Pulmonary edema (pulmonary oedema in British English) is fluid in the lungs ("Pulmonary" means "lungs"; "edema" means "swelling" or "fluid"). Normally, the lungs fill with air when a person breathes in. From the alveoli in the lungs, oxygen goes into the blood. The blood then carries oxygen to the entire body. Every part of the body needs oxygen to survive.