What is Atelectasis?

• Definition: Complete or partial collapse of part or all of a lung, resulting in non-aeration of alveoli.
• Effect: Decreased gas exchange, leading to hypoxia if large areas are affected.
• Mechanisms:
  • Characterized by: Impaired lung expansion.
  • Causes: inflammation, atrophy, and fibrosis.
  • Results: Both ventilation and perfusion are compromised.

Types of Atelectasis

1. Obstructive Atelectasis:

• Caused by airway blockage (e.g., mucus plug, tumor).
• Obstructs airflow distal to the blockage.
• Gas diffuses into tissue and is not replaced, causing alveolar collapse.
• Often appears on imaging as areas of collapse caused by obstruction.

2. Compression Atelectasis:

• External pressure on airway from:
  • Tumor.
  • Pleural effusion (fluid build-up).
  • Blood (e.g., hemothorax).
  • Air (e.g., pneumothorax).
• Causes lung tissue to be compressed and collapse.
• Results in decreased lung expansion and hypoxia.

3. Contraction Atelectasis:

• Due to fibrosis or scarring (from trauma, cystic fibrosis, tuberculosis).
• Fibrotic tissue contracts, restricting lung expansion.
• Leads to permanent lung volume reduction and hypoxia.

4. Postoperative Atelectasis:

• Common within 24-72 hours after surgery.
• Caused by pain limiting deep breaths, shallow breathing, and anesthesia effects.
• Preventative measures:
  • Encouraging mobility.
  • Deep breathing exercises.
  • Use of incentive spirometry.

Clinical Features and Imaging

• Small atelectasis: Asymptomatic.
• Large collapse: Shortness of breath, hypoxia, chest pain, asymmetry.
• Signs include:
  • Asymmetric chest expansion.
  • Tachypnea, hypoxia.
• Imaging:
  • Chest X-ray shows areas of collapsed alveoli.
  • CT scans reveal the extent and cause.

Pleural Effusion and Pneumothorax

Pleural Effusion:

• Accumulation of fluid in the pleural cavity.
• Causes:
  • Inflammation (pleurisy, pleuritis).
  • Heart failure (transudate/ hydrothorax).
  • Infection (exudate, empyema).
  • Blood (hemothorax).
  • Pus (pyothorax).
• Effects:
  • Increased pressure causes lung compression.
  • Tracheal deviation and mediastinal shift in large effusions.
  • Reduced venous return → decreased cardiac output → hypotension.
• Symptoms:
  • Shortness of breath, chest pain, rapid breathing.
  • On palpation and percussion, dullness to percussion.

Pneumothorax (air in pleural space):

• Types:

  • Closed (spontaneous or secondary): Due to rupture of blebs or bullae, often in emphysema or COPD.
  • Open: Penetrating injury (trauma, surgery) causes air to enter pleural cavity.
  • Tension pneumothorax: Most serious; flap-like tear traps air with each breath, leading to mediastinal shift.

• Signs:

  • Sudden chest pain, shortness of breath.
  • Tracheal deviation (away from affected side in tension pneumothorax).
  • Reduced breath sounds on affected side.
  • Cyanosis, hypotension.

• Management:

  • Immediate decompression with chest tube or needle thoracostomy.
  • Cover open wounds with sterile occlusive dressings to prevent air entry.
  • For tension pneumothorax, remove the flap or perform emergency decompression to relieve mediastinal shift.

• Emergency measures:

  • Maintain sterility when handling injuries.
  • Stabilize with occlusive dressings.
  • Newly inserted chest drain to re-expand lung.

Summary:

Atelectasis involves lung collapse due to blockage, external compression, fibrosis, or postoperative factors. It impairs gas exchange, leading to hypoxia. Pleural effusions and pneumothorax are conditions related to abnormal fluid or air accumulation, causing lung compression and potential mediastinal shift. Prompt recognition and intervention are critical to prevent morbidity and mortality.