What Is Pulmonary Edema? - Definition, Causes, Symptoms & Treatment

Instructor: Heather Zonts

Heather has taught in AD and BSN Nursing programs and has a master's degree in nursing.

Pulmonary edema severely impacts the lives of those suffering from it. This lesson will define pulmonary edema, what causes it, symptoms, and how to treat it to assist in your understanding of pulmonary edema.

Pulmonary Edema - Definition

Pulmonary means lungs and edema means swelling caused by fluid accumulation. So when talking about pulmonary edema, we mean when the lungs fill with fluid or blood. The fluid will move into the small airways, specifically the alveoli. When the fluid moves to these areas, it limits the body's ability to participate in the exchange of oxygen and carbon dioxide from the blood to the lungs.

This shows the alveoli. You can see how the arteries (carry deoxygenated blood to the lungs) and the veins (carry oxygenated blood to the heart) lead to the capillaries that encase the alveoli.
Alveolus diagram


A number of factors can cause pulmonary edema. When considering the definition, try to think about what would cause either a backup of fluid or excess fluid. Let's start with a backup of fluid. The heart pumps blood throughout the body. If the heart is having difficulties, such as in congestive heart failure, the fluid can become backed up in the lungs and because of pressure changes will move into the alveoli, causing pulmonary edema.

Look at how the blood flows from the heart to the lungs. If the heart is overwhelmed with fluid it will backflow into the lungs causing pressure changes in the capillaries leading to fluid shifts into the alveoli.
Pulmonary Circuit

Now let's look at what can cause excess fluid accumulation in the body. If someone has impaired function of their kidneys, they can have excess fluid. You may ask why. The kidneys are the filtering unit of the body. They eliminate excess wastes and fluids. If they are not functioning appropriately, excess fluid is not filtered out and the person experiences fluid overload. Impairments in heart function can also lead to excess fluid because the heart pumps the fluid to the kidneys. If the heart is not pumping efficiently, then the fluid does not arrive at the kidneys for filtering.

The heart pushes fluid to the kidneys. The kidneys then work to eliminate excess fluid through the filtration process. If the kidneys cannot filter, as you can see in this picture, the fluid will backup in the circulatory system, leading to pulmonary edema.
Kidney Blood Flow

Another reason for the fluid shift from the circulatory system to the lungs is the change in pressures associated with exposure to high altitudes. These pressure changes cause a shift from the vasculature into the lungs. Now let's consider infections. Infections in the respiratory system can compromise the function of the membrane between the alveoli and the blood vessels. Furthermore, this compromise can lead to fluid moving into the alveoli because it causes inflammation. With inflammation, fluid and cells will shift into the alveoli causing pulmonary edema.


Based on the definition and causes, now think about what you would see if an individual were suffering from pulmonary edema. Fluid accumulation and inability to transfer gases, i.e. bring in oxygen and eliminate carbon dioxide, would leave the individual experiencing shortness of breath. You may see this with limited activity or when the individual is trying to speak. It depends on the severity of the pulmonary edema. Now think about the fluid accumulation. What fluid is accumulating? Blood, therefore when the individual coughs you may see a 'frothy pink' sputum. This is one of the hallmark signs of pulmonary edema.

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