Blunt-force parenchymal lung injury with alveolar hemorrhage and edema, often progressive over 24-72 hours.
Also known as: lung contusion, traumatic lung injury, blunt chest trauma
Overview
Direct parenchymal injury to the lung from blunt thoracic trauma resulting in alveolar capillary disruption, hemorrhage, and interstitial edema, without laceration of the visceral pleura. Frequently associated with rib fractures, flail chest, hemothorax, and pneumothorax.
Epidemiology
Occurs in 30-75% of patients with significant blunt chest trauma. Most common cause is motor vehicle collisions, followed by falls, crush injury, and blast injury. Mortality 10-25% when severe or accompanied by multi-organ trauma.
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Question 1PulmonaryMedium
A 24-year-old man is brought to the emergency department after a high-speed motor vehicle collision in which he was an unrestrained driver. He reports left-sided chest pain at the point of impact. On exam there is ecchymosis and a seatbelt mark across the left chest with crackles over the left lung base; breath sounds are present bilaterally. Initial chest radiograph shows a faint non-segmental opacity that does not respect lobar boundaries. Over the next 36 hours his tachypnea worsens and his oxygen requirement steadily climbs, and a repeat CT chest shows a focal area of consolidation in the left lung corresponding to the site of impact. Which of the following is the most likely diagnosis?
AHemothorax
BAspiration pneumonitis
CPulmonary contusion
DCardiogenic pulmonary edema
Reveal answer & full explanation
Correct answer: C — Pulmonary contusion
AHemothorax
BAspiration pneumonitis
CPulmonary contusion✓
DCardiogenic pulmonary edema
Why Pulmonary contusion is correct
Direct blunt thoracic trauma (unrestrained high-speed MVC) causes compression-decompression shear forces that disrupt alveolar-capillary membranes, producing focal parenchymal hemorrhage and edema at the site of impact.
The classic time course is delayed and progressive: the initial CXR is often nearly silent, and dyspnea, hypoxemia, and a rising oxygen requirement worsen over 24-72 hours as the inflammatory cascade peaks.
Imaging shows non-segmental opacities that do not respect lobar boundaries; CT is far more sensitive and reveals the contusion corresponding to the impact site, exactly as described here.
Why the others are wrong
Hemothorax: blood collecting in the pleural space rather than parenchymal injury; it produces a layering pleural effusion with decreased breath sounds and dullness (not the present bilateral breath sounds), and is confirmed and managed by tube thoracostomy, not a focal consolidation mapping to the impact site.
Cardiogenic pulmonary edema: would show bilateral symmetric infiltrates with cardiomegaly, cephalization, Kerley B lines, and an elevated BNP; it is not localized to a single trauma site in a young patient with no cardiac history.
Aspiration pneumonitis: follows altered consciousness or emesis and produces a gravity-dependent distribution (typically right lower lobe or posterior segments), not an opacity that maps to the point of blunt impact.
Question 2PulmonaryMedium
A 24-year-old man is brought to the emergency department after a high-speed motor vehicle collision in which he was the restrained driver. He reports left-sided chest pain and shortness of breath. Vital signs show heart rate 104/min, respiratory rate 24/min, blood pressure 128/78 mm Hg, and SpO2 89% on room air. Examination reveals a seatbelt sign and ecchymosis over the left chest wall with scattered crackles over the left lung base. A supine portable chest radiograph shows no rib fractures, pneumothorax, or focal opacity. Which of the following is the most appropriate next diagnostic test?
AContrast-enhanced CT of the chest
BTransthoracic echocardiography
CBedside thoracic ultrasonography
DRepeat chest radiograph at 48 hours
Reveal answer & full explanation
Correct answer: A — Contrast-enhanced CT of the chest
AContrast-enhanced CT of the chest✓
BTransthoracic echocardiography
CBedside thoracic ultrasonography
DRepeat chest radiograph at 48 hours
Why Contrast-enhanced CT of the chest is correct
This mechanism (high-speed MVC with a chest seatbelt sign) with hypoxia, chest wall ecchymosis, and basilar crackles strongly suggests pulmonary contusion, yet the initial supine portable chest radiograph is frequently normal because contusion opacities are non-segmental, delayed in onset, and underestimated on the admission film.
CT is far more sensitive and reveals contusion within minutes of injury; with contrast it simultaneously screens for associated injuries (occult rib fractures, hemothorax, pneumothorax, aortic and diaphragmatic injury) that change management.
Why the others are wrong
Repeat chest radiograph at 48 hours — contusions do become more apparent at 24-72 hours, but a hypoxic trauma patient cannot wait two days, so a sensitive study is needed now to guide disposition and monitoring.
Transthoracic echocardiography — is reasonable when blunt cardiac injury is suspected after a seatbelt-sign chest impact, but it cannot show a pulmonary contusion, does not explain hypoxia with basilar crackles, and misses the aortic and diaphragmatic injuries this mechanism demands be excluded.
Bedside thoracic ultrasonography — detects pneumothorax and pleural fluid at the bedside but does not characterize parenchymal contusion or screen for aortic and diaphragmatic injury, so it cannot replace CT here.
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Pediatric chest wall compliance allows lung injury without rib fractures
Pathophysiology
Mechanical compression-decompression and shear forces disrupt alveolar-capillary membranes, producing hemorrhage and edema in the contused lung. Inflammatory cascade peaks 24-72 hours after injury, leading to worsening ventilation/perfusion mismatch, shunt physiology, and hypoxemia. Surfactant inactivation and reduced compliance compound the impairment. Severe contusion can progress to acute respiratory distress syndrome.
