Pneumothorax Workup

Updated: May 09, 2022
  • Author: Brian J Daley, MD, MBA, FACS, FCCP, CNSC; Chief Editor: Mary C Mancini, MD, PhD, MMM  more...
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Approach Considerations

History and physical examination remain the keys to making the diagnosis. When pneumothorax is suspected, confirmation by chest radiography affords additional information beyond confirmation, such as the extent of pneumothorax, potential causes, a baseline study from which to go forward, and assistance with the therapeutic plan.

In the evaluation of trauma patients, airway and breathing collectively are the primary concern. Portable chest radiography is veritably always included in the initial radiographic evaluation of a major trauma victim, as significant chest injuries may be masked by lack of physical findings or associated injuries. Chest trauma carries an estimated 10-50% risk of associated pneumothorax.

Computed tomography (CT) of the chest likewise should always be performed for significant chest injuries, because plain radiographs may miss associated thoracic trauma. Specifically for pneumothorax, the presence of a pneumothorax seen only on CT defines it as occult. In stable patients, however, chest radiography is often unnecessary. [35, 36]

Tension pneumothorax is a clinical diagnosis that now is more readily recognized because of improvements in emergency medical services (EMS) and the widespread application of educational programs such as Advanced Trauma Life Support (ATLS) and Fundamental Critical Care Support (FCCS).

Although laboratory and imaging studies help determine a diagnosis, as discussed earlier, tension pneumothorax primarily is a clinical diagnosis based on patient presentation. Suspicion of tension pneumothorax, especially in late stages, mandates immediate treatment and does not require potentially prolonged diagnostic studies (see the image below).

This chest radiograph has 2 abnormalities: (1) ten This chest radiograph has 2 abnormalities: (1) tension pneumothorax and (2) potentially life-saving intervention delayed while waiting for x-ray results. Tension pneumothorax is a clinical diagnosis requiring emergent needle decompression, and therapy should never be delayed for x-ray confirmation.

Go to Radiologic Diagnosis of Pneumothorax for complete information on this topic.


Arterial Blood Gas Analysis

Arterial blood gas (ABG) studies measure the degrees of acidemia, hypercarbia, and hypoxemia, the occurrence of which depends on the extent of cardiopulmonary compromise at the time of collection.

In patients with severe underlying lung disease and in those with persistent respiratory distress despite treatment, hypoxemia not only occurs with increased alveolar-arterial oxygen tension gradient, but it also tends to be more severe in patients with secondary spontaneous pneumothoraces.

ABG analysis does not replace physical diagnosis nor should treatment be delayed while awaiting results if symptomatic pneumothorax is suspected. However, ABG analysis may be useful in evaluating hypoxia and hypercarbia and respiratory acidosis.


Chest Radiography

When evaluating the chest radiograph for pneumothorax, one should use a systematic approach. Always assess rotation, which can obscure a pneumothorax and mimic a mediastinal shift. Compare the symmetry and shape of the clavicles, and look at the relative lengths of the ribs in the middle lung fields on each side on the anteroposterior (AP) or posteroanterior (PA) views. On an image with rotation, the ribs on each side often have unequal lengths.

In a nonloculated pneumothorax, air generally rises to the nondependent portion of the pleural cavity. Therefore, carefully examine the apices of an upright chest radiograph, and scrutinize the costophrenic and cardiophrenic angles on a supine chest radiograph.

Finding of pneumothorax on chest radiographs may include the following:

  • A linear shadow of visceral pleura with lack of lung markings peripheral to the shadow may be observed, indicating collapsed lung
  • An ipsilateral lung edge may be seen parallel to the chest wall
  • In supine patients, deep sulcus sign (very dark and deep costophrenic angle) with radiolucency along costophrenic sulcus may help to identify occult pneumothorax; the anterior costophrenic recess becomes the highest point in the hemithorax, resulting in an unusually sharp definition of the anterior diaphragmatic surface due to gas collection and a depressed costophrenic angle
  • Small pleural effusions commonly are present and increase in size if the pneumothorax does not reexpand
  • Mediastinal shift toward the contralateral lung may also be apparent
  • Airway or parenchymal abnormalities in the contralateral lung suggest causes of secondary pneumothorax; evaluation of the parenchyma in the collapsed lung is less reliable

Although expiratory images are thought to better depict subtle pneumothoraces (the volume of the pneumothorax is constant and hence proportionally higher on expiratory images), a randomized controlled trial revealed no difference in the ability of radiologists to detect pneumothoraces on inspiratory and expiratory images after procedures with the potential to cause pneumothoraces. (See the images below.)

