SE1451237A1 - Device and method for medical cooling of a body part of a patient - Google Patents

Abstract

A medical cooling device and a method for operating the same are provided.Figured to be published with Abstract: Fig. 1

Description

DEVICE AND METHOD FOR MEDICAL COOLING OF A BODY PART OF APATIENT TECHNICAL FIELDThe present invention pertains to a medical Cooling device and method for medical Cooling of a body part of a patient, and in particular the brain of the patient.

BACKGROUND Medical cooling of parts of the human body is a useful tool to reduce adverseimpacts on the same under certain conditions. For example, medical cooling may beused for cooling the brain of patient suffering from a stroke. By reducing thetemperature of the brain the risk of tissue damage is reduced for those parts of the brainlacking an adequate oxygen supply during the stroke. Another application of medicalcooling is to cool the scalp for patients going through chemo therapy, to avoidundesirable hair loss.

In animal models of stroke, target temperatures of between 24° C and 34°C aremost efficacious for reducing infarct size. However, even a brain temperature of 35° Creduces the infarct volume by 30%. Cooling to levels of 32° to 34° C generally requiressedation, mechanical ventilation and admission to an intensive care unit. OWing to thelimited availability of intensive care beds in most countries, treatment of even aminority of acute stroke patients to those levels is therefore precluded by substantialpractical and logistical problems. Temperature reductions to 35.5°C or 35.0°C havebeen shown to be feasible and safe in aWake patients With acute ischemic stroke bysurface cooling, in combination With for exapethidine to treat shivering. Some studies ofpatients With severe traumatic brain injuries indicate that temperatures of 35 to 35.5°Cseem to be the optimal temperature at Which to treat patients With severe traumatic braininjuries.

Under normal conditions When the body temperature decreases beyond acertain point, e.g. around 35°C, the body starts to shiver in an attempt of regaining theheat loss. Depending on the person involuntary shivering may be initiated at differenttemperatures. Moreover, there are also pharrnaceuticals that lower the onset temperatureof involuntary shivering.

An improved medical cooling device Would be advantageous.

SUMMARY An object of the present invention is to eliminate or alleviate at least one of thedrawbacks mentioned above, Which is achieved by assigning to the device thecharacteristics according to claim 1.

According to a first aspect a control unit configured to control the operation ofa medical cooling device conducting a medical cooling process for cooling a part of apatient is provided. The operation of the medical cooling device is based on a number ofprocess parameters. The control unit is configured to monitor at least one processparameter relating to a state of shivering of the patient. The control unit is furtherconf1gured to make a decision relating to the state or degree of shivering of the patientbased on the at least one monitored process parameter. The control unit is furtherconf1gured to adapt a control process parameter based on the at least one monitoredprocess parameter and the decision made to put the patient in a reduced state ofshivering or a non-shivering state. Moreover, the control unit is configured to re-startthe medical cooling process according to the adapted control process parameter.

According to a further aspect a medical cooling device for conducting amedical cooling process for cooling a body part of a patient is provided. The medicalcooling device comprises a cooling fluid supply source, a supply line for supplying afloW of cooling fluid from the cooling fluid supply source to a patient, a retum line forreceiving the floW of cooling fluid from the patient, and the control unit of the firstaspect.

In accordance With a further aspect, a method for controlling the operation of amedical cooling device conducting a medical cooling process for cooling a body part ofa patient is provided. The operation of the medical cooling device is based on a numberof process parameters, Wherein the method comprises monitoring at least one processparameter relating to a state of shivering of the patient. The method further comprisesmaking a decision relating to the state or degree of shivering of the patient based on theat least one monitored process parameter. Moreover, the method comprises adapting acontrol process parameter based on the at least one monitored process parameter and thedecision made to put the patient in a reduced state of shivering or a non-shivering state.Furthermore, the method comprises re-starting the medical cooling process according tothe adapted control process parameter.

