Why Does Fluid Build up in Lungs?

Fluids build up in the lungs due to toxin exposure, certain medications, heart problems and other serious medical conditions, according to the New Health Guide. Fluid in the lungs, called pulmonary edema, can result in a life-threatening condition. With pulmonary edema, the abnormal build up of fluid in the small air sacs of the lungs interferes with air flow.

The lungs contain 300 million air sacs, called alveoli. These tiny air sacs absorb oxygen when a person inhales and release carbon dioxide when a person exhales, according to the New Health Guide. When fluid fills the lungs, it becomes trapped in the alveoli and causes difficulties in breathing.

Numerous health problems cause fluid in the lungs, including cardiac problems. The New Health Guide lists coronary artery disease, cardiomyopathy, heart valve issues and high blood pressure as common cardiac causes. When the heart fails to work properly, it affects the lungs. Coronary artery disease can weaken the heart so that it does not pump blood as hard as it should. The reduced blood flow causes the blood to back up into the lungs, and the fluid in the blood passes into the air sacs. This results in pulmonary edema. Non-cardiac causes include pneumonia, toxins exposure, kidney disease, smoke inhalation and medication reaction, as well as, living at high elevations and other types of lung infections.