Pulmonary edema is a serious medical condition. Sometimes called pulmonary congestion or water on the lung, pulmonary edema is an excess accumulation of water in the lung tissues that results in the lungs not functioning properly. While pulmonary edema can result from a direct injury to the lung, it is commonly caused by heart failure.

When the heart is no longer effective in pumping blood away from the heart, the blood pressure in the lungs increases. The increased blood pressure causes fluid to leak out of the pulmonary veins and into the lung. This fluid in the lung then becomes a barrier to normal oxygen exchange, resulting in shortness of breath.

When severe, pulmonary edema can lead to respiratory distress and failure. Untreated pulmonary edema can be fatal. The final common pathway of pulmonary edema is fluid leaking from the blood vessels in the lung to the tissues of the lung itself. Fluid can leak from the blood vessels for two main reasons:

1. The blood vessels become injured through trauma, toxic exposure, or infection. The injured blood vessel then leaks fluid into the lung.

2. An increase of blood pressure in the vessels exceeds the blood vessels’ ability to contain the fluid, and so the fluid leaks out of the vessels and into the lungs.

Situations that can result in increased blood pressure in the blood vessels of the lung include:

• Complications of a heart attack.
• Malfunctioning heart valves.
• Cardiomyopathy.
• Increased fluid in the blood vessels due to renal failure.

Situations that can result in injury to the blood vessels in the lung include:

• Toxins such as poisonous gases.
• Excess heat, such as when a patient is in a house fire and inhales the superheated air.
• Severe viral and bacterial infections of the lung.

Like other diseases, the best treatment is fixing the underlying problem, such as lung infection, heart attack, or excessive fluid build-up in the body due to kidney disease. However, this may be difficult or impossible to accomplish in the short run.

In an emergency, physicians will treat pulmonary edema by trying to increase the amount of oxygen in the lungs, decrease the blood pressure in the lungs, and decrease the water in the lungs. An increase of oxygen can be accomplished by giving the patient oxygen by nasal cannula, oxygen mask, or endotracheal intubation.

Blood pressure in the lungs can be decreased through the use of diuretics and blood pressure–lowering medication, such as beta blockers, ACE inhibitors, or nitrate medications such as nitroglycerin. When effectively treated, pulmonary edema can resolve in a few hours, without damage to the lungs.