Control unit, medical cooling device, and method according to the aspectsabove are associated With a number of advantages. First and foremost, the negative impacts of the patient during medical cooling are avoided, by reducing or completely removing the Waste of energy used by the patient in terms of shivering to counteract themedical Cooling process. Another advantage is that the control unit, medical coolingdevice, and method may be used to detect a shivering state in any patient, irrespective of age, Weight, and other factors having impact on the onset temperature of shivering.

BRIEF DESCRIPTION OF DRAWINGS In order to explain the invention, a number of embodiments of the inventionWill be described below With reference to the draWings, in Which: Fig 1 is a schematic view of a medical cooling device according to oneembodiment; and Fig. 2 illustrates a method according to an embodiment.

DESCRIPTION OF EMBODIMENTS An idea of the present invention is to consider the impact of shivering on themedical cooling process. In particular, an idea is to identify certain parameters relatingto the state or degree of shivering of the patient during the medical cooling process.Based on the identified shivering state the medical cooling treatment process may beadapted such as to optimize the benefits to the patient and treatment result, and in thisWay the negative effects of the patient Working against the cooling process is reduced.Hence, the aim of the adapted cooling treatment process is to maintain the bodytemperature of the patient just above the temperature at Which shivering is detected.

The shivering activity of the patient, aiming at increasing the bodytemperature, opposes the purpose of the medical cooling process Which is to cool thebody part of the patient. The solution of the present invention takes this into account tooptimize the medical cooling process.

By definition, shivering is involuntary, oscillatory muscular activity that cangreatly increase one's metabolic heat production to counteract imminent hypotherrnia.Forceful shivering can increase heat production several fold. Shivering, in the absenceof methods for measurement of brain temperature in usual care, is acting as a biologicalsafeguard against temperatures beloW 35°C. At the same time, shivering may preventthe achievement of brain temperatures that are sufficiently loW to obtainneuroprotection. HoWever, there are pharrnacological means of reducing the shiveringthreshold. For example, the combined administration of buspirone and dexmedetomidine has been shoWn to reduce the shivering threshold to 34°C.

In an embodiment, according to Fig. 1, a medical cooling device 10 isprovided. The medical cooling device 10 comprises a cooling fluid supply source 11(schematically shown in Fig. 1 with dotted lines). The medical cooling device 10comprises a supply line 12 for supplying a flow of cooling fluid from the cooling fluidsupply source to a patient. A retum line 14 is connected between the fluid distributiondevice 13 and the cooling fluid supply source. The supply line and the retum line formpart of a cooling circuit and may comprise tubes.

The cooling circuit may further comprise at least one cooling fluid distributiondevice 13, e.g. a wearable garrnent, which distributes the supplied cooling fluid aroundthe body part of the body to be cooled. The at least one distribution device may containa channel pattem for improving the cooling efficiency. The cooling fluid distributiondevice is connected at one end to the supply line 12 and at the other end to the retumline 14. The cooling fluid distribution device 13 preferably has a shape being configuredto encompass and tightly fit the body part of the patient to be cooled. The cooling of thebody part of the patient is thus govemed by means of conductive heat transfer betweenthe cooling fluid in the distribution device 13 and the body part of the patient to thecooled. Hence, the cooling of the body part of the patient is preferably made ex vivowhereby there is no direct contact between the cooling fluid and the body part of thepatient to be cooled.

Ideally liquid cooling distribution device is preferably made of a materialshowing good heat conductive properties and comfortable fit in use. While metals havevery good heat conductive properties, they are less suitable too allow for a comfortablefit on the body part. According to one embodiment, the at least one fluid distributiondevice is made of a silicon material which allows for a very comfortable fit however,having less heat conductive properties than a metal.

Depending on the type of material the temperature of the cooling fluid coolingsupply source may be altered. For example, the temperature of the cooling fluid in thesupply source when the distribution device is made of a silicon material may bebetween -9 °C and -6°C, such as -7 °C. For a distribution device material having better(compared to silicon) heat conductive properties the temperature of the cooling fluid inthe supply source may be higher than -6 °C, such as -2°C, or even higher such as 4 °C to5°C. Depending on the type of condition the patient is in, more than one distributiondevice may be connected to the medical cooling device. Each distribution device issupplied using a separate cooling circuit, i.e. a separate supply line and a separate retum line.

