Final answer:
The symbol PO2 represents the partial pressure of oxygen, which measures the concentration of oxygen gas within a mixture and is calculated based on the percent content of oxygen in the mixture and total atmospheric pressure.
Step-by-step explanation:
The symbol PO2 is used to indicate the partial pressure of oxygen. The partial pressure is a measure of the concentration of an individual gas within a mixture of gases and is proportional to the percent content in the mixture. To calculate the partial pressure of oxygen, you can use the formula P = (Patm) X (percent content in mixture). In air at sea level, with an atmospheric pressure (Patm) of 760 mm Hg and oxygen making up approximately 21 percent of the atmospheric gas, the calculation would be PO2 = (760 mm Hg) X (0.21), resulting in a partial pressure of approximately 160 mm Hg for oxygen.