Atelectasis

Risk factors

• Postoperative state (upper abdominal, thoracic, or cardiac surgery)
• Prolonged bed rest, splinting from pain
• Mucus plugging (cystic fibrosis, bronchiectasis, asthma exacerbation)
• Endobronchial obstruction (tumor, foreign body, mucus plug, lymphadenopathy)
• Pleural effusion, pneumothorax, or large mass causing compression
• Neuromuscular disease and impaired cough (ALS, myasthenia, Guillain-Barre)
• Obesity, advanced age, smoking

Pathophysiology

Resorptive atelectasis follows complete airway obstruction; distal gas is absorbed into the bloodstream over hours faster when the patient is breathing high FiO2 (nitrogen washout). Passive atelectasis follows pleural separation by air or fluid. Compressive atelectasis results from intrathoracic space-occupying lesions. Cicatricial atelectasis reflects scarring from prior infection or radiation. Adhesive atelectasis occurs when surfactant is deficient (ARDS, neonatal RDS).

Clinical presentation

Differential diagnosis

• Lobar pneumonia — Fever, leukocytosis, productive cough, air bronchograms within consolidation (vs absent in obstructive atelectasis); volume is preserved or increased
• Pleural effusion — Layering fluid on decubitus film, meniscus sign, blunting of costophrenic angle; ultrasound or thoracentesis confirms
• Pulmonary embolism — Acute pleuritic pain, hypoxia disproportionate to imaging, normal or near-normal chest film with linear atelectasis; CTPA diagnostic
• Mucus plugging in asthma/CF — Recurrent lobar/segmental collapse responsive to airway clearance; underlying obstructive disease
• Endobronchial tumor — Recurrent same-lobe atelectasis or post-obstructive pneumonia in smoker; bronchoscopy diagnostic

Diagnostic workup

Diagnostic algorithm

flowchart TD
  A[Lung collapse<br/>on imaging] --> B{Mediastinal shift?}
  B -->|Toward whiteout| C[Atelectasis]
  B -->|Away from whiteout| D[Effusion or<br/>tension PTX]
  C --> E{Mechanism}
  E --> F[Resorptive<br/>obstruction]
  E --> G[Passive<br/>pleural air/fluid]
  E --> H[Compressive<br/>mass effect]
  E --> I[Adhesive<br/>surfactant deficiency]
  F --> J[Bronchoscopy /<br/>mucus clearance]
  G --> K[Drain pleural<br/>space]
  H --> L[Address mass<br/>lesion]
  I --> M[Treat ARDS /<br/>surfactant if neonatal]

Treatment

Complications

• Hypoxemia and respiratory failure
• Post-obstructive pneumonia
• Pulmonary fibrosis with chronic cicatricial collapse
• Delayed postoperative recovery and prolonged ICU/hospital stay

PANCE pearls

• Tracheal deviation TOWARD a white-out hemithorax = atelectasis. Tracheal deviation AWAY = effusion or pneumothorax.
• High inspired oxygen accelerates resorptive atelectasis — avoid 100% FiO2 for prolonged periods when possible.
• Recurrent lobar atelectasis in a smoker mandates bronchoscopy to exclude endobronchial cancer.
• Postoperative fever attributed to 'atelectasis' is largely myth — search for infection, DVT/PE, drug fever, or wound issues.
• Air bronchograms argue AGAINST complete obstructive atelectasis and favor pneumonia or non-obstructive collapse.

References

• CHEST — Restrepo RD, Braverman J. Current Challenges in the Recognition, Prevention and Treatment of Perioperative Pulmonary Atelectasis. Expert Rev Respir Med 2015;9:97-107
• ACR Appropriateness — ACR Appropriateness Criteria: Acute Respiratory Illness in Immunocompetent Patients (latest revision)
• ATS — Mahler DA et al. American Thoracic Society Statement on Pulmonary Rehabilitation. AJRCCM 2013