Systems and methods for cooling a person incorporating heart rate variability monitoring sensors

Abstract

A system for cooling a person includes a pump, a heat exchanger, a bladder, a thermometer, a heart rate variability (HRV) sensor, and a controller. The heat exchanger is in fluid communication with the pump. The bladder is configured to be placed on the person and is in fluid communication with the heat exchanger. The thermometer measures the temperature of fluid passing through at least one of the pump, the heat exchanger, and the bladder. The controller is in electrical communication with the thermometer, the HRV sensor, and the heat exchanger and is configured to control power supplied to or flow through the heat exchanger based on a signal received from the HRV sensor.

Description

[Background technology]

[0001] U.S. Patent No. 6,183,501 discloses a cooling system having a head and neck device that can provide cooling to reduce trauma to the brain. The head device includes panels that each house a cooling element to facilitate cooling. The head device is secured to an individual's head and covers the individual's carotid arteries, which supply blood to the brain. U.S. Patent Application Publication No. 2012 / 0288848 discloses a similar device connected to a pump and a cooling fluid source.

[0002] U.S. Patent Application Publication No. 2021 / 0128345 discloses a system for treating brain injury, including a pump, a heat exchanger, a bladder, a thermometer, and a controller. The heat exchanger is in fluid communication with the pump. The bladder is configured to be positioned on the carotid artery and is in fluid communication with the heat exchanger. The thermometer is positioned relative to the heat exchanger and configured to measure the temperature of a fluid downstream from the heat exchanger. The controller is in electrical communication with the thermometer and the heat exchanger. The controller is configured to control the power supplied to or the flow through the heat exchanger so that the temperature of the fluid downstream from the heat exchanger, as measured by the thermometer, is between 2°C and 10°C for 10 to 50 minutes. The system is configured to address comfort issues that may arise when an individual wears such a head cooling device.

[0003] Further controlling the degree of cooling and / or duration of cooling based on physiological measurements taken from the person receiving treatment can be useful to further tailor the treatment. Additionally, these measurements can be useful when treating a person for brain injury or simply cooling a person, for example, when cooling a person during strenuous physical activity. Summary of the Invention

[0004] A system for cooling a person includes a pump, a heat exchanger, a bladder, a thermometer, a heart rate variability (HRV) sensor, and a controller. The heat exchanger is in fluid communication with the pump. The bladder is configured to be placed on the person and is in fluid communication with the heat exchanger. The thermometer measures the temperature of fluid passing through at least one of the pump, the heat exchanger, and the bladder. The controller is in electrical communication with the thermometer, the HRV sensor, and the heat exchanger and is configured to control power supplied to or flow through the heat exchanger based on a signal received from the HRV sensor.

[0005] A method for cooling a person includes pumping a fluid through a heat exchanger to a bladder positioned on the person and removing heat from the fluid as it passes through the heat exchanger. The method further includes measuring a temperature of the fluid passing through the heat exchanger, monitoring the person's HRV with an HRV sensor in communication with a controller, and controlling at least one of power supplied to the heat exchanger and a flow of fluid through the heat exchanger based on a signal received from the HRV sensor. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram of a system for cooling a person.

[0007] [Figure 2] FIG. 2 is a perspective view of the bladder and carrier of the system shown in FIG.

[0008] [Figure 3] FIG. 3 is a schematic diagram of the chiller unit of the system shown in FIG.

[0009] [Figure 4] FIG. 4 is a flow chart illustrating an example method of operating the system shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] FIG. 1 illustrates a system 20 useful in cooling a person, whether for treating a brain injury or simply for cooling a person. System 20 generally includes a chiller unit 22 connected to bladders 24, 26, and 28 ( FIG. 2 ) carried by respective carriers 32, 34, and 36 via fluid lines 44, 46, 48, 52, 54, and 56, respectively. Referring to FIG. 2 , lower bladder 24 is configured to be positioned around neck 14, over the person's carotid artery. Upper bladder 26 can be wrapped around forehead region 12. A third bladder 28 can be wrapped around the person's wrist, for example, and other bladders (not shown) can be provided and connected to chiller unit 22 in a similar manner. Bladders 24, 26, and 28 can be held to the person using hook-and-loop fasteners 58, only one example of which is shown in FIG. 2 . Cold fluid from chiller unit 22 is pumped into bladders 24, 26, 28 to cool blood flowing through the arteries in a manner that provides cerebral cooling and generally provides cooling.