In an embodiment, one distribution device is arranged to be connected to thescalp of the patient, a further distribution device being arranged to be connected to theneck region of the patient, and yet a further distribution device being arranged to beconnected to one or several body parts having large muscle groups, such as the groin, orthe groin in combination with the lower back and stomach muscles. Such a system willhave three separate cooling circuits, each with an independent supply line and returnline. Hence, the medical cooling device will have three separate outlets for connectionto the separate supply lines and three separate inlets for connection to the separate retumlines.

In an embodiment, the medical cooling device is semiportable and contains abattery in order to allow the cooling system to run for 2-3 hours without access to asocket. This makes it possible to start the cooling in the emergency room (or already inthe ambulance) and continue the cooling during the a couple of hours when a patientwith for example stroke is moved around in the hospital before being placed in a bed ina hospital Ward with access to a socket.

The cooling fluid supply source ll may be integral with or connected to arefrigerator unit (not shown) for cooling the cooling fluid to a certain presettemperature.

The cooling fluid in the patient cooling circuit, i.e. flowing from the medicalcooling device through the supply line, distribution device, retum line and then back tothe medical cooling device may be a conventional refrigerator liquid, such as a glycolbased solution or optionally water. In the event the refrigerator unit utilizes acompressor for cooling the cooling fluid in the supply source, the compressor coolingcircuit being separate from the patient cooling circuit may be using a conventionalcompressor refrigerant.

The medical cooling device l0 may further comprise a flow pump forproviding flow rate of the cooling fluid in the cooling circuit according to the demand.

In an embodiment, the flow pump is a constant flow pump. Here the flow maybe controlled using one or several flow control valves.

In one embodiment the flow control valve is of an ON/ OFF type, e.g. solenoidbeing provided downstream the flow pump. In an ON position the flow of the coolingcircuit allows for the rated flow of the flow pump is supplied to the supply line. In anOFF position no flow is supplied to the supply line whereby, the cooling fluid betweenthe supply line and the retum line is stationary. A mean flow is attained by using a precise timing schedule being stored in the control unit.

In an embodiment, the flow control valves may be proportional valves, whichmay be set to more than two positions for allowing different flow rates to passdepending on the position of the valve.

Two main factors affecting the cooling efficiency of the body part of thepatient are the fluid flow rate and the temperature of the cooling fluid leaving themedical cooling device via the supply line 12. Increased flow for any cooling fluidtemperature being below the temperature of the body part of the patient results in ahigher rate of cooling. Similarly, for a constant flow rate any reduction in the coolingfluid temperature leaving the medical cooling device will result in a higher rate ofcooling of the body part.

The medical cooling device 10 further comprises a control unit 15 (beingschematically indicated with dotted lines in Fig. 1).

The control unit may be conf1gured to allow for a precise flow in the supplyline by means of controlling the flow control valves. For example, if the flow pumpprovides a rated flow of 6000ml-8000/min, and the control unit is configured to providea flow in the supply line of 2000ml/min flow, the flow control valve needs to be in theOFF position during 20 seconds each minute. For example, the timing schedule maydefine the flow control valve to be OFF 10 times /minute with duration of 2 secondseach time. Altematively, the flow control valve may be OFF 5 times/min with durationof 4 seconds each time in the OFF position. Altematively, the control valve may be setto OFF once during 20 seconds per minute.

In an embodiment, the timing schedule of the ON/ OFF valve(s) may bechanged depending on the closeness to the expected onset of shivering state. Forexample, the ON/OFF valve(s) may be open until the cooling fluid is reduced to thedemanded cooling fluid temperature, e.g. -7°C and for a predeterrnined time afterreaching the demanded cooling temperature, after which the flow is reduced by closingthe ON/ OFF valve(s) according a frequency/ duration govemed by the timing schedule.After another predeterrnined time period the closing frequency/ duration may be alteredfurther if desired.

Monitoring of the process parametersThe control unit is conf1gured to monitor at least one process parameterrelating to a state or degree of shivering of the patient. The control unit comprises a processor and a memory and is thus capable of computer processing capabilities.

