Author
Editors (continued)
Lars Grimm, MD, MHS
House Staff
Department of Diagnostic Radiology
Duke University Medical Center
Durham, North Carolina
Disclosure: Lars Grimm, MD, MHS, has disclosed no relevant financial relationships.
Reviewer
John A McPherson, MD
Assistant Professor of Medicine
Division of Cardiovascular Medicine
Vanderbilt University School of Medicine
Nashville, Tennessee
Disclosure: John A McPherson, MD has disclosed no relevant financial relationships.
A traumatic pneumothorax results from blunt or penetrating trauma that disrupts the parietal or visceral pleura. It is commonly caused by a rib fracture that penetrates pleura and damages lung tissue, but medical procedures can also lead to pneumothorax. Traumatic pneumothoraces occur more frequently than spontaneous pneumothoraces. Their incidence will likely continue to increase as intensive care treatment modalities become increasingly dependent on positive pressure ventilation, central venous catheter placement, and other causes that potentially induce iatrogenic pneumothorax.[1] This radiograph shows a right-sided iatrogenic pneumothorax after transbronchial biopsy.
Diagnosis of a pneumothorax by physical examination is often difficult, so a chest radiograph is usually used to confirm its presence. Management steps for traumatic pneumothoraces are similar to those for nontraumatic pneumothoraces. Selection between the various management options requires an understanding of the natural history of pneumothorax, the risk of recurrence, and the benefits and limitations of the available treatment options.[1] Image courtesy of Wikimedia Commons.
Some traumatic pneumothoraces (classified as occult) cannot be seen on chest radiographs but can be seen on computed tomography (CT) scans. In this CT scan of a patient with blunt chest trauma, the yellow arrow points to a comminuted rib fracture and the red arrows point to the displaced lung surface. The forces associated with blunt thoracic trauma can be transmitted to the lung parenchyma, resulting in pulmonary contusion, with subsequent pulmonary infiltrates and hemorrhage. Other parenchymal injuries (eg, lacerations) can be produced by fractured ribs and, rarely, by deceleration mechanisms. Image courtesy of Wikimedia Commons.
Answer: C. Supportive care
Pulmonary contusion (shown here with rib fractures and subcutaneous emphysema) is the most common thoracic injury in children and represents a defining contrast between children and adults. In contrast to rib fractures in adults after blunt trauma, the kinetic energy of blunt chest trauma is transmitted to the compliant chest wall in children. Thus, both pulmonary contusion and hemorrhage are far more common than pneumothorax. Hypoxia from shunting or ventilation perfusion mismatch is characteristic of pulmonary contusion. Successful treatment involves aggressive pulmonary toilet and pain management. Image courtesy of Wikipedia Commons.
A patient presents with a very shallow stab wound to the back. The injury does not penetrate the underlying musculature. The patient’s CT scan is shown.
Based on the CT scan, what is the likely cause of this pneumothorax?
A. Ruptured bleb
B. Cystic fibrosis
C. Collagen vascular disease
D. Tuberculosis
Answer: A. Ruptured bleb
This CT scan demonstrates a focal area of emphysema (yellow arrow), which is present in more than 80% of patients with spontaneous pneumothoraces (even lifelong nonsmokers). These areas are situated predominantly in the peripheral regions of the apex of the upper lobes. Patients with larger or more numerous blebs are more likely to experience recurrent pneumothoraces. CT scans of the chest are frequently ordered for patients with known pneumothorax (red arrow) and patients with suspected penetrating chest trauma. CT may be necessary to diagnose pneumothorax in critically ill patients for whom upright or decubitus films are not possible.
Answer: A. Barotrauma
In addition to a pneumothorax, this patient has developed subcutaneous emphysema (yellow arrow) secondary to barotrauma from mechanical ventilation. Subcutaneous emphysema may be palpable as crepitus under the skin. This crepitus can be detected anywhere over the chest and/or neck. In rare cases, auscultation reveals a systolic crunching sound over the precordium, which represents mediastinal air and is referred to as the Hamman crunch or Hamman sign. Obstructive lung conditions are major risk factors, including asthma, bronchiolitis, foreign body aspiration, and bronchopulmonary dysplasia.
A patient was involved in a serious motor vehicle collision and was intubated at the scene. He is hypotensive and difficult to ventilate. His chest radiograph is shown.
