What Causes Fluid in the Lungs? Top 5 Causes

Updated in December 2023

Fluid in the lungs is typically caused by a problem with the cardiovascular system, such as heart failure. It can also be caused by lung damage from infections or exposure to toxins.

Fluid in the lungs, also known as pulmonary edema interferes with breathing as it prevents oxygen from entering and carbon dioxide from leaving.

If you suspect you may have fluid in the lungs, you should see a doctor immediately for assessment and to prevent worsening. 

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Main causes

The main causes of fluid in the lungs are:

1. Cardiovascular problems

Problems in the cardiovascular system, such as increased in pressure within the heart, can prevent the blood from being pumped properly. As a result, blood can start to accumulate in the lungs, causing a further pressure the blood vessels in this area. This causes even more blood to be pushed from the heart into the lungs, which occupies even more space that should only be filled with air.

Some of the cardiovascular diseases that can lead to fluid in the lungs such as:

  • Coronary heart disease: This disease is associated with narrowing of the heart's arteries which weakens the heart muscle, reducing its ability to pump blood;
  • Cardiomyopathy: This condition is associated with weakening of the heart muscles, which also leads to inefficient pumping
  • Heart valve problems: When the valves cannot close completely or open properly, blood can start to backflow into the lungs
  • High blood pressure: This disease makes it difficult for the heart to function properly, as it has to work harder to pump blood to the rest of the body. Over time, the heart can lose the strength it needs to pump blood, leading to a build-up of blood in the lungs.

In addition, other conditions, such as kidney problems, can also increase blood pressure and make it harder for the heart to work. If left untreated, these conditions can lead to fluid in the lungs.

2. Lung infections

Some lung infections caused by viruses can cause changes in the pressures of the blood vessels in the lungs. This can lead to a build-up of fluid in the lungs.

3. Exposure to toxins or smoke

When you breathe in toxins, like ammonia, chlorine, or cigarette smoke, the lung tissues can become very irritated and inflamed, producing fluid that fills the space inside the lungs.

In addition, when inflammation is very severe, damage can occur to the lungs and the small blood vessels around them, triggering even more fluid to enter air spaces.

4. Drowning

In near-drowning situations, the lungs fill with water which is sucked in through the nose or mouth and accumulates inside the lungs. Although much of the water can be been removed with rescue maneuvers, pulmonary edema may remain and may need to be treated in the hospital.

5. High altitudes

People who scale cliffs or trail at high altitudes have a higher risk of developing pulmonary edema. When you are at high altitudes of over 2400 meters, the blood vessels undergo an increase in pressure, which can promote fluid to enter the lungs. People who are new to this type of sport are at most risk of this condition.

How to treat

If you notice symptoms of fluid in the lungs, it is important to consult a doctor so that tests can be carried out to identify the underlying cause. This will help to guide the most appropriate treatment. Treatment will also depend on the amount of fluid in the lungs as well as the patient's oxygen levels.

It is possible to prevent worsening of fluid in the lungs and ensure adequate oxygenation with the right treatment. The doctor may prescribe oxygen masks as well as diuretics to help eliminate excess fluids and maintain adequate lung functioning.