Effect of high local temperature on reflex cutaneous vasodilation

Area of Science:

• Physiology
• Thermoregulation
• Cardiovascular Science

Background:

• The body uses reflex vasodilation to dissipate heat.
• The impact of localized high skin temperature on this reflex is not fully understood.

Purpose of the Study:

• To investigate if high local forearm skin temperature (Tloc) affects reflex cutaneous vasodilator responses to whole-body heat stress.

Main Methods:

• One forearm was locally warmed to 42°C, while the other remained at ambient temperature.
• Whole-body skin temperature (Tsk) and internal temperatures were elevated in two protocols.
• Forearm blood flow (FBF) was monitored in both arms to measure skin blood flow (SkBF).

Main Results:

• In protocol 1, the locally warmed arm showed minimal FBF increase (0.76 ml/100ml/min) during heat stress, while the normothermic arm increased by 8.84 ml/100ml/min.
• In protocol 2, FBF in the normothermic arm converged with the warmed arm in most cases, not surpassing it.
• Local warming to 42°C attenuated or abolished reflex vasodilation.

Conclusions:

• Local warming of the forearm to 42°C prevents reflex cutaneous vasodilation during whole-body heat stress.
• This attenuation is likely due to reduced basal tone in cutaneous arteriolar smooth muscle.
• A local temperature of 42°C appears to achieve maximum forearm skin blood flow after sufficient duration.