WO2007098094A2

WO2007098094A2 - Thermoelectric cooler and reservoir for medical treatment

Info

Publication number: WO2007098094A2
Application number: PCT/US2007/004256
Authority: WO
Inventors: Denise C. Polacek; Aleks G. Ostrogorsky; Natacha Depaola
Original assignee: Polacek Denise C; Ostrogorsky Aleks G; Natacha Depaola
Priority date: 2006-02-16
Filing date: 2007-02-16
Publication date: 2007-08-30
Also published as: WO2007098094A3; US20070193278A1; CA2642886A1

Abstract

A device for providing cooling to a body is disclosed. The device operates in response to a measured change in temperature of the body's skin surface over a predetermined period of time or manually in response to a perceived or anticipated change in body temperature by the user. The device includes a controller, a temperature sensor, a power source, a thermoelectric cooler, and a heat absorbing reservoir containing a phase change material. The thermoelectric cooler has a heat absorbing surface engageable with the body to be cooled and a heat rejecting surface engaged with the heat absorbing reservoir. The controller is operatively connected to the temperature sensor, the power source, and the thermoelectric cooler and activates the cooler when the temperature sensor provides signals indicative of a predetermined rate of temperature change or in manual mode by user. A method of treating hot flashes with the device is also disclosed.

Description

COOLING DEVICE AND METHOD

Cross Reference to Related Application

This application is based on and claims priority to U.S. Provisional Application No. 60/773,945, filed February 16,. 2006, the contents of which are fully incorporated herein by reference. Field of the Invention

The present invention relates to a device that provides cooling to a body in response to a measured, sensed or anticipated change in the temperature of the body. Background of the Invention

Hot flashes are sudden increases in core and surface body temperature and are perceived as intense increases in body temperature that are characteristically manifested by nearly instant flushing, sweating, dizziness, nausea, palpitations, and diaphoresis. Hot flashes can disrupt sleep, interfere with mental concentration and adversely affect the quality of life. Hot flashes are characterized by a sudden onset of warmth in the face, neck and chest. Hot flashes may occur many times per day and several times per hour. Hot flashes typically pass within minutes, but can be debilitating until their passage and during a complete recovery period that can last up to 30 minutes.

Hot flashes in menopausal women, and in men following androgen-deprivation therapy for the control of metastatic prostate cancer, are common. Brief, episodic skin surface temperature rises due to thermoregulatory problems are also common in persons having diabetes, multiple sclerosis and cancer patients undergoing chemotherapy.

Hot flashes can be treated with hormone replacement therapy (HRT) . However, increasingly, women are reluctant to undertake this therapy because of a number of clinical trials that have indicated a significant correlation between HRT and an increased incidence of heart disease, stroke and breast cancer. For this reason, many women have shunned HRT, leaving them with few effective alternatives for treating or controlling their hot flashes. There are herbal remedies which are purported to relieve the discomfort or reduce the frequency or severity of hot flashes. Some women have been prescribed anti-depressant medication for^'I their hot flashes. While somewhat helpful in some women, neither herbal remedies nor anti-depressants have been proven generally effective and safe. There is clearly a need for a practical device and method for treating hot flashes which is both effective and avoids undesired and dangerous side effects of all known treatment methods. Summary of the Invention

The invention concerns a cooling device for providing cooling to a body. The cooling device comprises a thermoelectric cooler having a heat absorbing surface engageable with the body and a heat rejecting surface. A heat absorbing reservoir is engaged with the heat rejecting surface. The heat absorbing reservoir comprises a phase change material. A temperature sensor is positionable proximate to, and preferably in contact with, the body for sensing a temperature change thereon. A controller is operatively connected with the temperature sensor and the thermoelectric cooler. An electrical power source is operatively connected with the thermoelectric cooler and the controller and provides power to these components. The controller provides power from the power source to the thermoelectric cooler in response to an increase in body surface temperature at a predetermined rate as sensed by the temperature sensor. Alternately, the cooling may be user-activated. The heat absorbing reservoir maintains the heat rejecting surface at a substantially constant temperature during operation .

