What are the diagnostic criteria and management strategies for lung contusion?

Diagnosis of Lung Contusion

Lung contusion should be diagnosed primarily by chest CT scan, which is highly sensitive and can identify parenchymal injury not visible on plain radiographs, though clinical correlation with mechanism of blunt chest trauma and respiratory status is essential. 1, 2

Diagnostic Criteria

Clinical Presentation

• Mechanism of injury: Blunt chest trauma is the defining mechanism, occurring in 25-35% of all blunt thoracic injuries 1
• Respiratory symptoms: Hypoxemia, hypercarbia, and increased work of breathing develop progressively, typically peaking at 72 hours post-injury 2
• Timing: Alveolar hemorrhage and parenchymal destruction are maximal within the first 24 hours and usually resolve within 7 days 2

Imaging Modalities

Chest CT is the gold standard for diagnosis:

• CT scan is highly sensitive for identifying pulmonary contusion and detects injuries missed by plain radiographs in 89% of cases 3, 2
• CT can predict the need for mechanical ventilation based on extent of injury 2, 4
• Plain chest radiographs have limited sensitivity and fail to reliably identify patients at risk of clinical deterioration 4

Quantifying Severity

A validated scoring system using admission CT predicts clinical outcomes: 4

• BPC score >2 (extent of contusion on CT)
• >4 ribs fractured
• Glasgow Coma Scale <14

The combination of all three factors predicts need for mechanical ventilation in 100% of cases, while absence of all three factors precludes mechanical ventilation in 100% of cases 4

Pathophysiology

The underlying injury involves: 1, 2

• Alveolar capillary damage without lung tissue laceration
• Blood and fluid accumulation within lung parenchyma
• Ventilation/perfusion mismatching
• Increased intrapulmonary shunting
• Loss of lung compliance
• Increased lung water content

Management Approach

Treatment is primarily supportive, as no pharmacological agents can prevent progressive respiratory deterioration: 5

Core Supportive Measures

• Supplemental oxygen therapy 1, 3
• Mechanical ventilation when indicated (typically when all three predictive factors present) 1, 4
• Positive end-expiratory pressure (PEEP) 5
• Invasive cardiopulmonary monitoring 5
• Aggressive pulmonary hygiene and physical therapy 3
• Fluid balance maintenance and judicious use of diuretics 3
• Adequate analgesia 5
• Antibiotic therapy when indicated 3

Intervention Thresholds

• 68% of patients require no thoracic interventions 3
• Thoracocentesis performed in 25% of cases (when associated hemothorax/pneumothorax present) 3
• Pleural puncture in 14% of cases 3

Clinical Pitfalls and Caveats

Avoid overdiagnosis and overtreatment: 3

• Isolated pulmonary contusions visible only on CT have limited clinical significance
• Only 8% of isolated pulmonary contusions develop respiratory insufficiency 3
• In 31% of cases, there is no associated pneumothorax or hemothorax 3
• Clinical evaluation should guide management more than CT findings alone 3

Recognize high-risk scenarios:

• Respiratory insufficiency develops in 25% of all pulmonary contusion patients 3
• 16% require mechanical ventilation overall 3
• Adult respiratory distress syndrome occurs in 5-20% of cases 5
• Pneumonia complicates 5-50% of cases 5
• Mortality ranges from 5-10% 5
• Polytrauma is present in 54% of cases, requiring comprehensive evaluation 3

Use CT judiciously for follow-up: The routine use of serial CT scans for monitoring should be re-evaluated, as clinical assessment is often sufficient 3