SE539742C2 - An annular heat exchanger, a bag for use in the heat exchanger and a system for hypothermia treatment - Google Patents

Abstract

21 Abstract The disclosure relates to an annular heat exchanger for use in hypothermiatreatment, the annular heat exchanger being arranged for exchanging heat with afirst fluid contained within a flexible container, the annular heat exchangercomprising: a heat exchanging core comprising: an annularly shaped core element;a heat exchanging element arranged in contact with an outer surface of said coreelement; a supporting isolating element mountable inside of the conically shapedcore element such that a gap is formed between the inner surface of the coreelement and an outer surface of the supporting isolating element to allow fitting theflexible container within the gap, wherein heat is exchanged between the first fluidcontained within the flexible container and a second fluid contained within the heatexchanging element. The disclosure further relates to a system for hypothermiatreatment comprising a conical heat exchanger of the disclosure. Elected for publication: Fig 2

Description

AN ANNULAR HEAT EXCHANGER. Å BAG FÖR LJÉÉE iN THE HEAT EXCHÅNGERAND A SYSTEM FOR HYPOTHERIVIIA TREATIVIENT Field of the invention The present disclosure relates to a heat exchanger. I\/|ore specifically, thedisclosure relates to an annular heat exchanger for use in hypothermia treatment.The disclosure further relates to a flexible bag for use as a flexible container in theannular heat exchanger. The disclosure further relates to a system for hypothermiatreatment of a patient.

Background artHeat exchangers are known in the art. Typically it consists of two or more fluid-containing elements arranged to be in contact with each other. ln case thetemperature of the two or more fluids are different, heat will be exchanged betweenthe two or more fluids as a result from heat transfer. Heat exchangers may use liquidfluids. Alternatively, or additionally, heat exchangers may use gaseous fluids.

Heat exchangers are used in a variety of technical fields for a variety ofdifferent applications. One such application is therapeutic hypothermia treatmentwithin the medical field. The body temperature, or the temperature of body parts of ahuman may have an important effect on a healing process and the risk of apermanent damage for many pathological conditions. Therapeutic Hypothermia iscommonly used in an eifort to irrrprorfe irealth outoornes during reoovery efter a period ofstoppa-d blood flow to the brain. Peršods of poor blood flow ntay be dare to cardiac arrestor the blockage of arr artery by a clot as in the of a stroke. Lack of blood flow andoxygen deprivation is serious as it causes permanent damage to the brain unlesstreatment to restore blood flow and protect nerve cells is initiated at an early stage. ltis well known that cooling the brain effectively may reduce the development ofcellular damage in the aftermath of oxygen deprivation. Cooling of the brain havealso been shown to have positive effects with regards to other aspects. ln the caseof a circulatory arrest, the risk of permanent brain damage has been found todecrease if the temperature of the brain is lowered before, during or after the arrest.ln the case of a brain trauma, cooling of the brain has been shown to decrease therisk traumatic brain injury in certain patient categories.

There are several known methods to cool single organs such as the brain. 2 One example is the patent document WO 2005/087156 of the applicant's, thedocument disclosing a system for cerebral temperature control of a human beingcomprising a double lumen catheter to be inserted through the nostril of a human.The double lumen catheter comprises expandable balloons. This method, utilizingaccess for heat exchange with the brain via the nasal cavity, is often referred to asnasopharyngeal cooling. The double lumen catheter comprises a cooling fluid which,via inlet and outlet tubes are connected to a reservoir comprising a larger volume ofcooling fluid. ln an improved version of the system, a heat exchanger may be usedreplacing the reservoir. This is an improvement as it allows keeping the temperatureat a correct level for a prolonged period of time. At the heat exchanger side, thesystem deposits heat to the heat exchanger via a flexible container (such as e.g. aplastic bag) kept in contact with a heat exchanger core of the heat exchanger.