Radiograph of a patient with a small spontaneous p Radiograph of a patient with a small spontaneous primary pneumothorax
Close radiographic view of patient with a small sp Close radiographic view of patient with a small spontaneous primary pneumothorax (same patient as from the previous image).
Expiratory radiograph of a patient with a small sp Expiratory radiograph of a patient with a small spontaneous primary pneumothorax (same patient as in the previous images).
Radiograph of a patient with spontaneous primary p Radiograph of a patient with spontaneous primary pneumothorax due to a left upper lobe bleb.
Close radiographic view of a patient with spontane Close radiographic view of a patient with spontaneous primary pneumothorax due to a left upper lobe bleb (same patient as in the previous image).

Tension pneumothorax

Imaging studies should not delay the diagnosis and treatment of tension pneumothorax; this condition is a medical emergency. When considering radiography, utilizing a risk-benefit analysis has been suggested, in which the time taken to obtain the radiograph is balanced against the expected clinical course, with decompression preceding chest radiography in ventilated patients who are prone to rapid decompensation.

In a very select subset of patients, it may be preferable to radiologically confirm and localize tension pneumothorax before subjecting the patient to potential morbidities arising from decompression. The subset of patients are those who are awake, stable, and not in any distress in whom an immediate chest film can be obtained, with a continuously accompanying clinician ready to perform urgent decompression should the need arise.

In the rare case that a chest radiograph is obtained safely, findings can include ipsilateral lung collapse at the hilum, increased thoracic volume, trachea and mediastinum deviation to the contralateral side, widened intercostal spaces on the affected side, heart border ipsilateral flattening. With a left hemithorax, the left hemidiaphragm may be depressed, but the liver prevents this occurrence on the right side. (See the images below.)

Radiograph of a patient with a large spontaneous t Radiograph of a patient with a large spontaneous tension pneumothorax.
Radiograph of a new left-sided pneumothorax in a p Radiograph of a new left-sided pneumothorax in a patient on mechanical ventilation, requiring high inflation pressures.
Pneumomediastinum from barotrauma may result in te Pneumomediastinum from barotrauma may result in tension pneumothorax and obstructive shock.
Radiograph of a patient in the intensive care unit Radiograph of a patient in the intensive care unit (ICU) who developed pneumopericardium as a manifestation of barotrauma.
Radiograph of an older man who was admitted to the Radiograph of an older man who was admitted to the intensive care unit (ICU) postoperatively. Note the right-sided pneumothorax induced by the incorrectly positioned small-bowel feeding tube in the right-sided bronchial tree. Marked depression of the right hemidiaphragm is noted, and mediastinal shift is to the left side, suggestive of tension pneumothorax. The endotracheal tube is in a good position.
Radiograph depicting right main stem intubation th Radiograph depicting right main stem intubation that resulted in left-sided tension pneumothorax, right mediastinal shift, deep sulcus sign, and subpulmonic pneumothorax.

Although the initial chest radiograph may show no evidence of pneumothorax, one must consider the possibility of delayed traumatic pneumothorax developing in any penetrating chest wound. Stable patients without pneumothorax on initial films can be observed with serial chest radiographs at 3 hours after injury to rule this out. [37]


Mediastinal emphysema appears as a thin line of radiolucency that outlines the cardiac silhouette, as well as thin, lucent, vertically oriented streaks of air within the mediastinum (see the image below). The aorta and other posterior mediastinal structures are highlighted, and a well-defined lucency around the right pulmonary artery (“ring around the artery” sign) may be seen.

