Q. what is "pulmonary edema" and what are the risks? my Dr. told me I'm in a risk group for pulmonary edema, he tried to explain what it is but i didn't understand fully...if someone may give me a brief explanation- I'll appreciate it! A. pulmonary edema occurs when, lets say, your heart left ventricle stops working properly and your right ventricle works fine. that means your lungs getting lets presume- 1 liter of blood -but your left ventricle can pump out of it only 990 ml. that means you have high blood pressure in your lungs and fluid comes out of blood vessels and fills your lungs, making it harder and harder breathing.