What is the etiology of platelike atelectasis?

Etiology of Platelike Atelectasis

Platelike atelectasis is primarily caused by absorption of air distal to airway obstruction, compression of lung tissue, and increased surface tension in alveoli, resulting in collapsed lung segments at the corticomedullary junction of the lung. 1, 2

Main Mechanisms of Platelike Atelectasis

• Absorption (Resorptive) Atelectasis: Occurs when airways become obstructed, preventing air from reaching distal alveoli. The trapped air gets absorbed into the bloodstream, causing collapse of the affected lung segment 1
• Compression Atelectasis: Results from external pressure on lung tissue from pleural effusions, masses, or other space-occupying lesions 3
• Adhesive Atelectasis: Develops due to surfactant deficiency or dysfunction, increasing surface tension in alveoli and promoting collapse 1
• Cicatrization Atelectasis: Caused by pulmonary fibrosis and scarring that pulls on adjacent lung tissue 1

Specific Causes of Platelike Atelectasis

• General anesthesia: Occurs in approximately 90% of anesthetized patients, particularly at the lung bases, due to:

  • High oxygen concentration during induction and maintenance (causing absorption atelectasis) 4
  • Loss of muscle tone and decreased functional residual capacity 4
  • Supine positioning causing cephalad displacement of abdominal contents 5

• Airway obstruction:

  • Mucous plugging in airways 6
  • Endobronchial tumors (especially common in right upper lobe atelectasis in adults) 7
  • Foreign body aspiration 1

• Pulmonary embolism: Can present with platelike atelectasis as a non-specific radiographic finding 5

• Pulmonary pathologies:

  • Bronchopulmonary dysplasia can cause regions of atelectasis alternating with emphysema 3
  • COPD and other chronic pulmonary conditions increase risk of atelectasis 3

• Extrapulmonary causes:

  • Pleural effusion causing compressive atelectasis 3
  • External masses compressing airways 3
  • Malignant pleural effusions 3
  • Abdominal distention pushing up on the diaphragm 1

Pathophysiological Mechanism of Platelike Atelectasis

• Corticomedullary junction involvement: Platelike atelectasis specifically occurs at the junction between the cortex and medulla of the lung 2
• Contributing processes:
  • Air trapping in the cortex of the lung 2
  • Decreased distensibility of the whole lung due to interstitial infiltration 2
• Radiographic appearance: Linear or discoid opacities representing collapsed lung segments 1

Clinical Significance

• Atelectasis can persist for several days postoperatively 4
• May serve as a focus for infection, potentially contributing to postoperative pulmonary complications 4
• Can be misinterpreted as pneumonia or other intrathoracic pathology 1
• Diagnosis should be based on direct signs (crowded pulmonary vessels, crowded air bronchograms, displaced fissures) and indirect signs (pulmonary opacification, elevated diaphragm, mediastinal shift) 1

Prevention Strategies

• Avoid high oxygen concentrations during anesthesia when possible 4
• Consider head-up or ramped positioning during anesthesia induction, particularly in obese patients 5
• Alveolar recruitment maneuvers may temporarily reverse atelectasis, though benefits in the post-operative period are not well established 5