A collapsed lung happens when air leaks into the space between your lung and your chest wall, putting pressure on the lung and preventing it from expanding fully. The causes range from injuries and underlying lung diseases to seemingly random events in otherwise healthy people. In some cases, a medical procedure is the trigger.
Two Types of Lung Collapse
A full collapse of the lung is called a pneumothorax. When only part of the lung is affected, it’s called atelectasis. Most people searching for “collapsed lung” are dealing with pneumothorax, where air trapped in the chest cavity compresses the lung from the outside. The causes fall into a few distinct categories: spontaneous (with or without existing lung disease), traumatic, and iatrogenic (caused by a medical procedure).
Spontaneous Collapse in Healthy Adults
A primary spontaneous pneumothorax occurs without any obvious injury or known lung disease. It typically happens when small air-filled blisters on the lung surface, called blebs, rupture and release air into the chest cavity. These blebs can form without you ever knowing they’re there.
Tall, thin young men are the most commonly affected group. Rapid chest growth during adolescent growth spurts is thought to increase the likelihood of forming blebs in the first place. Long-term smoking significantly raises the risk in both men and women, even in those without a diagnosed lung condition. The combination of being tall, male, thin, and a smoker creates the highest-risk profile, though it can happen to anyone.
After a first episode, recurrence rates average between 10 and 30 percent over the following one to five years. The risk is highest in the first month. One large study found that about 8 percent of men experienced a recurrence within 30 days, rising to 20 percent within five years. Rates for women were similar, reaching 22 percent at five years.
Collapse From Existing Lung Disease
When a collapsed lung happens in someone who already has a lung condition, it’s called a secondary spontaneous pneumothorax. The underlying disease weakens lung tissue, making it more vulnerable to rupture. This type tends to be more dangerous because the person’s breathing capacity is already compromised.
The most common culprits include:
- COPD: the single most frequent cause of secondary spontaneous pneumothorax, due to damaged, over-inflated air sacs in the lungs
- Asthma: severe episodes can trap air and stress lung tissue
- Cystic fibrosis: thick mucus and repeated infections weaken the lung walls
- Tuberculosis and severe pneumonia: infections that destroy lung tissue can create holes that leak air
- Pulmonary fibrosis: scarring makes the lungs stiff and prone to tearing
- Lung cancer: tumors can erode through lung tissue into the pleural space
Less commonly, connective tissue disorders like Marfan syndrome and Ehlers-Danlos syndrome contribute to collapsed lungs. These conditions affect the structural proteins throughout your body, including in lung tissue, making it more fragile. Certain autoimmune conditions, including rheumatoid arthritis and sarcoidosis, can also damage the lungs enough to cause a spontaneous collapse.
Chest Injuries
Traumatic pneumothorax results from a physical injury that punctures the chest wall or damages the lung directly. The injury can be blunt (no open wound) or penetrating (something pierces the chest).
Motor vehicle accidents are by far the most common cause of significant blunt chest trauma. The force of impact can fracture ribs, and those broken rib ends can puncture the lung. Even without a fracture, a hard enough blow can damage lung tissue. Falls, sports injuries, and physical assaults account for most of the remaining cases.
Penetrating injuries from stab wounds, gunshot wounds, or any object that enters the chest create a direct path for air to leak into the pleural space. These cases are typically more immediately obvious and often involve bleeding into the chest cavity alongside the air leak.
Medical Procedures
A collapsed lung that results from a medical procedure is called an iatrogenic pneumothorax. Any procedure involving a needle or instrument near the chest carries some level of risk. Thoracentesis, where fluid is drained from around the lungs, is a well-studied example. Without ultrasound guidance, the pneumothorax rate runs between 4 and 10 percent. Using ultrasound to guide the needle drops that to roughly 1 to 5 percent, and more experienced operators have lower rates than less experienced ones.
Other procedures that can cause a collapsed lung include central line placement (inserting a catheter into a large vein near the collarbone), lung biopsies, and mechanical ventilation. Ventilators push air into the lungs under pressure, and if the pressure is too high or the lung tissue is already fragile, it can rupture.
Hormonal and Menstrual-Related Causes
Catamenial pneumothorax is a rare but distinct cause that affects women of reproductive age. It involves recurrent lung collapse occurring within 72 hours of the start of a menstrual period. Several mechanisms have been proposed: endometrial tissue may migrate to the lung lining, hormonal changes may trigger spasms in the small airways, or air may travel upward through the reproductive tract and through tiny holes in the diaphragm.
Estimates suggest this accounts for 1 to 5 percent of spontaneous pneumothorax cases in menstruating women. However, a prospective study looking specifically at women with recurring or persistent collapsed lungs found that 25 percent had a temporal link to menstruation, suggesting it may be underdiagnosed.
How a Collapsed Lung Feels
The hallmark symptoms are sudden, sharp chest pain and shortness of breath. The severity depends on how much of the lung has collapsed. A small pneumothorax might cause mild discomfort and slight breathlessness that you could initially mistake for a pulled muscle or a panic attack. A large or complete collapse causes intense pain, significant difficulty breathing, rapid heart rate, and sometimes a bluish tint to the skin from low oxygen.
In someone with existing lung disease, even a small pneumothorax can cause severe symptoms because there’s less healthy lung tissue to compensate. Diagnosis is confirmed with a chest X-ray or CT scan, which shows air in the pleural space and the degree of lung collapse.
Why Recurrence Is Common
Whatever caused the first collapsed lung often sets the stage for another. Blebs that didn’t rupture the first time are still there. Underlying lung disease continues to weaken tissue. Smoking continues to cause damage. The site where the lung healed may itself be a weak point. One systematic review of 29 trials found a pooled one-year recurrence rate of 29 percent for primary spontaneous pneumothorax managed conservatively. Surgical intervention to remove blebs and create adhesion between the lung and chest wall significantly lowers this risk, which is why it’s typically recommended after a second episode or sometimes after the first if the collapse was large.