Lung Ultrasound in Postprocedural Pneumothorax

An 84-year-old man with a history of diabetes, severe aortic stenosis, and chronic obstructive pulmonary disease was admitted to our medical center with a 1-week history of dyspnea. On admission he was normotensive, afebrile, and mildly tachypneic (respiratory rate 20 breaths/min), with an oxygen saturation of 94% on room air. Examination revealed unlabored breathing with breath sounds reduction at right basal pulmonary field. Chest radiography showed a moderate right pleural effusion. Laboratory tests yielded leukocytosis and increased levels of C-reactive protein.

Thoracentesis was performed using a 16-gauge needle inserted through the eighth intercostal space in the posterior axillary line with the patient placed in a side-lying position. Yellowish fluid was removed and laboratory analysis documented a transudative effusion. After the procedure, the patient complained of dyspnea and chest pain. Oxygen saturation was 85%, and oxygen was administered by mask. Semirecumbent chest radiography showed no signs of pneumothorax (Figure 1). Bedside ultrasound (US) performed by the emergency physician documented lung sliding absence in the right apical region and a lung point sign in the right anterior axillary line (Figure 2, Video Clip 1). Left scans were normal. A diagnosis of right pneumothorax was made.

Figure 1.  Chest x-ray: no evidence of pneumothorax.

Figure 2.  US image (M-mode): pneumothorax with lung point (arrow shows the “seashore sign,” indicating the presence of lung sliding; arrowhead shows the “stratosphere sign,” indicating abolition of lung sliding). US = ultrasound.

Approximately 3 hours later, semirecumbent chest radiography was repeated. At this point a 6-cm pneumothorax was seen (Figure 3). Because of the presence of clinical symptoms, a small-bore chest tube was inserted using the Seldinger technique. Immediate clinical and radiographic improvement occurred.

Figure 3.  Chest x-ray: apical right pneumothorax.

Incidence of pneumothorax after thoracentesis is about 20% and can be reduced to 3% with US guidance.¹ Chest radiography can miss a diagnosis of pneumothorax in many cases. Radiographic signs may be absent or sometimes misleading. In one study performed on trauma patients, this condition was missed in up to 76% of all seriously injured patients when radiography was interpreted by the trauma team.² When the examination is performed in supine position, or immediately after a procedure (central vein cannulation or thoracentesis), diagnostic accuracy can be reduced.

Lung US is a useful and simple tool for diagnosis of pneumothorax. Detection of lung sliding and lung point are the diagnostic hallmarks. Lung sliding is a horizontal movement visible at the pleural line observed when the visceral pleura slides on the parietal pleura during respiratory cycles. The lung point is the transition point in which lung sliding appears and disappears when the collapsed lung is or is not in contact with the chest wall. Detection of lung sliding excludes the presence of pneumothorax. Detection of lung point confirms the presence of pneumothorax.³

Utility of lung US in suspected pneumothorax is well documented for traumatized and dyspneic patients in the emergency department.^4,5 A recent study suggests that US is accurate in detection of postprocedural pneumothorax.⁶ For emergency physicians, lung US is a useful tool for making a diagnosis, for performing procedures, and for detecting complications.