A Proposed Miniature Red/Infrared Oximeter Suitable for Mounting on a Catheter Tip

A miniature red/infrared oximeter has, been developed that is suitable for mounting on a catheter tip and does not use fiber-optics. Two light-emitting diodes (LED's) and a phototransistor are mounted on the catheter tip such that conversion between optical and electrical signals takes place right at the tip. In vitro calibration shows that the infrared-to-red reflectance ratio is essentially linearly dependent on oxygen saturation (OS). The calibration constants depend on hematocrit and on blood flow.