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Pneumothorax, Tension and Traumatic: Differential Diagnoses & Workup

Author: Jeffrey Glenn Bowman, MD, MS, Consulting Staff, Highfield MRI, Columbus, Ohio
Contributor Information and Disclosures

Updated: Feb 5, 2009

Differential Diagnoses

Other Problems to Be Considered

Airway obstruction
Hemothorax

Workup

Laboratory Studies

• 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 the following:
  • Hypoxia
  • Hypercarbia and respiratory acidosis

Imaging Studies

• Translumination: In neonatal patients, one may notice increased transmission of light through the chest on the affected side.
• Chest radiography: Historical dogma has included the recommendation that a chest radiograph of tension pneumothorax is a film that should never be taken. In addition, as ultrasonography becomes increasingly available in emergency situations, the already limited role of radiography will be even 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. 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 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. However, this consideration should be limited to a subset of patients who are awake, stable, not in advanced stages of tension and when an immediate chest film can be obtained, with a continuously accompanying practitioner ready to perform urgent decompression should the need arise. 
  • Although the initial chest radiograph may show no evidence of pneumothorax, consider the possibility of delayed traumatic pneumothorax development in any penetrating chest wound. Obtain serial chest radiographs every 6 hours the first day after injury to rule this out. Some authors advocate the acquisition of only one or two serial examinations every 4-6 hours.
  • Air in the pleural cavity, with contralateral deviation of mediastinal structures, is evidence of a tension pneumothorax. Tension pneumothorax chest radiographic findings may include increased thoracic volume, increased rib separation, heart border ipsilateral flattening, contralateral mediastinal deviation, and hemidiaphragmatic depression.
  • Pneumothorax chest radiograph findings include ipsilateral lung edge seen parallel to the chest wall, increased lucency, and a deep sulcus sign (deep lateral costophrenic angle).
  • When evaluating the chest radiograph for pneumothorax, assess rotation. Rotation can obscure a pneumothorax and mimic a mediastinal shift.
  • In evaluating the radiograph for rotation, compare the symmetry and shape of the clavicles. Also, look at the relative lengths of the ribs in the middle lung fields on each side on the anteroposterior or posteroanterior views. On an image with rotation, the ribs on each side often have unequal lengths.
  • In a nonloculated pneumothorax, air 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.
  • A skin fold can be mistaken for a pneumothorax. 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.
  • In evaluating the chest radiograph, first impressions of pneumothorax size can be misleading. To assist in determining the size of pneumothorax on the radiograph, 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.
• Chest CT scanning
  • Collapse of the lung, air in the pleural cavity, and deviation of mediastinal structures are present in tension pneumothorax.
  • A CT scan is more sensitive than a chest radiograph in the evaluation of small pneumothoraces and pneumomediastinum, although the clinical significance of these occult pneumothoraces is unclear, particularly in the stable nonintubated patient.
  • A CT scan may allow for further evaluation of underlying pulmonary disease or injury.
• Ultrasonography
  • Use of bedside ultrasonography in the diagnosis of pneumothorax is a relatively recent development. In some trauma centers, pneumothorax detection is included as part of their focused abdominal sonography for 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 ultrasonography was a reliable modality for the diagnosis of pneumothorax in the injured patient.³  
  • Ultrasonographic features used in 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 pleura is detected by the ultrasound as lung sliding, which is a "kind of twinkling synchronized with respiration" seen in real-time and time-motion modes. 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, the location that lung-sliding and absent lung-sliding alternately appear, 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.⁴
  • In one study, ultrasonography had 95.5% sensitivity and 100% specificity for pneumothorax detection compared with chest radiography. In another study, ultrasonography performed on patients with blunt thoracic trauma had 94% sensitivity and 100% specificity for pneumothorax detection compared with spiral CT scanning. A prospective study involving 135 patients with multiple trauma using bedside ultrasonography performed by emergency department clinicians obtained 86% sensitivity and 97% specificity for the detection of pneumothorax.

Procedures

• Needle thoracostomy is performed as follows:
  • Locate puncture site. The second intercostal space in the midclavicular line on the affected side immediately superior to the rib is most commonly recommended site.
  • Prepare the puncture site with povidone-iodine (Betadine), alcohol scrubs, or both.
  • Insert a large-bore Angiocath (14-gauge in an adult, 18- or 20-gauge in an infant) into the desired intercostal space over the top of the rib and perpendicular to the chest wall. Listen for a rush of air.
  • Remove the needle.
  • Secure the Angiocath in place, and establish a water seal or flutter valve.
  • Immediately prepare to insert a chest tube.
  • Listen for a rush of air on insertion to confirm the diagnosis of tension pneumothorax. Note this finding on the patient's chart. In an area with high ambient noise, the escape of air may not be detected.
  • Needle thoracostomy requires follow-up placement of a chest tube.
  • Potential morbidity associated with needle thoracostomy includes pneumothorax (with potential to tension later), cardiac tamponade, hemorrhage (which can be life-threatening), loculated intrapleural hematoma, atelectasis, pneumonia, arterial air embolism (when needle thoracostomy is performed and no tension pneumothorax is present), and pain to the patient.
• Tube thoracostomy is performed as follows:
  • If the patient is hemodynamically stable, consider conscious sedation with careful titration of a short-acting narcotic and benzodiazepine. However, use of a local anesthetic often is adequate.
  • Place the patient in a 30-60° reverse Trendelenburg position, scrub the site with povidone-iodine (Betadine), alcohol, or both, and anesthetize the site with lidocaine.
  • Make a 3- to 4-cm incision over the fifth or sixth rib in the midaxillary line.
  • Use a curved hemostat to puncture the intercostal muscles and parietal pleura immediately superior to the rib border, avoiding damage to the underlying lung. Then, slide a finger over the clamp to maintain the formed tract.
  • Perform a digital examination to assess the location and to evaluate pulmonary adhesions. Sweep the finger in all directions, and feel for the diaphragm and possible intra-abdominal structures. To avoid losing the desired tract, keep the finger in place until the tube is inserted.
  • Insert the chest tube along side of the finger, using a clamp on the tube, if desired.
  • Direct the chest tube posteriorly and inferiorly, and insert it until it is at least 5 cm beyond the last hole of the tube.
  • Attach the tube to a water seal and vacuum device (eg, Pleur-Evac). Look for respiratory variation and bubbling of air through the water seal. Document the amount of blood or other fluids that may drain.
  • Suture the site, and secure the tube. A variety of anchoring and closure techniques exist, all of which are probably equivalent. Cover the site with petroleum jelly–impregnated gauze, and apply a suitable dressing.
  • Follow-up chest radiography is required to confirm tube placement and lung reexpansion.
  • Complications of tube thoracostomy include death, injury to lung or mediastinum, hemorrhage (usually from intercostal artery injury), neurovascular bundle injury, infection, bronchopleural fistula, and subcutaneous or intraperitoneal tube placement.

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