Cerebral near infra-red spectroscopy in traumatic brain injury as a potential independent monitoring modality and alternative to invasive tissue oxygen tension sensors

Background: Traumatic brain injury (TBI) is pathology of growing international importance. Near Infrared spectroscopy (NIRS) represents a non-invasive, cost effective and easily applies cerebral tissue monitoring modality with the potential to direct therapy and guide management decisions. Currently the use of this technology within mainstream TBI care is limited considering its potential inherent advantages. Recent advances in NIRS parameter recovery techniques and data processing potentially offer an improvement on previously evaluated technology. Frequency domain (FD) parameter recovery NIRS is one such advancement now available in clinically viable and commercially available devices. This technology has not yet been evaluated within the context of TBI care. Aims: i) To assess the current evidence within the published literature regarding the use of NIRS within the field of TBI management. ii) To compare the abilities of a frequency domain clinically viable point of care NIRS device to radiological and invasive gold standards in measuring changes in cerebral physiology. Methods: A number of specific original investigations to assess the abilities of clinically viable NIRS technology benefiting from FD parameter recovery for use in the management of TBI patients were undertaken along with a review of the existing literature. Results. NIR.S has demonstrated certain useful abilities in the monitoring of cerebral oxygenation in the care of individuals who have sustained a TBI, however sufficient evidence does not exist to support its independent use in TBI. The FD NIRS device tested demonstrated good correlation with fMRI (Valsalva and Hyperventilation), and equivalent abilities in differentiating activity within superficial extra-cranial and cerebral tissue. Manipulating of blood flow into the overlying extra-cranial tissue did not significantly affect the output parameters seen in these models. However the FD NIRS device tested did not demonstrate sufficient abilities to replace invasive brain tissue oxygen tension measurement in TBI patients. Also, within the context of controlled hypoxia (relevant to TBI) no discernable advantage was observed in utilising a device benefiting from frequency domain parameter recovery. Conclusion: NIRS still remains the best available prospect for a non-invasive monitoring modality to direct therapy and guide management in TBI care. However, further development and translation of the multitude of advancements in NIRS technology achieved recently in the science of biological optics may be required to realise this potential

Hypoxic-State Estimation of Brain Cells by Using Wireless Near-Infrared Spectroscopy

Near-infrared spectroscopy (NIRS) is a modern measuring technology in neuroscience. It can be used to noninvasively measure the relative concentrations of oxyhemoglobin (OxyHb) and deoxyhemoglobin (DeoHb), which can reflect information related to cerebral blood volume and cerebral oxygen saturation. Therefore, it has the potential for noninvasive monitoring of cerebral ischemia. However, there is still a lack of reliable physiological information on the relationship between the concentrations of OxyHb and DeoHb in cerebral blood and the exact hypoxic state of brain cells under cerebral ischemia. In this study, we describe a wireless multichannel NIRS system, which we designed to noninvasively monitor the relative concentrations of OxyHb and DeoHb in bilateral cerebral blood before, during, and after middle cerebral artery occlusion. By comparing the results with the lactate/pyruvate ratio measured by microdialysis, we investigated the correlation between the relative concentrations of OxyHb and DeoHb in cerebral blood and the hypoxic state of brain cells. The results showed that the relationship between the concentration changes of DeoHb in cerebral blood and the hypoxic state of brain cells was significant. Therefore, by monitoring the changes in concentrations of DeoHb, the wireless NIRS can be used to estimate the hypoxic state of brain cells indirectly