In one embodiment according to the invention, the thermoelectric cooler is a Peltier device, the controller comprises a microprocessor, the electrical power source comprises a battery and the temperature sensor may be a thermistor, a thermocouple, an infrared sensor or a resistance temperature detector sensor. The phase change material comprises a solid which melts at a temperature between about 25⁰C and about 42⁰C. The phase change material may comprise metals or metal alloys having a melting point between about 25⁰C and about 42⁰C or may be salt hydrate phase change materials, organic phase change materials, linear crystalline alkyl hydrocarbons, fatty acids, fatty esters, polyethylene glycols, long alkyl side chain polymers, the solid state series of pentaerythritol, pentaglycerine, and neopentyl glycol, quaternary ammonium clathrates and semi-clathrates, salt hydrides and combinations thereof. The heat absorbing reservoir may be removably mounted on the heat rejecting surface of the thermoelectric cooler to allow for rapid replacement.

The invention also encompasses a method of treating hot flashes. The method comprises:

(a) providing a cooling device proximate to a skin surface of a body;

(b) monitoring skin surface temperature;

(c) activating the cooling device in response to a measured rise in the skin surface temperature over a first time period; and

(d) operating the cooling device for a second predetermined time period to provide cooling to the body. In an alternate embodiment, the method may include manual activation of the cooling device in response to a sensed or anticipated hot flash episode.

Monitoring the skin surface temperature may comprise sampling the skin surface temperature at predetermined time intervals . Additionally, the method may include providing a heat absorbing reservoir mounted on the cooling device and absorbing heat from the cooling device with the heat absorbing reservoir while maintaining a substantially constant temperature of the heat absorbing reservoir. Brief Description of the Drawings

Figure 1 is a schematic drawing of a cooling device according to one embodiment of the invention;

Figure 2 is a schematic view of the cooling device of Figure 1 in use; Figure 2A is a schematic view of another embodiment of a cooling device according to the invention;

Figure 3 is a graph showing measured skin temperature vs. time; and

Figure 4 is a schematic view of another embodiment of a cooling device according to the invention. Detailed Description of the Embodiments

In the drawings, like numerals indicate like elements throughout. The terminology includes the words specifically mentioned, derivatives thereof and words of similar import. The embodiments illustrated below are not intended to be exhaustive or to limit the invention to the precise form disclosed. These embodiments are chosen and described to best explain the principle of the invention and its application and practical use and to enable others skilled in the art to best utilize the invention.

An exemplary embodiment of a cooling device 100 according to the present invention is shown schematically in Fig. 1. The cooling device 100 includes a temperature sensor 110, a thermoelectric cooler 120, a heat absorbing reservoir 130, a power source 140 and a controller 150. Preferably, the cooling device 100 takes the form of a unitary, compact unit attachable to a body by means of a strap, sling, insert band or adhesive patch. The device could also be attached to an article of clothing such as an under garment, a shirt or blouse as well as a hat, cap or helmet. The device components will preferably be removable from the garment, headgear, strap or other mounting media so that the media can be washed- Alternately, the cooling device 100 may comprise a plurality of components connected to each other by wires or with a wireless communication system.

The temperature sensor 110 can be, for example, a thermistor, a thermocouple, an infrared temperature sensor or a resistance temperature detector sensor. The temperature sensor 110 is electronically connected to the controller 150 so that the controller receives a signal in the form of a change in voltage (if a thermocouple is used) or a change in resistance (if a thermistor is used) across the temperature sensor 110, which the controller correlates to a temperature at the temperature sensing device 110.

The thermoelectric cooler 120 has a heat absorbing surface 121 and a heat rejecting surface 123. These surfaces may be, for example, formed of a metal or a heat conducting ceramic. An exemplary thermoelectric cooler 120 is a Peltier Effect device, although other devices that perform the same function may also be used. The thermoelectric cooler 120 is electrically connected to the power source 140 which provides power to the thermoelectric cooler when cooling is required. When the temperature sensor 110 detects a temperature rise at a predetermined rate, for example, one that is known to be indicative of the onset of hot flashes, the controller 150 allows electrical energy to flow from power source 140 to power the thermoelectric cooler 120. The heat absorbing reservoir 130 is used to absorb the heat generated during operation of the thermoelectric cooler. Preferably the heat absorbing reservoir 130 contains a material that has the capacity to absorb heat without significantly changing its temperature, such as a phase change material. To absorb energy at constant temperature, the phase change material changes from solid to liquid (melts), liquid to gas. (evaporates), or solid to gas (sublimates) . In a preferred embodiment of the invention, the phase change material is in a solid state when the thermoelectric cooler 120 is inactive, i.e., when no power is being provided.

