Pneumothorax develops when air enters the pleural space as the result of disease or injury. This leads to a loss of negative pressure between the two pleural membranes, which can result in the partial or complete collapse of the lung. Pneumothorax is classified as spontaneous or traumatic. Spontaneous pneumothorax can be further classified as primary (i.e., no underlying lung disease) or secondary (i.e., due to underlying lung disease). Any type of pneumothorax can progress to tension pneumothorax, which is a life-threatening variant of pneumothorax. Patients with pneumothorax usually present with sudden-onset dyspnea, ipsilateral chest pain, diminished breath sounds, and hyper-resonant percussion on the affected side. Tension pneumothorax further manifests with distended neck veins, tracheal deviation, and hemodynamic instability. There should be a high index of suspicion for both conditions on clinical evaluation. Unstable patients with tension pneumothorax require immediate needle decompression. Chest x-ray may be used to confirm the diagnosis in stable patients. Small pneumothoraces may resorb spontaneously, but larger defects usually require placement of a chest tube.
- Pneumothorax: a collection of air within the pleural space between the lung (visceral pleura) and the chest wall (parietal pleura) that can lead to partial or complete pulmonary collapse. May be classified as: 
- Spontaneous pneumothorax
- Traumatic pneumothorax: a type of pneumothorax caused by a trauma (e.g., penetrating injury, iatrogenic trauma)
- Tension pneumothorax: a life-threatening variant of pneumothorax characterized by progressively increasing pressure within the chest and cardiorespiratory compromise
- Primary (idiopathic or simple pneumothorax)
- Secondary (pneumothorax as a complication of underlying lung disease)
- Blunt trauma (e.g., motor vehicle accident in which the thorax hits the steering wheel or rib fracture occurs)
- Penetrating injury (e.g., gunshot, stab wound)
- Iatrogenic pneumothorax: mechanical ventilation with high PEEP (barotrauma), thoracocentesis, central venous catheter placement, bronchoscopy, lung biopsy
Any type of pneumothorax may lead to tension pneumothorax.
Increased intrapleural pressure → alveolar collapse → decreased V/Q ratio and increased right-to-left shunting. 
- Spontaneous pneumothorax: rupture of blebs and bullae → air moves into pleural space with increasing positive pressure → ipsilateral lung is compressed and collapses
- Closed pneumothorax: air enters through a hole in the lung (e.g., following blunt trauma)
- Open pneumothorax: air enters through a lesion in the chest wall (e.g., following penetrating trauma)
- Disrupted visceral pleura, parietal pleura, or tracheobronchial tree
- One-way valve mechanism, in which air enters the pleural space on inspiration but cannot exit
- Progressive accumulation of air in the pleural space and increasing positive pressure within the chest
- Collapse of ipsilateral lung; compression of contralateral lung, trachea, heart, and superior vena cava; angulation of inferior vena cava
- Impaired respiratory function, reduced venous return to the heart
- Reduced cardiac output
- Hypoxia and hemodynamic instability
Patients range from being asymptomatic to having features of hemodynamic compromise. 
- Sudden, severe, and/or stabbing, ipsilateral pleuritic chest pain and dyspnea
- Reduced or absent breath sounds, hyperresonant percussion, decreased fremitus on the ipsilateral side
- Subcutaneous emphysema
- Additional findings in tension pneumothorax 
- Severe acute respiratory distress: cyanosis, restlessness, diaphoresis
- Reduced chest expansion on the ipsilateral side
- Distended neck veins and hemodynamic instability (tachycardia, hypotension, pulsus paradoxus)
- Secondary injuries may be present (e.g., open or closed wounds).
- Signs of tension pneumothorax in ventilated patients 
General principles 
- The diagnosis of pneumothorax is usually confirmed by chest x-ray.
- Tension pneumothorax is primarily a clinical diagnosis and prolonged diagnostic studies should be avoided in favor of initiating immediate treatment.
In cases of tension pneumothorax, immediate decompression is a priority and should not be delayed by imaging.
Imaging of pneumothorax
Chest x-ray 
- Indications: all patients suspected of having pneumothorax
- Procedure: Upright PA chest x-ray in inspiration is the modality of choice. 
