4. Atelectasis

Question 1

Definition of atelectasis

Answer 1

Refers to either the incomplete expansion of the lungs (as in neonatal atelectasis) or the collapse of a previously inflated lung (acquired atelectasis), resulting in respiratory insufficiency and a risk of infection

Question 2

Types of atelectasis

Answer 2

1. Neonatal
   - Patchy atelectasis
2. Acquired
   - Resorption atelectasis
   - Compression atelectasis
   - Contraction atelectasis

Question 3

Patchy atelectasis

Answer 3

Due to insufficient surfactant

Question 4

Resorption atelectasis

Answer 4

1. Due to a complete obstruction of an airway, with
   progressive resorption of oxygen trapped in the downstream alveoli, diminishing the volume of the downstream lung segment
   - Obstructive lung diseases (asthma, bronchiectasis, chronic bronchitis)
   - Aspiration of foreign body
   - Bronchial neoplasms
2. Mediastinum shifts towards the atelectatic lung

Question 5

Compression atelectasis

Answer 5

1. Due to accumulation of fluid exudates (hydrothorax),
   blood (hemothorax), tumour or air (pneumothorax)
   within the pleural cavity
2. Special case: tension pneumothorax (one-way valve defect in chest wall permitting entry to air during inspiration but prevents air from escaping)
3. Mediastinum shifts away from the atelectatic lung

Question 6

Contraction atelectasis

Answer 6

Due to local or generalized fibrotic changes in the lung or pleura preventing full expansion