How Can You Tell If You Have a Collapsed Lung?

A collapsed lung, known medically as a pneumothorax, usually announces itself with sudden, sharp chest pain on one side and a feeling that you cannot get enough air. The pain tends to come on abruptly, sometimes while you are doing nothing strenuous at all, and it can range from a mild ache to something severe enough that you think you are having a heart problem. But the presentation varies depending on how much of the lung has deflated, your underlying health, and whether air continues to leak into the chest cavity, so recognizing the signs early matters more than most people realize.

What the Symptoms Actually Feel Like

The two hallmark symptoms are chest pain and shortness of breath. The pain is typically on the side where the lung has collapsed, and patients often describe it as sharp or stabbing rather than the squeezing pressure associated with a heart attack. It tends to worsen with deep breaths or coughing. The shortness of breath can be subtle if only a small pocket of air has leaked out, or it can be severe if a large portion of the lung has deflated. Difficulty breathing and chest pain are, in fact, two of the most common reasons people show up at an emergency department with a thoracic problem.¹

Beyond pain and breathlessness, you may notice a rapid heart rate, a feeling of tightness across the chest, or fatigue that seems disproportionate to what you are doing. Some people feel lightheaded. In smaller pneumothoraces, symptoms can be mild enough that you convince yourself you just pulled a muscle or strained something while exercising. That ambiguity is one reason collapsed lungs sometimes go undiagnosed for hours or even days in otherwise healthy people.

When It Becomes an Emergency

Most collapsed lungs are uncomfortable but not immediately life-threatening. The dangerous exception is a tension pneumothorax, where air keeps leaking into the chest cavity with each breath but has no way to escape. Pressure builds on the affected side, pushing the heart and the opposite lung out of position. Symptoms escalate fast: severe difficulty breathing, a visibly swollen neck (from distended veins), a drop in blood pressure, and sometimes a bluish tint to the skin from lack of oxygen. This is a medical emergency that can be fatal within minutes if not treated.²

If you are experiencing worsening shortness of breath alongside any of those signs, call emergency services. A tension pneumothorax requires immediate needle decompression or a chest tube to release the trapped air, and waiting to see a doctor in the morning is not an option.

How Doctors Confirm the Diagnosis

You cannot definitively diagnose a collapsed lung at home. Even doctors need imaging. The standard first step is an upright chest X-ray, which can show the edge of the collapsed lung as a thin white line with no lung markings beyond it. But chest X-rays have real limitations, particularly when taken with a portable machine at your bedside while you are lying down. In that position, the accuracy of detecting a pneumothorax drops sharply. One study of blunt trauma patients found that a supine chest X-ray caught only about one in eight pneumothoraces, with an overall diagnostic accuracy of under half.³

Bedside ultrasound has become an increasingly popular tool in emergency departments because it is fast and does not involve radiation. Clinicians look for specific signs: the normal sliding motion of the lung against the chest wall disappearing, the absence of certain artifacts that healthy lung tissue produces, and a telltale “lung point” where normal lung meets the area of collapse.⁴ Ultrasound can detect pneumothoraces that chest X-rays miss, especially in trauma patients who cannot sit upright.

A CT scan of the chest is the most sensitive test and catches even small collections of air that other methods miss. Many of the pneumothoraces found only on CT, sometimes called “occult” pneumothoraces, would have gone undetected by a standard X-ray. In the same trauma study mentioned above, subcutaneous emphysema visible on the X-ray, where air leaks into the tissue under the skin and gives a crackling sensation when you press on it, was a strong clue that a pneumothorax was hiding. Over 96% of patients who had subcutaneous emphysema on their X-ray turned out to have a pneumothorax on CT.³ That crackling feeling under the skin near your collarbone or ribs is itself a useful self-check: if you feel something like tiny bubbles of air under the skin, get to an emergency room.

Who Gets a Collapsed Lung

A primary spontaneous pneumothorax, meaning one that happens without any obvious injury or known lung disease, follows a recognizable demographic pattern. It occurs most often in tall, thin, young men.⁵ The reason is partly structural: taller people have greater differences in pressure between the top and bottom of their lungs, which can stress small air sacs near the apex. Tiny blebs, essentially weak-walled blisters on the lung surface, can rupture and allow air to escape into the chest cavity. You may never know these blebs exist until one of them pops.

Smoking raises the risk substantially, and cannabis use appears to carry its own specific dangers. Research has shown that cannabis smokers have a higher incidence of bullous lung disease, the formation of those weakened air pockets, compared to both tobacco smokers and nonsmokers, and they also appear to face a higher rate of tension pneumothorax.⁶ The mechanism likely involves deep inhalation and prolonged breath-holding during cannabis use, which puts extra strain on already weakened lung tissue.

Underlying Lung Disease and Secondary Pneumothorax

When a collapsed lung occurs in someone who already has lung disease, it is classified as a secondary spontaneous pneumothorax.⁷ The distinction matters because these cases tend to be more dangerous: the affected lung is already compromised, so even a partial collapse can cause severe breathing difficulty. Conditions like chronic obstructive pulmonary disease (COPD), asthma, and tuberculosis are among the more common underlying culprits.

Cystic fibrosis deserves special mention. Pneumothorax is a recognized and life-threatening complication in people with CF, especially when respiratory function is already seriously compromised. The structural damage and abnormal airflow in CF lungs create an environment ripe for air leaks. Certain infections common in CF patients, as well as treatments like inhaled medications and non-invasive ventilation, can further increase the risk.⁸ If you have CF and notice a sudden change in your breathing or new chest pain, a pneumothorax should be high on the list of possibilities.

