During the first 5 minutes of thermotherapy, how should the skin respond to light pressure?

• A. Swell
• B. Blanch with light pressure
• C. Turn red
• D. No change

Answer: (B)

In the early minutes of thermotherapy, the skin’s superficial blood vessels dilate to bring more blood to the surface for heat dissipation. When you apply light pressure, the circulating blood in those capillaries is momentarily displaced, which causes the skin to blanch. This blanching shows that the microvasculature is still intact and capable of responding to pressure, and after you release, blood returns quickly and you may see a brief blush as reactive hyperemia occurs. If the skin didn’t blanch, it could indicate impaired perfusion, but blanching with light pressure is the normal, expected response in the first few minutes of heating.