PCO2 is the partial pressure of carbon dioxide. This identifies the concentration of gas in the air or in a fluid. It is helpful in reference to blood, oceanography and in life support systems.
In the human body, high values indicate slow blood flow and respiration. Low values are caused by hyperventilation. pCO2 shows the exchange of carbon dioxide through the lungs to the outside air. This value is dependent on how heavily someone is breathing and what their lung capacity is for exchanging CO2 across the alveolar membrane.
Changes in pCO2 in nature come about by variations in temperature and CO2. This is a helpful indicator in plasma, sea water, and much more.