Think Ultrasound When Evaluating for Pneumothorax

Abstract

hen evaluating a patient with hypoxia, dyspnea, or pleurisy, the differential diagnosis a clinician generates oftentimes includes ruling in or ruling out pneumothorax. Indeed, the clinical scenarios in which this diagnosis is important to consider are almost too numerous to list: a patient begins coughing just after a difficult attempt at central line placement; ventilator setting alarms start to go off and oxygen saturations drop in a patient with obstructive pulmonary disease; a young healthy person presents to the emergency department with dyspnea and pleurisy; a trauma patient presents with hypotension; or a patient becomes short of breath immediately after a diagnostic or therapeutic thoracentesis. Moreover, in settings in which radiography is not available such as office practices and in remote settings, thoracic sonography for pneumothorax can be especially helpful. In these clinical scenarios a quick diagnostic imaging test to rule in or rule out pneumo thorax not only facilitates the patient’s treatment when its findings are positive but also helps eliminate this diagnosis from the differential. In some respects the latter is even more crucial because it allows the care team to move on to treat the true source of dyspnea and not perform unnecessary therapeutic maneuvers but rather focus on accurate treatment. As has been well described, supine chest radiographs are notoriously unreliable in making the diagnosis of pneumothorax, and sensitivity values of 25% to 75% have been reported.1 This situation occurs largely because layering air in the supine patient can be distributed evenly over the anterior chest and therefore can be invisible on supine radiographs. Even upright chest radiography can be challenging, however, because lines, tubes, and other folds can hide subtle pleural line abnormalities. Although chest computed tomography is quite accurate, it involves moving potentially unstable patients to a less monitored environment; it involves radiation exposure; and its increased cost makes it an inefficient screening tool. Sonography is portable, can be performed at the bedside, and has no risk associated with repeated measures as clinical scenarios change. These advantages can make it less expensive because there are no additional burdens placed on radiologic technologists, and the performance is physician dependent. Indeed, numerous studies have described near 100% sensitivity and 90% to 95% specificity if a thorough examination is performed.1–5 Received November 22, 2011, from the Department of Emergency Medicine, Massachusetts General Hospital, Boston, Massachusetts USA. Revision requested November 30, 2011. Revised manuscript accepted for publication December 30, 2011. Address correspondence to Vicki E. Noble, MD, Department of Emergency Medicine, Massachusetts General Hospital, 0 Emerson, 3B, 55 Fruit St, Boston MA 02114 USA. E-mail: vnoble@partners.org W