When a blood clot travels to the lungs, doctors refer to it as a pulmonary embolism. Most clots that reach the lungs are small and non-life threatening. With that said, smaller clots can still cause substantial damage to the lungs. If the clot is large, it can stifle proper blood flow and become deadly, so quick treatment is essential. One of the most common symptoms to look for is a sudden shortness of breath; if an individual is short of breath with lack of physical movement, he or she may be suffering from a pulmonary embolism. This condition can cause the patient to experience chest pain, breathing problems and heart palpitations. In some cases, a pulmonary embolism causes one to cough up blood as well.