Bluish colour of the skin
As we mentioned previously, pulmonary embolism causes an alteration in the exchange of oxygen and CO2. There will be an impaired oxygenation of the blood because the lungs are directly affected by the blood clot and the reduction of nutrients to the tissue. In some cases, there is an irreversible loss of lung tissue, which becomes unable to exchange oxygen anymore. Therefore, in principle, there’s an increase in deoxygenated blood in the organism.
Oxygenated blood runs through the arteries, which are often pictured as red. Deoxygenated blood runs through the veins, which are often portrayed as blue. These differences are only made for educational reasons, but in practice, there’s a different colour between oxygenated and deoxygenated blood. Your blood has iron, and when this element is in contact with oxygen it will show a reddish hue, but the colour turns darker when there’s no oxygen around.
That’s why people with a pulmonary embolism get a bluish colour in their skin. Their blood is not carrying enough oxygen and starts changing colours. This can be measured by blood tests when it is not visible from the outside, but the typical patient with a pulmonary embolism would enter the emergency room with cyanosis (which is the clinical name of this coloration of the skin), shortness of breath, and chest pain.