Which feature should be checked to confirm suction is functioning after setting to a lower negative pressure?

• A. The delta mark alignment on the E chamber
• B. The drainage color
• C. The external monitor reading
• D. The seal water temperature

Answer: (A)

In a chest tube system with suction, the way you confirm that suction is actually being delivered is by checking the delta mark in the suction control chamber (often labeled the E chamber). When you set a lower negative pressure, the delta mark should align with the corresponding line on that chamber. This alignment shows the system is reaching and maintaining the new suction level. If it isn’t aligned, suction may not be functioning properly due to a kink, leak, or regulator issue, and you’d need to inspect and adjust.

Drainage color doesn’t indicate suction function, and external monitor readings or seal water temperature don’t reliably reflect whether suction is being delivered. The delta mark alignment is the direct cue that suction is active at the set level.