Diagnosis: Spontaneous Pneumothorax

The patient's chest x-ray revealed a right apical pneumothorax estimated 10-15% in size with some mild right basilar atelectasis. No focal consolidation or edema. No acute osseous abnormality.

The pulmonology service was consulted and recommended a period of observation on 100% oxygen. A repeat chest x-ray after 6 hours showed no significant change in size. At discharge the patient continued to endorse pain with deep inspiration, but otherwise reported feeling comfortable. She was given a follow-up appointment with pulmonology for repeat imaging in a week or two.

Pneumothorax

Air between the visceral and parietal pleura

Due to an alveolar-pleural defect between intrapleural space (normally under negative pressure) and the airways (positive pressure)

Defect leads to equalization of pressure until the defect is closed

Simple

• lung collapse on the side of the defect --> decreased lung capacity
• VQ mismatch --> potential hypoxemia depending on size and comorbidities

Tension

• defect acts as a one-way valve --> accumulation of air in the intrapleural space
• mediastinal contents shift away from affected side --> compresses opposite lung
• hypoxia and impaired venous return --> cardiovascular collapse and death

Causes

• Traumatic - blunt or penetrating trauma 
• Iatrogenic - often due to penetrating trauma (i.e. procedure) 
• Spontaneous - no clear precipitating cause
• Primary (no lung disease) = 2/3 cases
• Risk factors: male, smoker, tall, change in ambient pressure, Marfan's
• Secondary (history of lung disease, usually COPD) 
• Risk factors: asthma, cystic fibrosis, lung abscess, TB, interstitial lung disease, malignancy, PJP

Presentation

• sudden onset unilateral chest pain, usually pleuritic, dyspnea, cough
• tachycardia, hyperresonance to percussion, diminished breath sounds

Diagnosis

• clinical suspicion should prompt imaging
• CXR - classically shows pleural line parallel to contour of chest wall with gap of absent lung markings
• CT chest = very sensative
• Grade: small, moderate, large, total

Management

• largely depends on the clinical status of the patient and the size of the pneumothorax

• observation (6 hours) 
• small size pneumothorax <20%
• otherwise young healthy patient
• intrinsic reabsorption 1%-2% per day (increases to 4%-8% on 100% O2)
• may discharge after observation if reliable follow up established for repeat CXR
• simple catheter aspiration 
• moderate size pneumothorax >20%
• less invasive but not always successful
• tube thoracostomy
• most common therapy, especially when more conservative measures fail
• treatment of choice with pleural effusion, respiratory distress, tension pneumothorax
• 20-28 French standard, >28 preferred if pleural fluid present
• water-seal valve (Heimlich or flutter valves) don't require hospitalization
• complications: malposition, infection, pain, obstruction, reexpansion pulmonary edema

management of tension pneumothorax to be discussed in a future post

References: 

Levy SJ, Lex JR, Emergency Medicine: A Focused Review of the Core Curriculum, 1st Ed, 2008, Chapter 4: Thoracic and Respiratory Disorders, pages 237-242

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