To achieve an efficient heat exchange, it is preferable to maximize thecontact area between the expandable balloons and the walls of the nasal cavity. Oneway to achieve this is to use an elevated pressure of the cooling fluid in the system,thus expanding the balloons inside the nasal cavity. An unwanted side effect of theincreased pressure is that it also expands and deforms the flexible container at theheat exchanger side of the system, thus lowering the contact area for heat exchangeto the heat exchanger core. ln order for the flexible container to efficiently deliverheat to the heat exchanger core of the heat exchanger, it therefore needs to be firmlyfixed to the heat exchanger core by a pressing plate exerting a force on the flexiblecontainer such that it is pressed against the heat exchanger core. The linear forceexerted by the flexible container on the pressing plate is relatively high, havingrequired relatively heavy and sturdy fixating elements. This, in turn, has resulted in mounting and dismounting the flexible container being inconvenient for the user.

Summarylt is an object to mitigate, alleviate or eliminate one or more of the above- identified deficiencies in the art and disadvantages singly or in any combination andsolve at least the above mentioned problem.

According to a first aspect, these and other problems are solved in full, or atleast in part, by an annular heat exchanger for use in hypothermia treatment, theannular heat exchanger being arranged for exchanging heat with a first fluidcontained within a flexible container, the annular heat exchanger comprising: a heat 3 exchanging core comprising: a annularly shaped core element; a heat exchangingelement arranged in contact with an outer surface of said core element; a supportingisolating element mountable inside of the annularly shaped core element such that agap is formed between the inner surface of the core element and an outer surface ofthe supporting isolating element to allow fitting the flexible container within the gap,wherein heat is exchanged between the first fluid contained within the flexiblecontainer and a second fluid contained within the heat exchanging element.

The word annular should here be interpreted in a broad sense includingcircular shapes but also non-circular shapes such as e.g., oval shapes, ellipticalshapes and stadium (i.e. discorectangle, obround) shapes. Furthermore, the wordannular should be interpreted as describing a three-dimensional structure comprisingan annular two-dimensional shape defined within a plane arranged along two of itsdimensions, the normal of the plane being parallel with the third dimension. Thethree-dimensional structure may not be annularly shaped along the third dimension.The annular two-dimensional shape may be allowed to vary dependent on position ofthe plane along the third dimension. Thus, an annular structure of the disclosure maybe a conical structure. Alternatively, the annular two-dimensional shape may be thesame independent on the of the plane along the third dimension. Thus, an annularstructure of the disclosure may be a cylindrical structure.

By using an annularly shaped core element and a supporting isolatingelement therein, a fluid within a flexible container arranged within the gap formedbetween the inner surface of the core element and the outer surface of thesupporting isolating element may be pressurised without a need for the fixatingelements to take up the total force exerted by the flexible container on the coreelement and supporting isolating element. lnstead, a major part, or all, of the forceswill be absorbed by the core element itself as tensile stress directed along thetangential direction of its annularly shaped wall. Likewise, a major part, or all, of theforces exerted by the flexible container on the supporting isolating element will beabsorbed by the supporting isolating element as compressive stress within thesupporting isolating element. ln case a remaining part of the forces exist, it will resultin the establishment of a repulsive force between the core element and thesupporting isolating element directed along their symmetry axes. This repulsive forcewill occur for a case where the annular two-dimensional shape in the plane varieswith the position of the plane along the third dimension, such as for example for aconically shaped core element. ln order to counteract such a repulsive force, it may 4 be required that the core element and the supporting isolating element is anchoredto each other. However, as the repulsive force is considerably smaller than thecorresponding force for a non-annular heat exchanger core, the fixating element canbe made smaller and mounting and dismounting of the flexible container inside theheat exchanger can be made more convenient.

The heat exchanging element may be a tube formed as a coil. This is arelatively simple yet effective way to control the temperature of the core element.

The heat exchanging element may be attached to the outer surface of saidcore element. The heat exchanging element may be attached to the outer surface ofthe core element in different ways. For example, the heat exchanging element maybe soldered, glued or pressed to the outer surface of said core element.

The heat exchanging element may comprise an inlet and an outlet. The inletand the outlet may be fluidly connected such as to form a closed loop. The secondfluid may be arranged to circulate in the loop. This implies that the second fluid maybe continuously transported through the heat exchanging system.

The heat exchanging core may further comprise an insulating layer arrangedto cover the heat exchanging element and/or at least parts of the core element. Theinsulating layer may prevent condensation of water vapour to occur on the relativelycold parts of the heat exchanging core. The insulating layer may also improve theefficiency of the heat exchanger as it reduces unwanted heat exchange with thesurrounding air.