Air most easily is detected retrosternally on the lateral chest radiograph. An AP chest radiograph may not depict the finding in 50% of cases. An expiratory radiograph may help detect small apical pneumothoraces. Unlike air in a pneumothorax or pneumopericardium, the air remains fixed in pneumomediastinum and does not rise to the highest point.

This chest radiograph shows pneumomediastinum (rad This chest radiograph shows pneumomediastinum (radiolucency noted around the left heart border) in this patient who had a respiratory and circulatory arrest in the emergency department after experiencing multiple episodes of vomiting and a rigid abdomen. The patient was taken immediately to the operating room, where a large rupture of the esophagus was repaired.

Estimating the size of the pneumothorax

In evaluating the chest radiograph, first impressions of pneumothorax size can be misleading. The following methods may be used to estimate the size of the pneumothorax:

  • Calculate the ratio of the transverse radius of the pneumothorax (cubed) to the transverse radius of the hemithorax (cubed); to express the pneumothorax size as a percentage, multiply the fractional size by 100 (this formula assumes a constant shape of the lung when it collapses and is invalid if pleural adhesions are present); the ratio of lung size to hemithorax size to estimate pneumothorax size avoids the subjective underestimation of pneumothorax expressed as a percentage of previous lung volume
  • A 2.5-cm margin of gas peripheral to the collapsing lung corresponds to a pneumothorax of about 30%; complete collapse of the lung is a 100% pneumothorax
  • A simple approach involves measuring the distance from the apex of the lung to the top margin of the visceral pleura (thoracic cupola) on the upright chest radiograph, so that a small pneumothorax is a distance to the apex that measures less than 3 cm and large pneumothorax has greater than 3 cm distance to the apex

The cut point distinguishing small and large pneumothoraces varies somewhat among professional societies and experts. The British Thoracic Society uses 2 cm as the cutoff, [38] the American College of Chest Physicians uses 3 cm as the cut point, [39] and the Light Index uses 15% of the thoracic volume on the posterior-anterior film as the cut point. [40]

Disadvantages of chest radiographs

Chest radiographs may fail to reveal pneumothorax or radiologists or interpreting physicians may fail to recognize the presence of the pneumothorax. Other disadvantages are as follows:

  • In patients with underlying pulmonary disease, the classic visceral pleural line may be harder to detect, because the lung is hyperlucent, and little difference exists in the radiographic density between the pneumothorax and the emphysematous lung
  • A vertical skin line can be mistaken for a pneumothorax, leading to unnecessary and possibly harmful therapy
  • Large bulla can simulate pneumothorax on chest radiographs, so that CT may be required to clarify the diagnosis.
  • Occasionally, skin folds, the scapula, and bed sheets can mimic the pleural line, falsely suggesting pneumothorax on the chest radiograph; unlike pneumothoraces, skin folds usually continue beyond the chest wall, and lung markings can be seen peripheral to the skin fold line; viewing the film under the hot lamp may be necessary to discern obscure peripheral lung markings

As ultrasonography becomes increasingly available in emergency situations, the already limited role of radiography in tension pneumothorax will be further minimized. Multiple recent studies have shown bedside ultrasonography to be more accurate than supine chest radiography in detecting and quantifying the presence of pneumothorax, including traumatic pneumothorax.

Go to Radiologic Diagnosis of Pneumothorax for complete information on this topic.


Other Radiographs and Transillumination

Confirmation of a suspected pneumothorax that is not readily observed on standard supine anteroposterior (AP) radiograph can be demonstrated by obtaining a lateral decubitus film with the involved hemithorax positioned uppermost (see the images below).

Lateral radiograph demonstrating tension and traum Lateral radiograph demonstrating tension and traumatic pneumothorax.
Lateral radiograph demonstrating tension and traum Lateral radiograph demonstrating tension and traumatic pneumothorax.
Lateral radiograph depicting tension and traumatic Lateral radiograph depicting tension and traumatic pneumothorax.

In neonatal patients, transillumination may reveal an increased transmission of light through the chest on the affected side.


