Tube Thoracostomy
Tube thoracostomy is a procedure used to evacuate an abnormal accumulation of fluid or air from the pleural space and can be performed on an elective, urgent, or emergency basis. Air or fluid can accumulate in the pleural space as a result of spontaneous or traumatic pneumothorax, pleural fluid accumulation of blood, malignancy, infection (empyema), or lymph (chylothorax). The first modern methods to evacuate the contents of the pleural space were developed in the 19th century, but these techniques did not become widespread until 1918, when they were used to treat postinfluenza empyema. Military experience demonstrated that thoracic drainage combined with antiseptics and antibiotics reduced mortality related to thoracic trauma from 62.5% during the Civil War, to 24.6% in World War I, and to 12% in World War II.1
Pathophysiology
Pneumothorax
A pneumothorax is caused by the presence of air in the pleural space and the loss of negative pressure (Fig. 10-1). Air can enter the pleural space from the outside as a result of a penetrating injury or internally from a ruptured lung bleb or damaged trachea. Iatrogenic causes from needle procedures such as subclavian venous cannulation, transthoracic biopsy, thoracentesis, positive pressure ventilation (PPV), or cardiopulmonary resuscitation (CPR) are also common (Fig. 10-2). Pneumothoraces are commonly divided into “open” and “closed.” An open pneumothorax indicates that the skin and underlying soft tissue sustained an injury that penetrated into at least the pleural space.
Spontaneous (Closed) Pneumothorax
Spontaneous pneumothorax is caused by rupture of a subpleural lung bleb with little or no trauma and can be categorized as either primary or secondary based on the presence of underlying lung disease. Primary spontaneous pneumothorax occurs in a patient without overt lung disease. The typical patient with spontaneous pneumothorax is a tall, thin, 20- to 40-year-old male smoker (Fig. 10-3). Secondary spontaneous pneumothoraces occur in patients with underlying lung or pleural disease, including emphysema, chronic bronchitis, asthma, Marfan’s syndrome, infection, and neoplasm. The morbidity, mortality, and long-term complications associated with pneumothorax increase in patients with underlying lung disease. Whereas a primary pneumothorax may be selectively observed or simply aspirated, a secondary pneumothorax often requires a more aggressive approach to management.
The sudden onset of pleuritic chest pain and dyspnea with exertion or at rest is the most common finding. More subtle manifestations occur with little or no pain and only mild dyspnea on excursion that the patient may ignore for days. A person with a small spontaneous pneumothorax may never seek medical attention, and the process will resolve without treatment. The signs and symptoms do not always correlate well with the size or cause of the collapsed lung. Tube thoracostomy is the most common treatment, but new trials suggest that conservative management or aspiration of first-time primary pneumothoraces results in similar outcomes as traditional tube thoracostomy, though with fewer complications, shorter hospital stay, and lower cost. Conservative management and aspiration are both reasonable initial interventions in clinically stable patients. However, to date no high-quality clinical trials have definitely demonstrated that aspiration is a superior treatment methodology.2–4 Rarely, a spontaneous pneumothorax may be bilateral or progress to tension pneumothorax, a potentially life-threatening condition that is described in more detail later in this chapter.
Tension Pneumothorax
An open pneumothorax can occasionally be manifested as a tension pneumothorax, which is a life-threatening condition that requires immediate intervention. A tension pneumothorax occurs when an injury creates a one-way “flap valve” mechanism that allows air into the pleural space with inspiration but then closes with expiration and traps the air (Fig. 10-4). The progressive accumulation of air in the pleural space leads to ipsilateral complete lung collapse and then impingement on the mediastinum with a shift of the heart toward the uninvolved side, which restricts ventricular filling and subsequently decreases cardiac function. This severe disruption in both respiratory and cardiac function can lead to hypotension and reduced ventilation (both hypoxia and CO2 retention) and eventually to cardiopulmonary collapse.
