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Blood gas（BG）analysis is a means of testing the human respiratory function and acid-base balance by detecting the concentration of H+ of human blood and the gas dissolved in the blood (mainly CO2, O2) by a blood gas analyzer.
It directly reflects the lung ventilation function and its acid-base balance. Generally, the samples are arterial blood.
Blood gas analysis is applied to: diagnosis of hypoxemia and respiratory failure, differential diagnosis of dyspnea and coma, selection of surgical indications, application, adjustment and weaning of ventilator; observation of respiratory therapy, diagnosis of acid-base imbalance diagnosis, etc.
The blood gas analyzer can test the arterial oxygen partial pressure (PaO2), arterial carbon dioxide partial pressure (PaCO2), pH (pH), and derive a series of parameters, and today, more than 50 indicators can be measured.
Main indicators of blood gas: PaO2, PaCO2, CaO2, SaO2, TCO2, P50
The main indicators of acid-base balance: pH, PaCO2, HCO3-, TCO2, AB, SB and electrolytes (K+, Na+, Cl-, AG).
Blood gas analysis is used to judge whether the body has acid-base imbalance and the degree of hypoxia and hypoxia.
1. The pH value indicates the actual state of blood acid and alkali, reflecting the index of H ion concentration. pH>7.45 is alkalosis. pH <7.35 is acidemia.
2. PaO2 refers to the partial pressure produced by the physically dissolved O2 in the arterial plasma.
The level of PaO2 is related to respiratory function and directly affects the release of O2 in tissues.
In respiratory dysfunction, PaO2 decreased, PaO2 was lower than 60mmHg, and entered respiratory failure; when PaO2 was lower than 55mmHg, there was respiratory failure.
When PaO2 is less than 20 mmHg, the tissue cells lose the ability to take oxygen from the blood. Therefore, PaO2 is often used as one of the indicators for oxygen in patients.
3. PaCO2 refers to the partial pressure produced by the physically dissolved CO2 in plasma.
PCO2>45mmHg primary acid or secondary compensatory base.
PaCO2<35mmhg is primary or secondary compensatory acid.
CO2 has a strong diffusion capacity, so arterial blood PaCO2 basically reflects the average value of alveolar PCO2, which is an objective indicator reflecting lung respiratory function.
4. Anion gap (AG): refers to the difference between undetermined anion (UA) in plasma and undetermined cation (UC). Reactive metabolic acidosis.
1. Blood collection location: If the blood collection artery has infusion, hemolysis and dilution may occur, causing K+ to increase and Ca2+ to decrease.
If it is mistakenly collected as venous blood, because venous blood can not accurately reflect the arterial blood gas condition, its pH value is close to arterial blood under normal conditions, but when the body is sick, various metabolisms have different degrees of obstacles.
There is a significant difference in the pH of the arteries and veins.
2, blood collection and heparin concentration: heparin concentration is the core guarantee of accurate blood gas analysis results, excessive heparin dosage can cause dilution error, low pH, PaO2 value, high PaCO2 value, pseudo-hypocapnia.
However, if the amount of heparin is too small, the anticoagulant effect will not be achieved. The International Federation of Biochemistry (IFCC) recommends a final concentration of heparin in blood gas specimens of 50 u/ml.
3.bubbles: because the bubbles will affect the blood gas pH, PaCO2, PaO2 detection results, especially the PaO2 value. The ideal blood gas sample should have air bubbles below 5%.
4.Specimen mixing degree: As with other anticoagulant specimens, insufficient mixing will increase the occurrence of blood coagulation, thereby affecting the accuracy of hemoglobin and hematocrit results.
5. Storage of specimens: Specimens for the detection of lactic acid must be stored in ice water before testing. Other test items can be stored for 1 h at room temperature or in ice water.
6.the time of testing: PaCO2, PaO2 and lactic acid detection must be completed within 15 minutes, the rest of the project such as: pH, electrolytes, BUN, hemoglobin, blood sugar and red blood cell ratio product, required to complete within 1 h.
7. Using blood gas analyzer, the excellent blood gas analyzer can provide more detailed reference data for clinical patient rescue treatment in a better and more timely manner, and provide more effective guarantee and support for the success rate of clinical treatment and rescue!
Contact Person: Mr. Bob Zhu