What Is a Pneumothorax (Collapsed Lung)?

Can a lung just collapse? That sounds dramatic — and, honestly, a little alarming — but the short answer is yes, it can, and it happens more often than most people realise. A pneumothorax is the medical name for a collapsed lung, and it means air has got into the space between the lung and the chest wall, the pleural space, where air doesn't belong. That trapped air presses on the outside of the lung and stops it filling properly. The video at the top of this page, "Pneumothorax: What Is a Pneumothorax or Collapsed Lung," explains exactly that in a little over two minutes, and it's worth watching first — the picture it gives you of air pushing on a lung makes the rest of this guide much easier to follow.

So what has actually gone wrong inside the chest?

Think of the lung as a soft balloon sitting inside a sealed box — the chest wall. Normally the thin space between the balloon and the box holds only a tiny film of fluid, and the gentle suction in that space keeps the lung pulled open against the chest wall as you breathe. A pneumothorax breaks that seal. Air leaks in — from a small blister (a bleb) on the lung surface that bursts, from an injury to the chest, or from a medical procedure that involves the chest — and once air is in the pleural space, the lung can't stay fully open. Sometimes only part of the lung collapses; sometimes the whole lung goes down. Either way, less air is moving in and out, and breathing gets harder.

What does it feel like?

The usual story is sudden. A sharp chest pain on one side, often worse when you breathe in, and shortness of breath that wasn't there a few minutes ago. Some people notice a dry cough, or a tight, heavy feeling in the chest. Others feel fine at first and only notice that they get breathless walking up stairs. How bad it feels depends on how much air has leaked in and how much lung has collapsed — and on whether the lung underneath was healthy to begin with. Someone with an existing lung condition such as the one our guide to COPD describes will usually feel a small collapse much more than someone with healthy lungs. Any sudden chest pain with breathlessness deserves prompt medical attention, and a pneumothorax is one of the reasons that rule exists.

Is a tension pneumothorax the same thing?

It's the same condition, in its most dangerous form — and the distinction matters. In most pneumothoraces, the leak is small and the air in the chest stays roughly where it is. In a tension pneumothorax, air keeps entering the pleural space with each breath but can't get out, like a one-way valve. Pressure builds, the lung collapses further, and the rising pressure can start to push on the heart and the big blood vessels in the chest. That's a medical emergency, and it's treated immediately, usually by letting the trapped air out with a needle before anything else. If you've ever heard the phrase "needle decompression," that's what it refers to — a rapid, first step to release the pressure.

How do doctors find it and decide what to do?

A chest X-ray is the usual first test: it shows the edge of the collapsed lung and the dark band of air where lung should be. A CT scan gives a clearer picture when the X-ray is uncertain or the team needs more detail. What happens next depends on how big the collapse is and how breathless you are — and this is where the treatment really is a spectrum, not a single answer. A small pneumothorax in someone who is comfortable may simply be watched, with oxygen and repeat X-rays to check that the air is being reabsorbed on its own. A bigger one, or one that's making breathing hard, is usually treated by removing the air.

What does the treatment actually involve?

Removing the air usually means a needle or a tube. A fine needle can draw air out of the chest in a procedure called aspiration, and for many people that's enough. When more air needs to come out, or keeps leaking, a chest tube (also called a chest drain) is placed between the ribs into the pleural space, so air — and any fluid — has somewhere to go while the lung re-expands. Our guide to the chest tube walks through what living with one is like. The second video on this page, "Chest tube insertion for pneumothorax or hematothorax," runs to just under five minutes and shows a drain being placed in a trauma setting, positioned so that a blocked drain doesn't let a tension pneumothorax develop. For a leak that won't seal, or a pneumothorax that keeps coming back, surgeons can use the keyhole chest approach our guide to VATS explains, to deal with the leaking spot and, sometimes, to stick the lung's lining to the chest wall so it can't collapse again.

What happens after it heals?

Most people recover well once the air is out and the lung is back up, but the honest answer about the future is that it depends on the cause. A one-off collapse after a chest injury often heals and never returns. A collapse from a burst blister on an otherwise healthy lung can recur, and your team will talk through what to watch for and when to come back quickly — sudden chest pain, worsening breathlessness, or pain spreading to the shoulder are the warning signs to act on. Flying and diving are worth asking about specifically before you book anything, because pressure changes affect the air in the chest. And if you smoke, this is a good moment to hear the advice plainly: smoking is linked to the blisters that cause many spontaneous collapses, so stopping is one of the few things that genuinely lowers the chance of it happening again.

References & further reading

• MedlinePlus — Collapsed Lung: https://medlineplus.gov/collapsedlung.html
• MedlinePlus Medical Encyclopedia — Collapsed lung (pneumothorax): https://medlineplus.gov/ency/article/000087.htm
• MedlinePlus — Pleural Disorders: https://medlineplus.gov/pleuraldisorders.html

MedicalVideos.com has published trusted medical videos since 2007. The site was founded by Dr. Mohamed Ibrahim, MD, PhD — physician-scientist.

Frequently Asked Questions

Can a lung collapse on its own, without an injury?

Yes. This is called a spontaneous pneumothorax, and it usually happens when a small air blister on the lung surface bursts. It can happen in people with no known lung disease, as well as in people with an existing lung condition.

Is a pneumothorax always an emergency?

Not always, but it should always be assessed promptly. A small collapse in a comfortable person may only need watching, while a large one, a tension pneumothorax, or one in someone with lung disease needs urgent treatment.

Does a chest tube hurt?

The area is numbed first, and most people describe pressure and discomfort rather than sharp pain during the placement. It can be sore afterwards, and pain relief is part of the care while the tube is in.

How long does a pneumothorax take to heal?

It varies. The air is often reabsorbed or drained over days, and the lung re-expands as the leak seals. Your team will follow up with repeat X-rays, and they'll give you their own expected range and the symptoms that should bring you back sooner.

This article is for general education only and is not medical advice. It does not replace consultation with a qualified clinician. Sudden chest pain with breathlessness needs prompt, urgent medical assessment.

Dr. Mohamed Ibrahim, MD, PhD

Physician-scientist · Founder, MedicalVideos.com

Dr. Ibrahim founded MedicalVideos.com in 2007 to make medical and surgical education freely accessible to students, clinicians, and patients.

Last reviewed: 11/07/26