A collapsed lung, medically called a pneumothorax, happens when air leaks into the space between your lung and your chest wall. That trapped air presses on the lung from the outside, causing it to partially or fully deflate. It can happen suddenly and without warning, even in otherwise healthy people, though certain body types and habits raise the risk. Most cases are treatable, but some forms are life-threatening emergencies.
What Happens Inside Your Chest
Your lungs don’t inflate on their own. They expand because of a pressure difference. The space between your lung and your chest wall (called the pleural space) normally has negative pressure, like a vacuum seal. When your chest wall expands as you breathe in, that vacuum pulls your lung open with it.
A collapsed lung disrupts this system. Air enters the pleural space either through a wound in the chest wall or through a tear in the lung tissue itself. Once air fills that gap, the vacuum seal breaks. The lung’s natural elasticity takes over and it recoils inward, collapsing like a deflated balloon. The collapse continues until the pressure equalizes or the tear seals itself.
What It Feels Like
The most common symptom is a sudden, sharp chest pain on one side, especially when you breathe in. Shortness of breath comes on quickly, and you may notice your heart racing. Other signs include a dry cough, rapid shallow breathing, and fatigue that feels out of proportion to what you’re doing.
In severe cases, particularly with a tension pneumothorax (more on that below), your skin, lips, or fingernails may turn bluish. That color change signals your blood oxygen is dropping dangerously low. If you experience chest pain with difficulty breathing and any blue discoloration, that’s an emergency requiring immediate medical attention.
Three Types of Collapsed Lung
Not all lung collapses happen for the same reason, and the type matters because it affects both treatment and the chance of it happening again.
Primary Spontaneous
This type strikes people with no known lung disease. It typically affects young adults, particularly men, those who are tall and thin, and smokers. Research published in the Annals of the American Thoracic Society found that men had about 1.5 times the odds of experiencing one compared to women, and non-Hispanic white individuals had nearly twice the risk. Smoking intensity also plays a clear role: for every additional 10 pack-years of smoking, the risk increased by 20%. The collapse usually results from the rupture of tiny air-filled blisters (called blebs) on the lung surface that the person never knew they had.
Secondary Spontaneous
This occurs in people who already have an underlying lung condition, such as COPD, cystic fibrosis, or severe asthma. Because the lungs are already compromised, these episodes tend to be more dangerous and harder to manage. Guidelines from the American College of Chest Physicians recommend surgical consultation after even a first episode, since the air leak is less likely to resolve on its own and recurrence carries a higher mortality rate.
Traumatic
A physical injury to the chest, whether from a car accident, a stab wound, a broken rib, or even a medical procedure like a lung biopsy, can puncture the chest wall or lung tissue and let air into the pleural space. The treatment follows the same principles as other types, but the underlying injury needs attention too.
When It Becomes Life-Threatening
A tension pneumothorax is the most dangerous form. It works like a one-way valve: air enters the pleural space with each breath but can’t escape. Pressure builds continuously, and the consequences escalate fast. The expanding pocket of trapped air doesn’t just collapse the lung. It pushes the heart and major blood vessels toward the opposite side of the chest.
Animal studies have mapped exactly how this unfolds. Blood oxygen drops almost immediately. Heart rate and blood pressure initially hold steady as the body compensates, but once the trapped air occupies roughly 57% of total lung capacity, the cardiovascular system starts failing. Heart rate spikes, blood pressure plummets, and cardiac output drops sharply. Full cardiovascular collapse occurs when the trapped air fills nearly all available space, at which point pressure inside the chest essentially stops blood from returning to the heart. The critical detail: once the trapped air is evacuated, blood pressure and heart rate return to normal almost immediately. Speed of treatment is everything.
How a Collapsed Lung Is Treated
Treatment depends on how much of the lung has collapsed and how stable you are.
- Observation: Small collapses (less than about 35 mm on imaging) in stable patients can sometimes resolve on their own. You’ll be monitored in the hospital while the air slowly reabsorbs. This can take several days.
- Needle aspiration or catheter drainage: For moderate collapses, a doctor inserts a needle or small tube to suction out the trapped air, allowing the lung to re-expand.
- Chest tube: Larger or symptomatic collapses require a tube inserted between the ribs to continuously drain air from the pleural space. The tube stays in place until the lung fully re-inflates and the air leak seals, which typically takes a few days.
- Emergency needle decompression: For tension pneumothorax, a needle is inserted immediately to release pressure before a chest tube is placed. This is done before imaging because waiting can be fatal.
Recurrence Is Common
One of the most important things to know about a collapsed lung is that it often happens again. A large study spanning nearly five decades, published in JAMA, tracked recurrence rates across thousands of patients. For primary spontaneous pneumothorax, about 13% of people had another collapse within one year, and roughly 21% within five years. For secondary spontaneous pneumothorax, those numbers were significantly higher: 27% within one year and 33% within five years.
After a second episode, the recurrence rate jumps to 60 to 80%. That steep increase is why doctors typically recommend surgery after a second collapse rather than continuing with drainage alone.
Surgery to Prevent Future Collapses
The most effective way to prevent recurrence is a procedure called VATS (video-assisted thoracoscopic surgery). It’s minimally invasive, performed through small incisions with a camera. During the procedure, the surgeon can identify and remove the blebs or blisters that caused the original leak. They also roughen or partially remove the lining of the pleural space, a process called pleurodesis, which causes the lung to scar and stick to the chest wall. This eliminates the gap where air could accumulate.
For primary spontaneous pneumothorax, VATS is generally recommended after a second episode. For secondary spontaneous pneumothorax, surgical consultation typically happens after the first episode because of the higher recurrence and mortality risk. The procedure has the lowest recurrence rates of any treatment option and relatively low complication rates.
Recovery and Getting Back to Normal
Recovery time varies depending on severity and treatment. A small pneumothorax managed with observation may resolve within one to two weeks. After chest tube removal, you’ll have follow-up imaging within 48 hours to confirm the lung is staying inflated. Most people recover fully, though soreness at the tube site can linger for a few weeks.
Air travel is one of the biggest practical concerns after a collapsed lung. At cruising altitude, cabin pressure drops, which can cause any remaining trapped air to expand and trigger a recurrence. The British Thoracic Society recommends waiting at least one week after a chest X-ray confirms full resolution, with a two-week delay after traumatic pneumothorax or chest surgery. The Aerospace Medical Association advises two to three weeks as a general guideline. Before booking a flight, you’ll need a repeat chest X-ray confirming the collapse has fully resolved.
Scuba diving carries an even greater risk because of the dramatic pressure changes involved. Most pulmonologists advise against returning to diving after a spontaneous pneumothorax unless you’ve had definitive surgical repair, and even then, the decision requires careful discussion with a specialist familiar with dive medicine.