Examples of phase change materials contained in the heat absorbing reservoir 130 include salt hydrate phase change materials, organic phase change materials, linear crystalline alkyl hydrocarbons, fatty acids and esters, polyethylene glycols, long alkyl side chain polymers, the solid state series of pentaerythritol, pentaglycerine, and neopentyl glycol, quaternary ammonium clathrates and semi-clathrates, and salt hydrides. Metals and metal alloys having a low melting point are also feasible. By mixing some of the above compounds, or by mixing the low melting point metals (including Gad, Son and/or In, BP, Bi, etc.), a material having a desired single phase change temperature may be produced. By adjusting the percentage of the constituents that comprise the phase change material, it is possible to achieve an optimum phase change temperature that will allow the cooling device 100 to operate effectively in view of an expected ambient temperature range, as well as the location of the cooling device 100 on the user. In an exemplary embodiment, the phase change material melts at a temperature between approximately 25°C"and 42°C. The heat absorbing reservoir 130 may be comprised of several components, including a container that will prevent leakage or evaporation of the phase change material and an internal structure, such as cooling fins to augment heat transfer to the phase change material. The heat absorbing reservoir is preferably easily connectable and removable from the heat rejecting surface 123 of the thermoelectric cooler 120 in order to quickly switch to a fresh heat absorbing reservoir if additional hot flashes are expected and there is insufficient time for the melted material to resolidify. While connected to the thermoelectric cooler 120, the heat absorbing reservoir 130 maintains good thermal contact with the heat rejecting side of thermoelectric cooler. In a practical application of the device according to the invention, the melting point temperature T_meit of the phase change material is higher than the maximum temperature T_poWer off of the heat rejecting side of thermoelectric cooler 120 with power off, when the cooling device 100 is positioned in contact with the human body, typically under the clothing. Therefore, the phase change material will undergo a phase change only during "power on" operation, for example, when the device is operated in response to a hot flash, in which the peak heat sensation typically lasts about 1 to 2 minutes. During "power off" periods between activations (typically an hour between hot flashes) , the phase change material will resolidify, because the device temperature T_{power Off} is lower than the melting point T_mei_t- The magnitude of T_{power off} is approximately equal to the skin temperature under clothing, about 30⁰C, but may vary depending upon the ambient temperature, and clothing being worn.

As an example, T_{power off} = 30°Cand T_meit = 35°C. As the heat absorbing reservoir 130 absorbs heat from the thermoelectric cooler 120 during operation of the device 100 in response to a hot flash, the temperature of the heat absorbing' component 130 will increase from 30⁰C to 35°C. At 35°C, the phase change material will start undergoing a phase change (i.e. melting, evaporating, or sublimating) . During the change of phase, the temperature of the heat absorbing reservoir 130 will not change (it will stay at 35°C in this example) . Consequently, even though heat energy is being absorbed by the heat absorbing reservoir 130, it does not heat up, thereby allowing the thermoelectric cooler to operate efficiently and prevent discomfort.

The power source 140 can be a DC power source, preferably approximately 1.5 to 12 volts, provided by an electric battery that is preferably integrated into the cooling device 100. Alkaline batteries may be used, but rechargeable batteries, such as lithium ion or nickel cadmium are preferred to enable the user to easily keep the power source 140 at or near full charge capacity. The power source 140 may be removable and replaceable within the device 100 or, alternatively, a power cable, for example, a USB cable (not shown) may be connectable to the power source 140 to recharge it from a computer or other source of electrical energy. The power source 140 is electrically connected to the thermoelectric cooler 120 and to the controller 150 to provide electrical power to both components.

