Abstract: A cardiac output measurement device volumetrically heating a predefined quantity of blood flowing through a heart by arbitrarily applying a containable energy field to the blood using a thermodilution catheter having an emitter that uniformly emits electromagnetic radiation. Blood temperature is measured at the pulmonary artery by a sensor that provides a signal representing the temperature of the mixed blood to a controller. The controller determines the flow rate, or cardiac output, by performing a heat balance analysis based upon the applied power and resultant blood temperature. The cardiac output measurement device includes a catheter having an emitter and, preferably, a temperature sensor located at its distal end. The catheter is coupled to a laser or other energy source capable of generating containable electromagnetic radiation, such as an ultraviolet or microwave energy source.

Abstract: A technique for measuring temperature by a thermistor sensor which technique provides for a linearization of the temperature sensed by the thermistor by utilizing circuitry which responds to the thermistor and produces an output which is an exponential function of the temperature sensed by the thermistor. A further circuit, such as a logarithmic amplifier, responds to such output to provide a signal which represents the temperature.

Abstract: A device for heating a medium with which the device is in thermal contact for use in determining the thermal or flow properties of the medium. The device has a heater for supplying heat to the medium at an interface of the device with the medium and a temperature sensor for sensing the temperature at such interface.

Abstract: A method for determining the properties of a medium by activating temperature changing means to change the temperature of the medium from a first unperturbed temperature to a second different temperature during a first time period and permitting the temperature to relax to a final unperturbed temperature during a second time period. In a particular embodiment, for example, the intrinsic thermal conductivity and diffusivity of the medium are calculated during a selected portion of the first time period assuming an arbitrary value for the perfusion, and the perfusion of the medium is calculated during a selected portion of the second time period using the calculated intrinsic thermal conductivity and diffusivity. The calculated perfusion is then used to recalculate the intrinsic thermal conductivity and diffusivity during the selected portion of the first time period and the perfusion is then recalculated using such recalculated intrinsic thermal conductivity and diffusivity.