[0011] FIG. 3 schematically illustrates the chiller unit 22. The chiller unit 22 includes a pump 60, a heat exchanger 62, a controller 64, and a thermometer 66. The pump 60, the heat exchanger 62, the controller 64, and the thermometer 66 are disposed within a housing 68, which is also shown schematically in FIG. 3. The chiller unit 22 includes a chiller inlet 72 that receives relatively warm fluid from the bladders 24, 26, and 28. The pump 60 moves the incoming fluid through the heat exchanger 62, which can cool the fluid to a desired temperature, and then pumps the fluid back toward the bladders 24, 26, and 28 through the chiller outlet 74. The heat exchanger 62 can be activated to heat the fluid as needed. The chiller unit 22 also includes a valve 76 that, when open, allows fluid from the pump 60 to bypass the heat exchanger 62. The valve 76 is configured to open to allow fluid to bypass the heat exchanger 62. The valve 76 is operable in different operating states, such as fully open, fully closed, and partially open. In the fully closed state, the valve 76 does not allow fluid to pass. Upon receiving a signal from the controller 64, the valve 76 can act like a throttle between the fully open and fully closed positions to control the volume of fluid per unit time that flows through the valve 76 and bypasses the heat exchanger 62.

[0012] The chiller unit 22 of the illustrated embodiment receives power from an external power source 78, which can provide power to each component of the chiller unit 22. The power source 78 can also be located within the housing 68, for example, if the power source is a battery or battery pack. Locating the power source 78 on or within the housing 68 can be desirable when it is desired to reduce the size of the chiller unit so that it is portable, such as by allowing a user to wear the chiller unit 22, for example, in a backpack, while engaging in strenuous physical activity. The chiller unit 22 can also include a display and user interface, not shown, to enable an operator to operate the chiller unit 22.

[0013] The thermometer 66 is positioned relative to the pump 60, the heat exchanger 62, and the bladders 24, 26, and 28 to measure the temperature of the fluid passing through at least one of the pump 60, the heat exchanger 62, and the bladders 24, 26, and 28. As shown in FIG. 3 , the thermometer 66 can measure the temperature of the fluid exiting the heat exchanger 62 before the fluid leaves the housing 68 and enters the fluid lines 44, 48, and 54, respectively. Alternatively, the thermometer 66 can be positioned elsewhere, such as in one of the bladders 24, 26, and 28, and can communicate with the controller 64 via a wired or wireless connection, such as Bluetooth or other short-range wireless transmission protocol. The thermometer 66 communicates with the controller 64 to provide the controller with the measured temperature of the fluid exiting the heat exchanger 62. Based on the measured temperature, the controller 64 can adjust the power supplied to the heat exchanger 62, for example, by using pulse-width modulation (PWM). If the measured temperature is higher than the desired temperature, more power can be supplied to the cooling side of the heat exchanger 62. If the measured temperature is lower than the desired temperature, power can be provided to the heating side of the heat exchanger 62. In addition to, or instead of, controlling power to the heat exchanger 62, the controller 64 can open or close a valve 76. For example, if the measured temperature is lower than the desired temperature, the valve 76 can be opened to allow fluid to bypass the heat exchanger 62 on its way to the chiller outlet 74. As an example, if the thermometer 66 measures that the temperature of the fluid exiting the heat exchanger is too cold (based on a predetermined threshold), the controller 64 can open the valve 76 to allow relatively warm fluid from upstream of the heat exchanger 62 to bypass the heat exchanger and increase the temperature of the fluid sent to the chiller outlet 74. Alternatively, the flow rate of the pump 60 can be adjusted, e.g., reduced, to send less fluid to the heat exchanger 62 if the measured temperature is lower than the desired temperature.

[0014] While heart rate focuses on the average heart rate per minute, heart rate variability (HRV) measures the specific temporal changes (or variability) between successive heartbeats. A person's heart always beats at a specific rate. That rate changes depending on what the person is doing at the time. When a person is at rest or relaxed, their heart rate slows, and when a person is active, stressed, or in danger, their heart rate increases. A person's heart rate fluctuates depending on their body's needs and breathing patterns. Certain medications and medical devices can also affect heart rate variability. FIG. 2 shows a heart rate variability (HRV) sensor 90 mounted on the lower carrier 32, which is typically worn around the wearer's neck. However, it should be understood that the HRV sensor 90 can be attached to the other carriers 34, 36 or worn separately, e.g., without being coupled to a carrier. The HRV sensor 90 communicates with the controller 64, which in the illustrated embodiment is via a wired or wireless connection, e.g., Bluetooth or other short-range wireless transmission protocol.