Empyema and Effusions
An empyema is an accumulation of pus in the pleural space, usually from a parapneumonic infectious effusion (Fig. 10-5). An empyema can also be caused by violation of the thoracic space by surgical procedures (e.g., tube thoracostomy), trauma, and esophageal perforation. Pleural infection rates have increased 3% per year in the United States in the last 2 decades. The bacteriology of pleural infections appears to track closely with classification of pneumonia as community or hospital acquired. Nearly 60% of cases of community-acquired pneumonia are caused by Streptococcus pneumoniae species, whereas Staphylococcus species account for nearly 45% of hospital-acquired infections.5
Diagnosis
Physical Examination
During the initial phase of resuscitation (airway, breathing, circulation, disability), consider the diagnosis of pneumothorax in patients who are tachycardic, hypotensive, and dyspneic. Similar symptoms occur with pulmonary embolism, pericardial tamponade, and severe pneumonia. Conduct multiple examinations because the diagnosis of tension pneumothorax by physical examination can be very subtle. Use the phrase “look, listen, and feel” as your guideline. Observe the chest wall, which may reveal asymmetric chest expansion, and the neck and forehead veins, which may be distended, even if the patient is hypotensive. The trachea may be deviated away from the side of the pneumothorax. When percussing the chest wall, hyperresonance on the affected side and subcutaneous emphysema may be present. Auscultation may demonstrate diminished breath sounds on the injured side. In one prospective study, the sensitivity, specificity, and diagnostic accuracy of auscultation for hemothorax and pneumothorax were 84%, 97%, and 89%, respectively.6 A false-negative auscultation is more likely than a false-positive one.6 Pulsus paradoxus may be evident. For intubated patients, an early sign of tension pneumothorax is difficulty ventilating because of increased airway pressure.
Stable Patients
In more stable patients (and those with smaller accumulations) the findings on physical examination are less sensitive, and a chest radiograph or even a computed tomography (CT) scan is usually necessary to make a definitive diagnosis. Physical findings may include unilaterally decreased breath sounds, tachypnea, tachycardia, decreased tactile fremitus, increased resonance with percussion, or subcutaneous emphysema, but the examination may reveal little to no abnormalities with a small pneumothorax. Patients with a pneumothorax involving less than 20% of the hemithorax will often have completely normal findings on chest examination, including equal breath sounds (Fig. 10-6). Pleural fluid collections are difficult to detect by physical examination, particularly with less than 500 mL of fluid in the pleural space. Breath sounds may be decreased and percussion of the bases may be dull.
Parapneumonic empyemas are often accompanied by fever, cough, chest pain, dyspnea, and purulent sputum (see Fig. 10-5). Physical examination may reveal diminished breath sounds, dullness on percussion, egophony, and diminished tactile fremitus on the involved side. Fever will often develop in patients with an indwelling chest tube and empyema. The pleural fluid drainage may be copious and purulent, and respiratory symptoms may worsen.
Radiography
A chest radiograph is an essential tool for diagnosing a pneumothorax in stable patients. In unstable patients with a potential tension pneumothorax the diagnosis should be made clinically, but in rare cases a portable radiograph may be obtained in the resuscitation room if carefully monitored by a clinician. The best plain radiographs for hemothorax or pneumothorax are traditional upright inspiratory posteroanterior and lateral chest radiographs. Diagnostic sensitivity is not increased with an expiratory upright chest radiograph. Upright is preferable to a supine chest radiograph, particularly for a hemothorax, because even with large amounts of blood there may only be slight differences in the density of the lung fields since the blood may layer out evenly. With an upright chest radiograph, 300 to 500 mL of fluid is needed to cause blunting of the costophrenic angle (Fig. 10-7).7 When CT is not available, other useful views include a bilateral decubitus chest radiograph, with the pneumothorax expected to be seen on the side away from the table as gravity pulls the affected lung down.
On a chest radiograph the partially collapsed lung of a pneumothorax appears as a visceral pleural line with no pulmonary markings beyond it (see Figs. 10-1, 10-3, 10-6, and 10-7). It is easy to initially mistake large blebs for a pneumothorax or to identify the scapular border, skin folds, or indwelling lines as a pneumothorax, but a CT scan quickly resolves the issue (Fig. 10-8). Other radiographic findings include hyperlucency of the affected hemithorax, a double diaphragm contour, increased visibility of the inferior cardiac border, better visualization of pericardial fat at the cardiac apex, and possibly a depressed diaphragm. If subcutaneous air is noted on the chest radiograph of a patient with blunt chest trauma, it can be assumed that the air came from an injured lung and that a pneumothorax exists.
It is difficult to accurately predict the size of a pneumothorax on plain radiographs. Greater accuracy in predicting size can be accomplished with a CT scan. With a tension pneumothorax, the chest radiograph reveals lung collapse, a depressed hemidiaphragm on the affected side, and a shift of the mediastinum and trachea to the opposite side (see Fig. 10-4). With a bilateral pneumothorax, no mediastinal shift may be seen.
