MULTI-WAVELENGTH SPATIAL DOMAIN NEAR INFRARED OXIMETER TO DETECT CEREBRAL HYPOXIA-ISCHEMIA

摘要

The inventions involve methods and apparatuses for measuring cerebral O2 saturation and detecting cerebral hypoxia-ischemia using multi-wavelength near infrared spectroscopy (NIRS). In practice, an apparatus like the embodiments described herein may be secured to the head of a patient believed to be potentially suffering from cerebral hypoxia-ischemia. Then, light of a particular near infrared wavelength is be sent through an amount of brain tissue using a near infrared light emitter positioned on the apparatus. At least three intensities of the light that passes through the amount of brain tissue is then measured using at least three photodiode detectors positioned at distinct distances from the emitter, also located on the apparatus. This process is repeated for at least two other wavelengths of light. One of the wavelengths used is substantially at an isobestic point for oxy-hemoglobin and deoxy-hemoglobin, but the other two may be any wavelengths within the near infrared spectrum (700nm to 900nm), so long as one of the additional wavelengths is greater than the isobestic point and the other is less than the isobestic point. To calculate the saturation of tissue oxygenation, the measured intensities are then plugged into an algorithm derived from the Beer-Lambert law and based at least upon one or more ratios of measured intensities at two or more wavelengths and one or more ratios of measured intensities at two or more photodiodes. From the calculated saturation of tissue oxygenation, a physician may determine whether or not the patient suffers from cerebral hypoxia-ischemia.