Within the context of the present invention the at least one process parametermay relate to any one or combination of the following: the flow rate of the pump, thesupply line fluid temperature, the retum line fluid temperature, the temperaturedifference between the supply line fluid temperature and the retum line fluidtemperature, the instant and/or demanded cooling fluid temperature of the cooling fluidsupply source, or the energy consumption of the cooling fluid supply source.

In practice the instant expression levels, e.g. in the form of magnitude or value,of the individual process parameters may be measured using at least one temperaturesensor e. g. being provided connection to the supply line 12, the retum line 14, and/or inor in the vicinity of the cooling fluid supply source.

A flow meter could be used to measure the cooling fluid flow rate in the supplyline.

Altematively, if on/off valves and a constant flow pump are used, a mean flowmay be calculated based on the rated flow (e.g. 21/min) of the pump and the time periodduring which the valve is in the on and off state, respectively. When the ON/ OFF flowcontrol valves using are set to OFF the cooling fluid may be stationary in the coolingcircuit. This will mean that the temperature between the supply line and the retum linewill be heated by the distribution device by the body heat. Hence, in this case thecontrol unit is configured to disregard temperature indications from the supply linetemperature and retum line temperature indicating an increase in retum line temperatureuntil the volume of cooling fluid being stationary in the supply line, distribution device,and the retum line has been flushed out setting the ON/ OFF valve to ON again.

The energy consumption could be measured e. g. by any conventional powerconsumption measuring device etc, such as an ammeter connected in series with therefrigerator unit.

In the normal case the medical cooling treatment may be started with atemperature of the cooling fluid in the cooling fluid supply source corresponding to theambient temperature, e.g. being around 20°C. Hence, initially the supply sourceincluding the refrigerator unit, will require maximum power to cool the cooling fluiddown to the set demand temperature of -9 °C to -6°C. During this time, the energyconsumption will thus be high. Accordingly, the control unit may be configured tomonitor the energy consumption of the refrigerator unit once the temperature of thecooling fluid supply source has reached the set demand temperature. Hence, when monitoring the energy consumption of the refrigerator unit the control unit also monitors the temperature in the supply liquid in order to make a decision of increasedenergy consumption due to onset of shivering.

In an embodiment, two temperature sensors are provided in the cooling fluidsupply source.

Moreover, the control unit may be configured to store instant expression levelsin its memory in order to derive rate of change, eg. first derivative, and secondderivative, based on at least two instant expression levels.

In an embodiment, the at least one process parameter relates to an instanttemperature difference between the temperature of the cooling fluid exiting the medicalcooling device 10 to the patient and the temperature of the cooling fluid retuming to themedical cooling device 10 from the patient. An instant temperature difference beingbelow a predeterrnined threshold may be considered being an indication of the patientbeing in a state of shivering.

In another embodiment, two or more successive instant temperature differencesbeing below a predeterrnined threshold may be an indication of the patient being in astate of shivering.

In an embodiment, the at least one process parameter relates to a rate oftemperature difference between the temperature of the cooling fluid exiting the medicalcooling device 10 to the patient and the temperature of the cooling fluid retuming to themedical cooling device 10 from the patient. Two or more successively monitored ratesdescribing increasingly smaller temperature differences between the exiting coolingfluid and the retuming cooling fluid may be considered being an indication that thepatient is in a state of shivering.

In an embodiment, the at least one process parameter relates to the instantenergy consumption of the medical cooling device being required to maintain a presetpatient temperature, wherein an instant energy consumption increasing beyond athreshold is considered being an indication that the patient is in a state of shivering.

In an embodiment, the at least one process parameter relates to the rate ofenergy consumption of the medical cooling device being required to maintain a presetpatient temperature. A rate of energy consumption increasing beyond a predeterrninedthreshold is considered being an indication that the patient is in a state of shivering.

