To prevent pulmonary embolism, doctors usually use drugs that limit blood clotting. However, for some people, doctors may recommend that a filter (formerly called an umbrella) be temporarily or permanently placed in the inferior vena cava. This filter device typically is recommended when drugs that limit clotting cannot be used, for example, when a person is also having bleeding. The filter can trap emboli before they reach the heart but allow blood to flow through freely. Emboli that are trapped sometimes dissolve on their own.