Clinical presentation
Symptoms
Chest wall pain at site of impact
Dyspnea, tachypnea worsening over 24-72 hours after trauma
Hemoptysis (variable)
Increasing oxygen requirement during initial hospitalization
Crepitus from rib fractures or subcutaneous emphysema
Decreased breath sounds and crackles over contused area
Paradoxical chest wall motion with flail chest (≥3 contiguous ribs each fractured in ≥2 places)
Hypoxia (SpO2 <90% on room air) and tachypnea
Differential diagnosis
Aspiration pneumonitis — History of altered consciousness or emesis; gravity-dependent distribution; resolves more slowly with infection superimposed
ARDS — Bilateral infiltrates within 1 week of insult, P/F ratio criteria (Berlin), not fully explained by cardiac failure
Hemothorax — Pleural blood collection rather than parenchymal opacity; thoracostomy diagnostic and therapeutic
Atelectasis — Volume loss with mediastinal shift toward opacity; resolves rapidly with reexpansion
Cardiogenic pulmonary edema — Cardiomegaly, cephalization, Kerley B lines, elevated BNP; bilateral symmetric distribution
Pulmonary laceration — Cavitary lesion within contusion; may form pneumatocele or hematoma
Diagnostic workup
Labs
CBC, CMP, coagulation studies, type and crossmatch
Arterial blood gas to quantify hypoxemia and assess for respiratory acidosis
Lactate to assess perfusion
Imaging
Chest radiograph as part of trauma workup — non-segmental opacities not respecting lobar boundaries, often underestimated and delayed in onset
CT chest is more sensitive and reveals contusion within minutes of injury; assess for associated rib fractures, hemothorax, pneumothorax, aortic injury, diaphragmatic injury
FAST/E-FAST ultrasound at bedside for pneumothorax and pleural fluid
Repeat imaging at 24-48 hours if clinical worsening
Diagnostic algorithm
flowchart TD
A[Blunt chest trauma] --> B[ATLS primary survey<br/>CXR + E-FAST]
B --> C[CT chest if stable<br/>or high mechanism]
C --> D{Contusion severity}
D -->|Mild, SpO2 maintained| E[Floor admit<br/>O2 + analgesia + IS]
D -->|Moderate / Flail| F[ICU admit<br/>regional analgesia<br/>NIV vs intubation]
D -->|Severe / ARDS| G[Lung-protective vent<br/>prone + ECMO if refractory]
F --> H{SSRF candidate?}
H -->|Yes| I[Surgical rib fixation]
H -->|No| J[Continue medical mgmt]
Triage and management algorithm for pulmonary contusion from initial trauma evaluation to definitive care.
Treatment
First-line
Resuscitation per ATLS — airway, breathing, circulation; intubate for refractory hypoxemia or respiratory failure
Judicious fluid management: avoid both under-resuscitation (worsens shock) and over-resuscitation (worsens lung edema); target euvolemia
Aggressive pain control — multimodal analgesia including thoracic epidural, paravertebral block, intercostal nerve blocks, IV/oral analgesics; avoid respiratory depression from excessive opioids
Pulmonary toilet: incentive spirometry, cough/deep breathing, early mobilization, chest physiotherapy
Supplemental oxygen titrated to SpO2 ≥92%
Noninvasive ventilation (BiPAP, high-flow nasal cannula) for hypoxemic respiratory failure to avoid intubation when possible
Mild contusion (SpO2 maintained on supplemental O2, small volume)
Observation, pain control, pulmonary toilet, oxygen as needed
Outpatient follow-up with imaging at 1-2 weeks if discharged
Moderate-to-severe contusion or flail chest
ICU admission and continuous monitoring
Mechanical ventilation with lung-protective strategy (TV 6 mL/kg ideal body weight, plateau pressure <30 cm H2O, PEEP titration)
Surgical stabilization of rib fractures (SSRF) is reasonable for severe flail chest with respiratory failure (multiple trials and the CWIS guidelines support reduced ventilator days and ICU stay in selected patients)
Empyema if associated hemothorax becomes infected (retained hemothorax syndrome)
Long-term reductions in DLCO and lung compliance, especially in elderly patients
PANCE pearls
Pulmonary contusion is often radiographically silent on initial CXR and peaks at 24-72 hours — clinical re-examination matters more than the admission film.
Children sustain severe pulmonary contusion WITHOUT rib fractures because of compliant chest walls — high index of suspicion in any pediatric blunt trauma.
Avoid fluid overload: every additional liter of crystalloid worsens lung water in a contused lung.
Flail chest is a clinical diagnosis (paradoxical motion). The injury that determines outcome is the underlying pulmonary contusion.
Lung-protective ventilation (TV 6 mL/kg) reduces mortality even when ARDS criteria are not yet met.
References
EAST — Eastern Association for the Surgery of Trauma. Practice Management Guidelines for Pulmonary Contusion and Flail Chest. J Trauma Acute Care Surg 2012;73(5 Suppl 4):S351-S361
CWIS — Chest Wall Injury Society Recommendations on Surgical Stabilization of Rib Fractures (2020 update)
ARDSnet — Acute Respiratory Distress Syndrome Network. Ventilation with Lower Tidal Volumes for ALI/ARDS. NEJM 2000;342:1301-1308
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