Determination of carbon monoxide

Carbon monoxide (CO, carbon monoxide, carbon monoxide) is a gas without color, taste and smell, which does not cause irritation, an incomplete combustion product. It is a part of many industrial gases (blast furnace, generator, coke); the content of carbon monoxide in the exhaust gases of internal combustion engines can reach 1-13%.

Carbon monoxide, when inhaled, combines with the oxygen-binding regions of hemoglobin (has an affinity for hemoglobin 220 times greater than oxygen). The resulting product - HbCO - can not attach oxygen. Moreover, the presence of HbCO reduces dissociation of oxygen from the remaining oxyhemoglobin, which reduces the transport of oxygen in the tissue. Stronger than all suffer from the brain and heart. In healthy non-smoking adults, the HbCO level in the blood is less than 1%. This level corresponds to the endogenous formation of CO under heme catabolism. For smokers, the HbCO content is 5-10%. In people in an atmosphere containing 0.1% CO, the level of HbCO in the blood can reach 50%.

The main signs of CO intoxication are associated with hypoxia and develop in the following sequence: psychomotor disorders, headache and a sense of compression in the temporal region, confusion, tachycardia, dyspnea, fainting and coma. Further deep coma, convulsions, shock and respiratory arrest develop. Individual variability of clinical manifestations of intoxication at a specific concentration of HbCO in the blood is traced. At a HbCO level below 15%, symptoms of poisoning rarely occur; the collapoid state and fainting may be observed at a concentration of approximately 40%; and at concentrations above 60% there may be a fatal outcome.

In addition to determining HbCO in the blood, which requires special equipment, there is an easier way to diagnose CO poisoning. Blood containing CO, with the addition of 1% solution of tannin acquires a red shade, not containing CO - gray.

The relationship between HbCO concentration in the blood and clinical manifestations

Concentration of HbCO,%	Clinical manifestations
0-2	No Symptoms
2-5	Detect from moderate smokers, usually no symptoms, but there may be a decline in intelligence
5-10	They are found in malicious smokers, accompanied by mild dyspnea with stress
10-20	Dyspnoea with moderate stress, mild headache
20-30	Headache, irritability, violation of self-control and memory, fast fatigue
30-40	Severe headache, blurred vision, confusion, weakness, dyspnea
40-50	Tachycardia, dyspnea, severe headache, confusion, fainting, ataxia, collapse
50-60	Coma, intermittent seizures
More than 60	Insufficiency of breathing and death, if no help is available
80	A quick death

In a CBS study, p _a O ₂ is normal, although in reality the oxygen content in tissues is reduced, p _a CO ₂ can be normal or slightly reduced, the pH is lower (metabolic acidosis due to tissue hypoxia).

In acute intoxication treatment should be aimed at maintaining the function of breathing. Oxygenotherapy with 100% oxygen is important, which must be started as early as possible. Its goal is to increase the oxygen content in the blood by maximizing its fraction dissolved in the plasma. It should be remembered that at an air pressure of 1 atm, the half-life of CO is approximately 320 minutes, with 100% oxygen inhalation it is reduced to 80 minutes, and during hyperbaric oxygenation (2-3 atm) - up to 20 minutes. The HbCO level should be determined every 2-4 hours and continue treatment with oxygen until HbCO drops to 10%.

[1], [2], [3], [4], [5], [6],