In an embodiment, the instant energy consumption or rate of energyconsumption of the cooling fluid supply source is calculated using the followingforrnula relating to the first law of therrnodynamics: Q(energy) =1ñ *CP*(T2-TI), wherein Q is the energy, rñ is the mass flow of the Cooling fluid in the supplyline, CP represents a specific heat constant for the cooling fluid at constant pressure, Tlbeing the temperature of the exiting cooling fluid, and T2 being the temperature of theretuming cooling fluid. Hence, instead of actively measuring the energy consumption ofthe cooling fluid supply source this can be calculated using the above forrnula.

In an embodiment, the at least one process parameter relates to the flow of cooling fluid exiting the medical cooling device.

Decision processThe control unit is conf1gured to make a decision relating to the state or degree of shivering of the patient based on the at least one monitored process parameter.

In an embodiment, when ON/ OFF valves are used in the medical coolingdevice, the control unit is configured only to make a decision about shivering whenthere is a flow in the supply line. Hence, when the flow control valve(s) is set to OFF nodecision about shivering will be made.

In order for a decision to be made the control unit may be conf1gured tocompare the instant expression level, e.g. magnitude or value, of the at least onemonitored process parameter to a reference for said process parameter. The referencemay relate to an expected expression level of the monitored process parameter.Altematively, the reference may relate to a preset expression level threshold of theprocess parameter.

Altematively or in combination with comparing instant expression levels, thecontrol unit is capable of comparing expression level rates, e. g. the first or secondderivative of the instant expression levels, of the monitored process parameter with areference in form of an expression level reference rate. For example, a suddenaccelerated increase of the energy consumption of the refrigerator unit may be a strongindication of the onset of shivering. Another significant indication of shivering is in theevent that the retum temperature starts to increase or in other words that the differencebetween the retum line temperature T2 and the supply line temperature Tl starts toincrease.

In order to utilize an expression level reference rate as reference the controlunit is configured to derive a rate of the expression level based on at least twosucceeding instant expression levels.

In an embodiment, as long as at least one comparison between either an expression level and reference expression level or a comparison between an expression lO level rate and an expression level reference rate indicates a state of shivering, thecontrol unit is conf1gured to make a decision that the patient is in a state of shivering.

In another embodiment, at least two comparisons in view of expression levelsor expression level rates, both indicating a state of shivering, are required for the control unit to make a decision that the patient is in a state of shivering.

Example lIn the table below one example of information relevant for the control unit to make a positive decision that the patient is in a state of shivering is shown. Forsimplicity, the example only refers to one cooling circuit comprising only onedistribution device. However, more than one cooling circuits and/or more than one distribution device is also possible within the scope defined herein.

Time Tank Return Flow Consta nt Power Power Core Shivering[minut temp flow (m) (Cp) consump- consump- Temp.es] (T1) temp (T2) [kg/s] [J/kgK] tion tion [°C][°C] [°C] [W] (Exludinglosses)[W] 0 -7 -4,8 0,033 4180 303 101 37 NO20 -7 -4,5 0,031 4180 324 108 36,7 NO40 -7 -4,6 0,032 4180 321 107 36,4 NO60 -7 -4,5 0,033 4180 345 115 36,1 NO80 -7 -4,7 0,031 4180 298 99 35,8 NO100 -7 -4,9 0,033 4180 290 97 35,5 NO120 -7 -1 0,031 4180 777 259 35,5 YES140 -7 -1 0,032 4180 803 268 35,5 YES160 -7 -2 0,015 4180 314 105 35,5 NO180 -7 -1 0,012 4180 301 100 35,5 NO 200 -7 -1 0,011 4180 276 92 35,5 NO220 -7 -1 0,013 4180 326 109 35,5 NO240 -7 -1 0,011 4180 276 92 35,5 NO As may be seen in the table during the first 100 minutes no indication ofshivering is noticeable. After 100 minutes of cooling treatment the core temperature ofthe patient has been reduced from 37 °C to 35,5°C, and the retum flow temperature liessteady at around -4,9°C. After 120 minutes from the start of treatment the situation haschanged. Now the retum temperature has increased to -1°C, which results in a significant increase in power consumption. Based on this information the control unit is ll arranged to decide that the patient is in a state of shivering. In this example theshivering state remains after 140 minutes. The second indication of shivering after 140minutes from the start of treatment also verif1es that the first indication of shivering wascorrect. Based on the positive shivering decision the control unit is configured toreduces the flow from 0,031 to 0,015 kg/s in the cooling circuit. After 160 minutes fromthe start of treatment there is no further shivering indication as the power consumptionhas retumed to a non-shivering level. The retum temperature is relatively constantbetween -2 to -1 °C throughout the cooling treatment, whereas the flow rate remainsbetween 0,011 and 0,015 kg/ s, since the power consumption remains at a non-shiveringlevel. This means that the patient is put in a reduced state of shivering or a non-shivering state, thereby avoiding unnecessary waste of energy by the patient during the cooling treatment.

