165 RADIOLOGIC CLINICS OF NORTH AMERICA Radiol Clin N Am 44 (2006) 165–179 Chest Pain: A Clinical Assessment Kenneth H. Butler, DO*, Sharon A. Swencki, MD & Major pathologies that produce chest pain Pericarditis Pneumothorax Thoracic aortic dissection Pneumonia & Summary Acute coronary syndrome & References Pulmonary embolism Chest pain is one of the most common chief com- location, duration, radiation, quality, and exacer- plaints in emergency medicine. During the acute bating and relieving factors. A detailed history sets presentation of a patient who has chest pain, chest in motion further diagnostic testing and manage- imaging is invaluable, especially in the initial sta- ment decisions. bilization of a life-threatening cardiac or pulmo- nary event. The initial approach to evaluating chest pain includes excluding life-threatening causes, such Major pathologies that produce chest pain as aortic dissection, pulmonary embolism (PE), pneumothorax, pneumomediastinum, pericarditis, Pneumothorax and esophageal perforation. Perfect coupling between the visceral and parietal The evaluation of an unstable patient who has pleura is required for effective ventilation. Patients chest pain or shortness of breath begins with a pri- who have pneumothorax have gas in the intra- mary medical survey to evaluate airway, breathing, pleural space. This abnormality uncouples the vis- and circulation. In tandem with this rapid assess- ceral and parietal pleura and thus elevates the ment, the emergency physician requests radio- intrapleural pressure, which affects ventilation, gas graphic images of the chest, which provide exchange, and perfusion. visualization of the thoracic anatomy. The first Pneumothorax commonly is divided into two image obtained is the anteroposterior chest radio- types: primary spontaneous pneumothorax (PSP), graph, using portable radiography or fixed equip- which usually occurs without a precipitating event ment, depending on the patient’s presenting in patients who have no clinical lung disease, and clinical appearance. The initial study is invaluable secondary spontaneous pneumothorax, a compli- in providing clinically relevant information that cation of underlying lung disease. In actuality, most directs the patient’s care. patients who have PSP have underlying lung dis- Although technologic advances have improved ease, most commonly rupture of a subpleural bleb diagnostic accuracy greatly in recent years, a thor- [1]. Iatrogenic pneumothorax is difficult to iden- ough history and physical examination remain the tify; its incidence is increasing due to the more most important components in the evaluation pro- widespread use of mechanical ventilation and cess. It is imperative to obtain as many details interventional procedures such as central line about the pain as possible, including its onset, placement and lung biopsy [2]. When pneumo- Division of Emergency Medicine, University of Maryland School of Medicine, Baltimore, MD, USA * Corresponding author. Division of Emergency Medicine, University of Maryland School of Medicine, 110 South Paca Street, Sixth Floor, Suite 200, Baltimore, MD 21201. E-mail address: [email protected] (K.H. Butler). 0033-8389/06/$ – see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.rcl.2005.11.002 radiologic.theclinics.com 166 Butler & Swencki thorax is suspected, correct interpretation of chest Pathogenesis radiographs and knowledge of the benefit of more The pathogenesis of the subpleural blebs that cause complex imaging techniques are essential. The causes PSP is related to airway inflammation that results of spontaneous and iatrogenic pneumothorax and from cigarette smoking. The risk of PSP is related of pneumomediastinum are summarized in Box 1. directly to the level of cigarette smoking (number The incidence of PSP (age-adjusted) is 7.4 cases of pack years) [6]. per 100,000 persons per year for men and 1.2 cases Pneumothorax occurs with increasing frequency per 100,000 persons per year for women [3,4]. The in patients who have Marfan’s syndrome and ho- incidence of secondary spontaneous pneumotho- mocystinuria [7]. Catamenial pneumothorax may rax (age-adjusted) is 6.3 cases per 100,000 persons result from thoracic endometriosis and should be per year for men and 2 cases per 100,000 persons considered in menstruating women who present per year for women [3,4]. The incidence of iatro- with spontaneous pneumothorax [8]. genic pneumothorax is not known, but it probably occurs more often than do primary and secondary spontaneous pneumothoraces combined. Pneu- Clinical presentation momediastinum occurs in approximately 1 of PSP usually develops at rest. The peak age is the 10,000 hospital admissions [5]. early 20s. The disorder is rare after age 40. Patients