A 57-year-old, 5'3", 165 lb female patient arrives in the open heart unit following coronary artery bypass surgery

The patient has a history of diabetes and no history of pulmonary disease. The most appropriate initial volume-controlled continuous mandatory ventilation (VC-CMV) settings are which of the following?
a. VT = 220 mL, rate = 25 breaths/min, PEEP = 10 cm H2O
b. VT = 360 mL, rate = 15 breaths/min, PEEP = 5 cm H2O
c. VT = 550 mL, rate = 12 breaths/min, PEEP = 12 cm H2O
d. VT = 750 mL, rate = 10 breaths/min, PEEP = 8 cm H2O

ANS: B
First calculate ideal body weight (IBW) for a female, using the formula 105 + 5(ht – 60). This patient's IBW is 55 kg. Minute ventilation is about 100 mL/kg IBW, which would be 5.54 L/min. Since the patient is post-op, the tidal volume should be set to between 5 and 8 mL/kg with rates of between 10 and 20 breaths/min. This would make the appropriate tidal volume range 275-440 mL. This fact eliminates choices "A," "C," and "D." The positive end-expiratory pressure (PEEP) may also be too high for a post-op open heart patient in choices "A," "C," and "D."