How does a chest drain one chamber underwater seal system work?

  • The underwater seal created by a tube placed 2-3 cm below the surface of the water:
    • Ensures minimum resistance to drainage of air and fluid
    • Acts as a one-way valve preventing re-entry during inspiration
  • The chamber should be 100 cm below the chest
  • During expiration:
    • Fluid or air drain into collection chamber under gravity
    • Bubbles are seen in the case of pneumothorax
  • During inspiration:
    • Negative pressure is generated in the pleura
    • Creates retrograde flow of fluid up the tubing (respiratory swing)
    • Low height of chamber and length of tubing prevents fluid reaching the pleural cavity
  • Respiratory swing useful for assessing tube patency and pleural position
One-bottle chest drain system