Pneumothorax is a medical condition characterized by the presence of air or gas in the pleural space, the area between the lung and the chest wall. This accumulation of air causes pressure against the lung, leading to its partial or complete collapse. The term “collapsed lung” is often used to describe this condition.
What is a Pneumothorax?
The lungs are normally inflated within the chest cavity because the pressure inside the airways is higher than the pressure within the pleural space. A pneumothorax occurs when air enters this pleural space, disrupting the pressure balance and causing the lung to recoil and collapse. This air can enter through a tear in the lung itself or from an opening in the chest wall.
Common causes of pneumothorax include spontaneous events, traumatic injuries, and medical procedures. Patients experiencing a pneumothorax typically report sudden, sharp, one-sided chest pain that worsens with deep breaths or coughing, along with shortness of breath. Other symptoms may include chest tightness, rapid heart rate, fatigue, and, in severe cases, a bluish discoloration of the skin due to low oxygen levels.
How a Chest X-ray Reveals Pneumothorax
A chest X-ray (CXR) is frequently the initial imaging tool used to diagnose a pneumothorax because it is quick, readily available, and non-invasive. On an erect CXR, air in the pleural space typically rises to the highest point in the chest, often appearing as a dark, air-filled region. The most definitive sign of a pneumothorax on a CXR is the presence of a visible visceral pleural line. This appears as a thin, sharp white line representing the edge of the collapsed lung, separated from the chest wall.
Beyond this distinct visceral pleural line, there will be an absence of lung markings. Lung markings are the normal branching patterns seen on an X-ray, created by pulmonary blood vessels and airways. Their absence in the peripheral space indicates that air, not lung tissue, fills that region.
In more severe cases, particularly with a tension pneumothorax, the CXR may show a shift of the mediastinum—the central compartment of the chest containing the heart and major blood vessels—away from the affected side. This mediastinal shift is a sign of significant pressure buildup.
In some instances, an expiratory film may be ordered when a small pneumothorax is suspected but not clearly visible on a standard inspiratory CXR. During exhalation, the lung decreases in volume and becomes denser, which can make the air in the pleural space appear relatively larger and more distinct, thereby accentuating the pneumothorax. While some studies suggest inspiratory and expiratory films are equally sensitive for detection, many clinicians still find expiratory views useful for subtle cases. It is important to differentiate a true pneumothorax from artifacts like skin folds or clothing, which can sometimes mimic the appearance of a pleural line. Skin folds, for example, often extend beyond the chest cavity or show lung markings beyond their apparent edge.
Different Kinds of Pneumothorax
Pneumothoraces are broadly categorized based on their cause: spontaneous, traumatic, and iatrogenic.
Spontaneous Pneumothorax
This type occurs without an external injury. Primary spontaneous pneumothorax typically affects young, tall, thin individuals without underlying lung disease, often linked to the rupture of small air-filled sacs called blebs. Secondary spontaneous pneumothorax develops in patients with pre-existing lung conditions, such as chronic obstructive pulmonary disease (COPD), cystic fibrosis, or tuberculosis, where damaged lung tissue is more prone to air leakage.
Traumatic Pneumothorax
This results from direct chest injuries, like those sustained in accidents or from penetrating wounds. These injuries can create an opening in the chest wall or directly damage the lung, allowing air to enter the pleural space.
Iatrogenic Pneumothorax
This is a specific type of traumatic pneumothorax caused inadvertently by medical procedures, such as lung biopsies, central line insertions, or mechanical ventilation. These occurrences highlight the potential risks associated with certain medical interventions.
Tension Pneumothorax
This severe form occurs when a one-way valve effect allows air to enter the pleural space during inspiration but prevents it from escaping. The progressive accumulation of air leads to a rapid increase in pressure within the chest, compressing the affected lung and shifting the mediastinum, including the heart and major blood vessels, to the opposite side. This severe pressure buildup can impair blood return to the heart, leading to dangerously low blood pressure and potentially life-threatening respiratory and cardiovascular compromise.
Next Steps After a Pneumothorax Diagnosis
Once a pneumothorax is diagnosed, immediate medical attention is necessary, as the severity can range from minor to life-threatening. Treatment strategies depend on the pneumothorax’s size, the patient’s symptoms, and the underlying cause.
For small pneumothoraces with minimal symptoms, close observation may be sufficient, as the air can often be reabsorbed by the body over several weeks. Supplemental oxygen administration can accelerate this reabsorption process.
Larger or symptomatic pneumothoraces typically require intervention to remove the excess air. This can involve needle aspiration, where a hollow needle and catheter are inserted between the ribs to withdraw air from the pleural space using a syringe. Another common procedure is chest tube insertion, where a flexible tube is placed into the pleural space and connected to a drainage system to continuously remove air, allowing the lung to re-expand.
In cases of tension pneumothorax, immediate needle decompression is performed to relieve the pressure before a chest tube is inserted. Patients may also require surgery if air leaks persist, the lung does not re-expand, or if there are recurrent episodes.