usually complain of the sudden onset of dyspnea and pleuritic chest pain. The severity of symptoms is related to the volume of air in the pleural space; Box 1: Causes of pneumothorax dyspnea is more predominant if the pneumotho- rax is large. In patients who have a large pneumo- Spontaneous pneumothorax thorax, the physical findings include decreased • Rupture of subpleural apical emphysema- chest excursion on the affected side, diminished tous blebs breath sounds, and hyperresonant lungs. Many • Smoking (increases the risk of a first sponta- affected individuals do not seek medical attention neous pneumothorax by more than 20-fold for days after symptoms develop. This sequence is in men and by nearly 10-fold in women, important, because the incidence of re-expansion compared with the risks in nonsmokers) • Physical height (taller patients are at risk be- pulmonary edema increases in patients whose chest cause alveoli are subjected to a greater tubes were placed 3 or more days after the pneu- mean distending pressure over time, which mothorax occurred. leads to subpleural bleb formation; because Pneumomediastinum usually occurs when intra- pleural pressure is more negative at the apex thoracic pressures become elevated. This elevation of the lung, blebs are more likely to rupture may occur with an exacerbation of asthma, cough- and cause pneumothorax) ing, vomiting, childbirth, seizures, and a Valsalva Iatrogenic pneumothorax maneuver. Patients usually complain of a sudden onset of chest pain and dyspnea. • Transthoracic needle aspiration procedures • Subclavian and supraclavicular needlestick • Thoracentesis • Mechanical ventilation (directly related to Radiographic features peak airway pressures) The main radiographic abnormality that is indica- • Pleural or transbronchial biopsy tive of pneumothorax is a white visceral pleural • Cardiopulmonary resuscitation line—straight or convex toward the chest wall— • Tracheostomy which is separated from the parietal pleura by an avascular collection of air. In most cases, no pul- Pneumomediastinum monary vessels are visible beyond the visceral edge. • Acute production of high intrathoracic pres- The size of a pneumothorax is difficult to esti- sures (usual cause) mate. The measurement of the distance between • Asthma the ribs and the visceral pleura can be used to • Smoking marijuana decide whether to perform a tube thoracostomy. • Inhalation of cocaine If the distance is greater than 3 cm laterally or 4 cm • Athletic competition at the apex, a chest tube may be needed to re- • Respiratory tract infection expand the lung. A pneumothorax of less than • Parturition • Emesis 10% will reabsorb on its own and does not require • Severe cough placement of a chest tube. • Mechanical ventilation In upright patients who have pneumothorax, gas accumulates primarily in an apicolateral location. Chest Pain: A Clinical Assessment 167 As little as 50 mL of pleural gas can be seen on chest tion develops when injured tissue forms a one-way film. A lateral chest film with a 1-cm intrapleural valve and allows air to enter the pleural space but space corresponds to a 10% pneumothorax. The prevents it from escaping naturally. Arising from size of the pneumothorax is accounted for by the numerous causes, this condition progresses rapidly collapsed lung and, to a lesser degree, the expand- to respiratory insufficiency, cardiovascular collapse, ing chest cage. and, ultimately, death if it is unrecognized and un- The value of expiratory chest radiographs in treated. Favorable patient outcomes require urgent detecting pneumothoraces has been overstated. In clinical diagnosis and immediate management. a study of 85 patients who had pneumothoraces and 93 controls, inspiratory and expiratory upright Conditions that mimic pneumothorax chest radiographs had equal sensitivity for pneu- Large subplural bullae can mimic a loculated pneu- mothorax detection [9]. Because expiratory films mothorax. In most cases, the medial border of the provide no added benefit, only inspiratory films bulla is concave toward the chest wall, whereas a are recommended as the initial radiograph of visceral pleural contour is straight or convex later- choice for pneumothorax. ally. Skin folds can be differentiated from a pneu- In the supine patient, approximately 500 mL of mothorax by density profile: they form a negative pleural air is needed for definitive diagnosis of black Mach band instead of the white visceral pneumothorax [10]. The pleural gas accumulates pleural line. Skin folds increase gradually in opac- in the subpulmonic location and outlines the ante- ity, with an abrupt drop-off at the edge, and rior pleural reflection, the costophrenic sulcus, and usually extend beyond the ribcage or stop short of