often be the case even in mild weather with a fair number of windows open. This writer in his book gives the result of blood examinations carried out by Mayers [16] in 1930 on twenty-seven garage workers exposed to 0·11 to 0·023 per cent of carbon monoxide from exhaust gases. These showed blood on September 27, 2021 concentrations varying from 0·00 to 30·1 per cent, most of the readings. being .between 2 and 20 per cent. Carbon monoxide is produced also by the detonation of explosives, and it 'is stated that 1 kilogramme of modern high explosive will give rise to 600 to 800 millilitres of carbon monoxide. It is clear, therefore, that this. aspect of the matter under discussion is a most important one from the J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

88 Carbon Monoxide Poisoning Service point of view, and readers are reminded that it is dealt with very fully in" The Medical History ofthe War, Diseases of the War," Volume lI. The gas is slightly lighter than air, and diffusion takes place so rapidly that in open spaces there is no great risk from high explosive shells, as far as poisoning is concerned, to those in the neighbourhood. When, however, such a shell, particularly if it has a delay-action fuse, penetrates the soil and bursts in the neighbourhood of a deep dug-out or other relatively confined space, the carbon monoxide generated may find its way into the dug-out and poison the occupants. Large numbers of casualties occurred in this way during the Great War, and the explosion of mines and camouflets similarly was responsible for many cases of poisoning. Mine warfare was a prominent feature of the. campaign in France and Flanders, and as evidence of this may be mentioned the fact that in 1916 alone the enemy fired 696 mInes and camoufiets and the British 750. As

warfare of this nature is likely to be indulged in again to a material extent, by guest. Protected copyright. it will be well to call to mind some of its salient features from the particular aspect of carbon monoxide intoxication. During the Great War nearly all the explosives used were of the ammonium nitrate group, chiefly ammonal. Gunpowder was employed to a negligible extent owing to the fact that it produces .excessive quantities of carbon monoxide (40 per cent with complete detonation, 54 per cent with incomplete) and that there is grave difficulty in clearing the ground of the gas afterwards. Explosives of the ammonium nitrate group used contained, generally speaking, an excess of oxygen, and theoretically should giv:e rise to little or no carbon monoxide. They are, however, hygroscopic, and in the presence of moisture comparatively large quantities of the gas may be evolved on detonation. On this account this group of explosives affords less risk of carbon monoxide poisoning when employed in the deeper and dryer mines

than when used in the shallower and moister types. http://militaryhealth.bmj.com/ Certain general considerations in connexion with and irrespective of the nature of the explosive used are of some practical importance and might well be borne in mind. In the first place, with any given explosive the amount of carbon monoxide it produces may be much increased if it is of poor quality or if insufficient or weak detonators are employed. Secondly, the experience of the Great War showed that there was very much less trouble from gas after the enemy had fired a mine (crater-formed) than after a camoufiet, when. the surface of the ground was not broken; also that when the galleries were driven through clay, mines became quickly on September 27, 2021 cleared of gas and the ground did not become impregnated with carbon monoxide to any such degree' as occurred when the galleries were driven through chalk or other pervious strata. . Thirdly, that in ground of a pervious nature it was by no means unusual for collections kno.wn as " pockets " of gas to be formed and for these to be J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

A. E. Richmond 89 tapped later, when the gas would come through with a whistling sound showing that it was under pressure. Finally, sudden inrushes of gas into galleries at the time free of gas must occasionally be expected and may be due perhaps to sudden settling of ground or possibly to changes in or in the subsoil water level. "The Medical History of the War" gives special mention to carbon monoxide poisoning in craters, and points out that the continuous fighting for craters was one of the most important features of stationary trench warfare. In view, moreover, of the fact that often only a very few minutes elapsed between the moment when the mine was exploded and the occupation of the crater by the infantry, it might have been expected that many cases of gas poisoning would have occurred in this way. In actual practice such cases were comparatively few owing to the porous condition of the earth in the crater and of the ground in the immediate vicinity, with consequent rapid dispersal of the gas .

