METHOD FOR OPTIMIZING SKIN COOLING LEVEL OF AN OCCUPANT SUPPORT SURFACE
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.
This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 62/802,920, filed Feb. 8, 2019, which is expressly incorporated by reference herein.
TECHNICAL FIELDThe present disclosure is related to bed mattresses for supporting patients. More specifically, the present disclosure is related to a coverlet for hospital beds, medical beds, or other types of beds where the coverlet includes structure that allows for the control of heat withdrawal from a surface supporting a patient. More specifically, the present disclosure relates to the operations of an air supply system to determine an optimal heat withdrawal rate for a particular patient and control air being delivered to the coverlet to maintain the optimal heat withdrawal rate.
BACKGROUNDIn a care facility, such as a hospital or a nursing home, patients are often placed on patient support apparatuses for an extended period of time. Patients who are positioned on the patient support apparatus often have a risk of developing certain skin condition, such as bed sores (also known as pressure sores or decubitus ulcers), due to heat and moisture along the interface of the patient with the surface of the bed mattress. In an effort to mitigate or prevent such conditions, some bed mattresses have a built-in microclimate structure. The microclimate structure may conduct air along the interface of a patient with the surface to keep the patient's skin cool and dry. Some microclimate structures require a large volume of air to be supplied to them in order to provide an effective amount of cooling and drying to a patient's skin.
SUMMARYThe present disclosure includes one or more of the features recited in the appended claims and/or the following features which, alone or in any combination, may comprise patentable subject matter.
According to a first aspect of the present disclosure, a method for controlling performance of a heat withdrawal coverlet for removing heat from a surface supporting a person that has a flow path for guiding a stream of air along at least a portion of the surface comprises 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, and measuring a skin temperature of an occupant at each increment of increase of the heat withdrawal rate. The method also include 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.
In some embodiments, 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.
In some embodiments, 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.
In some embodiments, the optimal heat withdrawal rate determines the rate at which heat is withdrawn from the skin of an occupant prior to vasoconstriction.
In some embodiments, 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.
In some embodiments, the method further comprises 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.
According to a second aspect of the present disclosure, a method for controlling performance of a heat withdrawal coverlet for removing heat from a surface supporting a person having a flow path for guiding a stream of air along at least a portion of the surface comprises 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, and maintaining the heat withdrawal rate of the coverlet to operate below the vasoconstriction threshold of the person.
According to a third aspect of the present disclosure, an apparatus for controlling the heat withdrawal from a patient's skin comprises 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. The controller includes a processor and a memory device. The memory device includes 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.
In some embodiments, the air treatment system includes a blower.
In some embodiments, the air treatment system includes a cooler for cooling the ambient air.
In some embodiments, the air treatment system includes a heater for heating the ambient air.
In some embodiments, the air treatment system includes a water removal system for removing water from the ambient air.
In some embodiments, the air treatment system includes a valve assembly for controlling the flow of the air out of the air treatment system.
Additional features, which alone or in combination with any other feature(s), such as those listed above and/or those listed in the claims, can comprise patentable subject matter and will become apparent to those skilled in the art upon consideration of the following detailed description of various embodiments exemplifying the best mode of carrying out the embodiments as presently perceived.
The detailed description particularly refers to the accompanying figures in which:
A patient support system 10 according to one illustrative embodiment of the current disclosure is shown in
The patient support apparatus 12 includes a base frame 18 and an upper frame 22 supported on a lift system 20. The lift system 20 is operable to raise and lower the upper frame 22 relative to the base frame 18 and to tilt the upper frame 22 relative to the base frame 18 to achieve Trendelenburg and reverse-Trendelenburg positions as known in the art. The upper frame 22 supports a deck 38 that is movable to multiple positions as is known in the art. In the illustrative embodiment, the patient support surface 14 includes a coverlet 26 attached to and supported by a mattress 28. The patient support surface 14 is configured to support a person thereon and move with the deck 38 between the various configurations. The patient support surface 14 includes a calf section 28, a thigh section 30, a seat section 32, and a head and torso section 36 as shown in
The coverlet 26 includes a heat withdrawal structure 44, a top layer 46, a bottom layer 48, an inlet 50, an outlet 52, and a 3-dimensionally engineered spacer 54 as shown in
The 3-dimension engineered spacer 54 is positioned within the inner chamber 56 and is air and moisture permeable. The 3-dimensional engineered spacer 54 maintains a path for air to flow through when a person is supported on the coverlet 26. In the illustrative embodiment, the 3-dimensionally engineered spacer 54 is Spacenet®. The 3-dimensionally engineered spacer 54 is positioned within an inner chamber 56 and is configured to be air and moisture permeable. The inlet 50 and outlet 52 are generally located on opposite ends of the coverlet 26 and allow a fluid, such as air, to be communicated into the inner chamber 56 of the coverlet 26, and to be exhausted from the coverlet 26, respectively, as shown in
Referring to
The coverlet 26 further includes a plurality of sensors 24 in electrical communication with a controller 80. The sensors 24 are configured to measure the temperature, moisture, humidity, and/or heat withdrawal levels of the occupant and detect the presence of liquid on the coverlet 26 so that the heat withdrawal structure 44 may record and store such measurements in the controller 80 such that a caretaker may access the measurements. If the sensors 24 detect a level exceeding a predetermined threshold level, the controller 80 is configured to automatically stop the flow of air from the air treatment system 16 by closing the inlet 50. The cessation of air prevents over or under drying of the patient's skin.
