Few sensations are as frightening as not being able to get enough air. Although shortness of breath known as dyspnea is likely to be experienced differently by different people, it's often described as an intense tightening in the chest or feeling of suffocation. You may experience shortness of breath just once or have recurring episodes.

Unaccustomed or strenuous exercise — even if you're in good shape — extreme temperatures and high elevations can cause shortness of breath. More often, though, shortness of breath is a sign of a medical problem. No matter what the cause, breathing problems should be taken seriously. If you have unexplained shortness of breath, see your doctor as soon as possible.

Call 911 or emergency medical help if you have:

• Severe shortness of breath that comes on suddenly and affects your ability to function
• Shortness of breath along with other symptoms of a heart attack, including pressure, fullness or a squeezing pain in your chest that lasts more than a few minutes, fainting, and nausea and vomiting

See your doctor as soon as possible if you have:

• Shortness of breath after slight exertion or when you're at rest
• Trouble sleeping because you can't breathe or you need to be propped up with pillows in order to breathe
• Wheezing, which may be a sign of asthma or emphysema
• Shortness of breath along with a high fever, chills and cough
• Swelling in your feet and ankles and trouble breathing when you lie flat
• Shortness of breath that gets worse when you exercise or are physically active, possibly with chest pain and a dry cough