. It was only when large quantities of gas were produced, as with an by guest. Protected copyright. incompletely detonated mine, and when atmospheric conditions were favourable (absence of wind or a dull heavy atmosphere), that gas collected and poisoned the men who had rushed the craters. Carbon monoxide is also generated in the firing of guns, and a good inany cases of intoxication with the gas occurred during the War in gun pits and especially in closed machine-gun emplacements [17] owing to the blow-back from the guns, and at one period the disablement of machine-gun crews from this cause became a somewhat serious question until measures were taken to reduce the amount of firing in prescribed periods of time within certain fixed limits. The risks, of course, were identical in tanks [18] and armoured cars from which machine guns were fired, and adequate mechanical ventilation of such armoured fighting vehicles is essential to deal not only with accumulations of carbon monoxide but also with the excessive heat and humidity which, http://militaryhealth.bmj.com/ combined with the gas referred to, are likely to exert an extremely malevolent effect on the crews. Finally, and of importance from the Service point of view, is the necessity for a word of warning in regard to the possible risks of poisoning from small petrol engines and from the use of braziers, particularly in enclosed or semi-enclosed spaces. Small power petrol engines were used for power purposes to a material extent along the whole front in France and quite frequently were installed in dug-outs. The danger from this is too obvious to need further emphasis, as also is the urgent need for ensuring that adequate arrangements for on September 27, 2021 disposing of the exhaust gases produced are made. For warming purposes, braziers also were in common use in the winter in the trenches and elsewhere, and the proper supervision of these, together with the taking of adequate steps to ensure satisfactory ventilation of any enclosed or semi-enclosed spaces in which they are employed, is clearly a 7 J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

90 Carbon )J;lonoxide Poisoning matter of extreme moment if casualties from carbon monoxide poisoning are to be avoided. ACUTE POISONING The symptoms of acute poisoning with carbon monoxide may most conveniently be considered with reference to three stages, these being

as follows: > (1) Onset; (2) established poisoning; (3) later developments and sequelre. As regards the first of the stages, Haldane's invaluable and courageous work, which included many experiments upon himself, has contributed largely to our knowledge of the symptoms. Those likely to predominate are headache, giddiness, nausea and perhaps vomiting, while in a large proportion of cases confusion of mind and inability to concentrate will appear early. The importance of these effects from the point of view of military efficiency will be fully realized, and it is clear that the fighting qualities of

troops, after being subjected to toxic amounts of carbon monoxide, even by guest. Protected copyright. for short periods, may be seriously affected. Muscular weakness may also be expected to commence development at this stage, and is of special moment as it often means that a man, while knowing he should get away from the contaminated atmosphere, is incapable of doing so. With the onset of the second stage, drowsiness becomes a marked feature of the case, and it progresses gradually to complete unconsciousness. At the same time respiration commences to fail, the manner in which this occurs tending to vary with different individuals. Sometimes, as described by Drinker, it is of the gasping type, sometimes a feeble rapid respiration so slight as to be hardly visible, sometimes rapid fluttering respirations interspersed between gasps. As regards the cardiovascular system, it is interesting to note that the action of the heart and condition of the peripheral circulation are often http://militaryhealth.bmj.com/ surprisingly good, and it is on this account that artificial respiration with inhalation of oxygen and carbon dioxide produces in many cases such rapidly beneficial results. In general the heart rate is much increased, and cardiac dilatation of greater or lesser degree occurs, while the blood-pressure falls, but natmally symptoms and signs will vary much with the degree of poisoning and with the condition of the heart prior to its occurrence. It appears clear, moreover, that only those with sound hearts develop chronic cardiac diseases as the. result of carbon monoxide intoxication, the others being killed off. Hence on September 27, 2021 the greatly increased risk to the individual who has a cardiac lesion. Considering for a moment the results of electrocardiographic and clinical examinations, the conclusions come to by Stearns, Drinker and Shaughnessy [19], who in 1938 made examinations of this nature of twenty-two patients who had been poisoned by illumination gas, are important. J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

