* We also found cerebral hypoxia (expression levels and prolonged periods of low PbtO2 value) were independent risk factors of mortality include low PbtO2 <10 mm Hg after placement; average PbtO2 lower <15 mmHg coordinate with average ICP higher > 30 mmHg; PbtO2 lower <10 mm Hg lasted over 7 hours and the poor outcome is PbtO2 lower <15 mmHg lasting over 4 hours in patients with severe TBI.