Detecting changes of arterial and venous blood flow in flaps

Island skin flaps based on the latissimus dorsi muscle were raised in domestic pigs. Simultaneous recordings of laser Doppler flowmetric and laser photometric values were made on the skin in the middle of the flap. Occlusion of either the artery or the vein of the pedicle was accompanied by very low laser Doppler flow values. In laser photometry the total intensity of backscattered light remained unchanged or was sightly increased during arterial occlusion. In response to venous occlusion, however, it decreased markedly. As venous outflow pressure was increased step by step, both the laser Doppler flow value and the laser photometry value fell proportionally; thus, the greater the increase in pressure the lower were the steady state levels of both variables. Stepwise reductions of arterial inflow pressure were followed by proportional decreases in both mean blood volume flow, recorded using electromagnetic flowmetry, and in laser Doppler flowmetric values. However, laser photometric values varied only minimally. Laser Doppler flowmetry thus might be a useful clinical aid in detecting decreased blood flow in transferred flaps, and laser photometry may determine whether the decreased flow is due to arterial or venous causes.