Most people experience shortness of breath if they exercise harder or do heavier work then they did before. In a healthy person, shortness of breath improves with rest. There are many physical disorders that may cause shortness of breath even when resting. Shortness of breath happens when the body's needs exceed the ability of the lungs and chest muscles to deliver oxygen. There are many possible causes.
Some heart problems cause breathing problems only when one is lying down or sleeping.
It usually stops when the person sits up or stands. This is a sign of a serious problem. If you are a smoker, stop now. All Rights Reserved.