A lung bleb is a small, air-filled pocket that forms just beneath the thin membrane covering the lung’s surface. These pockets develop when air leaks out of tiny air sacs and gets trapped under the outer lining, creating a bubble typically less than one or two centimeters across. Most people with blebs never know they have them, but when a bleb ruptures, it can cause a pneumothorax, a collapsed lung, which is why the term tends to come up in emergency rooms and surgical consultations rather than routine checkups.
How a Bleb Differs from a Bulla
You will often see “blebs” and “bullae” mentioned together, and the two are sometimes used interchangeably in casual medical conversation, but they are structurally different. A bleb sits entirely within the pleura, the membrane that wraps the lung surface. It forms when air from damaged air sacs dissects into and collects between the layers of that membrane, creating a small raised blister. A bulla, by contrast, involves destruction of actual lung tissue underneath and tends to be larger, sometimes much larger, than a bleb. Bullae are associated with emphysema, where the walls between air sacs break down and merge into bigger air spaces.
Research into the tissue structure of both lesions has shown that blebs develop in connection with areas of localized scarring in the air sacs, while bullae arise from the broader destruction pattern of emphysema. Both contain abnormal elastic fibers, but their origins are distinct.1Acta Pathologica Japonica. Histogenesis of abnormal elastic fibers in blebs and bullae of patients with spontaneous pneumothorax: Ultrastructural and immunohistochemical studies In clinical practice, however, the distinction gets blurry. Imaging often cannot clearly separate a tiny bulla from a bleb, and a patient’s surgical report might mention both. The important thing for treatment decisions is the size of the lesion and whether it has ruptured, not the precise pathological label.
How Blebs Form
The basic mechanism starts with tiny ruptures in the walls of air sacs at the very top of the lung. When air escapes through those breaks, it can track along the sheaths of small blood vessels in the lung tissue. Early experimental work showed that overinflated air sacs develop small tears in their walls, and the escaped air then travels along the blood vessel coverings toward the lung surface.2Archives of Internal Medicine. Transport of Air Along Sheaths of Pulmonic Blood Vessels from Alveoli to Mediastinum: Clinical Implications Once that air reaches the outer membrane, it can pool and form a bleb.
Why the lung apex specifically? One widely cited explanation involves the pressure gradient inside the chest. The pressure difference between the top and bottom of the lung means the tissue at the apex is under greater stretching force. In taller people, this gradient is more pronounced, which may explain why the lung tips are the most common location for bleb formation.3PubMed Central. Bullae formation hypothesis in primary spontaneous pneumothorax That said, the exact chain of events that turns a healthy lung apex into one with blebs is still not fully understood. Researchers have proposed several contributing mechanisms, and the reality is probably a combination of mechanical stress, localized inflammation, and individual susceptibility.
Who Gets Blebs and Why
The classic profile for someone who develops a spontaneous pneumothorax from a ruptured bleb is a tall, thin, young male. This body type appears so consistently in clinical data that it is considered a constitutional risk factor.3PubMed Central. Bullae formation hypothesis in primary spontaneous pneumothorax The thinking is that a taller chest creates a steeper pressure gradient from the top of the lung to the bottom, putting more mechanical stress on the apex where blebs tend to form. This does not mean shorter people or women cannot get blebs. They certainly can and do. But the statistical pattern is striking enough that clinicians think of it as a signature risk factor.
Smoking is another major contributor. Cigarette smoke damages the small airways and air sacs, promoting the kinds of localized tissue changes that lead to bleb and bulla formation. More recently, vaping has come under scrutiny for similar reasons. The compounds inhaled through e-cigarettes are thought to injure the cells lining the airways and trigger inflammation, which could contribute to the development or rupture of blebs.4PubMed Central. Pneumothorax secondary to vaping Case reports of young vapers developing spontaneous pneumothorax have accumulated enough to draw clinical attention, though large-scale studies quantifying the risk are still catching up.
