The therapist is about to determine the respiratory system compliance of a patient receiving mechanical ventilation. The patient's tidal volume is 700 ml. Based on the pressure-time scalar presented below, which of the following pressures or pressure gradients does the therapist need to use in this calculation?

A. The pressure reading at "f" needs to be used.
B. The pressure gradient from "g" to "f" must be selected.
C. The "g-h" pressure gradient must be chosen.
D. The pressure measured at point "g" needs to be taken.

?ANS: C
A. Incorrect response: Label "f" on the pressure-time tracing represents the peak inspiratory pressure. This pressure is used in the denominator (minus total PEEP) of the formula used to calculate the dynamic compliance.
B. Incorrect response: The pressure gradient "f" minus "g" is the pressure generated during VT delivery required to overcome airway resistance. Specifically, these labels signify the difference between the peak inspiratory pressure minus the plateau pressure.
C. Correct response: The pressure gradient required for the calculation of respiratory system compliance is plateau pressure minus total PEEP. On the pressure-time scalar here, the gradient is "g" minus "h."
D. Incorrect response: The pressure measure at "g" is the plateau pressure. The plateau pressure is used in the denominator (minus total PEEP) of the formula used to calculate the static compliance.