The temperature sensor 110 is electrically connected to the controller 150 such that electrical signals in the form of voltage or resistance differences indicative of changes in temperature generated by the sensor are processed by the controller. The controller thereby monitors the rate of temperature change of the body over time. The controller 150 is preferably a microprocessor, and may provide ON-OFF, proportional, derivative, integral, or programmed process control, or any combination thereof, as well as any other type of process control.

The controller 150 is also electronically connected to the power source 140. When a predetermined rise in temperature over a predetermined time period is sensed by the temperature sensor 110 and communicated to the controller 150, the controller recognizes this data, for example, as indicative of a hot flash, and transmits a signal which closes a switch, allowing the power source 140 to supply electrical power to the thermoelectric cooler 120 and thereby activate the device 100. The controller 150 is programmed to allow electrical power to flow to the thermoelectric cooler 120 for a predetermined time period, for example, approximately two minutes to effectively treat hot flashes. While the time period of device operation may be longer than two minutes for other applications, it is generally impractical for the time period to significantly exceed the time required for the heat absorbing reservoir 130 to completely change phase. Although the time period over which electrical power is supplied to the thermoelectric cooler 120 may be preset by the controller programming, the time period may also be varied by the user, such as by using a switch or dial electronically connected to the processor 150, which will allow the user to selectively determine the operational time of the device 100 from a range of potential durations. Additionally, the device may be capable of different modes of operation, for example, one mode which may provide intense cooling and another for less intense cooling. The device 100 may also include an "ON/OFF" switch 160 that may be employed to prevent operation of the device 100, overriding the actions of the controller.

Referring now to Figure 2, the device 100 is shown in use as securely attached to a body 170 with the heat absorbing surface 121 of the thermoelectric cooler 120 engaged with the body to facilitate providing cooling thereto. Temperature sensor 110 is positioned, either in contact with or proximate to the body as well. The "ON/OFF" switch 160, if employed, is switched to the

"ON" position. During periods of time when the user is not experiencing a hot flash, the device 100 is in a passive mode, wherein the controller 150 monitors signals from the temperature sensor 110, converting those signals to temperature values, and comparing the change in temperature values over a predetermined time period to determine whether the body temperature is rising at a sufficiently fast rate indicative of a hot flash.

In the embodiment shown in Figure 2, a thermally conductive medium may be applied between the heat absorbing surface 121 of the thermoelectric cooler 120 and the surface of body 170 to facilitate heat conduction away from the body. The medium, may be a gel, paste or other suitable substance such as the medium that is commonly used in ultrasound procedures to enhance heat conduction. The medium may be omitted without departing from the scope of the present invention .

Figure 2A schematically illustrates another embodiment of the cooling device 100 having a plurality of thermoelectric coolers 120. Each cooler has an associated heat reservoir 130 and is controlled by the controller 150 and powered by the power source 140. The thermoelectric coolers 120 may be judiciously positioned in spaced relation to one another on the body 170 to augment the cooling effect.

Figure 3 shows a graph of body temperature vs. time to illustrate the rate of change of body surface temperature over time during a hot flash. Arrows A and B point out rises in temperature of over 0.5⁰C in less than 1 minute, which are indicative of a hot flash. When such rates of temperature change are communicated to the controller 150 by the temperature sensor 110, the device 100 switches from passive mode to an active mode, wherein the controller 150 transmits a signal to operate the thermoelectric cooler 120 by providing electrical power from power source 140.

As the heat absorbing reservoir 130 absorbs heat during a hot flash, the phase change material changes phase, for example, from solid to liquid. Preferably, the controller 150 is programmed to operate for a time period long enough to mitigate the hot flashes but short enough such that the phase change material of the heat absorbing reservoir 130 does not completely change phase. Studies thus far have shown that about two minutes of operation is sufficient for a device having a heat transfer capacity of about 1 to about 10 watts, worn on the chest of the subject, is sufficient for relieving symptom of a hot flash. After the predetermined time period of operation has passed, the controller 150 shuts off the power source 140 so that electrical power ceases to be supplied to the thermoelectric cooler 120. The heat absorbing reservoir 130 ceases to absorb heat from the thermoelectric cooler 120 and returns to its no power equilibrium phase, which is preferably a solid state. The device 100 is again ready for operation, the controller continuing to monitor the body temperature, ready to activate the device at the onset of the next hot flash.