Genetics also plays a role. Spontaneous pneumothorax sometimes runs in families, and several genetic conditions are linked to an increased risk. Connective tissue disorders like Marfan syndrome and Ehlers-Danlos syndrome weaken the structural proteins that help hold lung tissue together. Birt-Hogg-Dubé syndrome, caused by mutations in a gene called FLCN, is another recognized cause.5PubMed Central. The Genetics of Pneumothorax Even outside of named syndromes, pneumothorax can cluster in families, and FLCN mutations have been found in both familial and apparently random cases.6PubMed. Pediatric bilateral spontaneous pneumothoraces in monozygotic twins If you have a close relative who has had a spontaneous collapsed lung, it is worth mentioning to your doctor, especially if you are tall and thin.
Symptoms and When Blebs Become Dangerous
An intact bleb sitting quietly on the surface of your lung causes no symptoms. You will not feel it, and it will not affect your breathing. The trouble starts only if it ruptures. When a bleb breaks open, air leaks out of the lung and into the space between the lung and the chest wall. This is a pneumothorax, and the symptoms tend to come on suddenly.
The hallmark is a sharp pain on one side of the chest, often described as stabbing, followed by shortness of breath. Some people feel the onset while doing nothing in particular, not during exercise or exertion. The severity depends on how much air escapes. A small pneumothorax might cause mild discomfort and a sense that breathing takes more effort than usual. A large one can leave you seriously short of breath, with a rapid heart rate and a feeling of tightness across the chest. In rare cases, a tension pneumothorax develops, where leaked air keeps accumulating and starts compressing the heart and great vessels. That is a medical emergency.
A strikingly common feature of spontaneous pneumothorax from blebs is that it tends to happen at rest or during mild activity. It is not triggered by heavy lifting or intense exercise the way you might expect. If you are a young person with sudden one-sided chest pain and shortness of breath that started out of nowhere, a pneumothorax is high on the list of possibilities a doctor should consider.
How Blebs Are Detected
On a standard chest X-ray, blebs are easy to miss. They are small, and the resolution of a plain film often is not fine enough to pick them up. One study comparing chest X-rays to CT scans found that X-rays detected blebs or bullae in fewer than a third of cases, while CT scanning picked up abnormal lung changes in the vast majority.7Respiration. Value of Computer Tomography in the Detection of Bullae and Blebs in Patients with Primary Spontaneous Pneumothorax CT is the gold standard for finding and mapping blebs because it can show their number, size, and exact location. This matters when surgical planning is needed.
In an acute setting, though, the first imaging study is almost always a chest X-ray because the main question is whether there is a pneumothorax, not whether there are blebs. The collapsed lung is visible on X-ray, and treatment decisions can begin from there. A CT scan typically follows when surgery is being considered, when the clinical picture is unclear, or when the doctor wants to assess the bleb burden on both sides. In occasional cases, blebs are visible on a plain chest X-ray, and when they are, that visibility itself may indicate a higher risk of recurrence.8PubMed Central. Primary spontaneous pneumothorax due to high bleb burden
It is also worth knowing that blebs turn up incidentally. A postmortem CT study of people without known lung disease found small bullae or blebs in roughly a third of the general population.9PubMed. Prevalence of Pulmonary Bullae and Blebs in Postmortem CT Imaging With Potential Implications for Diving Medicine Most of these people had lived normal lives with no lung problems. The implication is that having a bleb does not mean you will ever have a pneumothorax. It simply means a small vulnerability exists.
Treatment After a Pneumothorax
Treatment depends on the size of the pneumothorax and whether it is a first episode or a recurrence. The options range from doing nothing to major surgery, and the choice is driven by how much air has leaked and how urgently the lung needs to re-expand.
- Observation: For very small pneumothoraces where the patient is stable and comfortable, doctors may simply monitor with repeat X-rays. The leaked air absorbs on its own over days to weeks. However, observation alone has been associated with higher recurrence rates, so it is generally reserved for truly minor episodes.10PubMed. Civilian spontaneous pneumothorax. Treatment options and long-term results
- Needle aspiration: A needle is inserted into the chest to remove the trapped air. This works well for moderate-sized pneumothoraces and avoids the need for a chest tube in some cases.
