Venox is a propriety Venous Oximetry system, capable of measuring peripheral venous oximetry. In this ongoing study, Venox is being compared against mixed central venous oximetry during human cardiac surgery, with Fibre optic reflectance spectrophotometry being used as the gold standard, placed in the pulmonary artery. A background review of the Pulse oximetry, current venous oximetry techniques and the potential advantage of the VENOX system are discussed. Lessons learnt, Preliminary results, and future plans are included in discussion.