Abstract
Skin is a representative microvascular bed providing easy access for the study of capillary haemodynamics. In this preliminary evaluation the authors have used laser Doppler flowmetry to measure the response of skin capillary blood flow to local thermal stimulation. The purpose of the study was to see if such measurements can be used to derive useful clinical information. Thirty subjects, fifteen male and fifteen female, were selected to establish 'normal' patterns of behaviour. All normal subjects studied showed similar patterns of response. There was a slight downward trend in red-blood-cell flux with age. Periods of vasomotor activity were present at rates ranging from 4-17 cycles/min. The mean temperature rise in the heated skin area was 4 degrees C. Blood flow over this range increased by a factor of ten or more. Clinical cases studied were strictly limited to three categories of disease with known or suspected microvascular changes: algodystrophy, lower-limb ischaemia and diabetic neuropathy. All the clinical cases studied showed deviations from the normal pattern. Patients with algodystrophy had impaired peripheral vascular function in the affected area. Patients with lower-limb ischaemic problems all had poor peripheral perfusion. In the limited number of diabetic neuropathic feet studied two patterns emerged: patients with no evidence of ulceration displayed striking vasomotor activity; those with more severe problems had reduced red-blood-cell flux and little evidence of vasomotor control.