What are the possible causes of shortness of breath?

Many possibilities: You're taking albuterol so asthma & copd/emphysema come to mind. Pleural effusion & pulmonary embolism, too. Bronchitis & pneumonia. Heart attack & heart failure. Abnormal heart rhythm. Pneumothorax. If that's not enough, check out http://www.Mayoclinic.Com/health/shortness-of-breath/my00119/dsection=causes. Check w/your doc for thorough evaluation.

Near infinite causes: Shortness of breath can be due to many reasons, but the common denominator is oxygen delivery. If you cannot get enough oxygen to your cells, your body feels short of breath. Wether this is significant depends on the reason - you may be out of shape, have some sort of lung disease, or some heart issue. There are many other possible reasons, so you should ask your personal doctor.