Pneumothorax

Classification and Epidemiology

Classification

• Traumatic: 
  • Open: a connection through the chest wall 
  • Closed: no connection to the outside air 
• Spontaneous:
  • Primary: No underlying disease can be identified.
  • Secondary: known pre-existing lung conditions

Epidemiology

• Traumatic:
  • Occurs more frequently than spontaneous pneumothorax
  • Iatrogenic incidence: 5–7 per 10,000 hospital admissions
  • 1%–2% of all neonates (higher risk in patients with respiratory distress syndrome)
• Primary spontaneous pneumothorax:
  • More common in younger patients, 20–30 years old
  • Patients are typically tall and slim.
  • Gender ratio of 3–6:1 men > women
  • Incidence of 7.4 per 100,000 per year in the United States
• Secondary spontaneous pneumothorax:
  • Occurs in middle-aged and older patients.
  • Gender ratio is 3:1 men > women.
  • Incidence:
    • Men: 6.3 per 100,000 per year
    • Women: 2 per 100,000 per year

Etiology

Traumatic pneumothorax

• Blunt or penetrating injury: 
  • Rib fractures causing lung laceration
  • Disruption of the tracheobronchial tree
  • Gunshot or stab wound 
• Iatrogenic: 
  • Lung surgery
  • Central venous catheter insertion
  • Thoracentesis
  • Mechanical ventilation
  • Esophageal procedures

Spontaneous pneumothorax

• Primary (idiopathic): ruptured apical subpleural blebs or bullae
• Secondary: 
  • Chronic obstructive pulmonary disease (COPD) accounts for 50% of spontaneous cases.
  • Bronchiectasis
  • Lung malignancies
  • Lung infections: 
    • Pneumocystis jirovecii 
    • Tuberculosis
    • Bacterial pneumonia
    • Particularly seen in patients with human immunodeficiency virus (HIV) infection
  • Genetic diseases:
    • Cystic fibrosis
    • Marfan’s syndrome
    • Ehlers-Danlos syndrome
    • Homocystinuria
  • Cystic lung disorders:
    • Lymphangioleiomyomatosis
    • Diffuse Langerhans cell histiocytosis
    • Lymphocytic interstitial pneumonitis
  • Thoracic endometriosis (catamenial pneumothorax)
• Smoking is a major risk factor for primary and secondary pneumothoraces.

Pathophysiology

As air enters the pleural space, which normally has a negative pressure, the elastic recoil in the lung tissues causes either a partial or full lung collapse.

Normal physiology

• Pleural space has a negative pressure.
• Chest wall expands → surface tension between parietal and visceral pleura expands the lung
• Lung tissue has an elastic recoil → innate tendency to collapse inward

Traumatic pneumothorax

• Closed pneumothorax: blunt trauma → lung damage → air flows from the lung into the pleural space
• Open pneumothorax: penetrating trauma to the chest wall → pathway for air directly into pleural space

Spontaneous pneumothorax

• Ruptured bleb → air flows from the lung into the pleural space → positive pleural pressure → compressed lung
• Lung collapses until an equilibrium is achieved or the rupture seals.
• ↓ Vital capacity and ↓ partial pressure of oxygen

Tension pneumothorax

• Life threatening and can develop from any type of a pneumothorax
• Air enters the pleural space through a 1-way valve mechanism → air cannot escape
• Air accumulates in the pleural space with each inspiratory phase → ↑ pleural space pressure → shifting of the mediastinum → compression of the contralateral lung → hypoxia
• Eventual compression of the vena cava and atria → ↓ venous return to the heart and ↓ cardiac function
• Leads to rapid cardiopulmonary collapse

Clinical Presentation

The clinical presentation will depend on the size of the pneumothorax. A tension pneumothorax will be associated with rapid clinical deterioration.

Symptoms

• Asymptomatic (small pneumothoraces)
• Dyspnea:
  • Can range from mild to severe
  • May be gradual or sudden
• Sudden sharp pain on the affected side
• Pleuritic chest pain

Physical exam

• Vital signs:
  • Tachypnea
  • Tachycardia
  • Hypotension
  • Hypoxia
• Respiratory:
  • Reduced or absent breath sounds on the affected side
  • ↓ Tactile fremitus
  • Hyper-resonance to percussion
  • ↓ Chest expansion
  • Tracheal deviation
• Cardiovascular:
  • Jugular venous distension
  • Pulsus paradoxus
• Cutaneous:
  • Evidence of trauma
  • Subcutaneous emphysema
  • Cyanosis

Mnemonic

The signs and symptoms of tension pneumothorax is summarized with: P-THORAX:

• P: Pleuritic pain
• T: Tracheal deviation
• H: Hyper-resonance
• O: Onset sudden
• R: Reduced breath sounds
• A: Absent fremitus
• X: X-ray showing collapse

Diagnosis

Imaging

The diagnosis is suspected based on the clinical presentation, and confirmed by imaging. Tension pneumothorax is a clinical diagnosis, and management should not wait for imaging confirmation.

