Signs of cerebral herniation and optimal ETCO2 range for these patients:
a. Hyperventilation and ETCO2 less than 20 mmHg
b. Bradypnea and ETCO2 greater than 50 mmHg
c. Hypertension and ETCO2 less than 30 mmHg
d. Decerebrate posturing and ETCO2 30-35 mmHg