Adapting control process parameters Based on the decision that the patient is in a state of shivering, the control unit15 is conf1gured to adapt at least one control process parameter and re-starting themedical cooling process according to the adapted control process parameter(s) therebyreducing the degree of shivering of the patient or completely avoiding the state ofshivering.

A key aspect of reducing the degree of shivering or complete avoidance ofshivering is to increase the body temperature to a level where little or no shivering maybe detected. This may be achieved by adapting one or several control processparameters.

The control process parameter may relate to any one or combination of thefollowing: the flow rate of the pump, the demanded cooling fluid temperature of the cooling fluid supply source, a limitation of the electrical power submitted to the cooling fluid supplysource, operation state and timing of flow control valves allowing or limiting thecooling fluid flow to the supply line.

In an embodiment, the control process parameter may be adapted according toany one of the following: flow rate of the cooling fluid is decreased (e.g. by demanding the pump to decrease the flow rate); 12 temperature of the cooling fluid exiting the medical Cooling device isincreased; electrical power to the refrigerator of the medical cooling device is reduced orrestricted.

When the flow is controlled using a constant flow pump and one or moreON/ OFF valves, the control unit may be configured adapt the operation state of the oneor more ON/ OFF valves, such as to change the flow in the cooling circuit. The controlunit may additionally be configured to adapt the timing schedule, such as to extend theduration of the OFF state compared to a predeterrnined time period.

The temperature of the cooling fluid exiting the medical cooling device may beadapted by the control unit by setting a new higher control demand temperature to therefrigerator unit. The refrigerator unit then heats the cooling fluid according to the new control demand temperature of the supply source.

Alarm signalIn an embodiment, the control unit 15 is further configured to activate an alarm signal in response to the decision made in that the patient is in a state of shivering. Thealarm signal may trigger an aural, tactile and/or visual alarm in the medical coolingdevice. For example, a visual alarm may be presented on a display device of the medicalcooling device. An aural alarm signal may be submitted via optional speakers providedon the medical cooling device. The control unit may be configured to provide an alarmsignal in accordance with the guidance for alarm systems in medical electricalequipment and medical electrical systems (e.g. IEC standard IEC 60601-1-8) Altematively, or in combination the control unit may be configured to transmitthe alarm signal to an extemal device, e. g. mobile terminal, to remotely indicate to thehealthcare personnel that the patient is in a state of shivering.

In an embodiment, according to Fig. 2, a method for controlling the operationof a medical cooling device 10 conducting a medical cooling process for cooling a bodypart of a patient is provided. The operation of the medical cooling device 10 is based ona number of process parameters. The method comprises the steps of: monitoring 21 at least one process parameter relating to a state of shivering ofthe patient; making 22 a decision relating to the state or degree of shivering of the patient based on the at least one monitored process parameter, 13 adapting 23 a control process parameter based on the at least one monitoredprocess parameter and the decision made; andre-starting 24 the medical cooling process according to the adapted control process parameter.

One body part of particular interest is the scalp of the patient, and here thedistribution device may be shaped like a cap or helmet. Scalp cooling particularlyadvantageous for lowering the brain temperature in patients suffering of acute stroke aswell as patients undergoing chemo therapy to reduce hair loss.

However, cooling of the brain may also be advantageous after cardiac arrest, inneonatal hypoxia ischemia, insomnia or traumatic brain injury.

