Posted in Web Pulmonary Embolism (Blood Clot in Lung) Causes & Risk Factors January 19, 2021 A pulmonary embolism (PE) happens when a blood clot gets caught in an artery in the lungs. This blockage can cause serious problems, like lung damage, low oxygen levels and even death. https://www.webmd.com/lung/what-is-a-pulmonary-embolism