Atelectasis

Collapse or incomplete expansion of part or all of a lung, with loss of air in the alveoli, shunting of blood through unventilated lung and hypoxaemia.

• Mechanisms:
  • Resorption (obstructive): airway blocked by mucus, foreign body, tumour or external node, with absorption of trapped gas.
  • Compression (passive): pleural effusion, pneumothorax, large mass, or raised diaphragm.
  • Adhesive: surfactant deficiency (preterm respiratory distress, acute respiratory distress syndrome).
  • Cicatricial: scarring of lung that shrinks it (tuberculosis, radiation).
  • Gravity-dependent or loss of tone: general anaesthesia, obesity, supine position, and immobility.
• Frequency: post-operative atelectasis occurs in up to 50 to 90% of patients under general anaesthesia, mostly mild and resolving within 24 to 48 hours; clinically important collapse affects about 10 to 20% of patients after major abdominal or thoracic surgery.

Often silent; breathlessness, dry or productive cough, pleuritic chest pain, low-grade fever in the first 48 hours after surgery, tachypnoea, tachycardia, hypoxaemia.

• Signs: reduced chest expansion on the affected side, dull percussion, reduced or absent breath sounds, bronchial breathing in small-airway sparing collapse, tracheal and mediastinal shift toward the collapse in lobar or lung collapse, raised hemidiaphragm.
• Obstructive causes: wheeze (partial), haemoptysis, weight loss, smoking history (tumour); sudden choking in a child or intoxicated adult (foreign body).
• Differential diagnosis: pneumonia, pleural effusion, pneumothorax with lung collapse, pulmonary embolism, pulmonary oedema, diaphragm paralysis, lung agenesis or hypoplasia, consolidation, phrenic nerve palsy.
• Complications: hypoxaemia and respiratory failure, pneumonia (collapsed lung traps secretions), lung abscess, bronchiectasis from long-standing obstructive collapse, empyema, pulmonary hypertension in prolonged collapse, and in children recurrent right middle lobe syndrome.

Chest X-ray: increased density, loss of volume, displaced fissures, crowded air bronchograms, shift of trachea and mediastinum toward the lesion, raised hemidiaphragm; patterns of lobar collapse (right upper lobe collapse lifts the horizontal fissure, left lower lobe collapse shows a triangular retrocardiac density with loss of the left hemidiaphragm outline).

• CT chest with contrast: confirms the collapse, shows the cause (endobronchial tumour, mucus plug, node, foreign body), and measures the volume; collapsed lung enhances brightly.
• Pulse oximetry, arterial blood gas (hypoxaemia, widened alveolar to arterial gradient).
• Bronchoscopy for persisting lobar or lung collapse without an obvious cause, suspected tumour or foreign body, or failure of physiotherapy: diagnostic and therapeutic.
• Full blood count, CRP, sputum culture when infection is suspected.

Post-operative and immobility atelectasis (prevention and treatment):

• Early mobilisation (out of bed within 6 hours where possible), sitting upright, frequent position changes.
• Incentive spirometry, 10 deep breaths every hour while awake; deep breathing and coughing with a splinted wound.
• Adequate analgesia: paracetamol 1 g four times daily, regular ibuprofen 400 mg three times daily if not contraindicated, local anaesthetic block (epidural or paravertebral) after thoracic and upper abdominal surgery, avoiding heavy opioid sedation.
• Humidified oxygen to keep SpO2 at 94 to 98% (88 to 92% in patients at risk of hypercapnia).
• Continuous positive airway pressure 5 to 10 cmH2O by mask for 1 to 2 hours three to four times daily, or continuously in severe disease; non-invasive ventilation for respiratory failure.

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• Chest physiotherapy: active cycle of breathing technique, oscillating positive expiratory pressure, postural drainage.
  • Nebulised salbutamol 2.5 to 5 mg followed by 3% to 7% hypertonic saline 4 mL twice daily.
  • Nebulised dornase alfa 2.5 mg once daily may be tried in ventilated patients or children with dense plugs (evidence limited).
  • N-acetylcysteine 600 mg orally once daily as a mucolytic (evidence limited).
• Bronchoscopy with suction and saline lavage (10 to 20 mL aliquots) for lobar or lung collapse that has not improved in 24 to 48 hours of physiotherapy, or earlier in ventilated patients with hypoxaemia and a large collapse.
• Treat the cause:
  • Foreign body: rigid or flexible bronchoscopic removal as soon as possible.
  • Tumour: endobronchial debulking, laser, cryotherapy or stenting, with oncology referral.
  • Large pleural effusion: drainage (up to 1.5 L at a time, stopping for cough or chest pain); pneumothorax: chest drain.
  • Infection: co-amoxiclav 625 mg three times daily orally for 5 to 7 days (or 1.2 g IV three times daily if unwell); doxycycline 200 mg then 100 mg daily when penicillin allergic.
• Neonates and infants: nasal CPAP 5 to 8 cmH2O; poractant alfa 200 mg/kg endotracheally for surfactant deficiency, then 100 mg/kg repeated at 12 hours if needed; hypertonic saline 3% 4 mL nebulised twice daily with chest physiotherapy in bronchiolitis.
• Special groups: children (look for foreign body, bronchiolitis, enlarged nodes from tuberculosis; flexible bronchoscopy early for unexplained persistent collapse); pregnancy (physiotherapy, CPAP, positioning on the left side; treat infection with amoxicillin 500 mg three times daily); elderly (early mobilisation, aspiration precautions, swallowing assessment); obesity (head-up position, CPAP); neuromuscular disease (mechanical insufflation-exsufflation at plus 40 to minus 40 cmH2O, 5 cycles of 5 breaths twice daily and when unwell).
• Red flags: SpO2 less than 90% on oxygen, lobar collapse persisting more than 48 hours, unexplained collapse in a smoker or older adult, haemoptysis, fever with a collapse, sudden onset after choking.
• Follow-up: repeat chest X-ray at 2 to 6 weeks to confirm re-expansion; CT and bronchoscopy for persisting collapse; review for malignancy in adult smokers; yearly review in recurrent right middle lobe syndrome.