What tidal volume would the therapist need to set on the ventilator to achieve the desired tidal volume of 750 ml?

A. 760 ml
B. 775 ml
C. 840 ml
D. 1000 ml

?ANS: C?A. Incorrect response: See the explanation associated with choice C.
B. Incorrect response: See the explanation associated with choice C.
C. Correct response: Because 90 ml of volume are compressed in the patient's breathing circuit at the end of inspiration, the therapist must add 90 ml to the original tidal volume, which was set at 750 ml. Therefore the therapist needs to reset the tidal volume to 840 ml to compensate for the 90 ml "lost" in the tubing. That is,
set VT – Vcompressed = patient tidal volume
840 ml – 90 ml = 750 ml
D. Incorrect response: See the explanation associated with choice C