eMedicine Specialties > Emergency Medicine > Pulmonary

Pneumothorax, Iatrogenic, Spontaneous and Pneumomediastinum: Differential Diagnoses & Workup

Author: Andrew K Chang, MD, Associate Professor, Department of Emergency Medicine, Albert Einstein College of Medicine, Montefiore Medical Center
Coauthor(s): Pinaki Mukherji, MD, Assistant Professor, Attending Physician, Department of Emergency Medicine, Montefiore Medical Center
Contributor Information and Disclosures

Updated: Jul 7, 2009

Differential Diagnoses

Workup

Imaging Studies

• Chest radiography for evaluation of pneumothorax
  • 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.
  • 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.
  • 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
    • The size of a pneumothorax may be estimated by using the ratio of the lung diameter cubed to the hemithorax diameter cubed.
    • This formula assumes a constant shape of the lung when it collapses and is invalid if pleural adhesions are present.
  • A simple approach to classification of the pneumothorax as small or large 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.
    • Small pneumothorax: <3 cm distance to the apex
    • Large pneumothorax: >3 cm distance to the apex
  • A supine chest radiograph may depict the deep sulcus sign (very dark and deep costophrenic angle). 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.

• Chest radiography for evaluation of pneumomediastinum
  • 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.
  • 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 anteroposterior chest radiograph may not depict the finding in 50% of cases.
  • Unlike air in a pneumothorax or pneumopericardium, the air remains fixed in pneumomediastinum and does not rise to the highest point.

• Contrast-enhanced esophagography: If emesis or retching is the precipitating event, 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.
• CT of the thorax
  • 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, as there has been no correlation between number of blebs and recurrence.
  • CT can detect occult pneumothorax in patients who will require mechanical ventilation in trauma and emergency surgery settings.
  • CT has also been shown to be more sensitive than radiography for hemothorax and pulmonary contusion.
  • While the role of CT in trauma patients is evolving, it is controversial whether it significantly alters management and is not indicated in primary spontaneous pneumothorax.
  • CT may have a role in secondary spontaneous pneumothorax, especially to differentiate from giant bullous emphysema.
  • CT may improve diagnostic sensitivity in pneumomediastinum, and if clinical suspicion is present, 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.
• Ultrasonography
  • Ultrasonography can be used as a possible bedside technique to detect pneumothorax.
  • It may be useful in unstable patients who cannot undergo radiologic studies outside of the emergency department.
  • Many trauma centers are incorporating chest ultrasonography as an adjunct to the Focused Assessment with Sonography in Trauma (FAST) examination used for trauma patient screening.
  • Ultrasonography is operator dependent.

Procedures

• Needle aspiration
  • Palpate the rib and intercostal space intended for needle aspiration. For needle aspiration, the anterior approach at the second or third intercostal space at the midclavicular line or a lateral approach at the fifth or sixth intercostal space at the midaxillary line is appropriate. For catheter aspiration, the lateral approach is preferred. 
  • Instill a local anesthetic to skin and soft tissue down to the pleura, directing the needle over the top of the rib into the desired intercostal space.
  • Insert a 16-gauge Angiocath or ready-to-use aspiration kit into the chosen intercostal space.
  • For simple needle aspiration, withdraw air once the pleural cavity is entered, and when resistance is felt, withdraw the needle.
  • For catheter aspiration, once the pleural cavity is entered, a soft pigtail catheter is advanced over the needle. A scalpel may be necessary to enlarge the entry site at the skin. Remove the needle once the pleural cavity is entered, and attach the catheter to a 3-way stopcock and 60-mL syringe.
  • Withdraw air continually until no more can be aspirated (discontinue if resistance is felt, if the patient coughs excessively, or if more than 2.5 L is aspirated). Close the stopcock, and secure the catheter to the chest wall.
  • Obtain a chest radiograph to assess the degree of success, and obtain another radiograph 4 hours later to confirm the absence of recurring accumulation.
  • If no recurrence is present, remove the catheter, and discharge the patient with appropriate return instructions. (Some authors suggest observation for an additional 2 h after catheter removal.)
  • If the pneumothorax persists, attach a Heimlich valve or a water seal and admit the patient.
• Tube thoracostomy
  • If the patient is hemodynamically stable, consider conscious sedation with careful titration of a short-acting narcotic and benzodiazepine.
  • Place the patient in a 30-60° reverse Trendelenburg position. Scrub the site (centered around the fifth or sixth rib in the midaxillary line) with povidone-iodine (Betadine), alcohol, or both.
  • Locally anesthetize the site with lidocaine. (Use a generous amount, and anesthetize all the way down to the pleura.)
  • Make a 3- to 4-cm incision.
  • Use a curved hemostat, puncture (in a controlled manner) through the intercostal muscles and parietal pleura immediately superior to the rib border, avoiding damage to the underlying lung. Spread the hemostat wide to create an adequate opening.
  • Perform a digital examination to assess the presence and location of pulmonary adhesions. Sweep the finger in all directions, and feel for the diaphragm and possible intra-abdominal structures. To avoid losing the desired tract, some recommend keeping the finger in place until the tube is inserted.
  • Insert the chest tube along the finger; use a clamp on the tube, if desired.
  • Direct the chest tube posteriorly, and insert it until it is at least 5 cm beyond the last hole in the tube.
  • Attach the tube to a water seal and vacuum device (eg, Pleur-Evac). Look for respiratory variation of the water seal and bubbling of air through the water seal. Document the amount of blood or other fluids drained.
  • Suture the site, and secure the tube to the chest wall. Cover the site with Vaseline-impregnated gauze, and apply a suitable dressing. A variety of anchoring and closure techniques exist, all of which are probably equivalent.
  • Obtain a chest radiograph to confirm placement and lung reexpansion.
• Needle decompression
  • Emergent intervention for tension pneumothorax should be performed prior to radiologic evaluation.
  • A large-bore (18 or 16 gauge) angiocatheter is introduced in the midclavicular line at the second or third intercostal space. This serves as a bridge until the definitive treatment of tube thoracostomy. The catheter is left in place until the chest tube is placed.
• Pleurodesis (See Further Inpatient Care).

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