Supportive findings of pneumothorax
- Ipsilateral pleural line with reduced/absent lung markings (i.e., increased transparency)
- Abrupt change in radiolucency
- Deep sulcus sign
- Hemidiaphragm elevation on the ipsilateral side
- If pulmonary disease is present: airway or parenchymal lesions
- Supportive findings of tension pneumothorax
- Trauma (eFAST)
- Quick bedside assessment
- Supportive findings 
Chest CT 
- Findings: similar to CXR
Determination of pneumothorax size
The size of a pneumothorax is assessed via imaging (e.g., CXR, CT chest). How a pneumothorax is measured depends on regional guidelines, hospital policies, and personal preferences:
- Apex-to-cupola distance 
- Interpleural distance at the level of the lung hilus 
- Collins method: Calculated pneumothorax size in percent of hemithorax 
Laboratory analysis is generally not indicated.
See also ““ and “ .”
- Definition: presence of gas (usually air) in the mediastinum
- Rupture of pulmonary blebs
- Predisposing factor: smoking
- Primary (spontaneous)
- Pathophysiology: ↑ intra-alveolar pressure → rupture of alveoli → air travel along the peribronchial and perivascular sheaths to enter the mediastinum
- Sudden in onset
- Radiates to the neck or back
- Subcutaneous emphysema
- Voice change
- Hamman sign: precordial crepitation that is audible synchronous to the heartbeat
- Chest pain
- Management: usually self-limited when associated with barotrauma
The differential diagnoses listed here are not exhaustive.
- All patients
Unstable or high-risk patients: e.g., with tension pneumothorax, bilateral pneumothorax, or who require mechanical ventilation
- Immediate chest decompression
- Treat if present.
- Stable : depends on the risk of progression and recurrence
- Most patients require chest tube placement.
- Follow the to trauma to assess for additional injuries.
Monitoring and disposition
- Consider the following consults :
- Regularly reassess patients for:
- Clinical features of deterioration
- Development or recurrence of a tension pneumothorax
- See also “ .”
- Upright positioning
- Provide supplemental high-flow oxygen as needed (target SpO2 ≥ 96–100%) 
- If a patient requires mechanical ventilation, emergency chest tube placement is indicated.
- See also “Airway management” and “Oxygen therapy”.
Start all patients without on high-flow oxygen as soon as pneumothorax is suspected because high-flow oxygen aids reabsorption of the pneumothorax, which accelerates recovery.
Spontaneous pneumothorax management
Stability criteria for spontaneous pneumothorax 
- All of the following must be present for the patient to be considered stable:
- All other patients are considered unstable.
Treatment based on stability, type, and size
For stable patients, management depends on apex-to-cupola distance. 
- Unstable (high risk) 
Stable (low risk): Primary spontaneous pneumothorax 
- Apex-to-cupola distance < 3 cm
Apex-to-cupola distance ≥ 3 cm
- Chest tube placement typically recommended
- Consider conservative management in otherwise healthy patients able to adhere to management instructions and experiencing : 
- Needle aspiration may also be considered. 
- Stable (higher risk): Secondary spontaneous pneumothorax OR primary spontaneous pneumothorax with risk factors (i.e., age > 50 years, history of smoking, or recurrent disease) 
Traumatic pneumothorax management 
- The treatment of unstable or high-risk traumatic pneumothorax (e.g., tension pneumothorax) is identical to the treatment of unstable spontaneous pneumothorax: emergency chest decompression.
- Consider observation only in hemodynamically stable patients with small pneumothoraces. 
- A chest tube is required for all patients with any of the following:
- Suspected hemopneumothorax: Use a large-bore chest tube.
- Significant chest trauma: Assess for other thoracic injuries, e.g., rib fractures, pulmonary contusions (see “Management of trauma patients”).
Open pneumothorax 
- Immediately apply simple, partially occlusive dressings taped at 3 out of 4 sides of the lesion.
- Follow dressing with tube thoracostomy.
- Observe for development of tension pneumothorax.
Never pack the chest wound in an open pneumothorax as the packing may be sucked into the chest cavity during inspiration!
Do not tape the dressing on all 4 sides of the lesion because this can lead to a tension pneumothorax resulting from air building up in the thoracic cavity instead of being released during exhalation.
