What is atelectasis?

Atelectasis: Definition, Mechanisms, and Management

Atelectasis is a condition characterized by the collapse of lung tissue with loss of volume in a previously inflated portion of the lung, resulting in non-aerated regions of lung parenchyma that can significantly impact respiratory function and oxygenation.

Definition and Mechanisms

Atelectasis can occur through three primary mechanisms:

1. Obstructive (resorption) atelectasis:

   • Caused by airway obstruction from mucus plugs, foreign bodies, or tumors
   • When airways are blocked, trapped gas is absorbed into the bloodstream, leading to alveolar collapse
   • Commonly seen with high oxygen concentrations during anesthesia 1

2. Compressive atelectasis:

   • Results from external pressure on lung tissue
   • Can be caused by pleural effusion, pneumothorax, tumors, or abdominal distention
   • Leads to decreased lung volume and impaired ventilation

3. Adhesive atelectasis:

   • Occurs due to increased surface tension in alveoli from surfactant dysfunction
   • Common in respiratory distress syndrome and after prolonged mechanical ventilation
   • Results in alveolar collapse due to inability to maintain alveolar stability 2

Clinical Significance

Atelectasis has significant clinical implications:

• Present in approximately 90% of patients undergoing general anesthesia 1, 3
• Typically affects 15-20% of the lung base during routine anesthesia 1
• Can persist for several days postoperatively
• Associated with decreased lung compliance and impaired oxygenation
• May serve as a focus for infection, potentially leading to pneumonia 4
• Contributes to increased pulmonary vascular resistance and potential lung injury 4

Radiographic Appearance

• Rounded atelectasis presents radiographically as a mass that may be mistaken for a tumor 5
• The classic "comet sign" (a band connecting the mass to an area of thickened pleura) is pathognomonic and often more visible on HRCT than plain films 5
• Chest CT with IV contrast is the preferred initial imaging for suspected tracheal or bronchial stenosis that may lead to atelectasis 5

Management Strategies

Preventive Measures

1. During anesthesia:

   • Avoid high oxygen concentrations during induction and maintenance
   • Use moderate FiO₂ (0.3-0.4) when possible to prevent absorption atelectasis
   • Consider PEEP when high FiO₂ is necessary 3

2. Recruitment maneuvers:

   • Inflation to airway pressure of 40 cm H₂O for 7-8 seconds (vital capacity maneuver) can re-expand collapsed lung tissue 3, 6
   • Recruitment maneuvers have been associated with lower mortality and improved oxygenation in ARDS patients 5

Treatment Approaches

1. Respiratory care techniques 7:

   • Position patient with head of bed elevated 30 degrees
   • Implement early mobilization to improve ventilation
   • Perform deep breathing exercises every 1-2 hours while awake
   • Use incentive spirometry (10 breaths every hour while awake)
   • Ensure adequate hydration to thin secretions

2. Airway clearance techniques 7:

   • Perform airway clearance 1-2 times daily with a trained respiratory therapist
   • Use manually assisted cough techniques for patients with ineffective cough
   • Consider mechanical insufflation-exsufflation devices for improved clearance

3. Ventilatory support 7:

   • Maintain adequate PEEP (10-15 cm H₂O) for intubated patients
   • Consider CPAP or non-invasive positive pressure ventilation if conservative measures fail
   • Implement alveolar recruitment maneuvers to reopen collapsed alveoli
   • Use controlled oxygen therapy to maintain SpO₂ ≥94% with lowest possible FiO₂

4. Interventional approaches:

   • Consider bronchoscopy for persistent atelectasis, particularly for removing mucous plugs 2

Monitoring and Follow-up

• Monitor arterial blood gases to assess improvement in oxygenation
• Obtain follow-up chest radiographs to document resolution
• Be vigilant for complications such as pneumonia and hypercapnic respiratory failure 7

Special Considerations

• Patients with chronic obstructive lung disease may show less or even no atelectasis 3
• Obese patients typically develop larger atelectatic areas than lean individuals 3
• Persistent atelectasis requires aggressive management to prevent infectious complications

Early recognition and management of atelectasis are crucial to prevent complications and improve patient outcomes, particularly in perioperative and critical care settings.