What does PCO2 stand for? 

PCO2

The pCO2, PCO2, p CO 2 {\displaystyle p_{{\ce {CO2}}}} or P CO 2 {\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 P CO 2 {\displaystyle P_{{\ce {CO2}}}} in arterial blood is P a CO 2 {\displaystyle P_{a_{{\ce {CO2}}}}} . Measurement of P a CO 2 {\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).

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