Thoracic CT
The gold standard for diagnosis is a thoracic CT scan, which can detect a pneumothorax not easily visible on a plain radiograph. CT scans of the chest are much more sensitive than plain radiographs in detecting hemothorax and pneumothorax. They are also more accurate for estimating the size and other characteristics of a pneumothorax (see Figs. 10-1, 10-4, and 10-8). CT scans are not routine for diagnosis of a pneumothorax but are more useful for hemothoraces and other fluid collections. They also offer invaluable information on the cause of such abnormalities. A CT scan may be useful when the diagnosis is unclear or when looking for small amounts of pleural fluid. CT scans are particularly helpful in determining whether an empyema is loculated or draining successfully. About 10% of trauma patients with normal findings on a chest radiograph will demonstrate a small hemothorax or pneumothorax.7–9 The clinical significance of a small, previously undetected occult injury is probably not great, and it has been suggested that a small pneumothorax seen only on CT may be left untreated and simply observed in otherwise stable patients. Some patients with a pneumothorax seen only on CT may also safely undergo PPV without placement of a chest tube.9
Ultrasound
Ultrasound is useful in diagnosing both hemothoraces and pneumothoraces, and its use is reviewed in the Ultrasound Box.10,11
Ultrasound
Recognizing Pneumothoraxby Christine Butts, MD
To evaluate for pneumothorax, a high-frequency transducer should be used to ensure a high degree of resolution. In a supine patient the transducer should be placed on the anterior chest wall in the midclavicular line at approximately the second to third intercostal space (Fig. 10-US1). The depth of the image should be adjusted until the ribs are seen as brightly echogenic (white) arcs with acoustic shadows behind them. The pleural line can be found just deep to the ribs and is represented as a horizontal, echogenic line (Fig. 10-US2). In a normal lung the visceral and parietal pleural layers are directly opposed to one another (save for a thin layer of pleural fluid). When the patient breathes in and out, the layers “slide” past each other to allow the lungs to expand. When this is viewed with ultrasound, the pleural line can be seen to slide back and forth with patient respiration. This is referred to as the “slide sign.” In cases in which this interface is disrupted (such as by a pneumothorax), the sliding is lost. When these patients are evaluated with ultrasound, the pleural line will be seen as a static echogenic line that does not change with respiration.
Although the slide sign carries significant sensitivity for ruling out a pneumothorax, other secondary confirmatory findings should be sought as well.1
Comet tail artifacts may be seen in a normal lung. These are hyperechoic vertical lines that extend deep to the pleural interface (Fig. 10-US3). Typically, they will be seen in small numbers in a normal lung. Patients in whom a pneumothorax is present are noted to lack comet tails because this artifact arises from the normal pleural interface, which is disrupted. The presence of comet tails may be used by the sonographer to further rule out a pneumothorax.2,3
In a normal patient, the pleura will slide back and forth as the patient breathes. Because this motion is neither toward nor away from the transducer but instead is parallel, the motion will be seen as a series of hazy lines deep to the pleura. The overlying soft tissue is not in motion and will be seen as a series of clear, flat lines. This typical appearance is described as the “seashore” sign (Fig. 10-US4).
In patients in whom a pneumothorax is present, no motion is detected by ultrasound. Therefore, the M-mode tracing will show clear, flat lines throughout the frame. This is referred to as the “stratosphere” or “bar code” sign (Fig. 10-US5).
References:
1. Blaivas, M, Lyon, M, Duggal, S. A prospective comparison of supine chest radiography and bedside ultrasound for the diagnosis of traumatic pneumothorax. Acad Emerg Med. 2005;12:844–849.
2. Lichtenstein, D, Meziere, G, Biderman, P, et al. The comet-tail artifact: an ultrasound sign ruling out pneumothorax. Intensive Care Med. 1999;25:383–388.
3. Chan, SS. Emergency bedside ultrasound to detect pneumothorax. Acad Emerg Med. 2003;10:91–94.
Indications for Tube Thoracostomy
Tube thoracostomy is by far the most common treatment of all types of pneumothoraces, but controversy exists over the treatment of small traumatic and spontaneous primary pneumothoraces. However, the American College of Chest Physicians has developed useful guidelines for the management of primary and secondary spontaneous pneumothoraces (Box 10-1).12
