When youhave your heart working on 20% why and what or hoow causes fluid in lungs?

Ejection fraction: The 20% you read is called ejection fraction and it usually is the left side of the heart. If you imagine a tank getting 100, it puts out 20 of it each time. The next beat another 100 goes in and puts out 20. Now 160 is accommodated in there, it will overflow backward to the lungs and cause too much pressure there that fluid sweats out hence the CHF and pulmonary edema. Simple to look at it.