Before removing a chest tube, what is the acceptable 24-hour drainage volume?

• A. <500cc over 24 hours
• B. <100cc over 24 hours
• C. <150cc over 24 hours
• D. <75cc over 24 hours

Answer: (C)

Before removing a chest tube, the amount of drainage in the last 24 hours should be minimal and show a downward trend, and there should be no ongoing air leak with the lung adequately expanded. The threshold most commonly taught for safe removal is less than 150 mL of drainage in 24 hours. This level suggests that the pleural space is no longer accumulating significant fluid or blood and that the risk of reaccumulation after removal is low, assuming the lung is fully expanded and there is no persistent air leak.

Why this is the best choice: less than 150 mL in 24 hours signals resolution of the initial problem (bleeding or drainage) and stability after drainage, making removal safer while avoiding unnecessary prolongation of chest tube placement.

Why the other options don’t fit as well: a higher figure like 500 mL in 24 hours implies substantial ongoing drainage and a higher risk of recurrence if the tube is removed. Very strict thresholds such as under 100 mL or under 75 mL may be used in some protocols, but the standard teaching scenario commonly cited for safe removal uses the <150 mL criterion, balancing safety with timely removal.