Question:

A 37-year-old man is brought to the emergency department 2 hours after being involved in a motor vehicle collision, where he was the unrestrained driver of a car without an airbag. He has a 15-year history of smoking two packs of cigarettes daily. On arrival, he had severe chest pain, most pronounced on inspiration.

• Height: 173 cm (5 ft 8 in)

• Weight: 113 kg (250 lb)

• BMI: 38 kg/m²

• Pulse: 130/min

• Respirations: 28/min

• Blood Pressure: 130/80 mm Hg

Physical examination reveals ecchymosis over the anterior chest but no fractures. The lungs are clear to auscultation. A chest X-ray shows bilateral interstitial infiltrates.

Which of the following is the most likely cause of this patient’s respiratory symptoms?

A) Fat embolism
B) Flail chest
C) Pulmonary contusion
D) Pulmonary edema
E) Pulmonary thromboembolism

Correct Answer: C) Pulmonary contusion

Here’s His Story:

Blunt Chest Trauma (e.g., car accident)

⬇️
Direct Impact on Chest Wall → Compression of Chest
⬇️
Rapid Deceleration/Shearing Forces
⬇️
 Lung Parenchyma Injury (alveoli & capillaries)
⬇️
Alveolar Hemorrhage → Blood Fills Alveoli
⬇️
Damage to Capillaries → Plasma Leakage
⬇️
Alveolar Edema Formation → Fluid Accumulation
⬇️
 ↓ Gas Exchange → ↓ Oxygen Diffusion into Blood
⬇️
Hypoxemia (↓ O₂ in blood)
⬇️
Interstitial Infiltrates on Chest X-ray → Bilateral
⬇️
Severe Chest Pain on Inspiration (pleuritic)
⬇️
 ↑ Respiratory Rate (Tachypnea) ↑
⬇️
↑ Work of Breathing
⬇️
 No Rib Fractures (Unlike Flail Chest)
⬇️
Tachycardia (↑ Heart Rate) ↑ due to Hypoxemia
⬇️
Ecchymosis on Chest (Surface Injury)
⬇️
 Pulmonary Contusion Diagnosed → Common in Trauma

Key Insights (🧠):

• Alveolar Hemorrhage + Edema → Direct result of trauma to the lung.

• Interstitial Infiltrates → Indicative of fluid and blood within the lung, seen on X-ray.

• No Rib Fractures → Differentiates it from other trauma-related conditions like flail chest.

• Tachypnea + Hypoxemia → Body’s response to impaired lung function and low oxygen levels

Why Other Answers Are Wrong?

A) Fat Embolism

• 🧠 Key Insight: Occurs 12-72 hours after trauma, typically involving long bone fractures (e.g., femur).

• Pathophysiology: Fat droplets from bone marrow enter the bloodstream, causing small vessel occlusion in the lungs and brain.

• Why Wrong?: This patient’s symptoms developed within 2 hours, which is too early for fat embolism syndrome.

B) Flail Chest

• 🧠 Key Insight: Caused by multiple rib fractures (≥3 consecutive ribs in ≥2 places), leading to paradoxical chest wall movement.

• Pathophysiology: Fractured rib segments move in opposite directions during breathing, impairing lung ventilation.

• Why Wrong?: There is no evidence of rib fractures or paradoxical movement in this patient.

  

  Source: Cleveland

D) Pulmonary Edema

• 🧠 Key Insight: Often results from heart failure or fluid overload, leading to fluid accumulation in alveoli.

• Pathophysiology: ↑ Hydrostatic pressure in pulmonary capillaries causes fluid leakage into alveoli (cardiogenic or non-cardiogenic).

• Why Wrong?: This patient’s presentation follows blunt trauma, and pulmonary edema is not typically caused by direct chest trauma without underlying cardiac issues.

E) Pulmonary Thromboembolism (PE)

• 🧠 Key Insight: Results from blood clots traveling from peripheral veins (usually legs) to the pulmonary arteries.

• Pathophysiology: Embolism blocks pulmonary blood flow, causing sudden dyspnea, pleuritic chest pain, and often normal X-ray findings.

• Why Wrong?: PE would not typically cause interstitial infiltrates on X-ray, and risk factors like deep vein thrombosis (DVT) are not indicated.

Flashcards

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Dr. Shoaib Ahmad