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These were as follows :- (1) Carbon monoxide asphyxia, even though severe enough to cause death, may produce no important electrocardiographic changes. (2) Changes in the T-waves and in the S-T segments occur most frequently. (3) Paroxysmal auricular fibrillation may appear in patients within the age-group in which any physiological insult or trauma may cause this condition. (4) One case of transitory intraventricular heart block occurred in the series. (5) No cases of auricular ventricular heart block definitely attributable to carbon monoxide poisoning were found. As regards the blood-vessels it would appear that carbon monoxide has but little effect except in severe cases of poisoning, but in these the fragility of the capillaries is undoubtedly increased. This is borne out by the evidence of autopsies at which changes are likely to be found in the blood­

vessel walls, and also by the fact that instances of thrombosis, embolism, and by guest. Protected copyright. capillary hremorrhages at times are seen. A number of observers report also the occurrence of a reddish skin coloration in the form of pink patches· on the breast, the inner surfaces of the thighs, and the cheeks. The effects of acute poisoning with carbon monoxide on the nervous system are of the greatest importance, these being due primarily to the anoxremia produced. The reactions seen will depend largely upon the rapidity of development of asphyxiation. Tetanic convulsions, grinding of the teeth, and biting movements of the jaw may be seen, while the eyes may protrude and roll. Vomiting, defrecation, urination, erection of the penis with ejaculation, may also be met with. Such symptoms will not, however, be seen so frequently in patients who have suffered from a prolonged period of asphyxia. This

is stressed by Drinker, as also. the fact that there is likely to be a great http://militaryhealth.bmj.com/ variation between the symptoms of the man who has been unconscious for some hours due to inhalation of a low percentage of gas, and of the individual who has been rapidly poisoned by a high concentration. In the former a greatly lowered temperature and serious dislocations of vital chemical equilibria are likely to predominate, while in the latter, and though on the verge of death, neuro-muscular reactions may be very rigorous. The author mentioned also refers in his book to patients supposedly suffering from dementia pr::ecox or other forms of insanity who have been proved ultimately to be cases of carbon monoxide poisoning. It might be well to mention here that though convulsions are looked on September 27, 2021 upon by many as a common symptom in intoxication with the. gas under discussion, yet they are not perhaps of as frequent occurrence as is supposed. It is reported that many men found dead from carbon monoxide poisoning have been in a natural position, some of them still holding tools, food, etc.; in their hands. Apparently, however, convulsions are more frequent with exposures to high concentrations of the gas over 0'5 per cent. J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

92 Oarbon Monoxide Poisoning

They also occur at times in recovering patients. It should be borne in mind that the symptoms of anoxremia in many respects resemble drunken­ ness, and that often a patient suffering from carbon monoxide poisoning has great confidence in his own sanity and only realizes the true state of affairs later. Also a patient possibly brought to the verge of uncon­ sciousness may think that nothing is wrong, this being particularly the case with poisoning by high concentrations.

We should now turn to a consideration of the more immediate effects of severe carbon monoxide intoxication on certain other systems and organs of the body, those symptoms of later development being dealt with in due course in connexion with the third stage or sequelre. In mild poisoning albuminuria and casts in the urine are quite frequently found but tend to disappear within some forty-eight hours. In severe cases, and after prolonged unconsciousness, occasional instances of acute renal

disease have apparently been reported, while paralysis of the bladder with by guest. Protected copyright. retention of urine is not unknown. Drinker, summarizing the available evidence, states that glycosuria will be found in practically all severe cases of carbon monoxide poisoning and that it may be present for eight to twenty-four hours, occasionally for three days, and very rarely for a week. There is, however, no valid evidence that poisoning of this nature causes diabetes or that diabetics experiencing this form of asphyxia are made worse by it. As regards visual symptoms, the patient may see flashes of light and black specks before his eyes, usually just prior to the supervention of total blackness, while dimmed vision is of frequent occurrence and early in appearance. The earliest and most constant sign of carbon monoxide poisoning is stated to be congestion of the retinal veins and hyperremia of the optic disc.

