PCO2

The PCO₂ is the partial pressure of carbon dioxide (CO₂), normally used in reference to blood, but also used in Oceanography to describe the partial pressure of CO₂ in the Ocean. 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).