Pneumothorax

PNEUMOTHORAX

Anatomic Alterations of the Lung

  • Lung Collapse
      - Can occur partially or fully.
  • Visceral and Parietal Pleura Separation
      - The visceral pleura covers the lungs, while the parietal pleura lines the chest wall; separation can cause pneumothorax.
  • Atelectasis
      - Collapse of the lung due to decreased lung expansion.
  • Chest Wall Expansion
  • Compression of the Great Veins
      - Leads to decreased cardiac venous return and potential cardiovascular implications.

Definition

  • Pneumothorax: Collection of air or gas in the chest or pleural space leading to part or all of the lung collapsing.
      - Typical Pressure Dynamics: In a healthy state, the pressure in the lungs exceeds that of the pleural space; during a pneumothorax, this pressure is reversed.

Pathology

  • Generally causes only partial collapse of the lung.
  • May result in:
      - Decreased oxygen levels in the blood.
      - Shortness of breath due to compromised respiratory function.
      - Potential for rapid progression causing severe cardiovascular impairment.

Etiology

  • Methods of gas entry into the pleural space include:
      - From the lungs: Perforation of the visceral pleura.
      - From the atmosphere: Perforation of the chest wall and parietal pleura (or rarer sources like an esophageal fistula).
      - From microorganisms: Gas-forming microorganisms in an empyema (rare).

Fist-and-Balloon Analogy

  • Describes the relationship between the pleural membranes:
      - Outer balloon wall = Parietal serous membrane.
      - Inner balloon wall = Visceral serous membrane.

Pneumothorax Classifications

Based on Communication with Atmosphere
  • Closed Pneumothorax: Gas in the pleural space is not in direct contact with the atmosphere.
  • Open Pneumothorax: Pleural space is in direct contact with the atmosphere, allowing gas to move freely; often referred to as a "sucking chest."
  • Tension Pneumothorax: Intrapleural pressure exceeds both intraalveolar pressure and atmospheric pressure.

Symptoms, Causes, and Diagnosis

  • Causes of Pneumothorax:
      - Ruptured bleb (common in COPD patients).
      - Thoracentesis or puncture from trauma.
      - Secondary infection or injury.
  • Symptoms:
      - Dyspnea (shortness of breath).
      - Anxiety and tachycardia.
      - Pleural pain and asymmetrical chest wall expansion.
      - Absent or diminished breath sounds on affected side.
  • Diagnosis:
      - Chest X-Ray: Identify presence of air, assess lung collapse.
      - Arterial Blood Gases (ABGs): Assess oxygenation levels.

Types of Pneumothorax

Spontaneous Pneumothorax
  • Occurs without external trauma, often due to:
      - Ruptured congenital blebs on the visceral pleura.
      - Underlying diseases like COPD, pneumonia, tuberculosis.
      - More common in tall, thin individuals aged 15-40.
Traumatic Pneumothorax
  • Associated with penetrating wounds, automobile accidents, or industrial accidents.
  • Features a one-way valve effect, allowing gas into the pleural space during inspiration but not allowing it to exit.
Tension Pneumothorax
  • Life-threatening condition where air becomes trapped in the pleural space, continuously increasing pressure.
  • This causes mediastinal shift, pushing lungs, trachea, and heart to the unaffected side.
Iatrogenic Pneumothorax
  • Occurs during medical procedures such as:
      - Pleural biopsy
      - Thoracentesis
      - Intercostal nerve block
      - Subclavian vein cannulation
      - Tracheostomy
  • Especially a hazard during positive-pressure mechanical ventilation.

Signs and Symptoms/Diagnosis

  • Symptoms of tension pneumothorax are more severe than those of pneumothorax:
      - Deviated trachea towards unaffected side.
      - Chest radiograph shows complete radiolucency on one side; heart and lung shift on X-ray.

Clinical Data

  • Due to reduced alveolar ventilation, the patient's V/Q ratio DECREASES:
      - Results in atelectasis and pulmonary shunting.
      - Peripheral chemoreceptor stimulation due to hypoxemia occurs.
      - Increased central venous pressure (CVP) and pulmonary arterial pressure (PAP), while pulmonary capillary wedge pressure (PCWP) and cardiac output (CO) decrease.

Diagnosis & Radiological Findings

  • Physical Assessment:
      - Hyperresonant percussion notes over the pneumothorax area.
      - Decreased breath sounds in the affected lung.
      - Displaced heart sounds and increased thoracic volume on the affected side.
  • Pulmonary Function Tests (PFT): Indicate a restrictive lung pathology (everything shows decreased values).
  • Chest X-Ray Findings:
      - Increased translucency on the affected side, depressed diaphragm, atelectasis, and decreased vascular markings.

Preventive Measures

  • No known specific prevention methods for pneumothorax, but risk reduction strategies include:
      - Avoiding smoking.
      - Wearing seatbelts to mitigate trauma risk.
      - Educating about preexisting lung diseases and avoiding extreme pressure changes.

Treatments

  • Small pneumothoraces often heal spontaneously within weeks.
  • Larger pneumothoraces require:
      - Removal of air using needle aspiration or insertion of a chest tube.
  • Management of pneumothorax includes:
      - Bed rest or limited physical activity for small pneumothoraces (15-20%).
      - Evacuation of larger pneumothoraces (>20%) via a chest tube.
      - Safer needle placement for aspiration; second intercostal space midclavicular for air, fifth-seventh intercostal mid axillary for fluid.

Management Protocols

  • Use suction to drain air from the pleural space.
  • Typical negative pressure not exceeding -12 cm H2O; -5 cm H2O is effective for lung re-expansion.
  • Chest tubes remain post-suction for 24-48 hours for monitoring.

Pleurodesis

  • A procedure where chemicals such as talc, tetracycline, or bleomycin sulfate are introduced into the chest cavity to induce adhesion between lungs and chest cavity, preventing future pneumothorax.

Review Questions & Self-Assessment

  1. Pneumothorax occurs when free air accumulates in the pleural space.
  2. Major pathologic changes include atelectasis and lung collapse, excluding pulmonary edema.
  3. Most serious pneumothorax type: Tension.
  4. Gunshot wound: Presenting pneumothorax type is open.
  5. Clinical manifestations may involve hyperresonant percussion notes, decreased breath sounds, cyanosis, and displaced heart sounds.