Effect of facial cooling on mucosal blood flow in the mouth in humans.

1. To determine the effects of facial cooling on intraoral thermal events, we placed a thermal conductivity sensor on the buccal surface of the left cheek in six normal and six asthmatic subjects. Room temperature and cold stimuli were then applied to the integument surface of both sides of the face while mucosal surface temperature and thermal conductivity, as an index of blood flow, were recorded. 2. The room temperature challenge had no effect. Application of the cold stimulus to the exterior of the left cheek caused a monotonic decrease in temperature in the mouth in all subjects and was associated with a change in thermal conductivity in which blood flow increased and then fell to baseline despite a continued drop in temperature. These responses were purely local in that cooling of the right side of the face did not change the temperature or blood flow on the left side. No differences were noted between the asthmatic and normal subjects. 3. The data indicate that lowering the temperature of the skin of the face produces significant alterations in the thermal environment within the mouth. With facial cooling, buccal temperature falls and mucosal blood supply transiently rises. This effect appears to be a purely local thermally mediated event. Facial pressure and cutaneous reflexes do not play a role. The above changes may contribute to the conditioning of inspired air during oral breathing.