In another embodiment, the phase change material is contained in a cartridge that is removably attached to the heat rejecting surface of the thermoelectric cooler so that it may be easily replaced in the event that a second hot flash is expected before the phase change material can solidify from a preceding hot flash. This embodiment can be used in a hot environment which does not allow the phase change material to solidify between the flashes or in an anticipated stressful situation. The user may place the cartridge on a cool surface, in a cold location such as air conditioned room, or in a refrigerator if very rapid cooling is desired to solidify the phase change material.

In an exemplary embodiment, if the device 100 is integrated into an article of clothing, the article of clothing includes at least one opening or surface to allow direct contact by at least a portion of the temperature sensor 110 with the body 170. The temperature sensor may be in proximate, but preferably in actual, contact with the wearer's body, allowing for accurate sensing of the body temperature proximate to the device. Preferably, the heat absorbing surface 121 is in direct contact with the body as well for rapid cooling of the body when the thermoelectric cooler 120 is in operation.

A manually operated embodiment of the present invention is shown schematically in the device 200, shown in Figure 4. This embodiment includes a controller or timer 250 programmed to turn the device 200 off after a specified period of time. The device 200 includes a thermoelectric cooler 220 that preferably operates on the same principle as the thermoelectric cooler 120 described above. The device 200 also includes a power source 240, similar to the power source 140 described above, that is used to provide power to operate the thermoelectric cooler and the controller. Further, the device 200 includes an "ON/OFF" switch 260 that is used to selectively transmit power from the power source 240 to the thermoelectric cooler. Although an exemplary use of the present invention is described for the alleviation of hot flashes, those skilled in the art will recognize that the device 200 may have other uses, such as for the alleviation of migraine headaches wherein cerebral vasodilation is a known symptom and where applied cold is a known effective treatment. The device 200 may be applied to the user's head or neck region 270 to provide cooling relief to that area of the user. When the user desires the cooling effect of the device 200, such as a recognizable prodrome preceding a migraine headache, or based on a perceived rise in skin surface temperature over a first time period, the user turns the "ON/OFF" switch 260 to the "ON" position. The switch 260 completes an electrical circuit, and the power source 240 provides electrical power to the thermoelectric cooler 220. The heat absorbing reservoir 230 absorbs the heat from the heat rejecting surface of the thermoelectric cooler by changing phase, for example, from solid to a liquid, without a change in temperature. After a second period of time, the user opens the "ON/OFF" switch 260, stopping operation of the device 200 or after a predetermined limit, the device automatically turns off

Although the size of the devices 100, 200 is preferably relatively small, such as a footprint of approximately 1 to 5 square inches, those skilled in the art will recognize that a larger version of the device 200 can be used to stem blood flow in an open wound, by cooling the wound opening and the skin area surrounding the wound. Further, the inventors believe that the devices 100, 200 can be used in other applications such as in patients suffering from diabetes, multiple sclerosis and cancer who are being treated with chemotherapy, where cooling is required to be applied to a surface for a period of time to relieve the discomfort of episodes of heating due to abnormal thermoregulation associated with these disorders or their treatment.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the pre'sent invention as defined by the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A cooling device for cooling a body, said cooling device comprising: a thermoelectric cooler having a heat absorbing surface engageable with said body and a heat rejecting surface; a heat absorbing reservoir engaged with said heat rejecting surface, said heat absorbing reservoir comprising a phase change material; a temperature sensor positionable proximate to said body for sensing a temperature change therein; a controller operatively connected with said temperature sensor and said thermoelectric cooler; an electrical power source operatively connected with said thermoelectric cooler and said controller and providing power thereto; said controller providing power from said power source to said thermoelectric cooler in response to an increase in temperature at a predetermined rate as sensed by said temperature sensor, said heat absorbing reservoir maintaining said heat rejecting surface at a substantially constant temperature.

