Atelectasis - types. Pathomorphology. Acute massive pulmonary collapse (post-surgical atelectasis).
Atelectasis is the collapse of part or all of the lung caused by inadequate expansion of air spaces (derived from ‘ateles‘ and ‘ektasis‘ meaning incomplete expansion). There are three types:
- Resorption atelectasis
- Occurs when an obstruction prevents air from reaching distal airways and air that is already there becomes resorbed
- Compression atelectasis
- Occurs when something (usually fluid, blood or air in pleural cavity) collapses the lung
- Most common in pleural effusion
- Contraction atelectasis
- Occurs when there is general or local fibrosis that contracts the lung
Remember: the shift follows lung volume: resorption atelectasis loses volume, so the mediastinum is pulled toward the collapsed lung; an effusion or pneumothorax adds volume and pushes it away. Resorption and compression atelectasis are reversible; contraction atelectasis, caused by fibrosis, is not.
Diagnosis is best done on chest X-ray, you’re looking for white out and to observe the displacement of central structures towards the affected lung (away from it in compression atelectasis). Treatment is based on the underlying cause (compression, remove compressive element, resorption, remove blockage etc).
Chest X-ray (AP, ventilated patient): near-total collapse of the left lung after mucus plugging (resorption atelectasis). The left side is white, and the trachea and heart are pulled toward the collapsed lung.
Image: “Subtotale Atelektase der linken Lunge 66M - CR ap - 001” by Hellerhoff, CC BY-SA 4.0, via Wikimedia Commons.
Acute massive pulmonary collapse (post-surgical atelectasis)
Also known as acute atelectasis, may occur as a postoperative complication or as a result of surfactant deficiency in neonates (leads to infant respiratory distress syndrome). In surgical cases, the main risk factors are:
- Age
- Smoking
- General anesthetic
- Duration of surgery
- Pre-existing lung or neuromuscular disease
- Prolonged bed rest
- Poor post op pain control (causing shallow breathing)