A blood test for gas composition occupies a rather important place in medicine, since it can be used to determine how much the body is saturated with air. And this, in turn, makes it possible to determine the effectiveness of therapy, as well as to diagnose a person with a primary form of hyperventilation and respiratory failure.
What is this analysis?
If you explain the features of the analysis of arterial blood gases in an understandable language, it can be noted that this study shows how well the lungs transport oxygen into the blood.
During the passage of blood through the lungs, it is saturated with oxygen. The blood then transports oxygen throughout the body. At the same time, carbon dioxide is removed from the blood with the help of the lungs. Blood sampling is carried out precisely from the artery, for the reason that arterial blood does not yet have time to transfer oxygen to other tissues, as a result, it becomes possible to realistically assessthe ratio of these gases in the body.
Thus, thanks to the analysis of blood for gases, you can find out about its acidity, about the degree of oxygen and carbon dioxide content. Based on the data obtained, we can conclude about the work of the lungs, namely, how they deliver oxygen to the body.
Blood passing through the lungs is saturated with oxygen. Then it spreads throughout the body to all organs. At the same time, the blood is cleared of carbon dioxide by the lungs. It is important to take the analysis before the blood is cleared, so it is taken from the artery. This allows you to measure the actual concentration of gas impurities in the blood.
Measurables
Blood gas analysis allows you to study the following indicators:
- Partial pressure of oxygen. This value is responsible for how easily oxygen is transported from the lung tissues to the blood.
- Partial pressure of carbon dioxide. Allows you to study how easily carbon dioxide is removed from the blood.
- Acidity. The level of acidity shows the amount of hydrogen ions in the blood.
- Bicarbonate. This is a substance that helps maintain the required level of acidity in the blood.
Indications
Blood gas testing is required in the following cases:
- there is a need to detect respiratory pathologies and lung diseases;
- to control the course of lung disease therapy;
- to determine the need for additional oxygen (mechanical ventilation);
- to measure acid-base balance in people with heart or kidney failure, diabetes, insomnia, severe infections.
Features of the analysis
Analysis of arterial blood gases does not require special training, the only thing you need to do is tell the doctor about the medications you use and the presence of various kinds of allergic reactions.
Before taking blood from an artery, an assessment of the state of blood flow is initially carried out. To do this, press the artery and analyze the degree of blanching of the distal region of the body. If the blood flow is weak, then other blood vessels are used to draw blood. Most often, blood is taken from the arm.
After a 2 ml blood sample is taken, the puncture site is pressed for 5-10 minutes. It is imperative to take into account the high pressure present in the arterial bed.
Complications
Since biomaterial for blood gas analysis is taken from an artery, a number of complications may develop:
- hematoma at the injection site;
- dizziness and feeling of nausea directly during biomaterial sampling;
- bleeding;
- occasionally a needle can damage a nerve ending.
Factors distorting results
When taking a blood gas test, there are a number of factors that can cause distortion of the final results:
- high or low temperaturebody indicators;
- anemia or erythrocytosis - these pathologies degrade the quality of oxygen, which is carried along with the blood;
- immediately before the delivery of the biomaterial there was contact with tobacco.
Indicators of acid-base balance
Analysis of the composition of gases in the blood includes the study of acid-base balance, the norm of which varies depending on age:
- adults - 7, 35-7, 45;
- children - 7, 31-7, 47.
As a result, it is concluded that if the value of the acid-base balance is less than 7.35, then the body contains an excessive amount of carbon dioxide. A value greater than 7.45 indicates an excess of alkali.
Oxygen pressure state study
The norm of oxygen pressure also differs depending on age:
- adults - 4, 7-6;
- children - 4, 3-8, 1.
When taking a blood gas test, this indicator may be within the normal range or be reduced. In the latter case, the formation of hypoxia is diagnosed, which is accompanied by an increase or decrease in the amount of carbon dioxide.
Carbon dioxide pressure indicator
The norm of such an indicator as the pressure of carbon dioxide is also completely dependent on age. In both cases, the pressure is between 35 and 45 mm.
If the studied indicator is less than 35 mm, then this indicates a violation of hyperventilation. ATthe body is deficient in carbon dioxide. With an indicator of more than 45 mm, an excess amount of carbon dioxide is diagnosed, which entails a decrease in heart rate and the development of a patient's anxiety.
Bicarbonate indicator
Depending on the age of the patient, the following normal bicarbonate levels are distinguished:
- adults - 22-28;
- children - 15-25.
If the value is below normal, then this may be a sign of the development of renal pathologies, dehydration or a metabolic form of acidosis. Exceeding the norm often develops with excessive use of steroids, hyperventilation and a metabolic form of alkalosis.
Acidosis and alkalosis
In layman's terms, a blood gas test determines whether the body is getting enough oxygen. You should also understand what acidosis and alkalosis are. These pathologies are among the conditions that signal the body about the complete depletion of its protective functions, as a rule, this is due to failures in the acid-base balance.
There are several types of acidosis:
- Respiratory acidosis is a pathology characterized by a decrease in acid-base balance and an increase in carbon dioxide pressure. The development of a pathological condition occurs due to a decrease in the volume of breathing. A similar condition can develop against the background of pneumonia, exacerbation of bronchial asthma, or obstructive bronchial diseases. With gas analysisblood is diagnosed with the presence or absence of respiratory failure.
- Metabolic acidosis - develops due to a decrease in the amount of bicarbonate and an increase in the amount of acid released. This condition can develop against the background of kidney failure or diabetes.
Alkalosis is a condition characterized by an increase in the acidity of the blood as a result of the accumulation of alkaline elements.
There are several types of such a state:
- Compensated type. There is a violation of the acid-base balance, in which the acidity is normal, and there are only minor shifts in the buffer systems.
- Uncompensated type. Acidity indicators are outside the normal range, this is most often caused by an excessive content of bases and a small number of physiological and physico-chemical mechanisms for regulating the acid-base balance.
When taking a blood test for gases, you must follow the same preparation rules as when taking a general blood test. A few days before the examination, fatty, fried, s alty and spicy foods should be excluded from the diet.
As a rule, the patient receives a transcript of the results of the study after a few days, a maximum of a week. With the results, the patient goes to the doctor and begins treatment under his guidance.