- Chest tube drainage: A tube is placed between the ribs and into the pleural space to continuously drain air. The tube stays in place until imaging confirms the lung has re-expanded and no more air is leaking. This is the most common intervention for a significant first-episode pneumothorax.
- Surgery: Recommended after a recurrence, for a persistent air leak that will not seal on its own, or when imaging shows a high bleb burden that predicts future problems.
The goal of any treatment is to get the lung fully re-expanded and, ideally, to prevent the same thing from happening again. As one long-term analysis put it, treatment should be prompt and aimed at both complete re-expansion and recurrence prevention.10PubMed. Civilian spontaneous pneumothorax. Treatment options and long-term results
Surgical Options for Blebs
When surgery is indicated, the standard approach today is video-assisted thoracoscopic surgery, commonly abbreviated VATS. This is minimally invasive: the surgeon works through small incisions using a camera and specialized instruments, rather than opening the chest widely. The typical procedure involves removing the blebs (blebectomy or bullectomy) and then doing something to encourage the lung’s outer surface to stick to the chest wall so that even if a new bleb forms, leaked air has nowhere to collect. This adhesion step might involve mechanical abrasion of the pleural surface, chemical pleurodesis, or partial removal of a strip of pleura.
VATS has largely replaced open thoracotomy for this problem. The minimally invasive approach causes less pain, allows faster recovery, and gets patients back to normal activity sooner.11PubMed Central. Uniportal video-assisted thoracic surgery for pneumothorax and blebs/bullae In a randomized trial comparing VATS to chest tube treatment alone, recurrence dropped substantially in the surgical group, with recurrence at about 13% after VATS versus about 34% after chest tube drainage alone.12European Journal of Cardio-Thoracic Surgery. Surgical treatment versus conventional chest tube drainage in primary spontaneous pneumothorax: a randomized controlled trial The benefit was clearest in patients who had bullae one centimeter or larger.
Long-term results from VATS with blebectomy and pleural abrasion are encouraging. One retrospective study with a median follow-up of three years reported a recurrence rate of only about 2.5%.13PubMed Central. Effectiveness of video-assisted thoracoscopic surgery with blebectomy and mechanical pleural abrasion in the treatment of primary spontaneous pneumothorax: a retrospective long-term single-centre analysis Older data on open surgical bleb resection combined with pleurodesis showed recurrence rates in the single digits over a mean follow-up of about nine years, with low complication rates.14PubMed. Resection of pulmonary blebs and pleurodesis for spontaneous pneumothorax The surgical literature is consistent on the broad point: removing the blebs and creating pleural adhesion is the most reliable way to prevent the lung from collapsing again.
Surgical technique matters, too. One study found that patients whose blebs were closed with instrument-based stapling had lower recurrence than those whose blebs were hand-stitched.15PubMed Central. What factors predict recurrence of a spontaneous pneumothorax? The precision of the seal around the bleb site seems to make a difference in whether it holds long-term.
Recurrence Without Surgery
If you have had one spontaneous pneumothorax and did not have surgery, the chance of it happening again is uncomfortably high. One study found that roughly a quarter of patients experienced a recurrence, and the vast majority of those recurrences happened within the first six months, with most occurring in the first three months after the initial episode.16PubMed Central. Spontaneous Pneumothorax Recurrence and Surgery This window of vulnerability is why guidelines generally recommend surgery after a second episode. Some clinicians argue for earlier surgical intervention in patients with visible blebs or bullae, even after a first episode, because those structural abnormalities are a persistent invitation for trouble.
