Pneumothorax

The pleural space lies between the parietal and visceral pleura and is normally negatively pressured at −5 mm Hg with fluctuations of 6 to 8 mm Hg between inspiration and expiration. With loss of the normal negative pressure, the affected lung collapses. Primary spontaneous pneumothorax occurs when a subpleural bleb, most commonly in the lung apex, ruptures into the pleural space. In secondary spontaneous pneumothorax, rupture of the visceral pleura and alveolar barrier is most commonly due to the underlying pulmonary disease process.

Pneumothorax

Classically, the symptoms of primary spontaneous pneumothorax are a sudden onset of ipsilateral, pleuritic chest pain and associated dyspnea. The pain typically begins at rest and is worsened with deep inspiration. It may eventually become a dull persistent ache that does not vary with respiration. Profound dyspnea is rare in the absence of tension pneumothorax or underlying parenchymal disease. Sinus tachycardia is the most common physical finding, with other classic signs such as decreased breath sounds, hyperresonance to percussion, unilateral enlargement of the hemithorax, absence of tactile fremitus, and decreased excursion volumes occurring less frequently. Symptoms may resolve in 24 hours without resolution of the pneumothorax. Many patients (45%) may delay seeking medical care for 48 hours. The severity of symptoms does not necessarily correlate with the size of the pneumothorax.

The ability of auscultation to detect hemothorax, pneumothorax, or hemopneumothorax associated with penetrating trauma had a sensitivity of 58%, a specificity of 98%, and a positive predictive value of 98% in one study.¹ Auscultation can miss up to 600 mL of hemothorax, a pneumothorax occupying up to 28% of lung volume, and a combined hemopneumothorax of up to 800 mL and 28%.¹ Physical examination alone is not sensitive enough to exclude the diagnosis of pneumothorax.

Open Pneumothorax

Patients with an open pneumothorax have significant dyspnea and a history of a penetrating wound to the thorax. Physical examination will reveal a chest wound that produces an audible, sucking air movement sound on inspiration and may bubble on expiration. Findings of a pneumothorax will also be present.

Tension Pneumothorax

Patients with tension pneumothorax exhibit extreme dyspnea, hypotension, and cyanosis. Physical findings are hyperresonance, hyperinflation, absence of breath sounds on the affected side, and deviation of the trachea (at the sternal notch) away from the affected side. Tachycardia is often present and is defined as a pulse greater than 120 beats/min. Patients with tachycardia should undergo immediate tube thoracostomy (or needle thoracostomy if a chest tube is not immediately available) without waiting for a confirmatory radiograph.

Secondary Pneumothoraces

Patients with pneumothoraces secondary to underlying lung disease may experience extreme dyspnea as a result of deflation of one lung and limited capacity and function of the remaining lung. Classically, symptoms do not resolve without intervention. Because of the underlying lung disease (most commonly COPD), lung findings may be abnormal, with hyperinflation and decreased lung sounds being noted.

Radiography

The primary evaluation tool is the standard posteroanterior chest radiograph to look for loss of lung markings in the periphery and a pleural line that runs parallel to the chest wall but does not extend outside the chest cavity. A lateral radiograph contributes to the diagnosis in 14% of cases.² There is no evidence that an expiratory radiograph adds any value even with small apical pneumothoraces.³ The sensitivity for flat anteroposterior chest radiography, versus computed tomography (CT) as the “gold standard,” has been found to be 75.5% (95% confidence interval [CI], 61.7% to 86.2%), and the specificity is 100% (95% CI, 97.1% to 100%).⁴

Table 51.1 Differential Diagnosis of Pneumothorax

Shift of the mediastinum away from a pneumothorax on a chest radiograph can be a normal phenomenon that occurs without tension physiology. In critically ill patients in whom a radiograph can be taken only in the supine position, the emergency physician (EP) should look for the presence of a deep sulcus sign—a deep lateral costophrenic angle on the ipsilateral side (Fig. 51.1). Diaphragmatic depression or ipsilateral transradiancy (fewer lung markings, clearer image) may also be seen.⁵

Fig. 51.1 Deep sulcus sign.

Large bullae can be mistaken for a pneumothorax. With a pneumothorax, the pleural line runs parallel to the chest wall, whereas bullae more commonly have a medially concave appearance and are limited to a single lobe. A chest CT scan can help differentiate these entities. Pleural adhesions may alter the appearance of the pneumothorax by tethering the lung to the chest wall. Clothing, hair, and skin folds may appear as visceral pleural lines but often continue beyond the chest wall.

