Shortness of breath has many causes affecting either the breathing passages and lungs or the heart or blood vessels. However, the causes fall into simple categories that we have listed for you below. Shortness of breath is also referred to as dyspnea. Doctors will further classify dyspnea as either occurring at rest or being associated with activity or exercise. They will also want to know if the dyspnea occurs gradually or all of a sudden. Each of these symptoms help to detect the precise cause of the shortness of breath.
An average 150 pound (70 kilogram) adult will breath at an average rate of 14 breaths per minute at rest. Excessively rapid breathing is referred to as hyperventilation.