Atelectasis
Basics
- Incomplete expansion or collapse of lung tissue.
- Types:
- Obstructive (resorptive): airway blockage (foreign body, mucus plug, tumor).
- Nonobstructive: includes passive, compression, adhesive, cicatrization, replacement atelectasis.
- Symptoms depend on extent and underlying lung status; often asymptomatic.
- Can cause hypoxemia due to reduced gas exchange.
Epidemiology
- Mean age ~60 years; all ages susceptible.
- Equal sex distribution.
- Common in mechanically ventilated and postoperative patients.
- Postoperative atelectasis incidence up to 90% after major CV or GI surgery.
- Rounded atelectasis prevalent in asbestos-exposed individuals (65-70%).
Etiology and Pathophysiology
- Obstructive: airway blockage leads to air resorption distal to obstruction, alveolar collapse.
- Nonobstructive:
- Passive: pleural effusion, pneumothorax.
- Compression: space-occupying lesions, cardiomegaly.
- Adhesive: surfactant dysfunction in ARDS, radiation, contusion.
- Cicatrization: scarring/fibrosis in granulomatous disease, radiation, drug toxicity.
- Replacement: tumor filling alveoli causing lobar collapse.
- Collateral ventilation varies with age, lung disease.
- Pediatric lungs have less developed collateral ventilation, higher risk.
Risk Factors
- Critical illness, surgery, prolonged immobilization.
- General anesthesia, muscle relaxants, epidural anesthesia.
- Positive fluid balance, massive transfusion (≥4 units).
- Nasogastric tube placement, hypothermia.
- Mechanical ventilation with high tidal volume (>10 mL/kg) and plateau pressure (>30 cm H2O).
- Patient factors: age >60 or <6, COPD, OSA, CHF, pulmonary hypertension.
- Alcohol, smoking, poor cough effort, low albumin (<3.5 g/dL), ASA class II + ADL dependence.
General Prevention
- Early mobilization, frequent position changes.
- Deep breathing exercises, coughing.
- Preoperative physical therapy reduces atelectasis and pneumonia.
- Avoid high Vt and plateau pressures during mechanical ventilation; use PEEP.
- Maintain lower FiO2 intraoperatively to prevent nitrogen washout.
Commonly Associated Conditions
- COPD, asthma, trauma, ARDS, neonatal RDS.
- Pulmonary edema, embolism, pneumonia, pleural effusion, pneumothorax.
- Respiratory infections (RSV, bronchiolitis).
- Bronchial stenosis, pulmonic valve disease, pulmonary hypertension.
- Neuromuscular disorders (muscular dystrophy, SMA, Guillain-Barré).
- Cystic fibrosis.
Diagnosis
History
- Often asymptomatic.
- Tachypnea, sudden dyspnea.
- Nonproductive cough, pleuritic chest pain.
- History of smoking, COPD, pulmonary disease, exposures (radiation, asbestos).
Physical Exam
- Hypoxia, cyanosis.
- Tracheal/precordial shift toward affected side.
- Dullness on percussion, bronchial breath sounds if patent airway.
- Wheezing or absent breath sounds in occlusion.
- Reduced chest expansion.
Differential Diagnosis
- Pneumonia
- Pleural effusion
- Neoplasm
Diagnostic Tests & Interpretation
- CBC, respiratory cultures if infection suspected.
- ABG: hypoxemia with normal or low PaCO2.
- Chest X-ray PA and lateral: key initial imaging.
- Chest CT/MRI if unclear etiology.
- Chest ultrasound to differentiate atelectasis vs effusion/consolidation.
- Pulmonary function tests: obstructive/restrictive patterns.
- Bronchoscopy: for refractory or unclear cases.
Treatment
General Measures
- Treat underlying cause.
- Adequate analgesia to enable deep breaths and cough.
- Position patient on unaffected side.
- Encourage coughing, deep breathing, early mobilization.
- PEEP intra- or postoperatively.
- Incentive spirometry routinely.
- CPAP beneficial in hypoxemic patients with few secretions.
- Suctioning and chest physiotherapy for secretion clearance.
Medications
- Address underlying etiology:
- Antibiotics for infection.
- Bronchodilators/corticosteroids for asthma.
- Chemotherapy/radiation for malignancy.
- Mucolytics may aid airway clearance.
- Pediatric: dornase alfa for refractory mucus plugging (esp. cystic fibrosis).
- Bronchoscopy for mucus plug removal when physiotherapy fails.
Surgery
- Resection for tumors or severe lymphadenopathy causing compression.
Alerts
- Postoperative atelectasis often coincidental with fever; fever usually not caused by atelectasis.
Admission/Inpatient Considerations
- Oxygen supplementation and humidification.
- Avoid excessive FiO2 in obstructive atelectasis to prevent nitrogen washout.
Ongoing Care
- Monitoring frequency depends on severity and comorbidities.
- Outpatient monitoring sufficient for uncomplicated cases.
Patient Education
- Maximize mobility, perform frequent coughing and deep breathing.
- Seek emergency care for worsening dyspnea or symptoms.
Prognosis
- Postoperative atelectasis often resolves within 24 hours but can persist.
- Lobar atelectasis resolution depends on treatment of underlying cause.
Complications
- Pneumonia, pulmonary infections.
- Acute: hypoxemia, respiratory failure, postobstructive lung injury.
- Chronic: bronchiectasis, pleural effusion, empyema.
References
- Hulzebos EHJ, et al. Preoperative physical therapy for elective cardiac surgery. Cochrane Database Syst Rev. 2012;CD010118.
- Lagier D, et al. Perioperative pulmonary atelectasis: clinical implications. Anesthesiology. 2022;136(1):206-236.
- Marret E, et al. Protective ventilation during anesthesia reduces complications after lung surgery. Eur J Anaesthesiol. 2018;35(10):727-735.
ICD10 Codes
- P28.10 Unspecified atelectasis of newborn
- J98.11 Atelectasis
- P28.19 Other atelectasis of newborn
Clinical Pearls
- Low serum albumin (<3.5 g/L) is a strong predictor of postoperative pulmonary complications including atelectasis.
- Atelectasis occurs in almost all anesthetized patients but can be reduced with PEEP.
- Early mobilization, coughing, deep breathing exercises, and treatment of underlying causes are key.
- Bronchogenic carcinoma must be excluded in patients >35 years presenting with atelectasis.
- No strong evidence links atelectasis as cause of early postoperative fever.