partial pressure of oxygen
This is called the Bohr effect where a increase in pC02 which decrease the pH leads to a decreased affinity of hemoglobin to oxygen. This means that hemoglobin unloads oxygen in areas where pC02 is high e.g. active tissue and that the binding coefficient of hemoglobin is highest in the lung where pC02 is negligible.
It means you have a high amount of carbon dioxide in your blood! Can be caused by shallow breathing or panting like during a panic attack or due to an environment where chemicals or gases remove oxygen from the air!
To find the partial pressure of oxygen, you can subtract the partial pressures of helium and carbon dioxide from the total pressure of 1 atmosphere (760 mm Hg). Partial pressure of oxygen = Total pressure - Partial pressure of helium - Partial pressure of carbon dioxide = 760 mm Hg - 609.5 mm Hg - 0.5 mm Hg = 150 mm Hg.