The width of the gap should be enough for the bag to be able to house thefirst fluid. The gap should not be too large, as it increases the cross sectional area forthe fluid flow. As said cross sectional area extends inwards from the inner surface ofthe core element, an increase of this extension will result in an increased volume offluid being transported in the bag relatively far away from the core element. This maydecrease the efficiency of the heat conduction process. The gap may be within theinterval 0.5-5 mm. ln an embodiment, the gap is within the interval 0.5-1.5 mm. lt follows from the disclosure hereinabove that the supporting isolatingelement may have a shape following the inner shape of the core element. Thus, if,for example, the core element is conical, at least a part of the supporting isolatingelement may be conical, but with someshat smaller dimensions to make room for thegap. Alternatively, if, for example, the core element is cylindrical, at least a part of thesupporting isolating element may be cylindrical, but with someshat smallerdimensions to make room for the gap. 5 The supporting isolating element may comprise a temperature isolatingmaterial. This may be advantageous as it may decrease condensation of watervapour on the cold parts of the heat exchanger.

The supporting isolating element may comprise a polymeric foam material.Such a polymeric foam material may be for example a polystyrene foam,polyurethane foam etc.

The supporting isolating element, along the side facing the inner side of theannularly shaped core element, may comprise a surface layer, said surface layercomprising a material which is harder than the material present inside the surfacelayer. The purpose of the surface layer may be to better withstand the pressureexerted on the supporting isolating body by the flexible container. Most of the forceexerted by the flexible container will thus be balanced by compression forces arisinginside the surface layer, along a tangential direction of the surface layer. Thus theinner core of the supporting isolating element will be effectively protected frompressure exerted by the flexible container on the supporting isolating element. Thismay be advantageous as it may prevent a long-term deformation of the isolatingsupporting element. Such a long term deformation of the isolating supoportingelement may be a problem as it causes the gap to increase with time, which allowsfor the flexible container to increase with it, risking operational problems and/ordecreased efficiency of heat exchange.

The annular heat exchanger may be a conical heat exchanger and theannularly shaped core element may be a conically shaped core element. Theconically shaped core element may form a frustum with its larger end open. Afrustum is a right-angle cone with its sharp end removed. This implies that theconically shaped core element will have a smaller end and a larger end, the smallerend and the larger end being opposed to each other and connected to each other bya curved surface. The smaller end may have a circular cross section. The larger endmay have a circular cross section. The smaller end may be closed, thus making theconically shaped core element obtaining a bowl-type shape. Alternatively, thesmaller end may be open or partially open, such as to comprise one or more holes ina wall covering the smaller end.

The conically shaped core element may have an aperture in the interval 10-45°. lt is understood that the aperture is the largest angle between any two linesconnecting the apex of the conically shaped core element and the perimeter of itslarger end. This implies that the aperture is two times the angle between the centre 6 symmetry axis of the conically shaped core element and its curved surface.

The choice of aperture is important. lf the aperture is increased, the repulsiveforce between the core element and the supporting isolating element will alsoincrease and the effect of the inventive concept will decrease. lt is thus understoodthat the aperture should not be too large. On the other hand, the aperture may not betoo small either. There may be a minimum value of the aperture for which the flexiblecontainer will be too difficult to fit inside the gap.

According to a second aspect, a use of the annular heat exchanger accordingto the first aspect for hypothermia treatment is provided.

According to a third aspect, there is provided a bag for use as a flexiblecontainer in the annular heat exchanger according to the first aspect, the bagcomprising: a main body comprising: an inner flexible layer and an outer flexiblelayer overlapping each other, the inner flexible layer and the outer flexible layerbeing sealed together to allow a fluid to be contained in-between the layers, one ormore inlets for inputting a fluid into the bag, one or more outlets for outputting a fluidfrom the bag. The one or more inlets may be arranged at a first end of the body andthe one or more outlets may be arranged at a second end of the main body.Alternatively, the one or more inlets and the one or more outlets may be arranged atthe same end of the main body.

The use of a bag of the type disclosed hereinabove may be advantageous asit allows for a cheap yet efficient way to produce a flexible container.

For a conical heat exchanger comprising a conical core element, the innerlayer and the outer layer may be shaped as an annulus sector such that the mainbody, when folded, fit inside the gap between the conically shaped core element andthe supporting body.

