Differentiation between arterial and venous vessel occlusion by simultaneous measurement with laser Doppler flowmetry and photoplethysmography

In abdominal cutaneous island flaps of rats (n = 16), either the artery or the vein was clamped, while flap perfusion was simultaneously monitored wit h laser Doppler flowmetry (LDF) and photoplethysmography (PPG) to identify the occluded Vessel responsible for insufficient perfusion. The LDF signal decreased promptly after arterial clamping. After venous clamping, only a s low decrease was noted. The LDF amplitude differed statistically significan tly between arterial and venous clamping only up to 90 sec after onset but not thereafter, allowing no further distinction between the two types of ve ssel occlusion. Power spectral analysis of the LDF signal did not show clea r differences in frequency ranges between arterial and venous occlusion. In contrast, PPG measurements demonstrated significant differences between bo th perfusion disorders throughout the entire observation period. These resu lts suggest that dependable differentiation between prolonged arterial and venous vessel occlusion is not possible based on the amplitude or power spe ctral analysis of the LDF signal alone. PPG may be reliably used to differe ntiate between arterial and venous perfusion disorders.