Check the 3MTM SpotOnTM Temperature Monitoring System website to ensure you have the most recent version of this document.

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Overview and Operation

How does it work?

The SpotOn temperature monitoring system uses zero-heat-flux thermometry to accurately measure a person’s core temperature as characterized in Figure 3 below. 1) The SpotOn temperature monitoring system gently warms the sensor creating an isothermal zone under the sensor. 2) Once equilibrated to the core temperature, skin-surface heat loss to the environment is prevented and a zero-heat-flux condition is established. 3) When the temperature sensor reaches equilibrium with the patient’s core temperature, the SpotOn control unit displays an accurate, noninvasive measurement of the patient’s core temperature.

Skin

 

Temperature
Surface

 

Sensor

Deep Tissue 1)Placement and connection2)Equilibration - isothermal zone development3)Equilibrated - isothermal zone establishedFigure 3: Isothermal tunnel formation with zero-heat-flux technologySpotOn control unit

The SpotOn control unit displays noninvasive core temperature measurements obtained from the SpotOn temperature sensor. The current temperature is displayed numerically, and previous temperature data is displayed graphically as a temperature trend graph. When the sensor is plugged into the sensor cable, the control unit reads up to the last two hours of stored temperature data and displays the temperature trend graph. Disconnections of the sensor from the sensor cable are indicated by gaps in the temperature trend graph. The current temperature measurement can be continuously transmitted to a patient vital signs monitor through the optional SpotOn monitor cable using a standard YSI-400 type input.

SpotOn temperature sensor

The SpotOn sensor is constructed of two layers of medical grade foam and a flexible circuit which contains a resistive warming circuit, two calibrated thermistors, and nonvolatile memory. The information that generates the temperature trend graph is stored on the SpotOn sensor. If the patient is transferred from one location to another, the SpotOn sensor is disconnected from the SpotOn sensor cable so the sensor is left in place on the patient. The SpotOn sensor may be reconnected to a different SpotOn sensor cable and control unit when the patient arrives at the next point of care. Once the SpotOn sensor is reconnected to the SpotOn sensor cable, the system will begin to reequilibrate and will regenerate the stored temperature trend graph and display the patient’s current temperature. The act of disconnecting and reconnecting the SpotOn sensor from the sensor cable is indicated by a gap in the temperature trend graph.

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