atelectasis
Meaning of atelectasis: Often confused with a punctured lung, this is airless lung tissue rather than air escaped into the chest around it.
Definition of atelectasis
Atelectasis is the partial or complete collapse of part of a lung, in which the tiny air sacs of that region empty and fail to reopen. Gas exchange stops where the tissue is airless, so blood passing through returns to the heart without picking up oxygen. It ranges from a small incidental finding to a cause of genuine breathlessness.
What makes lung tissue collapse?
| Type | What empties the air sacs |
|---|---|
| Obstructive | An airway is plugged from inside by mucus, an inhaled object or a tumor, and the trapped air beyond it is slowly absorbed |
| Compressive | Something outside the lung presses on it, such as fluid or air collecting in the surrounding chest space |
| Adhesive | Too little surfactant, the slippery substance that stops the air sacs sticking shut as they empty |
| Cicatricial | Old scarring contracts and holds the tissue down so it cannot expand |
Collapse after an operation is common enough to be expected rather than surprising, and it draws on more than one of those mechanisms at once. Anesthesia reduces the volume the lungs hold, pain from an incision discourages deep breaths, and lying still allows the lowest and most compressed parts of the lungs to empty and stay empty. Anyone confined to bed for a long period faces the same combination. Because nothing has been destroyed, the region can usually reinflate once the reason it emptied is dealt with.
How is it different from a collapsed lung?
The phrase collapsed lung is applied loosely to both this and a pneumothorax, which is a frequent source of confusion. In atelectasis the lung tissue is airless but still against the chest wall, and the affected part shrinks, so nearby structures are pulled toward it. In a pneumothorax air has escaped into the space around the lung and presses it inward, so the volume of air in that half of the chest is increased rather than lost. The two arise differently, look different on imaging, and are handled as separate problems.
What does it look like on a chest film?
The signs are those of lost volume. The affected tissue appears denser, the fissures between lobes shift toward it, the diaphragm on that side may ride higher, and the windpipe and heart can pull in the same direction. That pattern is what separates atelectasis from pneumonia, which fills the air sacs with inflammatory material and so occupies the normal space instead of shrinking it. Small areas often cause no symptoms at all and turn up incidentally on a film taken for some other reason. Larger areas lower the oxygen level in the blood and cause breathlessness and faster breathing, and collapse of an entire lobe leaves no breath sounds audible over that part of the chest.
Used in a sentence
Chest imaging showed a small area of atelectasis at the base of the lung following surgery.
Good to know
Atelectasis and pneumothorax are both described casually as a collapsed lung, although in atelectasis the lung tissue itself is airless and shrunken, while in pneumothorax air outside the lung has pushed it inward.
Word origin
Where “atelectasis” comes from
Formed from Greek ateles, meaning incomplete, and ektasis, meaning expansion, describing lung tissue that has not expanded fully.