In most cases, an upright radiograph is sufficient to identify a pneumothorax. If not, EPs should consider additional modalities if they strongly suspect a pneumothorax, particularly if the patient is unstable, if underlying lung disease is present (and thus no reserve if a pneumothorax is missed), or if the patient is being treated with positive pressure ventilation.

Ultrasonography

Normal lung shows a shimmering echogenic stripe of both the parietal and visceral pleura on ultrasonography. A sliding sign at the pleural stripe can be seen with movement of the visceral pleura in relation to the parietal pleura. The “seashore analogy” refers to movement of the lung (ocean) against the stationary chest wall (shore). A comet tail reverberation can be seen distal to the pleura when no pneumothorax is present. The sliding sign of the pleural stripe and the comet tail reverberation are lost with a pneumothorax because of intrapleural air⁶ (Fig. 51.2). Doppler mode may be of some help in detecting this movement. Multiple other reasons can account for loss of the sliding, including atelectasis, mainstem intubation, acute respiratory distress syndrome, pleural adhesions, and pulmonary contusion, thus limiting specificity for pneumothorax in some cases.

Fig. 51.2 Ultrasonograms of abnormal (A) and normal (B) pleura with M-mode and B-mode imaging.

(Courtesy Christopher L. Moore, MD, Yale University School of Medicine.)

Deep to this pleural line, vertical artifacts called B lines may be seen. They originate at the pleural line, align vertically, continue the entire depth of the screen without any fading, and move with breathing. The finding of B lines rules out the presence of a pneumothorax, but the absence of B lines does not signify the presence of a pneumothorax.⁷

The lung point sign has a specificity approaching 100% for pneumothorax and is determined by the absence of lung sliding and B lines. The probe is moved gradually toward the lateral lower aspect of the chest.⁸ The goal is to identify lung sliding and B lines suggesting the “point” at which the lung is adherent to the pleura again (Fig. 51.3). A large pneumothorax may not display this point, thus diminishing the sensitivity of the lung point sign.

Fig. 51.3 Lung point sign.

(Courtesy Christopher L. Moore, MD, Yale University School of Medicine.)

The sensitivity of ultrasound detection of pneumothorax has been found to be 98.1% (95% CI, 89.9% to 99.9%) and the specificity was 99.2% (95% CI, 95.6% to 99.9%), which makes it more sensitive than a flat-plate anteroposterior radiograph.⁴ The use of ultrasonography as part of the extended focused assessment with sonography for trauma (eFAST) examination has been suggested in unstable patients with suspected pneumothorax.

Computed Tomography

CT is more accurate than radiography for the detection of pneumothoraces; it detects between 25% and 40% of pneumothoraces after lung biopsy that were not visualized on postprocedure chest radiographs.⁹ Up to 50% of traumatic pneumothoraces may be occult. CT can detect other problems, such as pulmonary blebs, vascular abnormalities, contusions, infiltrates, and tumors. CT is recommended in uncertain or complex cases such as symptomatic high-risk patients with suspected occult pneumothorax, those who have underlying lung disease, patients undergoing positive pressure ventilation, or those just completing lung biopsy.

Determining the Size of the Pneumothorax

Foremost, the degree of clinical symptoms is more important than the size of the pneumothorax in determining the appropriate therapy. Chest radiography underestimates the size of pneumothoraces because it is a two-dimensional view of a three-dimensional abnormality.

U.S. guidelines suggest measurement from the apex of the lung to the cupula of the thoracic cavity on an upright posteroanterior radiograph (Fig. 51.4). Less than 3 cm is considered small. British guidelines (2010) suggest the interpleural distance at the level of the hilum (Fig. 51.5). A 2-cm distance correlates with an approximate 50% pneumothorax by volume.¹⁰

Fig. 51.4 Apex-to-cupula measurement performed in a patient with a left-sided pneumothorax.

Fig. 51.5 Intrapleural space measured at the hilum in a patient with a right-sided pneumothorax.

AP, Anteroposterior.

CT-directed size classification allows grading of occult pneumothoraces. Minuscule refers to air collections less than 1 cm thick that appear on fewer than five contiguous 10-mm slices. Anterior pneumothoraces are air collections more than 1 cm thick that appear on five or more contiguous 10-mm slices and do not extend to the midcoronal line (Fig. 51.6). Anterolateral pneumothoraces extend to the midcoronal line or beyond.

