PCO2

Carbon dioxide molecule.

The PCO₂ is the partial pressure of carbon dioxide (CO₂) in the blood. Usually the arterial blood is the relevant context; the symbol for PCO₂ in arterial blood is PaCO₂. Measurement of PaCO₂ in the systemic circulation indicates the effectiveness of ventilation at the lungs' alveoli, given the diffusing capacity of the gas. It is a good indicator of respiratory function and the closely related factor of acid–base homeostasis, reflecting the amount of acid in the blood (without lactic acid).

Values

• Its normal values are in the range 35-45 mmHg.
• If the PCO₂ is less than 35 mmHg, the patient is hyperventilating, and if the pH (potential hydrogen) is greater than 7.45, corresponding to a respiratory alkalosis.
• If the PCO₂ is higher than 45 mmHg, the patient is hypoventilating, and if the pH is less than 7.35, is in respiratory acidosis.

See also

• Acidosis
• Alkalosis
• Arterial blood gas
• Blood gas tension
• Chemical equilibrium
• pH
• pKa