Method for optimizing skin cooling level of an occupant support surface

Abstract

A method and apparatus for withdrawing heat from a surface for supporting a person including determining a vasoconstriction threshold for the person and operating the apparatus to maintain the rate of heat withdrawal below the vasoconstriction threshold for the patient.

1 . A method for controlling performance of a heat withdrawal coverlet for removing heat from a surface supporting a person, the coverlet having a flow path for guiding a stream of air along at least a portion of the surface, comprising:
 measuring heat withdrawal rate of the coverlet over time;   identifying when the coverlet is withdrawing heat at first rate;   increasing the heat withdrawal rate from the first rate between in predefined increments;   measuring a skin temperature of an occupant at each increment of increase of the heat withdrawal rate;   recording the skin temperature of the occupant at each increment of increase of the heat withdrawal rate;   comparing the skin temperature of the occupant and the heat withdrawal rate increment to determine a slope of the relationship between the skin temperature of the occupant and the heat withdrawal rate; and   determining the skin temperature and the heat withdrawal rate at which the slope breaks in linearity to determine a vasoconstriction threshold.   
     
     
         2 . The method of  claim 1 , wherein the relationship between the skin temperature of the occupant and the heat withdrawal rate is an inverse relationship such that as the heat withdrawal rate decreases, the skin temperature of the occupant increases. 
     
     
         3 . The method of  claim 2 , wherein an optimal heat withdrawal rate is located prior to a slope break, the optimal heat withdrawal rate configured to maximize the heat withdrawal from the occupant. 
     
     
         4 . The method of  claim 3 , wherein the optimal heat withdrawal rate determines the rate at which heat is withdrawn from the skin of an occupant prior to vasoconstriction. 
     
     
         5 . The method of  claim 2 , wherein the slope decreases after breaking such that the measurement of the slope before the break is greater than the measurement of the slope after the break. 
     
     
         6 . The method of  claim 1  further comprising the steps of:
 decreasing the heat withdrawal rate after identifying the vasoconstriction threshold; 
 waiting an amount of time so that the skin temperature of the occupant decreases and returns to a baseline temperature; 
 identifying when the coverlet is withdrawing heat at a predefined rate; 
 incrementally increasing the heat withdrawal rate from the predefined rate until the optimal heat withdrawal rate is reached; and 
 maintaining the optimal heat withdrawal rate. 
 
     
     
         7 . A method for controlling performance of a heat withdrawal coverlet for removing heat from a surface supporting a person, the coverlet having a flow path for guiding a stream of air along at least a portion of the surface, comprising:
 measuring the skin temperature of a person on the coverlet;   varying the operation of the coverlet to vary the heat withdrawal rate;   monitoring the slope of the rate of change in skin temperature to the heat withdrawal to determine a change in linearity of the slope;   using the heat withdrawal rate at the change in linearity to determine vasoconstriction threshold for the person;   maintaining the heat withdrawal rate of the coverlet to operate below the vasoconstriction threshold of the person.   
     
     
         8 . An apparatus for controlling the heat withdrawal from a patient's skin comprising:
 a coverlet having an upper surface that is vapor permeable and air impermeable, the coverlet have inlet and an outlet and an interior space that provides a flow path for air to flow from the inlet to the outlet, the coverlet including a sensor for monitoring the heat withdrawal from the coverlet and a sensor for measuring the temperature of the skin of a person supported on the upper surface of the coverlet;   an air treatment system having an inlet for admitting ambient air and an outlet for discharging treated air,   a conduit connecting the outlet of the air treatment system to the inlet of the coverlet, and   a controller including a processor and a memory device, the memory device including instructions that, when executed by the processor, cause the controller to monitor the sensors and operate the air treatment system to vary the heat withdrawal from the coverlet and monitor the skin temperature of the person to determine the slope of the rate of change in skin temperature to the heat withdrawal to determine a change in linearity of the slope, use the heat withdrawal rate at the change in linearity to determine vasoconstriction threshold for the person, and maintain the heat withdrawal rate of the coverlet to operate below the vasoconstriction threshold of the person.   
     
     
         9 . The apparatus of  claim 8 , wherein the air treatment system includes a blower under the control of the controller to vary the heat withdrawal. 
     
     
         10 . The apparatus of  claim 8 , wherein the air treatment system includes a cooler for cooling the ambient air under the control of the controller to vary the heat withdrawal. 
     
     
         11 . The apparatus of  claim 8 , wherein the air treatment system includes a heater for heating the ambient air under the control of the controller to vary the heat withdrawal. 
     
     
         12 . The apparatus of  claim 8 , wherein the air treatment system includes a water removal system for removing water from the ambient air under the control of the controller to vary the heat withdrawal. 
     
     
         13 . The apparatus of  claim 8 , wherein the air treatment system includes a valve assembly for controlling the flow of the air out of the air treatment system under the control of the controller to vary the heat withdrawal. 
     
     
         14 . The apparatus of  claim 8 , wherein the memory device further includes instructions that, when executed by the processor, cause the controller to,
 decrease the heat withdrawal rate after identifying the vasoconstriction threshold;   wait an amount of time so that the skin temperature of the occupant decreases and returns to a baseline temperature;   identify when the coverlet is withdrawing heat at a predefined rate;   incrementally increase the heat withdrawal rate from the predefined rate until the optimal heat withdrawal rate is reached; and   maintain the optimal heat withdrawal rate.   
     
     
         15 . The apparatus of  claim 14 , wherein the air treatment system includes a blower under the control of the controller to vary the heat withdrawal. 
     
     
         16 . The apparatus of  claim 14 , wherein the air treatment system includes a cooler for cooling the ambient air under the control of the controller to vary the heat withdrawal. 
     
     
         17 . The apparatus of  claim 14 , wherein the air treatment system includes a heater for heating the ambient air under the control of the controller to vary the heat withdrawal. 
     
     
         18 . The apparatus of  claim 14 , wherein the air treatment system includes a water removal system for removing water from the ambient air under the control of the controller to vary the heat withdrawal. 
     
     
         19 . The apparatus of  claim 14 , wherein the air treatment system includes a valve assembly for controlling the flow of the air out of the air treatment system under the control of the controller to vary the heat withdrawal.