A. Classification

1. Pneumothorax is air in the pleural space, within the thoracic cavity, outside of the lung
2. Major Types
   1. Spontaneous
   2. Traumatic
   3. Iatrogenic
3. Spontaneous Pneumothorax
   1. Not caused by any obvious precipitating factor
   2. Primary form occurs in patients without clinically apparent lung disease
   3. Secondary form occurs in patients with preexisting lung disease
4. Traumatic Pneumothorax
   1. Penetrating Trauma
   2. Blunt Trauma
5. Iatrogenic Pneumothorax
   1. Caused by medical intervention, diagnostic or therapeutic
   2. Transthoracic needle aspiration
   3. Placement of central venous catheter in subclavian vein
   4. Thoracentesis and/or pleural biopsy
   5. Barotrauma (mechanical ventilation)
6. Tension Pneumothorax
   1. Air entering pleural space (from lung or through chest wall) cannot escape
   2. Thus, air pressure increases with each breath (inspiration)
   3. Requires that a "valve" mechanism is involved
   4. Air pressure and volume in pleural space increases until lung completely collapses
   5. Tachycardia, hypotension, and cyanosis occur with rapid progression
   6. Acute right heart failure and/or myocardial infarction can occur
   7. Electromechanical dissociation / pulseless electrical activity or asystole can follow

B. Primary Spontaneous Pneumothorax

1. Incidence ~20 cases per 100,000
   1. Three to 5 times more common in men than women
   2. Usually occurs in tall, thin males age 10-30 years
2. Smoking increases risk in men by up to ~20 fold (dose dependent)
3. Usually not a life-threatening event because baseline lung function is good
4. Essentially all patients with spontaneous pneumothorax have subpleural bullae
   1. These bullae are subclinical and only seen on radiography or direct visualization
   2. Bullae likely form from degradation of elastin fibers in lung
   3. This explains increased risk with smoking
   4. Defect in visceral pleura through which air escapes into pleural space
5. Pathophysiology
   1. Small pneumothorax is asymptomatic or with mild dyspnea on exertion
   2. Larger pneumothorax leads to reduced vital capacity, increased A-a gradient
   3. Hypoxemia occurs due to reduced ventilation perfusion ratio and shunting
   4. Hypercapnia does not develop in primary pneumothorax because of normal lung function
6. Symptoms and Signs
   1. Shortness of breath
   2. Tachycardia - most common physical finding
   3. Decreased movement of chest wall
   4. Hyperresonant percussion note
   5. Diminished fremitus
   6. Decreased or absent breath sounds on affected side
   7. Hypotension
   8. Cyanosis
   9. Hypotension with cyanosis and tachycardia suggest tension pneumothorax
7. Diagnosis
   1. Patient's history is contributory
   2. Chest radiography shows thin, visceral pleural line (<1mm width) displaced from chest wall
   3. Small apical pneumothorax may best be seen on radiograph taken during expiration
   4. Arterial blood gas measurements should generally be taken
   5. Acute respiratory alkalosis and hypoxemia are usually found
8. Recurrences are common, ~30%, within 6-24 months after initial pneumothorax
9. Treatment discussed below

C. Secondary Spontaneous Pneumothorax

1. May be life-threatening because baseline lung function is compromised
2. Incidence is ~8 per 100,000 patients per year
   1. About 3 times more common in men than women
   2. Usually occurs in age 60-65 in chronic lung disease population
   3. In patients with known COPD, incidence is ~26 per 100,000 per year
3. Common Causes (in decreasing order of occurrence)
   1. Chronic obstructive pulmonary disease (COPD; emphysema) is most common cause
   2. Other Airway Disease: Cystic fibrosis, status asthmaticus
   3. Pulmonary Infection: Pneumocystis, necrotizing (such as staphylococcal) pneumonia
   4. Interstitial Lung Disease: Sarcoidosis, idiopathic pulmonary fibrosis, histiocytosis, others
   5. Inflammatory Disease: rheumatoid arthritis, ankylosing spondylitis, myositis, systemic sclerosis
   6. Connective Tissue Disorders: Marfan's Syndrome, Ehlers-Danlos Syndrome
   7. Cancer: Sarcoma, Lung Cancer
   8. Endometriosis (thoracic)
4. Symptoms and Signs
   1. Secondary pneumothorax is often a life-threatening emergency
   2. Dyspnea is nearly always seen because underlying lung function is compromised
   3. Ipsilateral chest pain is common
   4. Hypoxemia and hypotension often develop
   5. Hypercapnia is common, with pCO2 levels often >50 mm Hg.
   6. Physical findings are often unremarkable (except for marked cyanosis)
   7. Cardiovascular collapse is often imminent
5. Diagnosis
   1. Very high suspicion in all patients with chronic lung disease and decompensation
   2. Giant bullae on chest radiography and computed tomography (CT)
   3. Presence of visceral pleural line that runs parallel to chest wall
   4. If chest radiography does not provide clear diagnosis, CT scan should be done
6. Recurrence rates for secondary spontaneous pneumothorax are ~40%

D. Treatment

1. Observation with oxygen for small (<15%) primary pneumothorax
   1. Healthy young persons only
   2. No tension component
   3. Monitoring in emergency room for 6 hours or hospitalize for 1-2 days
   4. Oxygen increases pleural absorption of air by ~4 fold
   5. Chest radiography at least 6 hours after initial treatment should show improvement
2. Pulse oximetry and cardiac telemetry and recommended
3. Invasive Methods
   1. Simple aspiration with catheter, immediately removed after air is evacuated
   2. Chest tube insertion (to reverse pressure) is required for medium to large pneumothorax
   3. Pleuradesis may be required in some patients
   4. Thorascopy through single insertion point
   5. Video assisted thorascopic surgery
   6. Thoracotomy
   7. Presence of bullae by themselves on computed tomography should not prompt intervention
4. Large primary spontaneous pneumothorax (>15%)
   1. May be drained by 7-14 French catheter and then catheter is removed
   2. Insertion of chest tube may be required (~30% of cases)
   3. Chest tube recommended in age >50 or very large (>2.5L air) aspirations
5. Secondary Spontaneous Pneumothorax
   1. These do NOT resolve spontaneously and MUST be treated
   2. Chest tube 20-28 French is attached to a water-seal device
   3. Patients must be hospitalized and monitored closely
   4. Persistent air leaks for >2 weeks occur in ~20%
6. Complications of Chest Tube
   1. Pain
   2. Pleural infection
   3. Incorrect tube placement
   4. Hemorrhage
   5. Hypotension
   6. Pulmonary edema (due to lung reexpansion)
7. Prevention of Recurrence
   1. Smoking MUST be discontinued
   2. For primary pneumothorax, active intervention for prevention after first or second episode
   3. Sclerosing agents are generally NOT recommended for primary pneumothorax
   4. Thorascopy through single chest port allows resection of small (<2cm) apical bullae
   5. Video assisted thorascopic surgery is usually required for >2cm bullae
   6. In general, secondary pneumothorax is prevented with thorascopic surgery

References

1. Sahn SA and Heffner JE. 2000. NEJM. 342(12):868