How does a pulmonary embolus interfere with respiratory function?

PE: A pulmonary embolism occurs when a blood clot (or other material) traveling from some other part of the body obstructs the blood flow of the pulmonary artery or one of its branches. The blood in the pulmonary artery is low on oxygen and is traveling to the lungs to re-oxygenate. Since the clot prevents re-oxygenation, the cells in the body do not receive oxygen and they slowly start to die.

Blood flow: The pulmonary arteries are blocked by the clots shutting off blood supply to those areas of the lung. If enough blockage occurs cardiovascular collapse can occur and cardiac arrest. Smaller amounts of clot interfere with the normal matching of ventilation and blood flow to the air units - there is ventilation but no blood flow which impairs oxygen absorption and delivery.