Important concept for facilitation of ventilation

Definition of atelectasis

Collapsed alveoli  Areas involved: Small groups of alveoli  Lung segment  Whole lung

Types of atelectasis

1) Micro

2) Plate

3) Compression

4) Absorption

5) Surfactant impairment

Description of micro atelectasis

patchy areas of atelectasis w/ X shift of structures

Description of plate atelectasis

 small areas of collapse ( thin white lines on chest x-ray )

Pathogenesis of atelectasis

1) Compression

2) Absorption

3) Surfactant impairment

Causes of compression atelectasis

1. Tumour external to bronchi 

2. Pneumothorax 

3. Pleural effusion 

4. Cardiomegaly 

5. ↑ pleural pressure

6. Relaxed diaphragm ( surgery/ anaesthesia )

Causes of absorption atelectasis

• Blockage in bronchus/ bronchiole → gas in unit distal to obstruction trapped → continual uptake of gas by blood → gas pressure in alveolus ↓ → collapse of alveolus 

• High FiO2 → ↓ nitrogen → V/Q mismatch

Causes of surfactant impairment atelectasis

1. Anaesthesia 

2. Supplemental O2 ( dry ) 

3. Mechanical ventilation 

4. Infection 

5. Pre-term neonate

—> impairs production of surfactant

Signs of atelectasis

1. Palpation 

• Reduced chest wall movement ( unilaterally/ bilaterally ) 

• ↑ temperature ( if there are secretions in lung ) 

2. Ausculatation

• ↓/ absent breath sounds +/ fine end-inspiratory crackles

Special tests for atelectasis

• ↓SpO2, PaO2 

• CXR 

→ shift of structures towards collapse 

Possible structures shifting: 

• Fissures 

• Diaphragm

• Mediastinum 

• Trachea

→ increased density of collapsed lobe ( whiteness)

→ separation of lung markings in non-involved area 

→ silhouette sign: loss of border

Risk factors of atelectasis

1. Surgical incisions 

2. Previous respiratory condition 

3. Smoking history 

4. Obesity 

5. Age 

6. Impaired cognitive function

7. Monotonous pattern of mechanical ventilation 

8. Body position

Post surgical risk factors for atelectasis ( allie’s s )

1. Surgery 

2. Splinting 

3. Shallow breathing 

4. Supine + slumped 

5. Secretions 

6. Surfactant 

7. Senior 

8. Supplemental oxygen 

9. Synthetic ventilation/ sighs 

10. Smoking 

11. Size