It should be appreciated that the medical cooling device, control unit, andmethod according to the embodiments presented herein may be used in combinationwith other methods for brain cooling such as infusion of cold saline or pharrnacologicalcooling with antipyretics such as paracetamol. In the case of ischemic stroke, themedical cooling device, control unit, and method according to the embodimentspresented herein may also be used in conjunction with reestablishment of cerebralperfusion.

Hypotherrnia with lowered brain temperature has been shown to be a robustneuroprotectant against a variety of brain injuries. Recently, a randomized crossoverstudy showed that cooling of the frontal lobes with a scalp cooling device signif1cantlyreduced insomnia.

In usual care, the optimal target brain temperature seems to be 35.0° - 35.5° C.Such low temperatures in the deep brain tissue cannot be reached with scalp coolingonly. However, by adding cooling of the neck over the carotid arteries it is possible toreach the optimal brain temperature. The distribution device according to someembodiments may comprise such additional cooling of the neck over the carotidarteries.

In an embodiment, in addition to the scalp silicon cap, a separate neck bandwith temperature sensors is provided. The neck band is cooled by liquid coolant fromthe same cooling fluid supply source as the cap.

Brain cooling has been shown to be safe at least as long as the brain temperature stays at 34° C or above. 14 The duration of brain Cooling treatment may be anything from 30 minutes up to24 hours or more. For stroke applications, treatment duration of up to at least 72 hoursappears to provide advantageous results. However, some suggestions have been made toprovide cooling treatment for up to ll to 14 days or more depending on the type ofcondition of the patient.

Although some of the embodiments above have been described in relation to astroke application, in Which cooling of the brain is advantageous. It should be noted thatthe embodiments of the present invention is equally useful in the case of cardiac arrest.For patient suffering from a sudden cardiac arrest, body temperature control and coolingtreatment to cause hypotherrnia can be a life saving intervention. This means that thebody temperature of the patient is loWered to reduce the tissue damage due to lack ofoxygen. Patients suffering from a cardiac arrest Who receive a cooling treatment have agreater rate of survival and also have less risk of permanent injury, e.g. brain damage.Cooling treatment at cardiac arrest also protects all of the body organs, Which each hasdifferent sensitivity for ischemia. For example, muscle tissue may cope With ichemia forhours Whereas the brain may suffer great damage Within only a couple of minutes.During cooling treatment of patients suffering from cardiac arrest it may beadvantageous to reduce the body temperature to lower temperatures. According to anembodiment, the distribution device(s) may be provided one or more garrnents, eachconnected to one or more cooling circuits. In the case of cardiac arrest a larger part ofthe body, may be cooled down, and hence the distribution devices may cover a largerportion of the body, such as the legs, stomache area, arms, scalp and neck. In anembodiment, such a garrnent may be provided With a opening at the position of the heart such as to facilitate optional heart surgery, While keeping the garrnent on.

Claims (19)

1. A control unit (15) configured to control the operation of a medical coolingdevice (10) conducting a medical cooling process for cooling a part of a patient,Wherein the operation of the medical cooling device is based on a number of processparameters, the control unit (15) being configured to: monitor at least one process parameter relating to a state of shivering of thepatient; make a decision relating to the state or degree of shivering of the patient basedon said at least one monitored process parameter; adapting a control process parameter based on said at least one monitoredprocess parameter and the decision made to put the patient in a reduced state ofshivering or a non-shivering state; and re-start the medical cooling process according to the adapted control process parameter.

2. The control unit (15) according to claim 1, Wherein said at least one processparameter relates to a temperature difference between the temperature of the coolingfluid exiting the medical cooling device (10) to the patient and the temperature of the cooling fluid retuming to the medical cooling device (10) from the patient.

3. The control unit (15) according to claim 1, Wherein said at least one processparameter relates to the instant energy consumption of the medical cooling device being required to maintain a preset patient temperature.

4. The control unit according to claims 1 to 3, Wherein the monitoring of said atleast one process parameter comprises measuring an instant expression level of said at least one process parameter.

5. The control unit (15) according to claim 4, further configured to derive a rate of change based on at least two instant expression levels.

