A pneumothorax is a collapsed lung caused by air leaking into the space between your lung and your chest wall. Normally, that space (called the pleural space) has negative pressure that keeps your lung inflated as you breathe. When air enters this space, the pressure balance shifts, and the lung shrinks inward until the leak seals itself or the pressure equalizes. The result is sharp chest pain, difficulty breathing, and in severe cases, a medical emergency.
How a Lung Collapses
Your lungs don’t inflate on their own. They expand because the pleural space between each lung and the chest wall maintains lower pressure than the atmosphere. Think of it like a suction effect: when your chest wall moves outward during a breath, your lung follows because of this pressure difference.
Air can break into the pleural space in two ways: from outside, through a wound or puncture in the chest wall, or from inside, when a weak spot on the lung surface ruptures. Either way, the leaked air disrupts the pressure gradient. The lung’s natural elastic recoil takes over, and it begins to deflate like a balloon losing air. As the lung shrinks, it can hold less air with each breath, and blood oxygen levels drop.
Types of Pneumothorax
Primary Spontaneous
This type strikes people with no known lung disease. It typically affects young, tall, thin adults, especially men. The exact cause isn’t fully understood, but the most significant risk factors are smoking, being male, and having a family history of pneumothorax. Small air-filled blisters (called blebs) on the lung surface are thought to rupture, though why they form in otherwise healthy lungs remains unclear.
Secondary Spontaneous
This happens in people who already have an underlying lung condition. Chronic obstructive pulmonary disease (COPD) accounts for roughly 70% of cases. Other conditions linked to secondary pneumothorax include cystic fibrosis, severe asthma, tuberculosis, lung cancer, and connective tissue disorders like Marfan syndrome and Ehlers-Danlos syndrome. Because these patients already have compromised lung function, a secondary pneumothorax tends to cause more severe symptoms, including dangerously low oxygen levels.
Traumatic
Any blunt or penetrating injury to the chest can cause a pneumothorax. Car accidents, stab wounds, broken ribs, and even certain medical procedures (like a lung biopsy or the placement of a central IV line) can introduce air into the pleural space.
Tension Pneumothorax
This is the most dangerous form. It occurs when the leak acts like a one-way valve: air enters the pleural space with each breath but can’t escape. Pressure builds continuously, compressing not just the affected lung but pushing the heart and major blood vessels toward the opposite side of the chest. This compression reduces blood flow back to the heart and can cause shock. Signs include rapidly dropping blood pressure, visibly distended neck veins, and the windpipe shifting to one side. A tension pneumothorax is a life-threatening emergency that requires immediate intervention.
What It Feels Like
The most common symptom is sudden, sharp chest pain on the affected side, often described as a stabbing sensation that worsens with breathing. Shortness of breath comes on quickly and can range from mild to severe depending on how much of the lung has collapsed. Some people feel a tight or heavy sensation in their chest.
In a small pneumothorax, symptoms may be subtle enough that you wonder if you just pulled a muscle. In a large one, you may feel like you can’t catch your breath at all, your heart rate climbs, and your skin may look pale or bluish. If underlying lung disease is present, even a small collapse can produce significant distress because there’s less healthy lung tissue to compensate.
How It’s Diagnosed
A standard chest X-ray has been the traditional first step, but it misses a surprising number of cases. A meta-analysis comparing the two main imaging tools found that chest X-ray detected only about 48% of pneumothoraces, while bedside ultrasound caught roughly 79%. Both methods are equally good at ruling out a pneumothorax when one isn’t present, with specificity above 99% for each. CT scans are the most sensitive option and are often used when other imaging is inconclusive or when a tension pneumothorax is suspected.
Doctors also measure the size of the collapse on imaging, which guides treatment decisions. British Thoracic Society guidelines classify a pneumothorax as “large” when the visible gap between the lung edge and the chest wall is greater than 2 centimeters, which corresponds to about 50% of lung volume lost. American guidelines use a slightly different measurement, considering it large when the gap from the top of the lung to the top of the chest cavity exceeds 3 centimeters.
Treatment Options
A small, uncomplicated pneumothorax in a healthy person often resolves on its own. The approach is observation: monitoring with repeat imaging to confirm the air is reabsorbing. Supplemental oxygen speeds up this process. You might stay in a hospital for several hours or overnight, and if the pneumothorax isn’t expanding, you go home with follow-up X-rays scheduled.
For larger collapses, the trapped air needs to be removed. The least invasive method is needle aspiration, where a needle is inserted between the ribs to draw air out of the pleural space. If the lung doesn’t re-expand or the air keeps accumulating, a chest tube is placed. This is a small flexible tube inserted through the chest wall that continuously drains air, allowing the lung to reinflate. Chest tubes typically stay in for a few days until the leak seals and imaging confirms the lung is fully expanded.
When pneumothoraces keep coming back, surgery becomes an option. The most common approach uses a camera and small incisions to locate and remove the blebs or weak spots on the lung surface. During the same procedure, surgeons often roughen up the pleural surfaces (a technique called pleurodesis) to encourage them to scar together, essentially gluing the lung to the chest wall so air can’t accumulate in that space again. This can also be done chemically by introducing a substance like talc into the pleural space, which triggers inflammation and scarring that bonds the surfaces together.
Smoking and Cannabis as Risk Factors
Cigarette smoking is the single most modifiable risk factor. Daily smokers face a dramatically higher chance of a first spontaneous pneumothorax: roughly 8 times higher risk for women and nearly 5 times higher for men, compared to people who have never smoked. The more you smoke, the greater the risk, likely because smoking damages the small air sacs in the lungs and promotes the formation of blebs that can rupture.
Cannabis adds to this risk in men who also smoke tobacco. Men who smoke both cannabis and cigarettes face about 8.7 times the risk of a spontaneous pneumothorax compared to male nonsmokers. Interestingly, cannabis alone, in people who don’t smoke tobacco, does not appear to carry a significant independent risk. The combination seems to be what matters, at least in men. In women, cannabis use showed no clear link to increased pneumothorax risk regardless of tobacco habits.
Recurrence Rates
Once you’ve had one spontaneous pneumothorax, there’s a meaningful chance of having another. The overall recurrence rate is about 20%, with most repeat episodes happening within the first five years. Men are roughly twice as likely to experience a recurrence as women, with five-year rates of about 21% for men versus 11% for women.
Quitting smoking is the most effective way to lower your recurrence risk. For those who experience multiple recurrences, surgical pleurodesis offers the best long-term prevention by physically eliminating the space where air can collect.
Recovery and Activity Restrictions
After a pneumothorax resolves, most people recover fully within a few weeks. If a chest tube was placed, soreness at the insertion site is common for several days, and deep breathing exercises help the lung regain full capacity. Strenuous physical activity is typically limited for two to four weeks, depending on the severity and treatment approach.
Air travel is off-limits until at least one week after a chest X-ray confirms the pneumothorax has completely resolved. At high altitude, cabin pressure drops, and any residual trapped air could expand and cause a recurrence. British Thoracic Society guidelines are clear on this point: no flying until full resolution is confirmed on imaging, then wait an additional seven days.
Scuba diving carries even greater restrictions. The pressure changes during a dive are far more extreme than during a flight. Most diving medicine organizations advise against ever diving again after a spontaneous pneumothorax unless you’ve had definitive surgical repair, and even then, guidance varies. If diving is important to you, a specialist in diving medicine can help assess your individual risk.