Emergency chest decompression
- Indication: tension pneumothorax
- Immediate insertion of a large-bore needle
- Typically followed by the insertion of a chest tube
- If initial decompression fails, consider using a longer needle (especially in muscular/adipose patients) 
- Indications: see “Approach” and “ .”
Needle aspiration 
- Indication: stable patients with a large (apex-to-cupola distance ≥ 3 cm) spontaneous primary pneumothorax
- Indications 
Admission criteria 
Patients requiring a chest tube typically require hospital admission, except for those meeting select criteria for home management. However, these criteria do not apply to the following conditions, in which admission is always recommended:
- All patients with :
- Patients with spontaneous primary pneumothorax and any of the following:
Consider ICU admission for unstable patients or those with large secondary pneumothoraces.
Trauma center 
Transfer to a traumatic pneumothorax and any of the following once stabilizing procedures have been performed.is recommended for patients with
- Tension pneumothorax: after needle thoracostomy/finger thoracostomy and chest tube placement
- Open pneumothorax or hemopneumothorax: after portable CXR and chest tube placement
- Respiratory failure: after intubation and chest tube placement
- Other injuries that meet requirements for trauma center transfer, for example:
Criteria for outpatient management 
- Patients must be able to:
- Understand discharge instructions
- Attend 24–48 hour follow-up 
- Imaging criteria for stable patients with spontaneous primary pneumothorax
Discharge instructions 
- Advise patients to seek immediate medical attention if breathlessness or chest pain worsens.
- Arrange follow-up with the patient's primary care physician for 24–48 hours following discharge.
- Advise patients not to fly until they have had one week of full resolution of the pneumothorax.
- Inform patients that they should abstain from scuba diving for life.
- Educate patients on the risk of recurrence (1 in 3 patients).
Acute management checklist for tension pneumothorax 
- Administer high-concentration supplemental oxygen (100% FiO2).
- Avoid positive pressure ventilation.
- Perform emergency needle decompression if the patient is hemodynamically unstable, followed by tube thoracostomy.
- Serial CXR
- Continuous telemetry, continuous pulse oximetry
- Transfer to ICU.
Acute management checklist for spontaneous pneumothorax 
- Continuous telemetry, continuous pulse oximetry
- Start supplemental oxygen in all patients with no risk factors for hypercapnia: target SpO2 ≥ 96% (in the absence of chronic CO2 retention).
- Avoid positive-pressure ventilation.
- Any patient who requires mechanical ventilation should first undergo tube thoracostomy.
Unstable patients or patients with bilateral pneumothorax
- Chest tube insertion with water seal with or without suction
- Order repeat CXR after chest tube insertion.
- ICU transfer
- Consult thoracic surgery.
Primary spontaneous pneumothorax (stable patient)
Small pneumothorax (< 3 cm apex-to-cupola distance)
- Monitor closely.
- Order repeat CXR in 3–6 hours.
- If stable or improved, consider discharge.
- If worsening, start treatment for a large pneumothorax.
- Large pneumothorax (≥ 3 cm apex-to-cupola distance)
Secondary spontaneous pneumothorax (stable patient)
- Small pneumothorax (< 3 cm apex-to-cupola distance)
- Large pneumothorax (≥ 3 cm apex-to-cupola distance)
Acute management checklist for traumatic pneumothorax
- Assess for signs of instability; if present, perform immediate needle or finger thoracostomy followed by chest tube insertion.
- Review the mechanism of injury; consider the risk of extrathoracic injuries.
- Ensure adequate analgesia, particularly in patients with associated rib fractures.
- Transfer to trauma center for: tension pneumothorax, hemopneumothorax, open pneumothorax, respiratory failure, or associated injuries requiring trauma center level of care.
- Stabilize patients as needed prior to interfacility transfer: e.g., intubation, chest tube placement.
- Small pneumothorax
- Moderate to large pneumothorax
- Complete pulmonary collapse → respiratory failure
- Tension pneumothorax → cardiac failure
- Mediastinal flutter in open pneumothorax → hemodynamic shock
- Hemothorax in cases of trauma
- Post-surgical/procedural complications
We list the most important complications. The selection is not exhaustive.
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