Pneumothorax

GENERAL PRINCIPLES

• Pneumothorax may occur spontaneously or as a result of trauma.

• Primary spontaneous pneumothorax occurs without obvious underlying lung disease.

• Secondary spontaneous pneumothorax results from underlying parenchymal lung disease including COPD and emphysema, interstitial lung disease, necrotizing lung infections, Pneumocystis jirovecii pneumonia, tuberculosis, and cystic fibrosis.

• Traumatic pneumothorax occurs as a result of penetrating or blunt chest trauma.

• Iatrogenic pneumothorax occurs after thoracentesis, central line placement, transbronchial biopsy, transthoracic needle biopsy, or barotrauma from mechanical ventilation and resuscitation.

• Tension pneumothorax results from continued accumulation of air in the chest that is sufficient to shift mediastinal structures and impede venous return to the heart. This results in abnormal gas exchange, hypotension, and ultimately, cardiovascular collapse.

๎ The causes include barotrauma due to mechanical ventilation, a chest wound that allows ingress but not egress of air, or a defect in the visceral pleura that behaves in the same way (“ball valve” effect).

๎ Suspect tension pneumothorax when a patient experiences hypotension and respiratory distress on mechanical ventilation or after any procedure in which the thorax is violated.

DIAGNOSIS

Clinical Presentation

HISTORY

• Patients commonly complain of acute onset ipsilateral chest or shoulder pain. A history of recent chest trauma or medical procedure can suggest the diagnosis.

• Dyspnea is usually present.

PHYSICAL EXAMINATION

• Although examination of the patient with a small pneumothorax may be normal, classic findings include decreased breath sounds and more resonance to percussion on the ipsilateral side.

• With a larger pneumothorax or with underlying lung disease, tachypnea and respiratory distress may be present.

• If the pneumothorax is very large, and particularly if it is under tension, the patient may exhibit severe distress, diaphoresis, cyanosis, and hypotension. In addition, the patient's trachea may be shifted to the contralateral side.

• If the pneumothorax is the result of penetrating trauma or pneumomediastinum, subcutaneous emphysema may be felt.

• Clinical features alone do not predict the relative size of a pneumothorax, and in a stable patient, further diagnostic studies must be used to guide treatment strategy. However, tension pneumothorax remains a clinical diagnosis, and if suspected in the appropriate clinical scenario, immediate intervention should be undertaken before further evaluation.

Diagnostic Testing

ELECTROCARDIOGRAPHY

An ECG may reveal diminished anterior QRS amplitude and an anterior axis shift. In extreme cases, tension pneumothorax may cause electromechanical dissociation.

IMAGING

• A CXR will reveal a separation of the pleural shadow from the chest wall. If the posteroanterior radiograph is normal and pneumothorax is suspected, a lateral or decubitus film may aid in diagnosis.¹ Air travels to the highest point in a body cavity; thus, a pneumothorax in a supine patient may be detected as an unusually deep costophrenic sulcus and excessive lucency over the upper abdomen caused by the anterior thoracic air. This observation is particularly important in the critical care unit, where radiographs of the mechanically ventilated patient are often obtained with the patient in supine position.

• Although tension pneumothorax is a clinical diagnosis, radiographic correlates include mediastinal and tracheal shift toward contralateral side and depression of the ipsilateral diaphragm.

• Ultrasonography is a useful tool for bedside diagnosis of pneumothorax, especially on patients who must remain supine or who are too unstable to undergo CT scanning.

• Chest CT is the gold standard for diagnosis and determining the size of pneumothorax. Although not always necessary, it may be particularly useful for differentiating pneumothorax from bullous disease in patients with underlying lung conditions.⁴

TREATMENT

Treatment depends on cause, size, and degree of physiologic derangement.

• Primary pneumothorax

๎ A small, primary, spontaneous pneumothorax without a continued pleural air leak may resolve spontaneously. Air is resorbed from the pleural space at roughly 1.5% daily, and therefore, a small (approximately 15%) pneumothorax is expected to resolve without intervention in approximately 10 days.

๎ If the pneumothorax has not increased in size upon evaluation with a 6-hour repeat CXR and symptoms have not changed, the patient may be discharged if they are asymptomatic (apart from mild pleurisy). Obtain follow-up radiographs to confirm resolution of the pneumothorax in 7-10 days. Air travel is discouraged during the follow-up period because a decrease in ambient barometric pressure may cause a larger pneumothorax.

๎ If the pneumothorax is small but the patient is mildly symptomatic, far from home, or has barriers with follow-up, admit the patient and administer high-flow oxygen; the resulting nitrogen gradient will speed resorption.

๎ If the patient is more than mildly symptomatic or has a larger pneumothorax, simple aspiration is a reasonable initial management strategy. However, aspiration may not be successful for very large pneumothoraces. In patients in whom aspiration fails, proceed with thoracostomy tube insertion.¹

๎ Pleural sclerosis to prevent recurrence is recommended by some experts but, in most cases, is not used after a first episode unless a persistent air leak is present.

• Secondary pneumothorax

๎ Individuals with a secondary spontaneous pneumothorax are usually symptomatic and require lung reexpansion.

๎ Often, a bronchopleural fistula persists and a larger thoracostomy tube and suction are required.

๎ Consult a pulmonologist about pleural sclerosis for persistent air leak and to prevent recurrence.

๎ Surgery may be required for persistent air leak and should be considered for high-risk patients for prevention of recurrence.

• Iatrogenic pneumothorax

๎ If the pneumothorax is small and the patient is minimally symptomatic, they can be managed conservatively. If the procedure that caused the pneumothorax required sedation, admit the patient, administer oxygen, and repeat the CXR in 6 hours to ensure the patient's stability. If the patient is completely alert and the CXR shows no change, the patient can be discharged.

๎ If the patient is symptomatic or if the pneumothorax is too large for expectant care, a pneumothorax catheter with aspiration or a one-way valve is usually adequate and can often be removed the following day.

๎ Iatrogenic pneumothorax due to barotrauma from mechanical ventilation almost always has a persistent air leak and should be managed with a chest tube and suction.

• Tension pneumothorax

๎ When the clinical situation and physical examination strongly suggest this diagnosis, decompress the affected hemithorax immediately with a 14-gauge needle.

o Recognize that a patient with obesity or a patient with a large amount of breast tissue may not have resolution of tension with a standard angiocatheter because of the inability to reach the chest wall or weight of the tissue kinking off the catheter. These patients may require a longer needle to reach the intrathoracic space for decompression or require insertion of a larger gauge reinforced catheter to stent open the pathway for air release.

๎ If long-needle decompression or reinforced catheter insertion is unsuccessful, and the diagnosis is highly probable in an unstable patient, surgical decompression can be performed by incision of the pleura in the fourth to fifth anterior axillary line above the rib in the same space in which thoracostomy tubes are inserted. This technique has been shown to be effective; however, safety and complication rates are not able to be determined because of lack of studies.⁵

๎ Seal any chest wound with an occlusive dressing and arrange for placement of a thoracostomy tube.