II. Pathophysiology
-
Lung consolidates as gas is absorbed from obstructed segments
- Lung parenchyma decreases in volume and becomes more dense
- Consolidated lung gradually becomes more visible on plain Chest XRay
- Consolidated lung density matches the density of soft tissue
- Obscures normal lung landmark structures (e.g. mediastinum, costophrenic angle)
III. Causes
- See Atelectasis
- Obstructive Atelectasis (Bronchial Obstruction) from Lung Mass, mucus plugging, Foreign Body Aspiration
- Compression Atelectasis from Pneumothorax or Pleural Effusion
- Traction Atalectasis (lung scarring distorts alveoli) from chronic lung fibrosis or severe Pneumonia
- Relaxation Atelectasis (passive Atelectasis) from focal Splinting of respiratory Muscle (e.g. Rib Fractures)
IV. Findings
- Mediastinal shift
- Massive whole lung collapse
- Lower lobe collapse
- Tracheal Deviation
- Occurs with whole lung collapse
- Trachea deviates toward the area of lung collapse
- Upward hilar displacement
- Upper lobe collapse
- Downward hilar displacement
- Lower lobe collapse
- Shift of fissures
- Affects any segment
- May shift from horizontal to vertical orientation
- Narrowing of costal interspaces
- Massive Atelectasis
- Plate-Like Atelectasis
- White-streaks resulting from a narrow band of alveolar collapse
V. References
- Broder (2021) Crit Dec Emerg Med 35(6): 12-3