Key Facts

Tension pneumothorax is a medical emergency in which air progressively accumulates under pressure in the pleural space through a one-way valve mechanism, causing mediastinal shift, compression of the contralateral lung and great vessels, and ultimately cardiovascular collapse.

Epidemiology

• Most commonly occurs in trauma (penetrating and blunt chest injury)
• Iatrogenic: positive pressure ventilation, central line insertion, thoracentesis
• Can complicate any pneumothorax if inadequately managed
• Exact incidence difficult to quantify; occurs in ~2-5% of major trauma patients

Aetiology

• Traumatic: penetrating chest injury, blunt chest trauma with rib fractures
• Iatrogenic: positive pressure ventilation (especially high PEEP), central venous catheterisation (subclavian/internal jugular), thoracentesis, lung biopsy
• Spontaneous: complication of simple pneumothorax; underlying bullous emphysema, asthma (air trapping), cystic fibrosis
• Post-procedural: following chest drain removal, tracheostomy

Pathophysiology

• One-way valve: air enters pleural space during inspiration but cannot exit during expiration
• Progressive intrapleural pressure increase
• Ipsilateral lung complete collapse
• Mediastinal shift to contralateral side
• Compression of contralateral lung → bilateral ventilatory failure
• Compression/kinking of great veins (IVC, SVC) → reduced venous return → reduced cardiac output
• Cardiac arrest (pulseless electrical activity — PEA) if untreated

Clinical Features

• Severe respiratory distress
• Tachycardia
• Hypotension (late sign — indicates imminent arrest)
• Tracheal deviation away from affected side
• Distended neck veins (raised JVP)
• Absent breath sounds on affected side
• Hyperresonant percussion on affected side
• Cyanosis
• Subcutaneous emphysema (may be present)
• Cardiovascular collapse/cardiac arrest (PEA)

Context

• Trauma patient with deteriorating observations
• Ventilated patient with sudden increase in airway pressures and desaturation
• Post-procedure (central line, thoracentesis) with acute deterioration
• Worsening of known pneumothorax

Red Flags

• This entire condition is a red flag — immediate recognition and treatment is essential
• Any combination of: absent breath sounds + hypotension + tracheal deviation
• Cardiac arrest in trauma
• Sudden desaturation and rising airway pressures on ventilator

Bedside

• Clinical diagnosis: do NOT delay treatment for imaging
• Point-of-care USS (if available and experienced): absent lung sliding on affected side; can confirm diagnosis in seconds
• Post-decompression CXR: confirm position and resolution

Bloods

• ABG: post-decompression to assess gas exchange
• FBC, crossmatch: if traumatic (anticipate blood loss)
• Lactate: assess tissue perfusion

Imaging

• CXR: only AFTER decompression — large pneumothorax, mediastinal shift, flattened hemidiaphragm
• CT chest: after stabilisation if underlying pathology suspected

Special Tests

• Not applicable in acute setting — diagnosis is clinical and treatment is immediate

Non-pharmacological

• Immediate recognition: clinical diagnosis
• High-flow oxygen 15L/min
• Call for senior help/arrest team

Pharmacological

• Analgesia post-decompression
• Resuscitation drugs as per ACLS algorithm if cardiac arrest

Surgical/Interventional

Immediate decompression:

1. Needle decompression: insert 14G (orange) IV cannula into 2nd intercostal space, mid-clavicular line (or 4th-5th ICS, mid-axillary line — preferred in obese/muscular patients)

   • Insert perpendicular to chest wall, over superior border of rib (avoid neurovascular bundle)
   • Remove needle, leave cannula in situ
   • Hiss of air confirms tension pneumothorax
   • This is a temporising measure only

2. Chest drain insertion: definitive treatment

   • Insert Seldinger or surgical chest drain into safe triangle (4th-5th ICS, mid-axillary line, anterior border of latissimus dorsi, lateral border of pectoralis major)
   • Connect to underwater seal drain
   • CXR to confirm lung re-expansion

In cardiac arrest:

• Tension pneumothorax is a reversible cause (one of the 4 Ts)
• Perform bilateral needle decompression (or bilateral finger thoracostomies if in theatre/experienced)
• Follow ALS algorithm concurrently

Referral Criteria

• All tension pneumothoraces require hospital admission
• ICU if required mechanical ventilation
• Thoracic surgery if persistent air leak or underlying surgical pathology

• Untreated: near 100% mortality (cardiac arrest from obstructive shock)
• With prompt decompression: excellent survival if no significant underlying injury
• Needle decompression failure rate: ~10-40% (especially in obese patients — insufficient needle length)
• Outcome in trauma depends on associated injuries
• Iatrogenic tension pneumothorax: good prognosis with rapid recognition
• Delayed recognition is the primary cause of preventable death

Needle Decompression Technique

Reversible Causes of Cardiac Arrest (4 Hs and 4 Ts)