Auditory disturbances are often noted prior to the patient losing con­ http://militaryhealth.bmj.com/ sciousness. They usually assume the form of whistling, ringing, or thumping noises, though other varieties of such disturbances may be met with. Dizziness has already been mentioned as a very common symptom and one of the earliest to be noted. In severe poisoning, also, anresthesia, partial or sometimes complete, of certain areas of the skin may occur, either. early or later, and the ability to feel may be much reduced before consciousness is lost. On this account it is not uncommon to find that persons poisoned severely may be badly burned or otherwise injured. The effects of carbon monoxide poisoning on the and cerebrospinal fluid are of considerable interest, and it is noteworthy that the pressure of on September 27, 2021 the cerebrospinal fluid is invariably increased and that cerebral cedema is also present. It is the combination of these two changes which is respon­ sible for the acute headache which is a feature of this form of intoxication. Drinker quotes experiments of Haldane [20] and Forbes [21] which showed that headache, though commencing during inhalation of the gas, J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

A. E. Richmond 93 is worse during the recovery period, and that maximum congestion of the retinal vessels occurs during this time. Finally, it must be remembered that in many cases there is a very definite fall of body temperature, and although its occurrence, together with a fall in the metabolic rate, are useful to some extent owing to the' diminished oxygen demand of the tissues, yet the appearance of this sign is definitely of ill omen. This lowering of temperature was one of the more characteristic effects of carbon monoxide poisoning in British troops during the War, and a reference to " The Medical History of the War" gives evidence that even in mild cases the patients complained bitterly of cold. This state of affairs was much more marked in severe poisoning and added to the difficulties of treatment, especially if the shafts and galleries of a mine were wet. Recovering patients may go to the other extreme and the pyrexia may be high and last for a few days. Drinker considers that this usually signifies damage to the brain. We must now devote our attention to those later developments of acute by guest. Protected copyright. carbon monoxide poisoning which are included in the third or sequela stage. Dealing first with the nervous system amnesia is of frequent development after recovery from unconsciousness, and the patient cannot remember what happened prior to his being poisoned. Confusion may also accompany the amnesia. Leschke [22] stresses the fact that criminal acts may be performed during the confusion state. He quotes the case of the captain of a ship who had inhaled charcoal fumes in his cabin and shot the ships' boy who came to wake him, and that of a signalman who killed his wife and injured his sister­ in-law and who only escaped the penalty of the law owing to the finding of carbon monoxide in the blood from his wife's body. It would seem that in some cases it may be days or even weeks before cerebral disorders appear, and during this time. the patient may feel quite well. http://militaryhealth.bmj.com/ Mental disturbances are not dependent upon the severity of the poisoning and may occur in slightly poisoned patients. On the other hand, as stated by Leschke, they are usually present in victims who have been unconscious for days. It is of some moment to realize also that mental symptoms may be intermittent in their appearance and not continuous. Psychotic changes due to carbon monoxide poisoning are very variable in form and are again sometimes continuous and sometimes intermittent. Raving madness, attacks of destructiveness, and all stages of excitement may be found on the one hand, and acute depression, apathy, dementia, and on September 27, 2021 the like, on the other. Drinker, referring to the duration of a psychosis consequent upon carbon monoxide poisoning, states that it is usually in accord with the original severity of the poisoning. Mild cases may show mental symptoms for several weeks only. More serious cases showing complete dissociation and confusion, amounting J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

