Thermal-dilution technics.

نویسنده

K F HOSIE

چکیده

• .All thennal methods for the study of the circulation depend upon the induction of a change in the heat content of! the blood stream. As a result of the change, a particular time-dependent spatial distribution of temperature is developed in the blood according to the manner in which the change is brought about and as a function of the prevailing pattern of blood flow. In a general sense, any thermal method could be considered to involve thermal dilation, but, in keeping with the usual meaning of "indicator dilution," the term "thermal dilution" will be restricted to refer to those technics in which, following the artificial induction of a known change in the blood heat content at some point in the circulation, the resulting temperature change is followed at such a distance downstream that an even distribution of heat is presumed to have been developed over the whole vascular cross section. The induced change in heat content in a thermal-dilution technic may be either positive or negative, that is, heat is either added to or abstracted from the blood stream. One may speak, instead, of positive or negative heat addition in accordance with whether an increase or decrease in temperature is induced, but it is perhaps simpler and just as acceptable to refer to the addition of heat or cold. The change in the heat content of the blood may be achieved in several ways, for example by generation of heat within the blood itself (as is ideally the case in the diathermy-thermostromuhr of Eein), by conduction of heat across a vessel wall, by an intravaseular heating or cooling device, or by the injection into the blood stream of a mass miscible with the blood and at a different temperature. Thermal dilution using this last method of changing blood heat content most closely resembles other common indicator-dilution methods

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