pCO₂

The pCO₂, PCO₂, ${\displaystyle p_{{\ce {CO2}}}}$or ${\displaystyle P_{{\ce {CO2}}}}$ is the partial pressure of carbon dioxide (CO₂), often used in reference to blood but also used in oceanography to describe the partial pressure of CO₂ in the ocean and in life support systems engineering and underwater diving to describe the partial pressure in a breathing gas. Usually, the arterial blood is the relevant context; the symbol for ${\displaystyle P_{{\ce {CO2}}}}$ in arterial blood is ${\displaystyle P_{a_{{\ce {CO2}}}}}$. Measurement of ${\displaystyle P_{a_{{\ce {CO2}}}}}$ 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).

Carbon dioxide molecule.

Values in blood

• Its normal values are in the range 35–45 mmHg.
• If the ${\displaystyle P_{{\ce {CO2}}}}$ 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 ${\displaystyle P_{{\ce {CO2}}}}$ is higher than 45 mmHg, the patient is hypoventilating, and if the pH is less than 7.35, is in respiratory acidosis.[1][2]

See also

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

References

1. Dugdale DC, Zieve D. Gasometría arterial. Medline Plus. 09/01/2012.
2. Leticia Godoy Dias Sanderson. Gasometria arterial - Artigo de revisão. Fevereiro 2012. Archived 2014-10-17 at the Wayback Machine