Cerebral Arterial Oxygen Saturation Measurements Using a Fiber-Optic Pulse Oximeter

A pilot investigation was undertaken to assess the performance of a novel fiber-optic cerebral pulse oximetry system. A fiber-optic probe designed to pass through the lumen of a cranial bolt of the type used to make intracranial pressure measurements was used to obtain optical reflectance signals directly from brain tissue. Short-duration measurements were made in six patients undergoing neurosurgery. These were followed by a longer duration measurement in a patient recovering from an intracerebral hematoma. Estimations of cerebral arterial oxygen saturation derived from a frequency domain-based algorithm are compared with simultaneous pulse oximetry (SpO(2)) and hemoximeter (SaO(2)) blood samples. The short-duration measurements showed that reliable photoplethysmographic signals could be obtained from the brain tissue. In the long-duration study, the mean (+/- SD) difference between cerebral oxygen saturation (ScaO(2)) and finger SpO(2) (in saturation units) was -7.47(+/- 3.4)%. The mean (+/- SD) difference between ScaO(2) and blood SaO(2) was -7.37(+/- 2.8)%. This pilot study demonstrated that arterial oxygen saturation may be estimated from brain tissue via a fiber-optic pulse oximeter used in conjunction with a cranial bolt. Further studies are needed to confirm the clinical utility of the technique.