How To Know If You Have A Collapsed Lung? Expert Tips

A collapsed lung, known medically as a pneumothorax, happens when air leaks into the space between your lung and your chest wall. This air pushes on the outside of your lung, making it collapse. The clearest sign is sudden, sharp chest pain that gets worse when you breathe in, often paired with shortness of breath. If you have these symptoms, especially after an injury or even without one, you need to go to the emergency room immediately — this is not something to wait out at home.

What Does a Collapsed Lung Actually Feel Like?

The sensation is often described as a sharp, stabbing pain on one side of the chest. It comes on suddenly. Many people say it feels like someone stabbed them with a knife or like a popping sensation inside the chest.

The pain usually gets worse when you take a deep breath, cough, or sneeze. Within minutes to hours, you will likely feel short of breath. This shortness of breath happens because the collapsed lung cannot expand fully, so your body gets less oxygen with each breath.

Some people also feel a tightness in their chest or a sense of fullness on the affected side. Your shoulder or back may hurt, which is called referred pain. The nerve that runs near your lung also connects to your shoulder area, so your brain sometimes misinterprets the signal.

In a small number of cases, symptoms come on gradually. This is more common in people with a “tension pneumothorax,” where air keeps building up and puts pressure on the heart and the other lung. This is a medical emergency that can cause your blood pressure to drop and make you feel faint or lightheaded.

How To Know If You Have a Collapsed Lung Without an X-Ray?

You cannot diagnose a collapsed lung with certainty at home. No breathing test, no listening device, and no symptom checklist replaces a chest X-ray. That is the blunt truth.

However, there are signs that make a pneumothorax very likely. If you have sudden chest pain and shortness of breath, and you also have one of these risk factors, the chance goes up significantly:

• You are a tall, thin male between 20 and 40 years old (this body type is most prone to spontaneous pneumothorax)
• You have a lung disease like COPD, asthma, cystic fibrosis, or tuberculosis
• You smoke or vape regularly
• You recently had a chest injury from a car accident, fall, or sports collision
• You had a previous collapsed lung (recurrence is common)

If you put a stethoscope on the affected side, you would hear reduced or absent breath sounds. A doctor can also tap on your chest and hear a hollow, drum-like sound instead of the usual dull thud. But none of this is something you can reliably do yourself. If you suspect a collapsed lung, the only safe step is to get to an emergency department.

What Causes a Collapsed Lung?

A collapsed lung happens when air gets into the pleural space — the thin gap between your lung and your chest wall. This can happen in three main ways.

Traumatic pneumothorax is caused by a direct injury. A broken rib punctures the lung. A knife or bullet wound lets air in from outside. Even a hard hit during football or a car accident can do it. This is the most straightforward cause and usually the easiest to diagnose because there is a clear event.

Spontaneous pneumothorax happens without any injury. It is most common in tall, thin young men. The theory is that small air sacs called blebs form on the top of the lung, usually from genetics or smoking. When a bleb pops, air leaks out. This can happen while you are sitting still, sleeping, or doing something as mild as stretching.

Tension pneumothorax is the dangerous version. Air keeps entering the pleural space but cannot escape. The pressure builds up and pushes the heart and the other lung to the opposite side of the chest. This drops blood pressure and can stop the heart. It is most common after trauma or from mechanical ventilation in a hospital.

As of 2026, current research suggests that vaping may be a growing cause of spontaneous pneumothorax. The heat and chemicals from vaping devices can irritate lung tissue and make blebs more likely to form or burst. The data is still emerging, but it is something pulmonologists are watching closely.

How Is a Collapsed Lung Diagnosed and Treated?

Diagnosis starts with a chest X-ray. This is the gold standard. A doctor can see the collapsed lung clearly — it looks like a dark space where the lung tissue should be, with the lung edge visible as a thin white line.

If the X-ray is unclear, a CT scan may be used. This is more sensitive and can find small pneumothoraces that an X-ray might miss. An ultrasound is sometimes used in emergency rooms for faster diagnosis, especially in trauma cases.

Treatment depends on how large the collapse is and whether symptoms are getting worse. Here is a simple breakdown of the three main approaches:

Oxygen therapy speeds up air reabsorption by about four times. For small collapses, this is often the only treatment needed. For larger ones, a chest tube is the standard approach. The tube can be uncomfortable but it is effective — most lungs re-expand within a few days.

Surgery is reserved for people who have had two or more collapses on the same side, or whose lung does not re-expand with a chest tube alone. The procedure involves removing the blebs and then rubbing the lining of the chest wall to create inflammation, which causes the lung to stick to the chest wall and prevents future collapses.

What Mistakes Do People Make With a Collapsed Lung?

The most dangerous mistake is waiting. Some people think the pain is just a pulled muscle or heartburn. They take pain relievers and go to bed. By morning, the lung can be fully collapsed and the person is in respiratory distress. If you have sudden chest pain with trouble breathing, do not wait to see if it goes away.

Another common mistake is flying. If you have a pneumothorax or even a small, undiagnosed air leak, the change in cabin pressure can make it much worse. Commercial airplanes are pressurized to about 8,000 feet, which is enough to expand trapped air by about 30%. People have had lungs collapse mid-flight. If you have had a collapsed lung, do not fly until a doctor clears you — typically at least two to three weeks after the lung has fully re-expanded.

Scuba diving is another risk. The pressure changes underwater are extreme. Even after a collapsed lung heals, diving can cause it to recur. Most pulmonologists recommend avoiding scuba diving permanently after a pneumothorax, especially if you had surgery for it.

Some people try to “pop” the lung back by holding their breath or coughing hard. This does not work. It can actually make things worse by increasing pressure inside the chest. There is no home remedy for a collapsed lung.

Can a Collapsed Lung Heal on Its Own?

Yes, a small collapsed lung can heal without any procedure. The body slowly reabsorbs the air from the pleural space. This usually takes one to two weeks. During that time, you will be monitored with repeat X-rays to make sure the lung is re-expanding and not getting worse.

However, “heal on its own” does not mean you should stay home. Even a small pneumothorax needs medical evaluation. The reason is that a small collapse can become a large one without warning. Also, the underlying cause — like a bleb or an injury — needs to be identified. You cannot know the size of the collapse or its cause without a chest X-ray.

If you are observed in the hospital with a small collapse, you will likely be given oxygen and kept for at least 24 hours. If the lung stays stable, you can go home with instructions to rest and avoid heavy lifting, coughing, or any activity that strains the chest. You will need a follow-up X-ray in one to two weeks.

The recurrence rate for a first-time spontaneous pneumothorax is about 30% within two years. After a second collapse, the rate jumps to over 50%. This is why surgery is often recommended after a second event — it reduces the recurrence rate to less than 5%.