Contrast-Enhanced Esophagography

If emesis or retching is the precipitating event for a pneumothorax, an esophagogram should be obtained to evaluate for Boerhaave syndrome (an esophageal tear), which has a high mortality rate. This is the study of choice in all cases of suspected esophageal perforation (ie, postendoscopy patients). Esophagoscopy could further be performed for esophageal perforations.


Computed Tomography of Chest

Chest CT is the most reliable imaging study for the diagnosis of pneumothorax, but it is not recommended for routine use in pneumothorax. This imaging modality can help to accomplish the following:

  • Distinguish between a large bulla and a pneumothorax
  • Indicate underlying emphysema or emphysemalike changes (ELCs)
  • Determine the exact size of the pneumothorax, especially if it is small
  • Confirm the diagnosis of pneumothorax in patients with head trauma who are mechanically ventilated
  • Detect occult/small pneumothoraces and pneumomediastinum (although the clinical significance of these occult pneumothoraces is unclear, particularly in the stable nonintubated patient)

CT is widely used in actual clinical practice to assess the possibility of associated concurrent pulmonary disease because of the inherent superiority of CT for visualizing the details of lung parenchyma and pleura (see the images below).

Computed tomography scan demonstrating blebs in a Computed tomography scan demonstrating blebs in a patient with chronic obstructive pulmonary disease (COPD).
Computed tomography scan demonstrating a bulla in Computed tomography scan demonstrating a bulla in an asymptomatic patient.
Computed tomography scan demonstrating secondary s Computed tomography scan demonstrating secondary spontaneous pneumothorax (SSP) from radiation/chemotherapy for lymphoma.
Computed tomography scan demonstrating emphysemato Computed tomography scan demonstrating emphysematouslike changes (ELCs) in a patient with chronic obstructive pulmonary disease (COPD).
Computed tomography scan in a patient with a histo Computed tomography scan in a patient with a history of bilateral pleurodesis and a strong family history of spontaneous pneumothorax.

Spontaneous pneumothorax

When performed on primary spontaneous pneumothorax patients, CT detects multiple blebs and bullae in the setting of negative chest radiographic findings. This may not impact management, in that there has been no correlation between number of blebs and recurrence. However, CT may have a role in secondary spontaneous pneumothorax, especially to differentiate from giant bullous emphysema.

Traumatic and tension pneumothorax

CT can detect occult pneumothorax in patients in trauma and emergency surgery settings. If the patient requires mechanical ventilation and/or anesthesia, all participants should be made aware of the findings; sometimes, prophylactic tube thoracostomy may be performed. [41, 42] This modality has also been shown to be more sensitive than radiography for hemothorax and pulmonary contusion.

Collapse of the lung, air in the pleural cavity, and deviation of mediastinal structures are present in tension pneumothorax.


CT may improve diagnostic sensitivity in pneumomediastinum, and if clinical suspicion is present for this condition, should be obtained. One small study suggested that mild pneumomediastinum was underdiagnosed based on chest radiographic findings, and CT was needed to make the diagnosis.

Go to Radiologic Diagnosis of Pneumothorax for complete information on this topic.



Prehospital portable ultrasonography (US) may provide diagnostic and therapeutic benefit when conducted by a proficient examiner who used goal-directed and time-sensitive protocols, as determined in an air rescue setting. [43, 44] Further study in this area may help to determine the indications and role of prehospital US. In experienced hands, US may be quicker and more accurate than radiography for distinguishing free pleural effusion (a finding in pneumothorax) in time-sensitive evaluations. [45]

US is increasingly used in the acute care setting as a readily available bedside tool, especially in the intensive care unit (ICU) and emergency department (ED) settings. [43] This modality provides a rapid imaging option for diagnosis of pneumothorax, but this evaluation should not delay treatment of a clinically apparent tension pneumothorax. [46, 47, 48]

Many trauma centers are incorporating chest US as an adjunct to the Focused Assessment with Sonography in Trauma (FAST) examination. Knudtson et al, in a prospective analysis of 328 consecutive trauma patients at a level 1 trauma center, obtained a specificity of 99.7% and an accuracy of 99.4%, and concluded that US was a reliable modality for the diagnosis of pneumothorax in the injured patient. [47]