[0015] FIG. 4 illustrates a specific example of a method for operating a system 20 useful for cooling a person using the HRV sensor 90 shown in FIG. 2. While FIG. 4 may depict a specific order of method steps, the order of the steps may differ from that depicted. Also, two or more steps may be performed simultaneously or with partial concurrence. Such variations will depend on the software and hardware systems selected and the designer's choice. All such variations are within the scope of this disclosure. Similarly, software implementations may be achieved with standard programming techniques, including rule-based and other logic to accomplish the various connection, processing, comparison, and decision steps. FIG. 4 is merely an example of such a method and should not be considered limiting of the invention, as defined by the claims.

[0016] At 100, the patient's HRV is monitored, for example, via HRV sensor 90 (FIG. 2) in communication with controller 64 (FIG. 3). Controller 64 can execute a program that determines, at 102 (FIG. 4), whether the measured HRV is outside a predetermined range, which may be defined by a lower threshold and an upper threshold. For example, an HRV measured between 50 milliseconds (ms) and 150 ms may be considered "normal," and thus, an HRV measured within this range may be considered not outside the predetermined range. If it is determined that the HRV measurement is not outside this predetermined range, then, at 104, a cooling protocol such as that described in U.S. Patent Application Publication No. 2021 / 0128345 may be continued, and HRV may be continuously monitored at 100. U.S. Patent Application Publication No. 2021 / 0128345, incorporated herein by reference, describes controlling the power supplied to or flow through heat exchanger 62 so that the measured temperature of the fluid exiting heat exchanger 62 is a treatment temperature of 2°C to 10°C (e.g., 6°C) for a desired treatment period, e.g., about 30 minutes. Other cooling protocols can also be used, for example, the fluid circulating through bladders 24, 26, 28 is maintained at about 6°C (or other desired temperature) while the person wearing the bladders is engaged in strenuous physical activity.

[0017] If the HRV is determined at 102 to be outside a predetermined range and below a lower threshold, then a determination is made at 106 as to whether the measured HRV is below a minimum threshold. For example, if the HRV is determined at 106 to be below a minimum threshold (which may be set, for example, at 20 ms), then an alarm 108 ( FIG. 3 ) may be activated at 110, and the fluid exiting the housing 68 and entering the fluid lines 44, 48, 54 leading to the bladders 24, 26, 28 may be further cooled at 112. Further cooling may be only to a lower temperature threshold (e.g., 2° C.). The alarm 108 may communicate with the controller 64 and may be provided on the housing 68 to provide a visual or audible indication to the wearer or a caregiver that the wearer's HRV is dangerously low. However, if it is determined at 106 that the HRV is above a minimum threshold, for example, if the measured HRV is still below the lower threshold of the predetermined range but above the minimum threshold (e.g., 21-49 ms), the fluid exiting the housing 68 and entering the fluid lines 44, 48, 54 may be further cooled at 112 without an alarm being provided.

[0018] The fluid can be further cooled at 112 by adjusting the power supplied to the heat exchanger 62 so that more power is supplied to the cooling side of the heat exchanger 62. The method of operating the system 20 can then return to monitoring the patient's HRV at 100.

[0019] If it is determined at 102 that the HRV is outside a predetermined range and higher than an upper threshold, then it is determined at 116 whether the measured HRV is above a maximum threshold. For example, if it is determined at 116 that the HRV is above the maximum threshold (which may be set at 200 ms, for example), then an alarm 108 can be activated at 118, and the fluid exiting the housing 68 and entering the fluid lines 44, 48, 54 can be warmed at 122. The alarm 108 can also provide a visual or audible indication to the wearer or caregiver that the wearer's HRV is dangerously high. However, if it is determined at 116 that the HRV is below the maximum threshold, for example, if the measured HRV is still above the upper threshold of a predetermined range but below the maximum threshold (e.g., 151-200 ms), then the alarm 108 can be disabled and the fluid exiting the housing 68 and entering the fluid lines 44, 48, 54 leading to the bladders 24, 26, 28 can be warmed at 122.

[0020] The fluid may be warmed by adjusting the power supplied to the heat exchanger 62 so that less power is supplied to the cooling side of the heat exchanger 62, by supplying power to the heating side of the heat exchanger 62, and / or by opening valve 76 so that the fluid bypasses the heat exchanger 62, allowing relatively warmer fluid from upstream of the heat exchanger 62 to bypass the heat exchanger and increase the temperature of the fluid sent to the chiller outlet 74. The fluid may also be warmed via the controller 64 controlling the pump 60 to control the flow rate through the pump 60, for example, to slow the flow rate. The method of operating the system 20 may then return to monitoring the patient's HRV at 100.