Based on the radiograph, what is the next step in this patient’s management?
A. Measurement of arterial blood gas
B. Insertion of a needle or catheter into the left chest
C. Adjustment of the endotracheal tube
D. Insertion of a chest tube on the right side
Answer: B. Insertion of a needle or catheter into the left chest
The patient needs immediate left chest decompression. He has developed a left-sided tension pneumothorax (red arrow). Note the marked shift of the mediastinal structures to the right (yellow arrow), the partial collapse of the left lung (green arrow), and the inversion and downward displacement of the left hemidiaphragm. In the mediastinum, air can track along tissue planes, creating a pneumomediastinum, whereas increased pressure that ruptures through the mediastinal pleura produces a pneumothorax.
A 36-year-old trauma patient is admitted with bilateral femur and pelvic fractures. Because of difficulties in ventilation, positive end expiratory pressure (PEEP) of 10 cmH2O is added. At night, the machine’s alarm indicates high peak pressures. The patient’s blood pressure is 85/50 mmHg and pulse is 120 bpm. A portable chest radiograph is ordered (shown).
What is the next step in the management of this patient?
A. Measure arterial blood gas
B. Decrease positive end expiratory pressure
C. Insert bilateral chest tubes
D. Start intravenous furosemide
Answer: C. Insert bilateral chest tubes
Lucent areas in the bilateral hemithoraces are suggestive of pneumothorax (arrows). Bilateral chest tubes should be placed to treat the condition and prevent tension pneumothorax. PEEP is often required to treat patients with acute respiratory distress syndrome (ARDS); however, high PEEP can cause barotrauma. As PEEP is increased, cardiac output may fall; volume expansion or inotropic/pressor agents may be required. Low tidal volumes and limited plateau pressures can reduce the risk of barotrauma. No mortality benefit is reported with higher PEEP, and the optimal approach to PEEP remains to be determined.
A 22-year-old is stabbed in the back. The stab wound is very superficial. The patient’s radiograph is shown. The patient is told that he has a pneumothorax that does not require treatment.
In which location would a pneumothorax be visualized better on CT scan than chest radiograph?
A. Base of diaphragm
B. Along pericardial border
C. Along the lateral chest wall
D. Apex of the lung
E. Both A and B are correct
Answer: D. Apex of the lung
Small pneumothoraces in the apex of the lung are very rarely seen on a chest radiograph (shown). These pneumothoraces are often first seen on a CT scan. However, CT scan is not routinely used for the diagnosis of pneumothorax. Such pneumothoraces are usually small and do not require treatment.
Proper technique is required to avoid a pneumothorax during catheterization of the internal jugular vein (shown).
Which of the following is true concerning catheterization of the internal jugular vein?
A. The patient should be placed in negative Trendelenburg position
B. Have the head turned away from the catheterization
C. The sternocleidomastoid muscle is a key landmark
D. Ultrasound guidance is needed in most cases
E. Both B and C are correct
Answer: E. Both B and C are correct
Although ultrasound guidance for the procedure may be helpful (shown), a key part of placing a central line in the internal jugular vein is proper positioning of the patient. The Trendelenburg position dilates the internal jugular vein and makes the external jugular vein more prominent. The point at which the vein crosses the sternocleidomastoid muscle is a key landmark in the posterior approach. The patient’s head should be turned away, which provides access to the side of the neck and makes the sternocleidomastoid muscle more prominent.
Cannulation of a patient’s right internal jugular vein was attempted several times without success. The patient reports shortness of breath. His chest radiograph is shown.
What is the next step?
A. Attempt a central line in the left jugular vein
B. Attempt a central line in the right subclavian vein
C. Insert a needle in the third intercostal space
D. Administer oxygen via nasal cannula
Author
Editors (continued)
Lars Grimm, MD, MHS
House Staff
Department of Diagnostic Radiology
Duke University Medical Center
Durham, North Carolina
Disclosure: Lars Grimm, MD, MHS, has disclosed no relevant financial relationships.
Reviewer
John A McPherson, MD
Assistant Professor of Medicine
Division of Cardiovascular Medicine
Vanderbilt University School of Medicine
Nashville, Tennessee
Disclosure: John A McPherson, MD has disclosed no relevant financial relationships.
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