displacement of the point of maximal impulse; shift or alteration in the heart tones; or new murmurs, gallops, or friction rubs Evaluation The most important study when evaluating any patient with a thoracic emergency is a high-quality chest radiograph The radiographs of the chest in the posteroanterior (PA) and lateral views should be performed in an upright position (unless contraindicated by the patient’s condition) The width of the mediastinum and the degree of mediastinal shift are much better seen in the upright chest radiograph Moreover, abnormalities in the lung, pleural cavity, and diaphragm are also best appreciated in this view When a pulmonary effusion exists, lateral decubitus anteroposterior views of the chest or an ultrasound can be obtained to determine whether the effusion layers freely or is loculated In interpreting the chest radiograph, the clinician should distinguish between a diffuse pulmonary problem and a focal lesion Hyperaeration of one portion of the lung suggests air trapping in the involved lobe Hyperaeration of the entire lung field on one side is usually the result of compensatory enlargement of the lung because of atelectasis and loss of lung volume on the opposite side Depending on the condition, laboratory studies and advanced imaging modalities may be indicated AIRWAY COMPROMISE Airway compromise can occur anywhere in the respiratory tract from the nose to the alveolus Obstructive emergencies relating to the oropharynx, larynx, and proximal trachea are discussed in Chapters 106 ENT Trauma and 118 ENT Emergencies Compromise of the more distal tracheobronchial tree may be caused by lesions in the lumen, in the wall, or external to the bronchus Intrinsic bronchial obstructions may result from narrowing of the lumen by a tumor (e.g., carcinoid tumor), foreign body, or a mucous plug Obstruction from lesions in the wall of the bronchus includes collapse from tracheomalacia and stenosis after tracheostomy Extrinsic lesions (e.g., bronchogenic cyst or inflamed lymph nodes) become symptomatic when the compression impinges on a bronchus Table 124.1 lists intraluminal, mural, and extrinsic conditions that produce airway obstruction The anatomic level of the obstruction correlates with its effects: An obstruction of the distal tracheobronchial tree may lead to segmental lung overdistention or segmental infection An obstruction of the proximal trachea affects both lungs, with a much greater likelihood of catastrophe for the patient Similarly, greater degrees of obstruction, as a rule, lead to greater effects on gas exchange and severity Infection commonly follows obstruction of bronchial drainage because the clearance of bacteria or inhaled foreign materials by the mucociliary elevator is prevented TABLE 124.1 TRACHEOBRONCHIAL CONDITIONS ASSOCIATED WITH AIRWAY COMPROMISE Intraluminal Foreign bodies Aspiration (esophageal reflux, tracheoesophageal fistula, bronchial fistula, biliary fistula, or esophageal fistula) Mucous plugs (cystic fibrosis) Granuloma (chronic intubation, tuberculosis) Hemoptysis (vascular malformations, cystic fibrosis, tuberculosis, sarcoidosis, hemosiderosis, lupus) Acute infection (tracheitis) Mural Tracheomalacia Lobar emphysema Bronchial atresia Bronchial tumors Extrinsic Lymphadenopathy Bronchogenic cyst Cystic hygroma Esophageal duplication Mediastinal tumors Tracheal Obstruction CLINICAL PEARLS AND PITFALLS Although wheezing and stridor are very common presentations in children with intercurrent viral illnesses, structural problems should be considered in children with recurrent presentations or significant respiratory distress that does not respond to typical therapies Radiographic studies may not reveal the cause of tracheal obstruction, since these are often dynamic processes Direct laryngoscopy or bronchoscopy may be necessary Current Evidence Tracheal obstruction may be produced by stenosis or lesions within the lumen of the trachea (Fig 124.1 ), in the wall of the trachea, or by extrinsic compression One of the most common causes of intrinsic obstruction in children is an aspirated foreign body (please see Chapter 32 Foreign Body: Ingestion and Aspiration for details) Other causes include congenital anomalies such as subglottic stenosis, laryngomalacia, and vocal cord paralysis Acquired causes include subglottic stenosis after tracheostomy or prolonged intubation, viral or bacterial tracheitis or any process that causes significant mucosal edema particularly in an infant with small baseline airway diameter, or rarely a spaceoccupying lesion such as a hemangioma or primary tracheobronchial tumor Tracheomalacia, sometimes complicating lung disease of prematurity and prolonged intubation, is characterized by a floppy trachea that collapses during expiration when the intrathoracic trachea is compressed by the positive intrathoracic pressure Laryngomalacia, or tracheomalacia outside the thoracic inlet, may produce obstruction during inspiration when the negative intraluminal pressure transmitted from the chest causes the floppy wall to collapse Tracheomalacia often occurs in infants born with tracheoesophageal fistula (TEF) or other intrinsic anomalies Extrinsic compression can occur from mass lesions (Table 124.1 ) or as a result of anomalous arteries FIGURE 124.1 Acute and chronic obstruction of a bronchus owing to tumor or cyst (T) or lymph nodes (L) When the obstruction is acute, there may be bronchiectasis caused by recurrent pneumonia The right middle lobe as shown here is particularly prone to bronchial obstruction caused by pressure from encircling lymph nodes RUL, right upper lobe; RML, right middle lobe; RLL, right lower lobe Goals of Treatment