The ventilator volume is set at 575 mL. The low exhaled tidal volume alarm should be set at which value?

• A. 450 mL
• B. 525 mL
• C. 575 mL
• D. 500 mL

Answer: (D)

The idea behind a low exhaled tidal volume alarm is to catch real drops in delivered volume without tripping on normal breathing variability or small measurement errors. The threshold should be set below the intended tidal volume so that only meaningful reductions trigger the alarm, helping you detect problems like leaks, obstructions, or circuit issues early.

With the volume set at 575 mL, choosing 500 mL provides a margin of about 75 mL (roughly 13% below the set volume). This balance helps tolerate minor fluctuations from the circuit and measurement noise, while still signaling when the patient isn’t receiving enough volume.

Setting 525 mL would be a smaller margin and could result in more frequent alarms for normal variability, whereas 450 mL is a larger margin that might delay detection of clinically important drops. Setting it equal to 575 mL would produce no alarm at all. Therefore, 500 mL is the most practical choice.