How to show a tension pneumothorax using point-of-care ultrasound (POC u/s)?

Point-of-Care Ultrasound for Tension Pneumothorax

In an extreme emergency, diagnose tension pneumothorax immediately by demonstrating absent lung sliding, absent lung pulse, and absent B-lines on ultrasound—this combination allows prompt and safe diagnosis without needing to search for the lung point. 1

Immediate Diagnostic Approach

Use a systematic algorithmic sequence to rapidly identify tension pneumothorax:

Step 1: Assess for Lung Sliding

• Place the ultrasound probe in a longitudinal orientation between two ribs in the anterior chest (second intercostal space, midclavicular line is ideal for tension pneumothorax) 1
• Absent lung sliding (no rhythmic movement of pleural layers synchronized with respiration) is the first critical finding 1
• Lung sliding has a negative predictive value of 100%—if present, pneumothorax is excluded at that location 2

Step 2: Check for B-Lines

• If lung sliding is absent, immediately scan for B-lines (vertical artifacts originating from the pleural line) 1
• Presence of B-lines excludes pneumothorax because they prove the visceral pleura is opposing the parietal pleura 1
• Absence of B-lines combined with absent lung sliding strongly suggests pneumothorax 1

Step 3: Evaluate for Lung Pulse

• Look for subtle rhythmic movement of the visceral pleura synchronized with cardiac oscillations 1
• Absent lung pulse combined with absent lung sliding and absent B-lines confirms pneumothorax in an emergency setting 1
• This triad allows immediate diagnosis without searching for the lung point 1

Step 4: Additional Signs of Tension Physiology (If Time Permits)

• Mediastinal shift can be visualized on ultrasound even in hemodynamically stable patients 3
• Dilated, plethoric inferior vena cava (IVC) suggests impaired venous return from increased intrathoracic pressure 3
• These findings may precede clinical decompensation and indicate true tension physiology 3

Sensitivity and Specificity

Point-of-care ultrasound demonstrates superior diagnostic accuracy compared to chest radiography:

• Sensitivity: 92.0% for detecting pneumothorax 1
• Specificity: 99.4% for pneumothorax diagnosis 1
• Ultrasound is more accurate than supine chest X-ray for both ruling in and ruling out pneumothorax 1

Clinical Context Integration

Ultrasound findings must be interpreted with clinical presentation:

• History of chest trauma combined with progressive dyspnea and attenuated breath sounds establishes the diagnosis 4
• In mechanically ventilated patients, sudden deterioration (abrupt increase in peak airway pressure from 25 to 40 cmH2O) should trigger immediate ultrasound evaluation 5
• Classic signs like tracheal deviation are unreliable—tracheal deviation was not observed in any cases in a 111-patient trauma database 1
• Environmental noise on the battlefield or in chaotic settings makes auscultation unreliable, making ultrasound essential 1, 4

Critical Pitfalls to Avoid

Be aware of false-positive scenarios:

• Lung bullae, contusions, and adhesions can mimic pneumothorax findings 1, 6
• Absence of lung sliding alone is not specific—it can occur with mainstem intubation, severe consolidation, or pleural adhesions 7
• Always confirm with the complete triad (absent sliding + absent B-lines + absent lung pulse) in emergency situations 1

Do not delay treatment for imaging confirmation:

• In hemodynamically unstable patients with clinical signs of tension pneumothorax, perform immediate needle decompression without waiting for ultrasound or radiographic confirmation 4, 7
• Ultrasound is valuable for identifying tension physiology before clinical decompensation occurs 3

Scanning Technique

Use proper probe selection and positioning:

• Low-frequency curvilinear or phased-array probe with orientation marker directed cranially 6
• Scan multiple anterior chest locations bilaterally (at minimum, the second intercostal space midclavicular line bilaterally) 1
• Document probe position and patient positioning for each image 6

The lung point (optional in emergencies):

• The lung point represents the physical boundary where pneumothorax transitions to normal lung 1
• It appears as alternating patterns of absent sliding and normal sliding at a fixed location 1
• Pathognomonic for pneumothorax but only 60% sensitive—its absence does not exclude pneumothorax 2
• In extreme emergencies, do not waste time searching for the lung point 1

Immediate Management After Diagnosis

Once tension pneumothorax is confirmed:

• Perform immediate needle thoracentesis using a No. 14 puncture needle (8.25 cm length) at the second intercostal space, midclavicular line 1, 4
• Follow with definitive tube thoracostomy (chest tube) in the 4th/5th intercostal space, midaxillary line 4
• Timely treatment saves over 90% of patients 4