94 Carbon Monoxide Poisoning practically to coma, may exhibit mental symptoms for months or even permanently. Drinker emphasizes the point that improvement invariably starts a short time after the onset, and follows a fairly rapid course to complete recovery or to the final permanent condition. In discussing the incidence of permanent mental and neurological disease after poisoning, he points out that in a study of 21,143 cases over a ten-year period in New York City, permanent damage of this nature could only be found in thirty-nine patients. All of these had been severely poisoned and had records of long periods of unconsciousness, and none was an instance of chronic poisoning. In thirteen cases there was a clear period of seven to twenty days preceding the onset of symptoms. Carbon monoxide poisoning is a generalized asphyxia, and it is not to be wondered at that there is an extraordinary variation in the mental and nervous manifestations of this intoxication, and apart from those already mentioned there are others which may occur. Hypertonia of the muscles, increased deep reflexes, ankle clonus, Parkin­ by guest. Protected copyright. sonism, etc., due to the effects of the poison on the basal ganglia, may all be seen at times. Wrist-drop, toe-drop, skin anmsthesias and the like are described, but these peripheral nerve manifestations are stated by Drinker to be less characteristic of the neurological sequelm than is some degree of Parkinsonism. Finally, patients occasionally show hemiplegia, due usually to a cerebral thrombosis. As already indicated, the amount of nervous daIllage done is apparent very early in the course of the case and the maximum effect is reached very quickly. Drinker considers that some degree of improvement may confidently be expected during the first two years, but that after this time the changes are established permanently and no further improvement can be contemplated. As regards sequelm of acute poisoning in connexion with the special http://militaryhealth.bmj.com/ , a number of cases of permanent damage to vision are on record almost invariably as the result of severe poisoning with long periods of unconsciousness, the lesions being usually due to damage to the nuclei of the ocular nerves. Permanent damage to hearing occurs very rarely, while as regards smell and lasting interference with the functions of these organs of special is practically unknown. Temporary affections of the taste and smell are stated by Les~hke to be common, while temporary disturbances of hearing are of frequent occurrence.

Dizziness, although in a large proportion of cases an early symptom, very on September 27, 2021 rarely persists for any length of time. As in the case of brain and nerve damage, cardiac sequelm definitely attributable to carbon monoxide poisoning are rare. Drinker quotes a case of what seems to be the commonest type of cardiac sequel-a patient with dyspnooa and cardiac enlargement who died suddenly eleven months after J R Army Med Corps: first published as 10.1136/jramc-73-02-02 on 1 August 1939. Downloaded from

A. E. Richmond 95

being poisoned. Unconsciousness at the time of poisoning had lasted three days, but after recovery his pulse was regular though rapid till death. At autopsy on macroscopic examination nothing was found except dilatation of the heart. The patient had, prior to being poisoned with carbon monoxide, been in the best of health. Sudden death of cardiac origin consequent upon exposure to carbon monoxide is comparatively common, and is believed to be due to ventricular fibrillation; the situation would seem to be that acute poisoning will kill a fair proportion of individuals with healthy hearts, but only those with absolutely sound cardiac organs will produce the few cases of chronic cardiac disease definitely attributable to carbon monoxide poisoning. Those with defective hearts invariably succumb to the poison. A few words are necessary on the subject of pneumonia as a sequela of carbon monoxide poisoning, especially as a num.ber of such cases among British troops were reported during the War. In most of these it is stated exposure had been prolonged. and the per­

centage of carbon monoxide in the air, though not large, was sufficient to by guest. Protected copyright. cause prolonged oxygen of the lungs and nervous tissues. The disease apparently was a rare development following short exposures to high concentrations of the gas. Notable features of pneumonia as a of carbon monoxide are [23]: (1) Its development normally within four days of exposure to the gas and very often in the right lung; (2) it is almost always lobar in type except when caused by nitrous fumes in addition; (3) it is extensive in distribution and runs a rapid course; (4) the pulse-rate is out of all propor­ tion to the temperature, which is frequently low; (5) The heart collapses with great rapidity. The possible appearance of a reddish skin coloration in certain areas. has already been referred to. On these patches at a later stage persistent herpes may· develop or large blebs followed at times by sloughing.

Bed-sores, too, develop easily in severely poisoned individuals, while http://militaryhealth.bmj.com/ the occurrence of oodema is by no means unknown. Drinker considers that trophic phenomena of the nature mentioned are due rather to an underlying neuritis than to any other cause, and states that in his experience serious phenomena of this nature are quite uncommon. This brings to a conclusion our consideration of the more important sequelffi of acute poisoning with carbon monoxide with the exception perhaps that mention should have been made of the occurrence in a small proportion of cases of sexual impotence, probably cerebral in origin; while, as animal experiments quoted by Drinker would seem to indicate, there may also be in on September 27, 2021 some patients adverse effects on testes or ovaries resulting in loss of fertility. The reader will realize that with a general intoxicant such as carbon monoxide the effects may be manifold, and that all that has been attempted . by the writer is to tabulate those of this pathological condition which are the most likely to be met with. (To be continued.)