Atelectasis

Atelectasis - The Collapsed Lung

• Definition: Lung collapse due to inadequate air space expansion, leading to a V/Q mismatch.
• Pathophysiology: Results in hypoxia; collapse can be partial or complete.

• Clinical Features: Dyspnea, cough, diminished breath sounds, dullness to percussion.
• Diagnosis: Chest X-ray shows opacification and volume loss.

⭐ High-Yield: In resorption atelectasis, the trachea and mediastinum deviate towards the collapsed lung. In compression atelectasis (e.g., tension pneumothorax), they deviate away.

Types & Causes - Why Lungs Deflate

• Resorption (Obstructive): Airway blockage (mucus plug, tumor) prevents ventilation. Trapped air is resorbed, collapsing the lung.
  • Mediastinal shift toward the collapse.
• Compression: External force pushes air out. Caused by pleural effusion, pneumothorax, or tumor.
  • Mediastinal shift away from the pressure source.
• Contraction (Cicatrization): Fibrotic changes in the lung or pleura prevent full expansion (e.g., post-TB, radiation).
  • ⚠️ This type is irreversible.
• Microatelectasis: Loss of surfactant (e.g., in ARDS, NRDS) leads to widespread alveolar collapse.

⭐ In resorption atelectasis, the mediastinum shifts toward the collapsed lung, a key radiological sign to differentiate it from compression atelectasis where it shifts away.

Clinical Picture - Spotting the Collapse

• Symptoms: Often asymptomatic. If severe, may present with:

  • Sudden-onset dyspnea & chest pain
  • Cough, sputum production

• Physical Exam: Key signs point to volume loss.

  • Palpation: ↓ Tactile fremitus
  • Percussion: Dullness over the affected area
  • Auscultation: ↓ or absent breath sounds

⭐ On imaging, look for signs of volume loss: tracheal deviation towards the collapse, elevated hemidiaphragm, and crowding of ribs. This differentiates it from consolidation or effusion where the trachea is pushed away.

Management - Reinflating the Lung

• Primary Goal: Recruit and re-expand collapsed alveoli to improve ventilation/perfusion (V/Q) matching.
• Core Strategies (Non-invasive):
  • Chest Physiotherapy: Incentive spirometry, deep breathing exercises, directed coughing, and postural drainage.
  • Early Ambulation: Crucial post-operatively to promote deep inspiration.
  • Pain Control: Adequate analgesia enables effective deep breaths and coughing.
• Advanced Measures:
  • Positive Pressure: CPAP or PEEP via ventilation stents airways open.
  • Therapeutic Bronchoscopy: For suctioning thick mucous plugs or removing foreign bodies.

⭐ Supplemental O₂ corrects hypoxemia but does not resolve the underlying atelectasis. High FiO₂ can worsen it by accelerating gas absorption from poorly ventilated alveoli (absorption atelectasis).

High‑Yield Points - ⚡ Biggest Takeaways

• Resorption atelectasis follows complete airway obstruction (e.g., mucus plug), pulling the mediastinum toward the collapse.
• Compression atelectasis is from external pressure (e.g., pleural effusion), pushing the mediastinum away.
• Contraction atelectasis, caused by pleural or parenchymal fibrosis, is the only irreversible form.
• Adhesive atelectasis stems from surfactant deficiency, the hallmark of Neonatal Respiratory Distress Syndrome.
• Key findings include decreased breath sounds, dullness to percussion, and ipsilateral tracheal deviation.