Cause of pulmonary edema
Causes The causes of pulmonary edema vary. Pulmonary edema falls into two categories, depending on where the problem starts. If a heart problem causes the pulmonary edema, it's called cardiogenic pulmonary edema. Most often, the fluid buildup in the lungs is due to a heart condition. If pulmonary edema is not heart related, it's called noncardiogenic pulmonary edema. Sometimes, pulmonary edema can be caused by both a heart problem and a nonheart problem. Understanding the relationship between the lungs and the heart can help explain why pulmonary edema may occur. How the lungs work Lungs contain many small, elastic air sacs called alveoli. With each breath, these air sacs take in oxygen and release carbon dioxide. Typically, this exchange of gases occurs without problems. But sometimes, the alveoli fill with fluid instead of air. This keeps the bloodstream from taking in oxygen. How the heart works The left and right atria and left and right ventricles Chambers and valves of the heartOpen pop-up dialog box The typical heart is made of two upper and two lower chambers. The upper chambers (the right and left atria) receive incoming blood and pump it into the lower chambers (right and left ventricles). The lower chambers pump blood out of the heart. Typically, blood without oxygen from all over the body enters the right atrium then the right ventricle. From there it's pumped through large blood vessels (pulmonary arteries) to the lungs. There, the blood releases carbon dioxide and picks up oxygen as it flows by the alveoli. The oxygen-rich blood then returns to the left atrium through the pulmonary veins. It then flows through the mitral valve into the left ventricle. Finally, it leaves the heart through the body's main artery (aorta). The heart valves keep blood flowing in the right direction. The aortic valve keeps the blood from flowing backward into the heart