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Atelectasis

Absence of gas from all or part of the lung

Causes

1. Luminal obstruction / hypoventilation - distal gas trapping, gas absorbed (due to higher partial pressure than mixed venous blood) leading to progressive collapseof lung beyond obstruction
   1. FB: sputum
   2. inadvertant endobronchial intubation
   3. Upper abdominal/thoracic surgery = reduced lung expansion (from pain, spliting) leads to retained secretions and distal airways collapse
   • High FiO2: (loss of "splinting" from nitrogen mixture, so when oxygen is absorbed, lung unit collapses)
   • Underventilation: hypoventilation leading to progressive absorption of gas
2. Mural
   • Tumour
3. Extra-luminal
   • Compression from pleural effusion / pulmonary oedema

Consequences of atelectasis

1. VQ mismatch and hypoxaemia
2. Reduced lung compliance (smaller airways need more force to open - Laplace)
3. Pre-disposition to infection due to retention of secretions (vicious circle)

Management

1. Pre-operative anticipation
   • Chest exercise
   • Chest physiotherapy
2. Intraoperative
   • Humidified oxygen (improves mucociliary function)
   • Adequate tidal volumes - ensures good expansion
   • Avoid higg FiO2 (absorption atelectasis)
3. Post-operative
   • Sit upright
   • Adequate analgesia (facilitates breathing / good tidal volumes)
   • Early mobilisation
   • Breathing exercises
   • CPAP
   • Airway suction

Bronchiectasis

• Localised / generalised irreversible dilation of bronchi (as result of chronic necrotising infection)

Types

1. Follicular: loss of bronchial elastic tissue and multiple lymphoid follicles
2. Atelectatic: Localised dilation of airways associated with parenchymal collapse due to proximal airways obstructions
3. Saccular