ABSTRACT
A dual wavelength photoplethysmography (PPG) and laser Doppler flowmetry (LDF) sensor was developed to investigate the suitability of these techniques for monitoring bowel viability intraoperatively. Clinical measurements were obtained from thirty patients undergoing bowel surgery. Three measurements were performed at different stages of the operation. The amplitude of infrared PPG decreased from the baseline measurement to the pre-anastomosis measurement by 36% and LDF flux decreased by 21% for the same measurements. An increase of 33% in amplitude for infrared PPG was observed from the pre-anastomotic to post-anastomosis measurement; the equivalent increase was not seen for LDF flux. The results revealed that the sensor could potentially indicate changes in perfusion and blood flow at critical phases of surgery, thereby assisting in the early detection of inadequate blood supply in bowel tissue. The results also suggest that laser Doppler is more sensitive to movement artefact compared to PPG.