6. The control unit (15) according to any of the previous claims, Wherein a decision that the patient is in a state of shivering is made based on at least one 16 correlation between an instant expression level of said at least one process parameter and a reference expression level.

7. The control unit (l5) according to any of the previous claims, wherein adecision that the patient is in a state of shivering is made based on at least twosuccessive correlations between two successive instant expression levels of said at least one process parameter and a reference expression level.

8. The control unit (l5) according to any of the previous claims, wherein adecision that the patient is in a state of shivering is made based on at least onecorrelation between an expression level rate of said at least one process parameter and an expression level reference rate.

9. The control unit (l5) according to claim 8, wherein a decision that thepatient is in a state of shivering is made based on at least two successive correlationsbetween two successive expression level rates of said at least one process parameter and an expression level reference rate.

10. l0. The control unit (l5) according to claim 2 in combination with claim 6,wherein the temperature difference being below a temperature difference reference expression level is an indication of the patient being in a state of shivering.

11. ll. The control unit (l5) according to claim 2 in combination with claim 7,wherein two successive temperature differences being below a temperature difference reference expression level is an indication of the patient being in a state of shivering.

12. l2. The control unit (l5) according to claim 3 in combination with claim 7,wherein an increased rate of energy consumption of the medical cooling device beingabove a reference expression level is an indication of the patient being in a state of shivering.

13. l3. The control unit (l5) according to claims 2 and 3, wherein the instantenergy consumption is calculated using the following forrnula relating to the first law of therrno dynamics :Q(energy) =1ñ *CP*(T2-TI), 17 wherein Q is the energy, rñ is the mass flow of the Cooling fluid in the supplyline, CP represents a constant for the cooling fluid related to the specific heat at constantpressure, T1 being the temperature of the exiting cooling fluid, and T2 being the temperature of the retuming cooling fluid.

14. The control unit (15) according to any one of the previous claims, whereinthe control process parameter is selected from the group comprising: flow rate of thecooling fluid, temperature of the cooling fluid exiting the medical cooling device,electrical power to a refrigerator unit of the medical cooling device, or operation stateand timing schedule of a flow control valve allowing or limiting the cooling fluid flowto the supply line.

15. The control unit according to claim 14, wherein based upon a decisionmade, by the control unit, that the patient is in a state of shivering the control processparameter is adapted according to any one of the following: flow rate of the cooling fluid is decreased; temperature of the cooling fluid exiting the medical cooling device isincreased; electrical power to the refrigerator of the medical cooling device is reduced orrestricted; or setting the flow control valve to an OFF position for a predeterrnined time period or an extended time period in view of the predeterrnined time period.

16. The control unit (15) according to any one of the previous claims, beingfurther configured to activate an alarm signal in response to the decision made in that the patient is in a state of shivering.

17. A medical cooling device (10) for conducting a medical cooling process forcooling a body part of a patient, comprising a cooling fluid supply source (11), a supply line (12) for supplying a flow of cooling fluid from the cooling fluidsupply source to a patient, a retum line (14) for receiving the flow of cooling fluid from the patient, and the control unit (15) according to claim 1. 18

18. The medical cooling device (10) according to claim 17, further comprising a cooling fluid distribution device (13) being connected at one end to thesupply line (11) and at the other end to the return line (14), Wherein said fluiddistribution device (13) has a shape being configured to encompass the body part of thepatient to be cooled, Wherein the cooling of the body part of the patient is govemed bymeans of conductive heat transfer between the cooling fluid in the distribution device(13) and the body part of the patient to the cooled.

19. A method (20) for controlling the operation of a medical cooling device(10) conducting a medical cooling process for cooling a body part of a patient, Whereinthe operation of the medical cooling device is based on a number of process parameters,the method comprising: monitoring (21) at least one process parameter relating to a state of shivering ofthe patient; making (22) a decision relating to the state or degree of shivering of the patientbased on said at least one monitored process parameter, adapting (23) a control process parameter based on said at least one monitoredprocess parameter and the decision made to put the patient in a reduced state ofshivering or a non-shivering state; and re-starting (24) the medical cooling process according to the adapted control process parameter.