Traumatic pneumothorax is the third broad category. A broken rib, a stab wound, a car accident, or even certain medical procedures like a lung biopsy can puncture the lung and allow air to escape. These cases are usually diagnosed quickly because the mechanism of injury is obvious and imaging is done as part of the trauma workup.

A Collapsed Lung Timed to Menstruation

One of the most underrecognized forms is catamenial pneumothorax, a condition linked to endometriosis. It occurs in women of reproductive age and follows a striking pattern: the lung collapses within about 72 hours of the start of menstruation, and it tends to recur with subsequent cycles.⁹ It is the most common presentation of thoracic endometriosis, a condition where endometrial tissue ends up in or around the lungs and diaphragm.

Because it is rare and the association with menstruation can be missed, catamenial pneumothorax is frequently misdiagnosed as an ordinary primary spontaneous pneumothorax. The key diagnostic clue is the timing: recurrent right-sided pneumothoraces that seem to sync up with a menstrual cycle should prompt investigation for thoracic endometriosis.¹⁰ If you are a woman who has had more than one unexplained collapsed lung, mention the timing relative to your period to your doctor, even if they don’t ask. The research on effective treatments is still developing, but recognizing the pattern is the critical first step.¹¹

Conditions That Mimic a Collapsed Lung

One of the trickier aspects of a pneumothorax is that its symptoms overlap with several other chest conditions. Sudden chest pain and difficulty breathing can look like a heart attack, a pulmonary embolism (a blood clot in the lung), a rib fracture, or severe acid reflux. Even the electrical readings of the heart can be misleading: a spontaneous pneumothorax can produce abnormal ECG changes that have, on occasion, led doctors to initially and incorrectly diagnose a heart attack.¹²

This overlap is exactly why you should not try to self-diagnose. If you have sudden chest pain and cannot breathe comfortably, the right move is to seek medical attention. Doctors will sort out the cause through imaging and examination. Trying to distinguish between a collapsed lung and a heart attack by symptom alone is a gamble that even experienced clinicians find difficult without tests.

How a Collapsed Lung Gets Treated

Treatment depends on the size of the pneumothorax and how much it is affecting your breathing. A small one in an otherwise healthy person might simply be monitored. The body gradually reabsorbs the trapped air on its own, though this can take days to weeks. Supplemental oxygen speeds things up by changing the gas composition in the pleural space. In animal and clinical studies, high-flow oxygen therapy increased the rate of air reabsorption by roughly four-fold compared to breathing room air, and the time to full resolution dropped considerably at higher oxygen concentrations.¹³

For larger pneumothoraces, a chest tube is typically inserted between the ribs to drain the air and allow the lung to re-expand. This is an uncomfortable but straightforward procedure that usually happens in the emergency department. The tube stays in place until imaging confirms the lung is fully expanded and no more air is leaking.

When a pneumothorax recurs, or when the air leak does not seal on its own, surgery becomes the standard approach. The most common procedure is video-assisted thoracic surgery (VATS), where the surgeon removes or staples the blebs responsible for the leak. To prevent recurrence further, a chemical pleurodesis may be performed at the same time, essentially irritating the lung surface and chest wall so they stick together and leave no space for air to collect. Talc is one of the agents used during VATS, and recurrence rates after the combined procedure are low, generally in the range of 0 to about 3%.¹⁴

Flying, Diving, and Life After a Collapsed Lung

One of the first questions people have after recovering from a pneumothorax is whether they can fly or scuba dive. The concern is real. At altitude, cabin pressure drops and any residual air trapped in the chest cavity expands, which could cause a recurrence. Underwater, the pressure changes are even more dramatic. A primary spontaneous pneumothorax is considered an absolute contraindication for scuba diving and professional flying unless bilateral surgical pleurectomy, a procedure that removes the pleural lining to prevent recurrence, has been performed.¹⁵

For people with certain genetic lung conditions, the risk associated with air travel is easier to quantify. In a study of patients with Birt-Hogg-Dubé syndrome, a genetic condition that causes lung cysts, the risk of developing a pneumothorax within a month of flying was about 0.63% per flight, and the risk associated with diving was about 0.33% per episode.¹⁶ Those numbers sound small in isolation, but for frequent flyers with a known predisposition, they add up. General guidelines typically recommend waiting at least one to two weeks after a pneumothorax has fully resolved before flying, though the exact timing depends on how it was treated and your doctor’s assessment.

Beyond travel, most people recover fully and return to normal activities without restrictions, especially after a first episode treated conservatively. The real concern is recurrence. The chance of having a second spontaneous pneumothorax is significant, with most estimates putting it in the range of 30 to 50% within the first few years. That risk drops substantially after surgical intervention. If you have had one episode, be alert to the symptoms recurring, particularly if you are in the demographic that tends to get them: young, tall, thin, male, and a smoker. Knowing what a collapsed lung feels like the first time is the best preparation for catching it quickly if it happens again.

When a Collapsed Lung Was the Treatment, Not the Problem

There is an odd footnote in medical history that flips the entire concept on its head. Before effective antibiotics existed, one of the few treatments that actually helped people with tuberculosis was an intentionally collapsed lung. Doctors would inject air into the chest cavity on purpose to deflate the infected lung, depriving the TB bacteria of oxygen and buying the patient time to heal. This approach, called artificial pneumothorax, was a mainstay of TB treatment after 1910 and was only phased out about 30 years later when chemotherapy drugs became available.¹⁷ The procedure was uncomfortable, had to be repeated regularly, and came with real risks, but for decades it was the closest thing to a cure that doctors had. It is a reminder that the same condition feared as an emergency in one context was once deliberately induced as therapy in another.