Posterior placement of a chest tube is appropriate for draining which type of collection?

• A. Fluid
• B. Air
• C. Mixed air and fluid
• D. Blood

Answer: (A)

Fluid drains best into the dependent, posterior pleural space because gravity pulls liquid to the back when the patient is upright or semi-reclined. A chest tube placed posteriorly allows continuous drainage of pleural fluid as it pools in that posterior area. Air, by contrast, rises to the highest point of the pleural cavity (the apex), so evacuating air is more effective with a tube placed up high, typically anterior or apical. A mixed air-and-fluid collection would require addressing both components, and while blood behaves as a fluid, posterior drainage is specifically favored for fluid collections due to gravity.