Modeling the Effect of EtCO2 on Cerebral Oxygenation

Initial data collection during BCP was performed following three conditions were satisfied: after start of surgery; at least 15 min after BCP (for stabilization of MAP); after ventilation frequency was adjusted to produce EtCO2 of 27-29 mmHg with tidal volume of 8 ml/kg. Data was collected every 3 min after decreasing ventilation frequency by 1-2 breaths/min to increase EtCO2 until 42-45 mmHg. Once the value of EtCO2 42-45 mmHg was reached, ventilator frequency was increased in the same way to decrease EtCO2 until 27-29 mmHg. Fraction of inspired oxygen of 50% was maintained and end-tidal desflurane concentration was adjusted to achieve bispectral index values of 40-55 during data collection.