pneumothorax
Meaning of pneumothorax: Air in the wrong place: the lung does not burst, it simply loses the gentle suction that holds it open against the chest wall.
Definition of pneumothorax
A pneumothorax is a collection of air in the space between the lung and the chest wall, where no air normally exists. The lung is held expanded by slight suction in that space, so air leaking into it lets the elastic lung shrink away from the wall. The collapse may be small and barely noticed, or large enough to interfere with breathing and circulation.
Why does the lung collapse?
Lung tissue is elastic and would recoil to a fraction of its size if nothing held it out. It stays expanded because the pleura, the double membrane between lung and chest wall, encloses a sealed film of fluid at slightly below atmospheric pressure. That gentle suction keeps the lung surface tracking the moving chest wall. Puncture either layer and air rushes into the gap until pressures equalize, and the lung springs inward while the chest wall springs slightly out. The airless region takes no further part in gas exchange, much as in atelectasis from a blocked airway, although the cause is entirely different.
What are the types?
| Type | How air gets in | Typical setting |
|---|---|---|
| Primary spontaneous | A small blister on the lung surface ruptures | Tall slim young adults with no known lung disease |
| Secondary spontaneous | Already damaged lung tissue gives way | Emphysema, cystic fibrosis, severe infection |
| Traumatic | A wound or a broken rib breaches the chest | Injury, penetrating wounds, blast |
| Iatrogenic | A needle, drain or line punctures the lung | Chest procedures, ventilation at high pressure |
Sudden sharp one-sided chest pain with breathlessness is the usual presentation, and the pain is often worse on breathing in. A small collection in an otherwise healthy person can settle as the air is slowly reabsorbed. The same volume in a lung already damaged by disease causes far more trouble, because there is less reserve to lose.
Why is a tension pneumothorax an emergency?
Sometimes the leak acts as a one-way valve, letting air into the pleural space with each breath and refusing to let it out. Pressure then climbs above atmospheric and pushes the collapsed lung, the heart and the great veins toward the opposite side. Blood returning to the heart is squeezed off, so blood pressure falls while breathing becomes desperate. That form is immediately life threatening and is acted on from examination rather than after imaging, because the delay itself is dangerous. Sudden one-sided chest pain with breathlessness is separated from pneumonia by its abrupt arrival in a person who was previously well.
Also known as
Used in a sentence
A right-sided pneumothorax was visible on the chest radiograph.
Good to know
A tension pneumothorax raises pressure inside the chest and obstructs blood returning to the heart, which makes it immediately life threatening, and the abrupt onset of one-sided pain distinguishes any pneumothorax from the gradual course of a chest infection.
Word origin
Where “pneumothorax” comes from
From the Greek pneuma, meaning air or breath, and thorax, meaning chest.