Why does pulmonary embolism cause shortness of breath?

A clot commonly travels to a lung artery from elsewhere in the body. Air may still enter the affected air sacs, but less blood reaches them to collect oxygen. The body can respond with faster, harder breathing and a feeling of air hunger. Shortness of Breath is a very common presentation of Pulmonary Embolism. Breathlessness may begin suddenly and can occur with chest pain, a fast heartbeat, coughing, or feeling faint.

New or unexplained shortness of breath deserves prompt medical assessment, particularly when it starts abruptly or follows recent immobility, surgery, illness, or a leg that is swollen or painful. A clinician may check oxygen levels, heart rate, and signs of a clot, then arrange appropriate tests. Do not drive yourself if you feel severely unwell or faint.

Seek emergency help immediately for sudden trouble breathing, chest pain that worsens with breathing, coughing up blood, collapse, confusion, blue or grey lips, or severe dizziness. These symptoms can have several causes, but they need urgent assessment because a pulmonary embolism can become serious quickly.

Ask what may be causing your breathlessness, whether a clot needs to be ruled out, which tests are suitable, and what symptoms should prompt emergency care after you leave.