Fig. 51.6 Computed tomography scan of the chest showing an anterior pneumothorax and a chest tube.

Prehospital Management

Hospital Management

Oxygen should be administered to all patients with a pneumothorax because it helps in resorption of the pneumothorax and increases oxygenation of the available alveoli in the noncollapsed lung. The untreated resorption rate is 1% to 2% per day, and the rate increases fourfold with the administration of 100% oxygen.¹¹

The stability of the patient, the severity of the symptoms, the current size of the pneumothorax, the change in size over time, the cause of the pneumothorax (primary, secondary, traumatic), and the severity of the underlying lung disease must all be considered in the decision whether to intervene in a patient with pneumothorax.

A stable patient with pneumothorax has been described as one who has a respiratory rate of less than 24 breaths/min, a heart rate between 60 and 120 beats/min, normal blood pressure, oxygen saturation greater than 90% when breathing room air, and the ability to speak in full sentences between breaths.¹²

Figures 51.7 and 51.8 present algorithms to assess the need for intervention in patients with primary spontaneous pneumothorax or traumatic pneumothorax, respectively. Patients with bilateral pneumothoraces are treated by aspiration or chest tube placement.

Fig. 51.7 Algorithmic approach to the treatment of primary spontaneous pneumothorax.

CXR, Chest radiograph.

Fig. 51.8 Algorithmic approach to the treatment of traumatic pneumothorax.

CT, Computed tomography; PTX, pneumothorax.

Patients with secondary pneumothoraces should be admitted to the hospital. A patient who is not at risk for large air leaks and has a small pneumothorax can be treated by aspiration via a small-bore catheter. A clinically unstable patient or a stable patient with a large pneumothorax should be treated with a chest tube.

Chest tube sizes for patients with spontaneous pneumothoraces are recommended as follows. Catheter (simple) aspiration seems to be as effective as chest tube treatment in patients with a small pneumothorax. Aspiration of more than 2.5 L of air suggests an air leak and may require a small-bore chest tube. Clinically stable patients with a large pneumothorax are treated by aspiration via a small-bore catheter (14 to 16 gauge) or with a 14 French (14F) chest tube. Clinically unstable patients with a large primary pneumothorax should be treated by tube thoracostomy. A larger (14F to 28F) chest tube should be used for patients requiring positive pressure ventilation and those at risk for large pleural air leaks (bronchopleural fistula). With traumatic pneumothoraces, a 28F to 36F chest tube should be used because of the risk for associated hemothorax.

Postprocedure monitoring and radiographs should be obtained to assess the success of the intervention and the position of the chest tube.

Disposition

The disposition of patients with pneumothorax is detailed in the algorithms in Figures 51.7 and 51.8. A patient with a primary spontaneous pneumothorax who has been treated by observation or catheter aspiration can be discharged if the pneumothorax does not increase over a period of 3 to 6 hours and the symptoms do not worsen. For a patient discharged with a primary spontaneous pneumothorax without intervention, follow-up should occur in the next 24 to 48 hours to document stability or resolution of the pneumothorax.

In patients with a secondary (associated with underlying lung disease) spontaneous pneumothorax, the treatment algorithm is altered by the underlying lung disease. Clinically stable patients, regardless of the duration of symptoms, should not be monitored in the ED or treated with catheter aspiration and discharged. They should all be admitted to the hospital for observation, simple aspiration, or tube thoracostomy.¹³

Complications

Complications of pneumothorax include those related to hypoxia, hypercapnia, and hypotension. Reexpansion lung injury is rare but most commonly occurs after reexpansion of a large pneumothorax. Risk factors appear to include collapse of the lung for longer than 72 hours, a large pneumothorax, rapid reexpansion, and use of negative pleural pressure suction greater than 20 cm H₂O.¹⁴

Persistent air leaks occur when the volume of air escaping into the pleural space is greater than the volume of air being removed by the drainage device. This complication is more common with a pneumothorax secondary to underlying lung disease. Typically, such air leaks resolve spontaneously within a week (in 75% of patients with a primary pneumothorax and in 61% with a secondary pneumothorax). If an air leak persists beyond 7 days, surgical intervention should be considered.

Complications that can occur during chest tube placement or catheter aspiration include intercostal vessel damage and hemorrhage, lung parenchymal injury, and tube malfunction.