2. A cooling device according to Claim 1, wherein said temperature sensor is positionable in contact with said body.

3. A cooling device according to Claim 1, further comprising at least a second said thermoelectric cooler having a respective said heat absorbing reservoir, said controller and said power source being operatively connected with said second thermoelectric cooler.

4. A cooling device according to Claim 1, wherein said thermoelectric cooler is a Peltier device.

5. A cooling device according to Claim 1, wherein said controller comprises a microprocessor.

6. A cooling device according to Claim 1, wherein said electrical power source comprises a battery.

7. A cooling device according to Claim 1, wherein said temperature sensor is selected from the group consisting of a thermistor, a thermocouple, an infrared temperature sensor and a resistance temperature detector sensor .

8. A cooling device according to Claim 1, wherein said phase change material comprises a solid which melts at a temperature between about 25⁰C and about 42°C.

9. A cooling device according to Claim 1, wherein said phase change material is selected from the group consisting of metals and metal alloys having a melting point between about 25⁰C and about 42⁰C.

10. A cooling device according to Claim 1, wherein said phase change material is selected from the group consisting of salt hydrate phase change materials, organic phase change materials, linear crystalline alkyl hydrocarbons, fatty acids, fatty esters, polyethylene glycols, long alkyl side chain polymers, the solid state series of pentaerythritol, pentaglycerine, and neopentyl glycol, quaternary ammonium clathrates and semi-clathrates, salt hydrides and combinations thereof.

11. A cooling device according to Claim 1, wherein said heat absorbing reservoir is removably mounted on said heat rejecting surface of said thermoelectric cooler.

12. A cooling device for cooling a body comprising : a thermoelectric cooler having a heat absorbing surface engageable with said body and a heat rejecting surface; a heat absorbing reservoir engaged with said heat rejecting surface, said heat absorbing reservoir comprxsing a phase change material; an electrical power source operatively connected with said thermoelectric cooler; a switch controlling flow of electrical power from said power source to said thermoelectric cooler; and said heat absorbing reservoir maintaining said heat rejecting surface at a substantially constant temperature when power is supplied to said thermoelectric cooler for providing cooling to said body.

13. A cooling device according to Claim 12, further comprising at least a second said thermoelectric cooler having a respective said heat absorbing reservoir, said controller and said power source being operatively connected with said second thermoelectric cooler.

14. A cooling device according to Claim 12, wherein said thermoelectric cooler is a Peltier device.

15. A cooling device according to Claim 12, further comprising a timer operatively connected with said electrical power source and said thermoelectric cooler, said timer halting the flow of electrical power to said thermoelectric cooler at a predetermined time after said switch has been closed to provide power to said thermoelectric cooler.

16. A method of treating hot flashes, said method comprising: providing a cooling device proximate to a skin surface of a body; monitoring skin surface temperature; activating said cooling device in response to a measured rise in said skin surface temperature over a first time period; and operating said cooling device for a second predetermined time period to provide cooling to said body.

17. A method according to Claim 16, wherein monitoring skin surface temperature comprising sampling skin surface temperature at predetermined time intervals .

18. A method according to Claim 16, further comprising : providing a heat absorbing reservoir mounted on said cooling device; and absorbing heat from said cooling device with said heat absorbing reservoir while maintaining a substantially constant temperature of said heat absorbing reservoir.

19. A method of cooling a body, said method comprising: providing a cooling device proximate to a skin surface of said body; providing a heat absorbing reservoir mounted on said cooling device; manually activating said cooling device in response to an anticipated increase in temperature of said body; operating said cooling device for a second predetermined time period to provide cooling to said body; and absorbing heat from said cooling device with said heat absorbing reservoir while maintaining a substantially constant temperature of said heat absorbing reservoir.

20. A method according to Claim 19, wherein said cooling device is in contact with said skin surface of said body.

21. A method according to Claim 19, wherein said method is applied to treat thermoregulatory problems associated with a medical condition selected from the group consisting of hot flashes, diabetes, multiple sclerosis and cancer treatment.

22. A method according to Claim 19, wherein said method is applied to treat, migraine headaches.