When decreasing suction from -40 to -20 cm H2O, what action helps release pressure?

• A. Increase the suction to a higher negative pressure
• B. Check for kinks in the tubing
• C. Remove the chest tube
• D. Depress the negative pressure vent at the top of the system when moving from high to low

Answer: (D)

When you lower suction from a strong negative pressure to a milder one, the system can still hold air that’s been pulled in, so pressure inside the suction control chamber may stay more negative than the new setting. Depressing the negative-pressure vent at the top of the system opens the chamber to ambient air, allowing air to enter and the internal pressure to equalize with room pressure. This releases the excess negative pressure and lets the system settle smoothly to the new -20 cm H2O setting without a sudden mismatch in pressure.

Increasing suction would push pressure more negative rather than release it, checking for kinks helps with flow issues but doesn’t directly equalize pressure when changing settings, and removing the chest tube would stop drainage entirely.