Laser Doppler flowmetry in evaluation of lower limb resting skin circulation. A study in healthy controls and atherosclerotic patients.

Laser Doppler flowmetry (LDF) was used to evaluate lower limb resting skin perfusion in sixty subjects divided into four groups: healthy young and elderly controls, and patients with intermittent claudication or critical ischaemia. Measurements were performed in pulp skin containing microvascular AV anastomoses and in the skin of leg and thigh where these shunts are absent. In toe pulp controls and claudicators had higher perfusion values than in leg and thigh skin (p less than 0.01), indicating that the LDF method evaluates flow both in nutritional capillaries, AV anastomoses and in dermal vascular plexa. Elderly controls had higher flux values in the pulp than claudicators (p less than 0.01), and claudicators had higher values than patients with critical ischaemia (p less than 0.01), showing that LDF could differentiate between the clinical groups. Study of reproducibility confirmed that values were reproducible on a given population. Day to day variation was considerable in individual subjects, probably because of changes in sympathetic vascular tone and because of different vascular architecture in the measuring volumes which are only some few mm3. The fact that LDF measures total skin blood flow explains why several papers have found a poor correlation between LDF and methods which mainly evaluate nutritional blood flow. The method is non-invasive, continuous and easy to perform. Laser Doppler flowmetry may have several clinical applications, like evaluating progress of atherosclerotic disease or therapeutic effects of drugs or operations. To increase the reproducibility of resting skin flux measurements local heating of the skin is recommended and the measurements should be performed with an integrating probe, which averages the readings obtained at several positions simultaneously.