Review Question - QID 104319

A 14-year-old boy presents to the emergency department with altered mental status preceded by abdominal pain while camping. He did not eat anything unusual from the wilderness and has not had any vomiting or diarrhea. He has no known medical problems and takes no medications. He is doing well in school and plays soccer. His temperature is 100.5°F (38.1°C), blood pressure is 95/55 mmHg, pulse is 130/min, and respirations are 30/min. His weight is 68 kg. His pupils are equal and reactive to light bilaterally. The remainder of the physical exam is unremarkable. The results of his basic metabolic panel are displayed below:

Serum:
Na+: 116 mEq/L
Cl-: 70 mEq/L
K+: 4.0 mEq/L
HCO3-: 2 mEq/L
BUN: 50 mg/dL
Glucose: 1,010 mg/dL
Creatinine: 1.2 mg/dL

The remainder of his labs are pending. The patient becomes bradypneic and is intubated. His ventilator is set to volume control assist-control mode with a respiratory rate of 14/min, tidal volume (Vt) of 350 mL, positive end-expiratory pressure (PEEP) of 5 cm H2O, and fractional inspired oxygen (FiO2) of 40%. Intravenous fluids and appropriate medical therapy for this patient's condition are administered. An arterial blood gas obtained after 30 minutes on these settings shows the following:

pH: 7.05
Partial pressure of CO2 (pCO2): 40 mmHg
Partial pressure of O2 (pO2): 150 mmHg
Oxygen saturation (SaO2): 98%

Which of the following should be increased on the ventilator?