Pulmonary Edema Overview
Pulmonary edema literally means an excess collection of watery fluid in the lungs. (pulmonary=lung +edema=excess fluid). However, the lung is a complex organ, and there are many causes of this excess fluid accumulation. Regardless of the cause, fluid makes it difficult for the lungs to function (to exchange oxygen and carbon dioxide with cells in the bloodstream).
Air enters the lungs through the mouth and nose, traveling through the trachea (windpipe) into the bronchial tubes. These tubes branch into progressively smaller segments until they reach blind sacs called alveoli. Here, air is separated from red blood cells in the capillary blood vessels by the microscopically thin walls of the alveolus and the equally thin wall of the blood vessels. The walls are so thin that oxygen molecules can leave air and transfer onto the hemoglobin molecule in the red blood cell, in exchange for a carbon dioxide molecule. This allows oxygen to be carried to the body to be used for aerobic metabolism and also allows the waste product, carbon dioxide, to be removed from the body.
If excess fluid enters the alveolus or if fluid builds up in the space between the alveolar wall and the capillary wall, the oxygen and carbon dioxide molecules have a greater distance to travel and may not be able to be transferred between the lung and bloodstream. This lack of oxygen in the bloodstream causes the primary symptom of pulmonary edema, which is shortness of breath.
Medically Reviewed by a Doctor on 4/15/2016
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