Relative vs. Absolute Cerebral Oximetry: does a Skin Pigmentation Effect Normal values on cardiopulmonary Support?

Real?time cerebral oximetry has been used to monitor perfusion in the brain. Two types of oximetry devices employed at our institution are: INVOS (Covidien, Mansfield, MA) and FORESIGHT (CAS Medical Systems, Branford, CT) which are relative and absolute cerebral oximetry, respectively. We have observed inaccuracy with relative oximetry compared to absolute oximetry in patients with dense melanin pigmentation.