Skin heating in conjunction with laser Doppler is a useful technique for clinical and physiological assessments. It is easy to apply but the underlying mechanisms are complex; much has been done over the past 20 years to better understand skin responses.

When the skin is heated the skin blood vessels normally dilate, more blood flows and laser Doppler can be used to quantify this increase. The increase in blood vessel diameter is not the only way in which blood flow increases; under normal, moderate room temperatures (20 – 24°C, not all of the smallest vessels (capillaries) have blood flowing through them. Blood flow also increases by more of the capillaries allowing blood to flow through them (‘capillary recruitment’).

One reason for the increase in blood flow during local skin heating, is that it protects the skin from damage: higher blood flow conducts heat away from the surface so that a lower temperature is maintained within the skin. When the whole body is heated, during exercise for example, increased blood flow to the skin enables more efficient heat loss so that core body temperature is regulated to healthy levels.

Applications of skin heating include;

Measurements of the highest blood flow reached (recorded by laser Doppler).

Area of flare (flow increase in the skin surrounding the area actually heated).

Standardisation of the measurement temperature (e.g. 30 – 34°C) so that it is constant for laser Doppler measurements on different patients.

Please refer to the Skin Heating theory for a complete review of the technique.