Several factors influence recurrence risk beyond the presence of blebs. Having other medical conditions alongside the pneumothorax, a prior surgical history for pneumothorax on the opposite side, and, perhaps counterintuitively, being a nonsmoker have all been associated with higher postoperative recurrence in at least one study.15PubMed Central. What factors predict recurrence of a spontaneous pneumothorax? The nonsmoking finding is puzzling. It may reflect the fact that smokers who develop pneumothorax tend to have more obvious bullae that are easier to identify and completely remove during surgery, while nonsmokers may have subtler blebs that get missed.
Flying, Diving, and Practical Lifestyle Concerns
Two activities carry specific risk for anyone with known blebs or a history of pneumothorax: flying and diving. Both involve pressure changes that can expand trapped gas.
Commercial aircraft cabins are pressurized to the equivalent of roughly 6,000 to 8,000 feet above sea level. At that altitude-equivalent pressure, any trapped air in the body expands. If you have an unresolved pneumothorax, even a small one, it can enlarge during a flight. For this reason, it is well established that people with an untreated pneumothorax should not fly.17PubMed Central. A chronic pneumothorax and fitness to fly After a pneumothorax has been treated and confirmed resolved on imaging, most guidelines suggest waiting a period (often two to four weeks, though recommendations vary by institution) before flying. Case reports exist of patients developing symptoms during long flights, underscoring that the risk is real and not merely theoretical.18PubMed Central. Dangers of flying high and diving low! An unusual case of dyspnea
Diving is potentially more dangerous. Descending underwater dramatically increases the pressure on your body, and ascending reverses it. Any air trapped in a bleb compresses on the way down and expands on the way up. If a bleb ruptures during ascent, the result can be a pneumothorax at depth, which is a life-threatening emergency when you are underwater. The fact that roughly a third of the general population may have small blebs or bullae without knowing it raises genuine questions about how diving fitness screening should be handled.9PubMed. Prevalence of Pulmonary Bullae and Blebs in Postmortem CT Imaging With Potential Implications for Diving Medicine Most diving medical authorities consider known blebs a relative or absolute contraindication to diving, but the high background prevalence of undetected blebs in healthy people makes blanket screening impractical. If you have had a pneumothorax, you should discuss diving with a physician experienced in dive medicine before going back in the water.
Beyond flying and diving, day-to-day life with blebs or after a pneumothorax is fairly normal. There is no strong evidence that avoiding exercise prevents recurrence. Most doctors encourage patients to return to physical activity once they have healed, though some advise against extremely high-altitude activities and certain high-pressure situations. The single most impactful lifestyle change you can make to reduce your risk is to stop smoking or vaping, if you do either. Inhaled toxins accelerate the kind of airway damage that promotes bleb formation and rupture, and quitting removes a modifiable risk factor that compounds all the non-modifiable ones.
Catamenial Pneumothorax and Other Unusual Presentations
Not every pneumothorax in a young person is caused by a ruptured bleb. Catamenial pneumothorax is a rare condition in which a woman develops a collapsed lung in sync with her menstrual cycle. The suspected mechanism involves endometrial tissue that has migrated to the chest, creating small holes in the diaphragm or lung surface that leak air during menstruation. In at least one reported surgical case, a woman treated for a presumed bleb-related pneumothorax turned out to have catamenial pneumothorax after a recurrence correlated with her menstrual cycle.19PubMed Central. Video-Assisted Thoracoscopic Suture Closure of Blebs to Treat Primary Spontaneous Pneumothorax The distinction matters because the treatment is different: hormonal therapy or diaphragm repair rather than bleb resection.
Mechanical ventilation in hospitalized patients can also cause air to leak from overstretched air sacs, a form of injury that has historically been called barotrauma.20Oxford Academic. Ventilator-induced Lung Injury: Lessons from Experimental Studies This is a fundamentally different situation from a spontaneous bleb rupture in an otherwise healthy person, but it shares the same underlying physics: air sac walls can only stretch so far before they break, and once air gets loose, it causes problems. Understanding that a bleb is one specific version of this broader phenomenon helps make sense of why doctors talk about blebs in such different clinical contexts, from a healthy teenager’s sudden chest pain to an ICU patient on a breathing machine.