DefinitionPulmonary edema is an abnormal build up of fluid in the air sacs of the lungs, which leads to shortness of breathAlternative NamesLung congestion; Lung water; Pulmonary congestionCauses, incidence, and risk factorsPulmonary edema is usually caused by heart failure. As the heart fails, pressure in the veins going through the lungs starts to rise.As the heart fails, pressure in the veins going through the lungs starts to rise. As the pressure in these blood vessels increases, fluid is pushed into the air spaces (alveoli) in the lungs. This fluid interrupts normal oxygen movement through the lungs, resulting in shortness of breath.Pulmonary edema may be caused by damage directly to the lung, such as that caused by poisonous gas or severe infection, as a side effect of medications, o