CARBON MONOXIDE
This gas is formed in a variety of ways, one being the oxidation of carbon at a very high temperature in a limited supply of oxygen. It is given off by iron stoves at a red heat. It is one of the chief ingredients of the vapour of burning charcoal.
To this gas is due the suffocating quality of air in which coke or charcoal is burnt. It is inodorous, hence the dangerous insidiousness with which it produces its fatal results. It is said that 0.5 per cent. will cause death, and even 0.1 per cent. is injurious. The vapours from brick kilns and “burnt ballast” heaps are injurious to health, and the owners of them may be indicted for causing a nuisance.
The fumes from burning charcoal are taken advantage of for purposes of suicide, a method frequently used on the Continent, but almost unheard of in England. The suicide generally shuts himself up in a room, which he has closed against any ventilation, and in which he has placed a receptacle containing burning coke or charcoal.
Poisoning by carbon monoxide occurs in two forms—acute and chronic.
Symptoms: Acute.—The first symptoms may be those of excitation, which are quickly followed by intense headache, giddiness, throbbing of the temples, and nausea followed by vomiting. Muscular weakness occurs, sensation and the reflexes are lost, drowsiness and coma follow, and in fatal cases convulsions often come on before death. The pulse becomes imperceptible at the wrist. The conjunctivæ become hyperæmic, the eyes staring, the pupils dilated and insensible. The voluntary and involuntary muscles are relaxed, the skin cold and cyanotic, and the lips covered with froth.
Chronic.—The symptoms are headache, neuralgic pains, anæmia, shortness of breath, and wasting; when advanced they are those of peripheral neuritis and mental disturbances.
The less severe symptoms of chronic carbon monoxide poisoning are not uncommon, and occur in those who occupy small and badly ventilated rooms, in which there may be a heating stove, gas stove, or imperfect gas fittings; the last are especially dangerous when water gas is used for illuminating purposes, as it contains a high percentage of carbon monoxide.
It is a very powerful gas, speedily causing death by acting chiefly on the nervous system, the symptoms being those produced by a pure narcotic.
The post-mortem signs are redness of the face, with reddish patches on different parts of the body. The blood—and this is chiefly characteristic of carbon monoxide poisoning—is cherry-red, due to a chemical compound formed by the action of the gas on the colouring matter of the blood, thus paralysing the oxygen-carrying power of the blood corpuscles. The gas is supposed to combine with the hæmoglobin forming a fixed compound, the spectroscopic examination showing the two absorption bands of the hæmoglobin nearer to the violet end of the spectrum than under normal conditions. (See Blood Spectra, [p. 103].)
These bands resemble those of O₂Hb, so their position must be compared with a spectrum of O₂Hb, the two spectra being side by side.
There is another important difference, however, determined by the action of a reducing agent such as ammonium sulphide. The bands of COHb are unaltered, while those of O₂Hb are reduced. Death frequently takes place before all the Hb has been changed into COHb, so that the blood contains a mixture of COHb and O₂Hb, and on the addition of a reducing agent the spectrum is a composite one of COHb and reduced Hb. Only the broad band of reduced Hb is to be seen if the amount of COHb present be less than 28 per cent. In an atmosphere containing a large percentage of carbon monoxide death may occur before the blood contains sufficient COHb to give the characteristic spectrum.
The treatment consists in the removal of the sufferer into the fresh air, artificial respiration, venesection, and the transfusion of arterialised defibrinated blood. Oxygen inhalations should be given. In two cases subcutaneous injections of nitro-glycerine were followed by recovery.