Bicarbonate and CO₂
What is analysed?
Bicarbonate and CO₂ are chemical compounds: Bicarbonate helps maintain the pH balance in the blood and CO₂ (carbon dioxide) is exchanged for oxygen during the gas exchange process.
The Bicarbonate and CO₂ test measures the levels of bicarbonate ions and CO₂ in the blood.
What does the result mean?
The result indicates the concentration of bicarbonate ions and CO₂ in the blood.
Why conduct the analysis?
The Bicarbonate and CO₂ test is conducted to assess the acidity or alkalinity of the blood vital for physiological function, to evaluate the function of the respiratory system in removing carbon dioxide from the body, and to help diagnose metabolic and respiratory disorders.
When to conduct the analysis?
The Bicarbonate and CO₂ test is conducted when assessing acid-base balance in patients with suspected metabolic or respiratory disorders, when monitoring patients with chronic respiratory conditions, or when investigating electrolyte imbalances or kidney-related issues.
What sample is required?
A blood sample is used for the analysis of Bicarbonate and CO₂. The blood is drawn from a vein, usually in the arm.
Is any prior preparation necessary?
Patients should fast for 8-12 hours before the blood sample is taken. In addition, patients should also inform a healthcare professional about any medications being taken, as they could affect results.
How is it performed?
The collected blood sample is sent to a laboratory, where it is analysed using blood gas analysis, which measures the levels of gases in the blood. This can be done through arterial blood gas (ABG) testing or venous blood gas testing.
What are the normal values?
| Analyte | Normal range |
|---|---|
| Bicarbonate (HCO₃⁻) | 22 - 26 milliequivalents per litre (mEq/L) |
| Carbon dioxide (CO₂) | 35 - 45 millimetres of mercury (mmHg) or 23 - 30 mEq/L |
What does having altered values mean?
- Low bicarbonate: Low Bicarbonate levels indicates metabolic acidosis, kidney disease, or respiratory alkalosis.
- High bicarbonate: Raised Bicarbonate levels indicates metabolic alkalosis, respiratory acidosis, or compensation for respiratory acidosis.
- Low CO₂: Low CO₂ levels indicates respiratory alkalosis, hyperventilation, or metabolic acidosis.
- High CO₂: High CO₂ levels indicates respiratory acidosis, hypoventilation, or compensation for metabolic alkalosis.