Extensive investigations of failing skin flaps have been recorded in the literature. The histologic,' metabolic,2 and physiologic3 characteristics of the failing skin flap have been examined. Little attention has been devoted to the study of acute microcirculatory hemodynamic changes in the skin flap with arterial or venous occlusion.
The recent development and application of laser Doppler flowmetry (LDF) to the measurement of red blood cell flux within the capillary bed may reveal further information about waveforms of the microcirculation. Hirimoto and associates5 have described the waveform of the microcirculation using this method. In the present study, waveforms of the microcirculation were investigated in relation to varying degrees of arterial or venous occlusion in the saphenous island flap of the dog and the human digit.
MATERIALS A N D METHODS
Laser Doppler flowmetry is based on the Doppler principle and is a measure of blood flux within the skin. The Doppler principle states: light that strikes a moving object will undergo a shift in frequency proportional to the velocity of the moving object.6 Laser light is coherent, monochromatic, and may be transmitted through a fiberoptic cable to the skin surface. Reflected laser light from both nonmoving tissue (reference beam) and moving red blood cells (Dop-