Pneumothorax

TL;DR. Pneumothorax is a life-threatening emergency where air accumulates around the lungs, causing them to collapse; immediate veterinary care is critical, but with prompt treatment, about 86% of dogs and cats survive.

In a healthy pet, negative pressure keeps the lungs inflated. When air enters the pleural space, that vacuum is lost, causing the lungs to collapse.

What is it?

To understand pneumothorax, it helps to picture how your pet's chest works. The chest cavity is a completely sealed, airtight chamber. Inside this chamber, the lungs are surrounded by a thin space called the pleural space. Normally, this space contains no air and only a microscopic amount of lubricating fluid. This vacuum-like environment maintains a constant negative pressure, which is absolutely vital for breathing.

When your pet inhales, the chest wall expands and the diaphragm pulls backward. Because of the negative pressure in the pleural space, the lungs are pulled open along with the chest wall, drawing in fresh oxygen. If air somehow leaks into this sealed space, the vacuum is broken. Without negative pressure, the lungs lose their ability to expand. Instead, the natural elasticity of the lung tissue causes them to collapse, a clinical state known as atelectasis.

As the lungs collapse, they can no longer transfer oxygen into the bloodstream, leading to a severe drop in blood oxygen levels (hypoxemia) and a buildup of carbon dioxide. Depending on how the air enters the chest, veterinarians classify pneumothorax into several types:

• Closed Pneumothorax: Air leaks into the pleural space from an internal source, such as a tear in the lung tissue or the windpipe, while the outer chest wall remains completely intact.
• Open Pneumothorax: Air enters the pleural space from the outside environment through a wound in the chest wall, often referred to as a "sucking chest wound."
• Tension Pneumothorax: This is the most dangerous form. Air enters the pleural space during inhalation but cannot escape during exhalation, acting like a one-way valve. With every breath, pressure builds inside the chest, eventually compressing not only the lungs but also the heart and major blood vessels, rapidly leading to cardiovascular collapse.