The inner flexible layer and the outer flexible layer may comprise a flexiblepolymeric material. Such a polymeric material may be for example polyethylene,polypropylene, polyvinyl chloride. lt may be advantageous that the inner flexible layer and the outer flexiblelayer is flexible enough to be able to follow and fill the gap. At the same time, it maybe advantageous that the inner flexible layer and the outer flexible layer are not tooelastic, as that may risk unwanted expansion of the bag inside, and potentially evenoutside of, the gap when the fluid is being pressurized. Thus, an in-plane Young'smodulus of the inner flexible layer and the outer flexible layer may be higher than100 l\/lPa. 7 The bag may further comprise at least one inner barrier leaving an opening atone of its ends to allow fluid to pass the inner barrier thus forming a flow path withinthe bag, wherein the flow path comprises at least two portions essentially parallelwith each other.

The bag may comprise two inlets and two outlets. This allows for one bag tobe connected to two cooling circuits. ln such a case, only one conical heatexchanger is required. For such a bag, the bag may further comprise at least oneinner barrier arranged such as to form two flow paths within the bag, wherein the twoflow paths are essentially parallel to each other, and wherein each flow path is fluidlyconnected to its own inlet and its own outlet.

The inner layer and the outer layer may have different opacity. This allows fora user, such as medical personnel, to more easily mount the bag inside the heatexchanger with the correct side facing the core element.

One of the layers of the bag may contain a surface configured to reflect IRradiation. This may allow for detecting the temperature of the fluid within the bagusing infrared detection.

According to a fourth aspect, a system for hypothermia treatment of a patient,is provided. The system comprises: an annular heat exchanger according the firstaspect, a bag according to the third aspect, wherein the bag is fitted into the gap ofthe annular heat exchanger, a patient cooling element, and tubing arranged to fluidlyconnect the bag and the patient cooling element via the inlets and outlets of the bag,such that the fluid is allowed to circulate between the bag and the patient coolingelement for cooling the patient.

The system may be adapted for hypothermia treatment via a nasal cavity ofthe patient, the patient cooling element comprising a first balloon catheter adapted tobe introduced through a first nostril into the nasal cavity and a second ballooncatheter adapted to be introduced through a second nostril into the nasal cavity.

The system may further comprise a sealed cabinet enclosing the heatexchanging element and wherein the heat exchanging core constitutes a portion ofthe cabinet wall.

The system may further comprise an IR sensor arranged to measure thetemperature of the fluid within the bag. The IR sensor may be used to provide feedbackfor temperature control. The IR sensor may be arranged to measure the infraredradiation emitted by the bag. This may be based on the emitted infrared radiation beingdependent on the temperature of the emitting material, i.e. the bag. 8 The system may further comprise a control unit arranged to control thetemperature of the first fluid. The control unit may use data from the IR sensor as input.The temperature may be determined from an analysis of the data from the IR sensor.The analysis may be carried out by the control unit. Alternatively, the analysis may becarried out by the IR sensor. The control unit may be arranged to control thetemperature of the first fluid using the temperature reading determined from ananalysis of the data from the IR sensor as input.

The system may further comprise a temperature regulating unit arranged toregulate the temperature of the first fluid. The temperature regulating unit maycomprise a cooling unit. The cooling unit may be a cooling machine (i.e. a refrigerator)operating by initiating heat exchange between a warm and a cold side by arefrigeration cycle. Alternatively, or additionally, the temperature regulation unit maybe a Peltier element utilizing thermoelectric cooling. The temperature regulating unitmay further comprise a heating unit. Such a heating unit may for example be basedon electrical resistive heating.

The heat exchanging element may be f|uidly connected to the temperatureregulating unit, such as to allow the second fluid to circulate between the heatexchanging unit and the heat exchanging element. The circulation may be realizedby actively pumping the second fluid. Pumping may be carried out by a pump unitbeing f|uidly connected to the heat exchanging unit and the temperature regulatingunit in series.

