What does blood gas analysis check?

A routine blood test can be used to analyze the health status of the body and determine whether the body is suffering from any disease. Everyone knows about routine blood tests, but what does blood gas analysis check? This type of examination is mainly performed using a blood gas analyzer, which can detect whether the body's blood gas is sufficient or insufficient. Generally, arterial blood is used for the examination, and the final result is obtained through various indicators.

Blood gas analysis (BG) is a method of understanding the respiratory function and acid-base balance of the human body by measuring the H+ concentration of human blood and the gases dissolved in the blood (mainly CO2 and O2) using a blood gas analyzer. It can directly reflect the lung ventilation function and its acid-base balance. The specimen used is usually arterial blood. Applicable to: diagnosis of hypoxemia and respiratory failure; differential diagnosis of dyspnea; differential diagnosis of coma; selection of surgical indications; application, adjustment and withdrawal of ventilator; observation of respiratory therapy; diagnosis of acid-base imbalance, etc. The blood gas analyzer can directly measure arterial oxygen partial pressure (PO2), arterial carbon dioxide partial pressure (PCO2), arterial hydrogen ion concentration (pH), and calculate a series of parameters. Today, it can measure more than 50 indicators:

The main indicators of blood gas: PO2, PCO2, CaO2, SaO2, TCO2, P50.

The main indicators of acid-base balance: pH, PCO2, HCO3-, TCO2, ABE, SBE and electrolytes (K+, Na+, Cl-, AG).

Clinical significance

It is used to determine whether the body has acid-base imbalance, hypoxia and the degree of hypoxia.

1. The pH value indicates the actual state of blood acidity and alkalinity and reflects the H concentration. pH>7.45 is alkalinity.

2. PO2 refers to the partial pressure of physically dissolved O2 alone in arterial plasma. The level of PO2 is related to respiratory function and directly affects the release of O2 in tissues. When respiratory function is impaired, PO2 decreases. When PO2 is lower than 60 mmHg, it enters the stage of respiratory failure; when PO2 is lower than 55 mmHg, respiratory failure occurs. If PO2 is lower than 20 mmHg, tissue cells lose the ability to absorb oxygen from the blood. Therefore, PO2 is often used as one of the indicators for giving patients oxygen inhalation in clinical practice.

3. PCO2 refers to the partial pressure of CO2 physically dissolved in plasma alone. PCO2>45mmHg primary respiratory acidosis or secondary compensatory alkalinity. PCO2<35mmhg is primary respiratory alkalosis or secondary compensatory acidosis. CO2 has a strong diffusion capacity, so arterial blood PCO2 basically reflects the average value of alveolar PCO2 and is an objective indicator of pulmonary respiratory function.

Normal reference range

pH: 7.35～7.45, PO2: 60～90mmHg, PCO2: 35～45mmHg.