What is Pneumothorax? - Definition & Causes

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

Have you ever heard of a collapsed lung? It turns out there is more than one kind. This lesson focuses on the kind that is called pneumothorax as well as its causes.

A Collapsed Lung

Have you ever heard of a collapsed lung? Did you know this term can actually refer to one of two different conditions? One of them is called atelectasis and the other is called pneumothorax. This lesson will focus on the definition and causes of only one kind of collapsed lung, that of pneumothorax. It refers to a collapsed lung as a result of air in the pleural space.

The Basics of a Pneumothorax

The word itself comes from pneumo- ,which implies lungs or air in this case and -thorax, which implies chest. Thus, it's a condition involving the lungs where air is found in the chest. Now, normally air can be found in the chest only if it's within the lungs themselves. That's how we breathe and live, of course! Air should not be found in the part of the chest that lies outside of the inner passageways of the lungs. This part of the chest is called the pleural space. It is located between the chest wall and the lungs themselves.

If that's hard to picture, imagine cracking open any nut. The nut itself is like the lungs inside the chest. The hard shell is like your chest wall. In our bodies, the area between the two is the pleural space. No air should be found here because the absence of air in the pleural space establishes a pressure gradient that allows the lungs to expand and thus breathe.

A large pneumothorax on the right side of the chest (which is on left side of image). Note how the arrow points to a lung that has collapsed to the size of a fist. The left side of the image is thus much blacker on the x-ray due to a lot of gas within the right side of the chest, where the lung should normally be present.

Causes of Pneumothorax

The causes of a pneumothorax all boil down to the introduction of air into the pleural space. This disintegrates the previously held pressure gradient and collapses a lung into a little ball that can't inflate. It would be similar to using your hand to squeeze the air out of a balloon so it collapses into a little ball that can't inflate against the pressure of your clenched fist.

Now, the lung doesn't always collapse into a little ball; it all depends on how much air is introduced into the chest cavity, as well as some other factors. Most of the time, only part of the lung actually collapses inwards, towards the center of the chest.

The causes for a pneumothorax include:

  • Injury to the chest wall, such as a bullet or arrow piercing it. The hole created by either will introduce air into the pleural space.
  • Medical procedures, such as the improper use of a mechanical ventilator. Improper pressure differences created by the misuse of a mechanical ventilator can rip a hole from the inside of the lungs. Air will thus enter into the pleural space not from the outside of the body, but from the lungs themselves.
  • Various lung diseases, such as pneumonia, which can ultimately cause a similar situation as per the described medical procedure.
  • Idiopathic causes. Meaning, we have no idea what actually triggers the condition. Sometimes it seems to occur for no clear-cut reason.

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