The system may comprise more than one annular heat exchanger. Forexample, the system may comprise two annular heat exchangers. ln such a system,two heat exchanger cores may be enclosed by the sealed cabinet. The two heatexchanging cores may comprise two separate portions on the cabinet wall. Forexample, the two heat exchanging cores may be arranged opposed to each other onopposite sides of the cabinet. ln such a system, two bags, each comprising one inletand one outlet, may be used. This may allow for each balloon catheter to be f|uidlyconnected to its own annular heat exchanger. Thus, the first balloon catheter may bef|uidly connected via tubing to the inlet and outlet of a first bag residing inside thegap of a first annular heat exchanger. ln the same way, the second balloon cathetermay be f|uidly connected via tubing to the inlet and outlet of a second bag residinginside the gap of a second annular heat exchanger. This arrangement may allow amore efficient and reliable cooling.

The second, third and fourth aspect may generally have the same features and advantages as the first aspect.

Brief descriptions of the drawinds The inventive concept will by way of example be described in more detail withreference to the appended schematic drawings, which shows presently preferredembodiments.

Figure 1a shows a perspective of the annular heat exchanger according to anembodiment of the present disclosure. The isolating layer 122 has been illustrated ina cut-open view for the sake of clarity.

Figure 1b shows a cross-sectionai view of the annular heat exchanger shownin Fig. 1a. The isolating layer 122 has been omitted for the sake of clarity.

Figure 2 shows a perspective view of the heat exchanger core, the bag andthe stabilizing isolating element of the annular heat exchanger shown in Fig. 1a andb. The isolating layer 122 has been omitted for the sake of clarity.

Figure 3 shows a side view (3a) and a perspective view (3b) of a bag 550with one inlet and one outlet according to an embodiment of the present disciosure.

Figure 4 shows a side view (4a) and a perspective view (4b) of a bag 650 with two inlets and two outlets according to an embodiment of the present disciosure.

Figure 5 shows a side view (5a) and a perspective view (5b) of a bag 750with one inlet and one outlet and a barrier according to an embodiment of thepresent disciosure.

Figure 6 shows a side view (6a) and a perspective view (6b) of a bag 850with two inlets and two outlets and an inner barrier according to an embodiment ofthe present disciosure.

Figure 7 shows a schematic view of a system 200 for hypothermia treatmentof a patient according to an embodiment of the present disciosure.

Figure 8 shows a schematic view of a system 300 for hypothermia treatmentof a patient according to an embodiment of the present disciosure.

Detailed descriptionThe present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodimentsare shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey thescope of the invention to the skilled person.

The inventive concept relates to an annular heat exchanger. The purpose ofthe heat exchanger is to exchange heat with a circulating fluid which is in fluidconnection with a body heat exchange arrangement arranged in contact with one ormore parts of the body of a patient. One such application is for hypothermiatreatment of the brain where the body heat exchange arrangement may be forexample a catheter arranged to be inserted into the nasal cavity of the patient.Alternatively, the body heat exchanging arrangement may be part of a helmetarranged to be put on a patient”s head. However, the inventive concept should notbe construed as being limited to any of these applications. As the skilled person willreadily realize, the annular heat exchanger, in itself, will be working independentlyfrom the design and application of the body heat exchange arrangement and the wayheat is exchanged with the fluid inside the body heat exchange arrangement.

The annular heat exchanger is intended for medical applications. ln many ofthese applications time will be of utmost importance. Typical applications will includesituations at for example emergency rooms or trauma centers where patients mayhave developed conditions such as brain trauma or stroke. ln such situations, themedical equipment must be easy and fast to apply to the patient in order to reducethe risk of serious injury. At the same time the medical equipment needs to bereliable and durable. The present inventive concept contributes to theserequirements, as will be disclosed in the detailed description hereinbelow.

An example embodiment of an annular heat exchanger will now be describedin detail. The annular heat exchanger in the embodiment is a conical heatexchanger. Thus, in the following detailed description the example embodiment willbe described in terms of a conical heat exchanger. As readily appreciated by aperson skilled in the art, the detailed description is equally valid for an annular heatexchanger of another shape. An example of such an annular heat exchanger is acylindrical heat exchanger.

