Intra-Operative Pulse Oximetry

Bowel resection surgery is a commonly performed operation used to treat a variety of gastro-intestinal tract disorders, including cancer. The surgery entails excising the diseased portion of intestine, and then creating a surgical anastomosis, or reattachment of the remaining ends. One of the major complications following bowel resection surgery is breakdown or leakage from the anastomosis, which affects 20% of patients, with an associated 10-15% mortality rate. The surgical creation of anastomosis frequently involves dividing blood vessels and can introduce unrecognized twists and tension on the intestine. As a result, the blood supply to the site of anastomosis is often hampered, limiting the oxygen supply that is essential for adequate anastomotic healing. We are proposing a device that enables surgeons to obtain real-time feedback on local tissue oxygen saturation (SpO2) during operative procedures. Such data will not only help surgeons realize any bowel oxygenation compromising maneuvers, but also help perform an anastomosis at the site of maximal tissue oxygenation, thus minimizing the occurrence of postoperative anastomotic leakage and improve patient outcomes. This report details the specifications, fabrication, operation and performance of a handheld wireless pulse oximeter suitable for the intraoperative measurement of tissue SpO2 during bowel surgery. The device adapts principles and technology developed for non-invasive pulse oximetry, and introduces tissue interface, physician tools, and signal processing algorithms for intra-operative application. The handheld device includes local display of SpO2 level (⁠$<1s$ refresh) at the contacted tissue, and signals the operator on degraded signal quality/faults. An onboard micro-controller digitizes and processes signals transduced through a controlled LED array. Signal processing and display parameters were optimized for operating room conditions. A disposable functionally-transparent cover provides both device and tissue protection. Through serial or Bluetooth wireless transmission (250 Kbps), SpO2 and pulse signals can be processed on a PC or operating room VI. The incorporation of a pressure sensor to increase accuracy and robustness is explored. The device was validated intra-operatively on rodent and bovine surgical models.