A prospective study by Brook et al designed to assess the accuracy of radiology residents in detecting pneumothoraces as part of the extended FAST (eFAST) examination concluded that ultrasonographic pneumothorax detection by these radiology residents was both accurate and efficient in the early detection of clinically important pneumothoraces. [49]

The investigators compared ultrasonographic pneumothorax detection (by the absence of parietal-over-visceral lung sliding with "comet tail" artifacts behind it) with the reference standard of chest CT in 169 consecutive trauma patients (ie, 338 lung fields). A sensitivity of 47%, specificity of 99%, positive predictive value of 87%, and negative predictive value of 93% was found; none of the small pneumothoraces missed by US required drainage during the hospitalization period. [49]

In addition, Hernandez et al noted that US is the only radiographic modality allowing patients with nonarrhythmogenic cardiac arrest to continue undergoing resuscitation while clinicians search for easily reversible causes of asystole or pulseless electrical activity (PEA). [50] They proposed further investigation into the CAUSE (Cardiac Arrest UltraSound Exam) protocol, in which cardiac arrest patients, concurrent with resuscitation, receive bedside US to look for cardiac tamponade, massive pulmonary embolus, severe hypovolemia, and tension pneumothorax. The adoption of US in this setting may enhance "real-time" diagnostic acumen and shorten the time to appropriate condition-related therapy.

Notable features

Features of US examination for the diagnosis of pneumothorax include absence of lung sliding (high sensitivity and specificity), absence of comet-tail artifact (high sensitivity, lower specificity), and presence of lung point (high specificity, lower sensitivity).

In the absence of pleural disease, visceral pleura moves against parietal pleura while breathing. This movement of the two pleurae is detected by US as lung sliding, which is a "kind of twinkling synchronized with respiration" seen in real-time and time-motion modes. That is, lung sliding refers to normal pleural movement in patients without pneumothorax. [51] One study showed that absent lung sliding from an anterior approach indicated pneumothorax with 81% sensitivity and 100% specificity.

Comet-tail artifacts are vertical air artifacts that arise from the visceral pleural line (or, in the case of parietal emphysema or shotgun pellets, may arise above the pleural line). Lung point is the location that lung-sliding and absent lung-sliding alternately appear; it has been shown in multiple studies to allow determination of the size of a pneumothorax. Zhang et al obtained a 79% sensitivity in lung point's ability to determine pneumothorax size. [52]


US has high sensitivity (95.65%), specificity (100%), and diagnostic effectiveness (98.91%) for pneumothorax when CT is used as the criterion standard. In another study, US performed on patients with blunt thoracic trauma had 94% sensitivity and 100% specificity for pneumothorax detection compared with spiral CT.

This imaging modality can be used as a possible bedside technique to detect pneumothorax, which may be useful in unstable patients. [53] A prospective study involving 135 patients with multiple trauma using bedside US performed by ED clinicians obtained 86% sensitivity and 97% specificity for the detection of pneumothorax. Traumatic pneumothorax in the ICU setting can also be followed accurately and early (initial 24 hours) with US alone for resolution of the lesion. US does not use ionizing radiation and is repeatable.


US is heavily operator-dependent. In addition, this modality cannot be used to discriminate between a chronic obstructive pulmonary disease (COPD)-associated bleb and pneumothorax. [54]

The sensitivity of US drops in the ICU, especially in patients with acute respiratory distress syndrome (ARDS), [55] Moreover, in a preliminary study by Dente et al, though US evaluation for pneumothorax was found to be very accurate for the first 24 hours after insertion of a thoracostomy tube, its accuracy was not sustained over time. [46] By 24 hours after thoracostomy, the diagnostic sensitivity of US for pneumothorax had fallen to 55%, and its positive predictive value to 43%. This may be related to intrapleural adhesion formation. [46]

Go to Radiologic Diagnosis of Pneumothorax for complete information on this topic.