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Carbon monoxide (CO) is one of the most abundant in nature, poisonous and polluting gases in the modern energy-intensive world.
The main source of carbon monoxide is the incomplete combustion of fossil fuels, especially coal. Vehicle exhaust fumes are the most serious source of carbon monoxide in the environment. Smoking is another source. Cigarette smoke contains 3–6% CO, giving it 8 times higher concentration in the air than the allowed concentration of carbon monoxide in the industry.
Non-smokers are also exposed to the passive absorption of tobacco smoke; this is especially dangerous for children and pregnant women.
In recent years, all over the world, severe winters and the energy crisis have resulted in the improvement of housing insulation and the increased use of various types of domestic heating sources, which, in the event of inefficient ventilation, significantly increased the possibility of CO poisoning. Thus, these poisonings often occur in households when cooking on gas stoves in dishes with a large bottom surface. With poor oxygen availability, combustion is limited and CO is formed from the carbon compounds contained in the natural gas. It is believed that – unlike light gas – natural gas is quite safe and as long as the flame is burning, it does not emit, so there is no danger. The possibility of CO formation during normal gas combustion is not taken into account. Clogged chimney and ventilation ducts, improperly connected hood above the gas cooker may cause the accumulation or incorrect discharge of exhaust fumes, e.g. to a neighbor’s apartment. CO accumulated in the bathroom during bathing is especially dangerous.
Carbon monoxide mixes easily with air and spreads easily, is odorless, colorless, tasteless, non-irritating. These features prevent the victim from recognizing the potential danger, which is why the gas was dubbed the “silent killer”. There is often poisoning with carbon monoxide escaping from furnaces (so-called carbon monoxide), as a result of premature closing of the gate valve, leaks in the furnace, or even the passage of this gas through the red-hot casings of cast iron stoves.
The toxic effects of CO have been known for thousands of years. Already in the times of Hippocrates, it was used to kill political prisoners. It easily penetrates the alveolar-capillary membrane of the lungs into the blood and binds to hemoglobin (the red blood pigment), making it unable to carry oxygen to the tissues. Due to changes in the structure of the formed molecule of carbon monoxide hemoglobin (HbCO), the dissociation curve of HbO2 (oxyhemoglobin) shifts to the left, so the partial pressure at which oxygen becomes available to tissues decreases. In healthy people, the normal concentration of HbCO does not exceed approx. 0,5%. This concentration may increase to 4-6% in patients with eg haemolytic anemia. Carbon monoxide has about 240 times greater affinity for hemoglobin than oxygen. Therefore, inhalation of relatively low concentrations of this gas may induce a clinically significant decrease in the oxygen capacity of red blood cells. This means that the HbCO concentration will reach 50% when the CO concentration in the ambient air is only 1/240 part of the oxygen concentration, i.e. 0,08%.
In addition to hemoglobin, carbon monoxide also reacts with:
– with other Fe-containing haemoproteins2+;
– with myoglobin – red muscle pigment;
– with cytochrome oxidase, cytochromes, including cytochrome P-450.
Thus, as a result of the action of CO, both anemic and histotoxic hypoxia (hypoxia) occurs.
Carbon monoxide mainly damages the organs and tissues most sensitive to hypoxia and metabolic acidosis, i.e. the cardiovascular system and the central nervous system. The effect of high concentrations of CO over a short period of time is less harmful than the effect of low concentrations over a long period of time. The binding of CO to Hb is inversely proportional to the molecular pressure of oxygen. This rule is the basis for 100% oxygen treatment to displace CO from the HbCO complex.
Symptoms of poisoning
Acute CO poisoning can be considered a model of poisoning with a substance that does not undergo any changes in the body and affects all organs, especially the brain and heart. Most people experience headaches, dizziness, agitation, hyperventilation or coma. With sudden exposure, only weakness and dizziness may precede syncope and cardiovascular collapse. Observations of collective poisoning of young people, i.e. previously healthy people, indicate that despite the same exposure to a specific concentration of CO – symptoms in co-poisoned people are often different. Anemic and histotoxic hypoxia (hypoxia) causes lesions mainly in the organ “critical” for a given individual.
The neurological symptoms of poisoning are manifested, inter alia, by disorientation, toxic coma, muscle stiffness or laxity. Computed tomography shows changes in image density in certain subcortical nuclei of the brain, which indicates that CO poisoning is associated with cortical and subcortical brain atrophy.
The most insidious consequence of CO poisoning is the appearance of neuropsychic symptoms after a latent period of 1–6 weeks. About 10–30% of people after severe CO poisoning develop symptoms in the form of memory disorders, personality changes, euphoria, impaired judgment and the ability to think abstractly, poor concentration of attention.
CO poisoning in pregnant women also affects the fetus, posing a serious threat to the life and proper neurological condition of the child.
After poisoning with CO, inflammation of the respiratory tract is common, and in severe cases, even pulmonary edema and hemorrhage. In acute poisoning, there is also toxic damage to the liver. Muscle necrosis may occur. CO poisoning should be considered in cases of renal failure and myoglobinuria occurring without identifiable causes. CO poisoning damages the sense organs, especially the hearing and sight organs.
Symptoms of poisoning
1. General weakness, fainting.
2. Nausea, vomiting.
3. Heartbeat, palpitations, very fast heartbeat, uneven heartbeat.
4. Headaches, dizziness.
5. Imbalance.
6. Muscle tremors.
7. Visual and auditory disorders.
8. Loss of consciousness.
What to do in case of poisoning?
1. Take the poisoned carbon monoxide out of the atmosphere.
2. Check the airway patency in the unconscious (clear the mouth of secretions and excretions).
3. Place an unconscious person safely on their side with the head tilted back.
4. Give oxygen (possibly fresh air, open windows).
5. If there is no breathing, give mouth-to-mouth breathing.
6. In the absence of heart beat, hit the sternum – external heart massage.
7. Call an ambulance with a doctor.