The purpose of this study is to establish the accuracy of the non-invasive Mespere Oximeter that estimates venous oxygen saturation.

Correlation of Venous Oxygen Saturation Measurements by Non-invasive Mespere Venous Oximeter and Central Venous Catheter

Correlation of Venous Oxygen Saturation Measurements by Non-invasive Mespere Venous Oximeter vs Venous Oxygen Saturation From Blood Samples From the Jugular Vein vs Central Venous Oxygen Saturation vs Mixed Venous Oxygen Saturation, Measured by a CO-Oximeter.