[0021] While the present invention has been described with reference to specific exemplary embodiments thereof, many different changes, modifications, and the like will become apparent to those skilled in the art. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. Moreover, in the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. It will be understood that various forms of the above-disclosed embodiments and other features and functions, or alternatives or variations thereof, may be desirably combined into many other different systems or applications. Moreover, various presently unforeseen or unanticipated substitutions, modifications, variations, or improvements may subsequently occur to those skilled in the art, which are also intended to be encompassed by the following claims.

Claims

1. pump, a heat exchanger in fluid communication with the pump; a bladder configured to be placed on a person and in fluid communication with the heat exchanger; a thermometer positioned relative to the pump, the heat exchanger, and the bladder to measure the temperature of fluid passing through at least one of the pump, the heat exchanger, and the bladder; a heart rate variability (HRV) sensor; and a controller in electrical communication with the thermometer, the HRV sensor, and the heat exchanger, and configured to control power supplied to or flow through the heat exchanger based on a signal received from the HRV sensor; 1. A system for cooling a person, including:

2. The system of claim 1 , wherein the controller is configured to determine whether the measured HRV is outside a predetermined range defined by a lower threshold and an upper threshold.

3. 3. The system of claim 2, wherein the controller is further configured to determine whether the measured HRV is below a minimum threshold during or after determining that the measured HRV is outside the predetermined range and below the lower threshold.

4. 4. The system of claim 3, further comprising an alarm in electrical communication with the controller, the controller further configured to activate the alarm when the controller determines that the measured HRV is outside the predetermined range and below the minimum threshold.

5. 4. The system of claim 3, wherein the controller is further configured to control the heat exchanger to further cool fluid entering the bladder when the controller determines that the measured HRV is below the lower threshold.

6. 3. The system of claim 2, wherein the controller is further configured to determine whether the measured HRV is above a maximum threshold value during or after determining that the measured HRV is outside the predetermined range and above the upper threshold value.

7. 7. The system of claim 6, further comprising an alarm in electronic communication with the controller, the controller further configured to activate the alarm when the controller determines that the measured HRV is outside the predetermined range and above the maximum threshold.

8. 7. The system of claim 6, wherein the controller is further configured to control the heat exchanger to warm fluid entering the bladder when the controller determines that the measured HRV is above the upper threshold.

9. 7. The system of claim 6, further comprising a valve configured to open to allow fluid to bypass the heat exchanger, and wherein the controller is further configured to control at least one of power supplied to the heat exchanger, an actuation state of the valve, and a flow rate of the pump to warm fluid entering the bladder when the measured HRV is above the upper threshold.

10. pumping the fluid through a heat exchanger into a bladder positioned on the person; removing heat from the fluid as it passes through the heat exchanger; measuring the temperature of the fluid passing through at least one of the heat exchanger and the bladder; monitoring the person's HRV with an HRV sensor in communication with a controller; and controlling at least one of power supplied to the heat exchanger and fluid flow through the heat exchanger based on a signal received from the HRV sensor; 10. A method for cooling a person, comprising:

11. 11. The method of claim 10, further comprising determining whether the measured HRV is outside a predetermined range defined by a lower threshold and an upper threshold.

12. 12. The method of claim 11, further comprising, during or after determining whether the measured HRV is outside the predetermined range, determining whether the measured HRV is below a minimum threshold.

13. The method of claim 12 , further comprising activating an alarm upon determining that the measured HRV is below the minimum threshold.

14. 13. The method of claim 12, further comprising controlling the heat exchanger to further cool fluid entering the bladder upon determining that the measured HRV is below the lower threshold.

15. 12. The method of claim 11, further comprising, during or after determining whether the measured HRV is outside the predetermined range, determining whether the measured HRV is above a maximum threshold.

16. 16. The method of claim 15, further comprising activating an alarm upon determining that the measured HRV is above the maximum threshold.

17. 16. The method of claim 15, further comprising controlling the heat exchanger to warm fluid entering the bladder when the measured HRV is determined to be above the upper threshold of the predetermined range.

18. 16. The method of claim 15, further comprising controlling at least one of the heat exchanger and a valve to bypass the heat exchanger to warm fluid entering the bladder when the measured HRV is determined to be above the upper threshold of the predetermined range.

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