Thermal characterisation of the umbilical cord at birth through non invasive methods.

Abstract

There is growing evidence that infants benefit from receiving extra blood from the placenta at birth, some experts recommend delaying the cord clamping until the placental to infant blood transfusion is below a certain level. The aim of the present work is to add information to infer this moment. To accomplish this purpose a study case is analysed and presented. The studied period of time starts when the infant is delivered and finalizes with the clamping of the cord. Through thermography, the superficial temperature of the umbilical cord is obtained as experimental data. Anatomically, the umbilical cord is composed by two arteries and one vein surrounded by the Wharton’s jelly, a conjunctive tissue that provides the cord with an elastic and cushion effect. A two-dimensional model of a cross section of the mentioned tissue is developed using COMSOL to solve the bio-heat equation. Certain parameters that characterize the model are undefined: physical properties of the Wharton’s jelly, internal heat coefficients and the time when the blood flow stops, t∗. A sensitivity analysis is performed to identify which of these parameters have greater impact on the surface’s temperature of the cord. The study suggests that k, ω and t∗ are the more influential parameters and are then determined by calibrating the model in order to fit the infrared measured data. For this particular case it is possible to infer the moment when the blood flow inside the vessels of the cord present a change on its behaviour, being this value: t∗ = 255 s.