Ambient and perfusion normalized temperature detector

Abstract

A body temperature detector is particularly suited to axillary temperature measurements of adults. The radiation sensor views a target surface area of the body and electronics compute an internal temperature of the body as a function of ambient temperature and sensed surface temperature. The function includes a weighted difference of surface temperature and ambient temperature, the weighting being varied with target temperature to account for varying perfusion rate. Preferably, the coefficient varies from a normal of about 0.13 through a range to include 0.09. The ambient temperature used in the function is assumed at about 80° F. but modified with detector temperature weighted by 20%.

Description

BACKGROUND OF THE INVENTION In recent years, infrared thermometers have come into wide use for detection of temperature of adults. For core temperature readings, infrared thermometers which are adapted to be inserted into the patient's ear have been extremely successful. Early infrared thermometers were adapted to extend into the ear canal in order to view the tympanic membrane and provide an uncorrected, direct reading of tympanic temperature which correlates with pulmonary artery temperature. More recently, however, to provide for greater comfort and ease of use, ear thermometers have been designed to provide corrected readings of the generally cooler distal ear canal. Such thermometers measure temperature of distal ear canal tissue and calculate arterial temperature via heat balance. The arterial heat balance approach is based on a model of heat flow through series thermal resistances from the arterial core temperature to the ear skin temperature and from the ear skin temperatu...

AI Technical Summary

Benefits of technology

Further, it has been determined that perfusion rate varies according to the patient's temperature. Under febrile (fever) conditions, metabolic demand increases and oxygen consumption increases at a rate greater than that required to sustain a temperature, thereby requiring an increase in perfusion and thus reducing the required weighting coefficient. Under normal, afebrile conditions, normal thermal regulation varies skin temperature over a wider range for skin temperature variation of several degrees with core temperature variation of only a few tenths of a degree.

It has been determined empirically that a more appropriate ambient temperature to be used in the heat balance computation is an assumed temperature of about 80° F. That assumed temperature can be improved by giving some weight to the sensed detector temperature, though significantly less than the 100% weight given in prior heat balance calculations.

Problems solved by technology

Unfortunately, the accuracy and repeatability of axillary infrared thermometry with neonates has not extended to older patients.

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