Calculate the static compliance given the following clinical data: tidal volume 500 mL, peak in-spiratory pressure (PIP) 35 cm H2O, plateau pressure (Pplateau) 25 cm H2O, positive end-expiratory pressure (PEEP) 12 cm H2O,

measured unintended positive end-expiratory pressure (auto-PEEP) 3 cm H2O, and tubing com-pliance (CT) 2.5 mL/cm H2O.
a. 17.5 mL/cm H2O
b. 34 mL/cm H2O
c. 36 mL/cm H2O
d. 47.5 mL/cm H2O

ANS: D
Static compliance = tidal volume (VT) − [(Pplateau − PEEP) ? CT]/(Pplateau − PEEP) = 500 − [(25 − 15) ? 2.5]/25 − 15 = (500 − 25)/10 = 47.5 mL/cm H2O.