• Chest radiograph:
  • The easiest available imaging
  • Should be performed in the upright position (when possible)
  • General findings:
    • White visceral pleural line defining the lung and pleural air
    • Bronchovascular markings are not visible beyond the pleural edge.
    • Deep sulcus sign (gas outlines the costophrenic sulcus)
    • Ipsilateral hemidiaphragm elevation
    • Trauma patients may have a concurrent hemothorax.
  • Tension pneumothorax findings:
    • Potential mediastinal shift to the contralateral side
    • Tracheal deviation to the contralateral side
    • Ipsilateral hemidiaphragm flattening
    • Ribs are spread apart.
  • Small pneumothoraces will typically not show on an X-ray.
• Ultrasound:
  • More sensitive than X-ray, but is technician dependent
  • Can be done rapidly at the bedside
  • Findings:
    • Presence of a lung point (the boundary between the lung and pneumothorax)
    • Lung sliding will be absent at the location of a pneumothorax.
• Computed tomography (CT): 
  • The most sensitive
  • Used if the diagnosis remains uncertain after radiographs
  • Can provide additional information about associated causes
  • Findings:
    • Air in the pleural space
    • Can evaluate for loculations, pleural pathology, and lung disease

Pneumothorax size determination

• Based on imaging (radiographs, CT)
• Can be used in combination with the clinical presentation to guide management
• Accuracy is variable.
• There are several methods:
  • Light index: % = 100 – [(lung diameter³ / hemithorax diameter³) x 100]
  • Average interpleural distance (AID):
    • Interpleural space (area between the collapsed lung and inner chest wall) is measured at 3 points (apex, mid-thorax, and base).
    • The values of the 3 points are then averaged.
  • British Thoracic Society (BTS) guidelines: 
    • Interpleural space at the hilar level is measured.
    • < 2 cm is small, ≥ 2 cm is large
  • Apex-to-cupula distance:
    • Measured from the apex of the lung to the chest wall
    • < 3 cm is small, ≥ 3 cm is large

Management and Complications

The management of a pneumothorax depends on the amount of air collected in the pleural cavity and the stability of the patient.

Tension pneumothorax and unstable patients

• Supplemental oxygen
• Immediate chest tube thoracostomy:
  • A catheter is inserted into the chest wall.
  • Placed in the 4th to 5th intercostal space at the midaxillary line
• Needle decompression if chest tube placement needs to be delayed (e.g., prehospital care):
  • 14- or 16-gauge needle is inserted through the chest wall.
  • 2nd or 3rd intercostal space in the midclavicular line
  • 5th intercostal space in the anterior or midaxillary line is another option.
  • Should be followed by chest tube placement

Stable patients

Patients are deemed stable if:

• Respiratory rate < 24 breaths per minute
• Heart rate is between 60–120 beats per minute.
• Blood pressure is normal.
• Oxygen saturation > 90% on room air
• Patient is able to speak in full sentences.

Small pneumothorax:

• Can usually monitor if the patient is asymptomatic
• Serial radiographs are performed to monitor for progression.
• Supplemental oxygen for all patients with secondary spontaneous pneumothorax

Large pneumothorax:

• Traumatic pneumothorax: chest tube placement
• Primary spontaneous:
  • Catheter aspiration to remove pleural air is the 1st step.
  • If there is no improvement, or the pneumothorax recurs, a chest tube is placed.
• Secondary spontaneous:
  • Chest tube placement 
  • Treatment for the underlying disease
  • Thoracic surgery consultation for definitive management (due to a high likelihood of recurrence)

Definitive management:

• Indications:
  • Recurrence of primary spontaneous pneumothorax
  • 1st occurrence of a secondary spontaneous pneumothorax
  • Pneumothorax is unresponsive to chest tube placement.
• Video-assisted thoracic surgery (VATS):
  • Pleurodesis with mechanical pleural abrasion or talc to seal the pleural space
  • Bleb or bullae closure
  • Lung volume reduction (for patients with COPD)
• Chemical pleurodesis:
  • Intrapleural injections of talc or tetracycline
  • Used if a patient cannot undergo surgery

Complications

• Respiratory failure
• Cardiac arrest
• Pneumomediastinum (air is present in the mediastinum)
• Pneumoperitoneum (air is in the peritoneal cavity)
• Re-expansion pulmonary edema:
  • Occurs with rapid expansion of the lung
  • Higher risk if the lung has been collapsed for several days
• Procedure complications:
  • Infection
  • Fistula formation and air leaks
  • Intercostal nerve damage
  • Bleeding
• Recurrence

Differential Diagnosis

• Pulmonary embolism (PE): obstruction of the pulmonary arteries, most often due to thrombus migration from the deep venous system. Signs and symptoms include pleuritic chest pain, dyspnea, tachypnea, and tachycardia. Severe cases can result in hemodynamic instability or cardiopulmonary arrest. A chest CT with angiography is the primary method of diagnosis. Management includes oxygenation, anticoagulation, and thrombolytic therapy for unstable patients.
• Hemothorax: a collection of blood in the pleural cavity, typically following chest trauma. Patients present with shortness of breath and chest pain. Physical exam findings include hypotension, tachycardia, tracheal deviation, and dullness on percussion. Management includes fluid resuscitation, chest tube placement, and potential surgery.
• Pleural effusion: an accumulation of fluid within the pleural cavity. Pleural effusion can be caused by many conditions, including infection, malignancy, and heart failure. Symptoms can include chest pain, cough, dyspnea, and orthopnea. The diagnosis is made with imaging, and pleural fluid analysis can help determine an etiology. Management is dependent on the underlying condition and severity, but may include monitoring, thoracentesis, chest tube placement, or surgery.
• Myocardial infarction: myocardial damage due to obstructed blood flow in the coronary arteries. Symptoms include substernal chest pain, dyspnea, and diaphoresis. The diagnosis is made from electrocardiogram (ECG) changes, elevated troponins, and the demonstration of arterial disease during cardiac catheterization. Management includes antiplatelet agents, beta blockers, anticoagulation, statins, and revascularization. 
• Pericarditis: inflammation of the pericardium, which can be due to infection, myocardial infarction, and autoimmune disorders. Signs and symptoms include chest pain (which can worsen with laying down and improve with sitting up), dyspnea, and a pericardial rub. The diagnosis is based on the clinical picture and characteristic ECG findings. Treatment includes pain control, anti-inflammatory medications, and colchicine.