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Pulmonology - Pneumothorax - Fast Facts | NEJM Resident 360

Pneumothorax is defined as the presence of gas within the pleural cavity, which is the potential space bordered by the chest wall and lung. Gas enters this space when an abnormal communication forms between the alveoli or atmosphere and the pleural cavity. Normally, the pleural cavity only contains small amounts of serous fluid to facilitate lung expansion and minimize friction between the visceral and parietal pleura. The presence of gas in this space can cause lung collapse and subsequent ventilation–perfusion mismatch with attendant impacts on gas exchange. Pneumothorax in the presence of tachycardia, hypotension, cyanosis, and altered mental status should raise concern for tension pneumothorax, characterized by gas pressure in the pleural space that is high enough to impede the normal physiology of circulation and ventilation.

Pneumothorax of the Right Hemothorax

On the left, chest x-ray demonstrating a pneumothorax of the right hemothorax with partial collapse of the lung and visualization of the visceral pleura (arrowheads) and placement of a chest tube (arrows). On the right, the same patient is seen prior to chest-tube insertion, with a larger collection of gas in the pleural space causing leftward deviation of the trachea, heart, and mediastinum and herniation of air across the midline (arrows); radiographically consistent with tension pneumothorax.
(Source: Spontaneous Tension Pneumothorax. N Engl J Med 2010.)

Assessment

Etiology: In general, pneumothoraces can be classified into three categories based on etiology:

• Primary spontaneous pneumothorax (PSP) is a communication between the lung and pleural cavity that occurs in patients with no apparent lung disease. Despite the lack of obvious lung pathology, the majority of cases develop due to the rupture of subpleural blebs or bullae. PSP characteristically affects men younger than 30 with asthenic body types. Cigarette smoking is a known risk factor, with the risk increasing with the magnitude of exposure.

• Secondary spontaneous pneumothorax (SSP) is a communication between the lung and pleural cavity that occurs in patients with underlying lung disease. The distinction between PSP and SSP is critical because patients with lung disease are more likely to be symptomatic and lack the physiological reserve to compensate for the ventilation–perfusion mismatch. SSP is most common in patients with chronic obstructive pulmonary disease. However, SSP can also be seen in patients with the following conditions, listed according to frequency of occurrence:

Causes of Secondary Spontaneous Pneumothorax*

• airway disease: chronic obstructive pulmonary disease, cystic fibrosis, status asthmaticus

• **infectious lung disease:**Pneumocystis carinii pneumonia, necrotizing pneumonias (caused by anaerobic, gram-negative bacteria or staphylococcus)

• interstitial lung disease: sarcoidosis, idiopathic pulmonary fibrosis, Langerhans’-cell granulomatosis, lymphangioleiomyomatosis, tuberous sclerosis

• connective-tissue disease: rheumatoid arthritis (causes pyopneumothorax), ankylosing spondylitis, polymyositis and dermatomyositis, scleroderma, Marfan syndrome, Ehlers–Danlos syndrome

• cancer: sarcoma, lung cancer

• thoracic endometriosis (related to menses; causes catamenial pneumothorax)

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*Categories and disorders are listed according to frequency of occurrence.

Reference: Spontaneous Pneumothorax. N Engl J Med 2013.) 

• Traumatic or iatrogenic pneumothorax is typically caused by penetrating or blunt trauma to the chest, including iatrogenic complications (e.g., pleural catheter placement, central line placement, etc.). In these cases, gas enters the pleura space from communication with the atmosphere through the chest wall or due to visceral pleural penetration or alveolar rupture.

Physical examination: Clinical presentation of pneumothorax can vary depending on the underlying etiology. In spontaneous pneumothorax, patients most often describe sudden-onset dyspnea with ipsilateral pleuritic chest pain, usually occurring at rest. As described above, the presence of hemodynamic compromise should raise suspicion for tension pneumothorax, wherein air trapped within the pleural space displaces the mediastinal structures and therefore compromises cardiac function. 

Exam findings in a large pneumothorax reflect the absence of dynamic airflow in the affected hemithorax. On inspection, decreased diaphragmatic excursion on the affected side may be noted with reduction in chest wall expansion. On auscultation, absent breath sounds and loss of tactile fremitus are characteristic findings. Percussion of the affected side will be hyperresonant and subcutaneous emphysema may be present. Tracheal deviation away from the affected side may be present if the pneumothorax is large or if there is tension physiology.

Investigations

Although some laboratory testing may be valuable in the diagnosis of pneumothorax (particularly in determining etiology and ruling out other diagnoses on the differential), the diagnosis is based on imaging.

Chest x-ray is the most common modality used in stable patients. Often the visceral pleural line will be evident on the radiograph. Because air travels to the least-dependent position, the recommendation is for patients to be imaged in an upright position if possible. The size of the pneumothorax can be estimated according to the following guidelines:

• American College of Chest Physicians Guidelines

  • small: <3 cm between thoracic cupola and lung apex

  • large: ≥3 cm between thoracic cupola and lung apex

• British Thoracic Society Guidelines

  • small: <2 cm between chest wall and visceral pleural line at level of hilum

  • large: ≥2 cm between chest wall and visceral pleural line at level of hilum

Utrasound: In experienced hands, bedside ultrasonography has been shown to be more sensitive than chest x-ray at ruling out pneumothorax, with both specificity and sensitivity exceeding 90% in intensive care unit (ICU) patients. See a video demonstrating thoracic/pleural ultrasonography (video 3).

Treatment

Needle aspiration: The treatment of pneumothorax requires the evacuation of air from the pleural space, which is often accomplished by needle aspiration (see a video of this technique, including indications and contraindications).

Other techniques for evacuating air from the pleural space include observation, administration of supplemental oxygen (which displaces nitrogen from the circulating blood and thereby creates a gradient of gas that promotes resorption from the pleural space into the blood), insertion of a chest drain, and surgical intervention.

Chest-tube placement: The decision to pursue an interventional strategy is dependent on the etiology of disease and patient symptoms. Any unstable or severely symptomatic patient should undergo immediate intervention with chest-tube placement.

Patients with PSP: Based on the results of a recent clinical trial, clinically stable patients presenting with debut PSP can be managed conservatively without any intervention (see a NEJM Quick Take video summary of this study). In recurrent PSP, recommended management includes chest-tube placement followed by a definitive procedure to prevent recurrence (e.g., pleurodesis).

Patients with SSP: In general, all patients with SSP should be hospitalized and monitored. Most pneumothoraces in this population will require intervention (unless the pneumothoraces are small and the patient is asymptomatic). Noninvasive ventilation should be avoided in patients with pneumothorax; in the event of nonresolution, persistent air leak, or recurrence, definitive management with surgery or pleurodesis should be considered.

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