NOCTURNAL TEMPERATURE AND SUBCUTANEOUS BLOOD-FLOW IN HUMANS

The aim of this study was to investigate the possible relationship bet ween variations in local skin and body temperatures, and a subcutaneou s hyperaemia response during sleep in humans. Nocturnal subcutaneous b lood flow (SBF) was measured in the lower legs of 9 subjects for 8-12 h under outpatient conditions. The core temperature was measured by a tympanic membrane temperature sensor, and the local skin temperature w as measured by a skin temperature sensor. The Xe-133 wash-out techniqu e with portable CdTe(Cl) detectors was used for measurement of the SBF . The SBF increased significantly (P < 0.0001) after 1 h sleep, with t he hyperaemia persisting for 2 h. During the hyperaemic phase, the loc al skin temperature increased significantly (P < 0.0001) and then decr eased again in the post-hyperaemic phase (P < 0.01). The core temperat ure decreased significantly during the measurement period (P < 0.01). Separate ordinary linear regression analyses revealed no significant c orrelations between the measured temperature parameters and the blood flow levels during sleep. The results indicate no governing role of th e local skin or body temperatures on the local SBF. The local skin tem perature increased significantly secondary to the nocturnal subcutaneo us hyperaemia (i.e. active vasodilatation), which is believed to be in volved in a thermoregulatory effector mechanism.