[A thermodynamic model to predict oxygen consumption and peripheral blood flow in the newborn infant. II. Its validity under steady-state conditions].

A thermodynamic model, which allows to predict oxygen consumption and peripheral blood flow from temperature measurements, was tested for its validity in newborn infants. This model is based on the close relation between 1) oxygen consumption and heat production and 2) between circulation and heat convection. In this model 3 temperatures on the patient, 2 temperatures in the environment and geometrical variables (weight, length) are measured and known physiological relations used to calculate oxygen consumption (VO2) and peripheral blood flow (pBF). In 15 newborns the VO2 was synchroneously determined by means of the flow-trough method and the thermomodel. The VO2 and the VO2/kg bodyweight respectively correlated significantly (p less than 0.01) with the directly measured VO2 (correlation coefficients r 0.89 and 0.66 respectively). In 12 newborns the peripheral blood flow was synchroneously determined by means of the impedance plethysmography and the thermomodel. The directly measured peripheral blood flow correlated significantly (p less than 0.001) with the peripheral heat flow (r = 0.73, 34 measurements) and with the peripheral blood flow (r = 0.86, 34 measurements) both obtained from the thermomodel. The values of VO2 and pBF obtained by direct measurement and by the thermomodel are as closely correlated as values which were obtained comparing two conventional methods. These results demonstrate the validity of the theoretical model being suitable for clinical use to continuously predict VO2 and pBF.