A novel wireless optical technique for quantitative evaluation of cerebral perfusion pressure in a fluid percussion animal model of traumatic brain injury

Background: Cerebral perfusion pressure (CPP) calculated by mean arterial pressure (MAP) minus intracranial pressure (ICP) is related to blood flow into the brain and reflects cerebral ischemia and oxygenation indirectly. Near-infrared spectroscopy (NIRS) can assess cerebral ischemia and hypoxia non-invasively and has been widely used in neuroscience. However, the correlation between CPP and NIRS, and its potential application in traumatic brain injury, has seldom been investigated. Methods: We used a novel wireless NIRS system and commercial ICP and MAP devices to assess the trauma to rat brains using different impact intensity. The relationship between CPP and NIRS parameters with increasing impact strength were investigated. Results: The results showed that changes in CPP (∆CPP), oxy-hemoglobin {∆[HbO₂]}, total-hemoglobin {∆[HbT]}, and deoxy-hemoglobin were inversely proportional to the increase in impact intensity, and the correlations between ∆CPP, NIRS parameters {∆[HbO₂], and ∆[HbT]} were significant. Conclusions: The NIRS system can assess cerebral ischemia and oxygenation non-invasively and changes of HbO₂ and HbT may be used as reference parameters to assess the level of CPP in an animal model of traumatic brain injury.