Referring to
As shown in
The controller 80 is in communication with the air treatment system 16 and configured to receive input either automatically via the plurality of sensors 24, manually via the user interface 82, or some combination thereof. The input is then conveyed to the controller 80 via electronic communication such that the controller 80 is configured to wirelessly communicate with the sensors 24, the user interface 82, the air treatment system 16, or some combination thereof.
Manual input may be accomplished by the user through the user interface 82. The user interface 82 includes a display screen 94 and a plurality of buttons 96 for inputting patient information and/or controlling operation of the air treatment system 16 and patient support surface 14. Particularly, the controller 80 allows a user to adjust the air flow 74 provided by the air treatment system 16 to the coverlet 26 and, in some embodiments, to additionally adjust the temperature of the air provided by the air treatment system 16 to the coverlet 26. Specifically, in some embodiments, the controller 80 may include a patient information input panel, an alarm panel, a lateral rotation therapy panel, an inflation mode panel, a normal inflation control panel, a microclimate control panel, or some combination thereof. The controller 80 is configured to regulate the operation the air treatment system 16 and direct the flow of air created therein. Illustratively, the controller 80 is coupled for communication with a valve box 92 to control the rate by which treated air flows through the heat withdrawal structure 44.
The controller 80 comprises at least one processor 85 and at least one memory device 87. The memory device 87 is configured to store instructions for execution by the processor 85. The controller 80 is further configured to receive information from the sensors 24 and user interface 82 (via electronic communication as discussed above) as inputs to the processor 85 in executing the instructions stored in the memory device 87. The controller 80 is further enabled to communicate information as outputs signals to the air treatment system 16, the fluid control valve box (not shown), the other components of the patient support apparatus 12, or some combination thereof in order to control the operation of the heat withdrawal structure 44. Illustratively, the controller 80 is configured to wirelessly communicate with the sensors 24 and the user interface 82 as shown in
The controller 80 is further configured to individually control the cooler 86, the heater 90, the blower 84, or any combination thereof. As mentioned above, the conduit 98 is configured to facilitate communication of air between the air treatment system 16 and the coverlet 26 as shown in
Two principal mechanisms of heat transfer affect the operation of the heat withdrawal structure 44: dry heat transfer and wet heat transfer. Dry heat transfer is proportional to temperature difference and is independent of the presence or absence of liquid phase perspiration at the occupant/surface interface. The potential of the coverlet 26 to effect dry heat transfer at a given temperature difference is referred to as its dry flux capacity (DFC). The dry heat transfer actually realized during operation of the system described herein is the actual dry flux (DF).
The second mechanism of heat transfer, wet heat transfer, is proportional to the difference in the partial pressure of water vapor (perspiration) at the occupant's skin and the partial pressure of water vapor in the air flow 74. The potential of the support surface to affect wet heat transfer is its wet flux capacity (WFC). The wet heat transfer actually realized during operation of the system described herein is the actual wet flux (WF).
To optimize heat withdrawal and patient cooling, a method, as shown in
Ischemia (aka: poor perfusion, malperfusion) is linked to various health problems and lead to poor thermoregulation of an occupant due to the lack of blood flow reaching the skin cells of the patient. The lack of blood flow not only decreases the amount of oxygen the skin cells receive from the blood but also increases the occupant's skin temperature. Blood flow to skin cells dissipates the heat of an occupant by redirecting warm blood closer to the surface of the skin so that it may help cool an occupant through perspiration and thermal dissipation. Therefore, as shown in
Skin T(° F.)=−0.0697*HW+100.01
wherein HW represents surface heat withdrawal.
Operation of the heat withdrawal structure 44 can be understood by referring to the graph of
To determine the vasoconstriction threshold of an occupant, the coverlet utilizes sensors 24 and the heat withdrawal structure 44. As shown in
When a break in linearity is measured and recorded via the sensors 24 of coverlet 26, the controller 80 of the coverlet 26 is configured to decrease the rate of surface heat withdrawal so that the occupant experiences less cooling provided by coverlet 26 and maintains an optimal rate of perfusion as shown at step 210 of
As shown in
As shown in
Although this disclosure refers to specific embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the subject matter set forth in the accompanying claims.
Claims
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.
Type: Application
Filed: Feb 5, 2020
Publication Date: Aug 13, 2020
Inventors: Charles A. LACHENBRUCH (Batesville, IN), Rachel L. WILLIAMSON (Batesville, IN)
Application Number: 16/782,257