Introduction 
During cold stress, increased cutaneous vasomotor tone (vasoconstriction) may be inferred from reductions in skin blood flow (SkBF), skin temperature (TSk) or cutaneous heat flux (QSk)1, 2. However, in other scenarios, such as direct local heating or intrapartum epidural anaesthesia, this proportionate relationship is absent3, 4. We propose that the relationship between skin blood flow, skin temperature and cutaneous heat flux may be modelled using a conservation of energy principle:
                                                                          QD = QSk + QSt                                                                                (1)
where QD is the rate of heat delivery to the skin and QSt is the rate of heat storage in the skin. The rate of heat delivery may be estimated as follows:
                                                                           QD α SkBF ⦁ (TC – TSk)                                                                   (2)
and the rate of heat storage as:
                                                                           QSt = pSk ⦁ dSk ⦁ cSk ⦁ δTSk                                                            (3)
where TC is core temperature, pSk is the density of skin (1.02 g/cm2), dSk is the thickness of skin (1.5mm), cSk is the specific heat capacity of skin (3.47 KJ/kg) and δTSk is the rate of change in skin temperature.  Inserting equations (2) and (3) into (1), we hypothesise that the re