A collapsed lung is usually diagnosed with a chest X-ray, which can show air trapped between the lung and chest wall. A clinician will also ask about symptoms and recent injuries or procedures, check breathing and oxygen levels, and listen to the chest. A CT scan or bedside ultrasound may be used if the X-ray is unclear or the situation needs a faster assessment.
The term collapsed lung most often refers to a pneumothorax, which occurs when air collects in the space between a lung and the chest wall, pushing on the lung and causing it to shrink. The phrase can also be used when discussing atelectasis, a condition in which part of the lung loses air volume. These conditions have different causes, so the clinician considers the examination and imaging findings to determine which problem is present. MedlinePlus explains these distinctions.
What happens during the first medical assessment?
The clinician begins by asking when the symptoms started, whether they appeared suddenly or developed gradually, and whether there has been a recent chest injury or medical procedure. They may also ask about previous episodes of pneumothorax, existing lung conditions, and recent respiratory problems. This information helps guide the examination and the choice of tests.
During the physical examination, the clinician checks breathing rate, heart rate, blood pressure, and oxygen levels. They listen to both sides of the chest with a stethoscope, comparing the sounds of breathing. Reduced or absent breath sounds on one side may raise concern about a pneumothorax, although the findings can be less noticeable when the amount of trapped air is small.
According to Cleveland Clinic, diagnosis usually combines the medical history and physical examination with imaging tests. The examination helps clinicians assess how urgently care is needed, but imaging is generally used to confirm a pneumothorax when the person's condition allows time for testing.
Which imaging tests can diagnose a collapsed lung?
Chest X-ray
A chest X-ray is the main test used to diagnose a pneumothorax in many situations. It produces an image of the chest that allows the clinician to look for air outside the lung and identify the boundary of the affected lung. The image can also help show the location and extent of the collapse and whether the structures in the center of the chest appear displaced.
The Mayo Clinic identifies chest X-rays as the usual diagnostic test for pneumothorax. The scan itself is quick and does not require the insertion of instruments into the chest. However, the image must be interpreted alongside the person's condition and examination findings, particularly when the suspected collapse is small or the initial image is difficult to interpret.
Chest ultrasound
Ultrasound uses sound waves to produce images of structures inside the chest. A trained clinician can perform it at the bedside and look for signs that air has collected between the lung and chest wall. This can be particularly useful during an emergency assessment, when moving the person to another area for imaging may be difficult.
The Merck Manual Consumer Version describes ultrasound as one of the methods used to diagnose a pneumothorax. Its usefulness depends on factors such as the patient's lung condition and whether the affected area can be seen clearly. Ultrasound may be used alongside other tests rather than as a replacement for every chest X-ray.
CT scan of the chest
A computed tomography (CT) scan takes multiple X-ray images to create detailed cross-sectional pictures of the chest. It may be requested when a chest X-ray does not provide a clear answer, a small pneumothorax is suspected, or clinicians need more information about a chest injury or another lung condition.
A CT scan can reveal a pneumothorax that is difficult to identify on a standard X-ray, including in some people who are lying down. The Merck Manual Professional Edition describes CT as a useful method for visualizing pneumothorax and related abnormalities. It is not necessary for every person; the decision depends on the initial findings, the person's condition, and the clinical question that needs to be answered.
Are blood tests or other examinations needed?
Blood tests do not usually establish the presence of a pneumothorax by themselves. However, they may help clinicians assess breathing problems, identify complications, or investigate other possible causes of symptoms. An arterial blood gas test, for example, measures oxygen and carbon dioxide levels in the blood and may be used when information about gas exchange is needed.
An electrocardiogram (ECG), which records the heart's electrical activity, may also be requested when chest pain or other findings require evaluation of possible heart-related causes. Additional tests depend on the circumstances, such as whether the person has experienced a significant injury or has another suspected medical problem. MedlinePlus Medical Encyclopedia lists chest X-rays, CT scans, arterial blood gas testing, and ECGs among the investigations that may be used during an assessment for a collapsed lung.
Can a collapsed lung be diagnosed without an X-ray?
In some situations, yes. When a pneumothorax is causing a rapidly worsening emergency, clinicians may identify the problem from the person's condition, vital signs, and physical examination. They must not delay urgent treatment while waiting for an X-ray if a tension pneumothorax is strongly suspected. In this dangerous form, trapped air creates increasing pressure inside the chest and can interfere with blood returning to the heart.
In a person whose condition is stable, imaging is generally used to confirm the diagnosis and assess the affected area. Bedside ultrasound may provide the answer in some cases, while CT can help when the results of other tests are uncertain. The method chosen depends on how urgently a decision is needed and which test can provide reliable information in that situation.
What happens if the first test does not show a collapsed lung?
A normal or unclear initial chest X-ray does not always settle the question when clinical concern remains. Small pneumothoraces can be difficult to see, and a person's position during imaging may affect how clearly the problem appears. The clinician may review the images again, arrange additional imaging, or repeat an examination as the situation requires.
If imaging instead suggests atelectasis, the investigation may focus on why part of the lung has lost volume. Depending on the findings, clinicians may use a CT scan or other tests to investigate the underlying cause. The goal is not simply to identify an area of reduced lung expansion, but to understand what the images show and whether another condition needs attention.
When is urgent assessment needed?
A suspected collapsed lung needs prompt medical assessment because symptoms can worsen and some forms are emergencies. Sudden chest pain, difficulty breathing, or rapidly worsening breathlessness should not be assessed at home. Blue or gray lips or skin, fainting, or marked weakness alongside breathing symptoms are additional reasons to seek emergency help.
If these symptoms are happening now, contact your local emergency service or seek emergency care immediately. A clinician can assess breathing and circulation, determine whether imaging is appropriate, and start urgent treatment when necessary. Testing should never delay emergency care when the person's condition suggests a life-threatening pneumothorax.