Referring to Fig. 1, a conical heat exchanger 100 is shown schematically in aperspective view according to an embodiment. The conical heat exchanger 100 ofFig. 1a is also shown in Fig. 1b in a cross-sectional view. Figure 2 shows, for clarity,the conical heat exchanger 100 unassembled. The conical heat exchanger 100 isintended for use in hypothermia treatment. ln the embodiment shown in Fig. 1, theconical heat exchanger 100 is arranged for exchanging heat with a first fluid 11 contained within a flexible container 150. The first fluid is a fluid comprising water asa major constituent. The flexible container 150 is fluidly connected to a body heatexchange arrangement in contact with a body of a patient. A purpose of the conicalheat exchanger 100 is to exchange heat with the flexible container 150. A furtherpurpose of the conical heat exchanger 100 is to control the temperature of the firstfluid within the flexible container 150.

The conical heat exchanger 100 comprises a heat exchanging core 110. Theheat exchanging core 110 comprises a conically shaped core element 112. The coreelement 112 may be made of metal. ln the embodiment, the core element 112 ismade of stainless steel. The core element 112 has a conical geometry with an openstructure where the larger end, i.e. the cone base, is open. The core element 112has a side wall 114 which is curved. The core element 112 is circular-symmetricaround a symmetry axis A. The core element 112 forms a frustum with its larger endopen. Thus, the core element 112 does not comprise a sharp end comprising theapex of the cone. The smaller end of the core element 112 has a bottom wall 116connected to the side wall 114. The core element 112 of the embodiment has anaperture of 42°. The aperture of the core element 112 may, however, be larger orsmaller than 42°. For example, the aperture may be within the interval 10-45°.

The heat exchanging core 110 further comprises a heat exchanging element120 arranged in contact with an outer surface of said core element 112. The heatexchanging element 120 is arranged in contact with the outer surface of the side wall114 of the core element 112. ln the embodiment, the heat exchanging element 120is a tube formed as a coil. The heat exchanging element 120 is attached to the outersurface of the side wall 114 of the core element 112. The attachment may berealised in many different ways. For example, the heat exchanging element 120 maybe soldered, glued or pressed to the outer surface of the side wall 114 of the coreelement 112. ln the embodiment, the heat exchanging element 120 is soldered to theouter surface of the side wall 114 of the core element 112.

The heat exchanging element 120 contains a second fluid. ln theembodiment, the second fluid comprises water as a major constituent. The first fluidand the second fluid are kept in separate systems and will never make contact withone another. The heat exchanging element 120 is fluidly connected to a temperatureregulation unit arranged to regulate the temperature of the second fluid. Such atemperature regulation unit may be for example a cooling machine (i.e. a refrigerator) operating by initiating heat exchange between a warm and a cold side by a |15 12 refrigeration cycle. Alternatively, or additionally, the temperature regulation unit maybe a Peltier element utilizing thermoelectric cooling. Alternatively, or additionally, thetemperature regulation unit may utilize electrical heating.

The heat exchanging core 110 further comprises an insulating layer 122arranged to cover at least the outer surface of the side wall 114 of the core element112 and the heat exchanging element 120. The insulating layer 122 preventscondensation of water vapour present in the air to occur on the relatively cold partsof the heat exchanging core 112. The insulating layer 122 also improves theefficiency of the heat exchanger 100 as it reduces unwanted heat exchange with thesurrounding air.

The heat exchanger 100 further comprises a supporting isolating element13114110. The supporting isolating element 1313/1110 is mountable inside of theconically shaped core element 112 such that a gap 113 is formed between the innersurface of the core element 112 and an outer surface of the supporting isolatingelement 1fi4fl§0 to allow fitting the flexible container 150 within the gap 113.

The supporting isolating element 130 is shaped such that at least a part ofthe supporting isolating element 130 is conical, but with someshat smallerdimensions than the core element 112 (in which it is inserted) to make room for thegap 113. ln the embodiment, the supporting isolating element 130 and the coreelement 112 is circular-symmetric and coaxial with each other.

The supporting isolating element 130 comprises a temperature isolatingmaterial. ln the embodiment, the isolating material is a polymeric foam material.Examples of polymeric foam materials are for example polystyrene foam orpolyurethane foam.

The supporting isolating element 130 comprises, along the side facing theinner side of the conically shaped core element, a surface layer 132. This isillustrated in Fig 1b. The surface layer 132 comprises a material which is harder thanthe material present inside the surface layer. A purpose of the surface layer 132 is tobetter withstand the pressure exerted on the supporting isolating body 130 by theflexible container 150. l\/lost of the force exerted by the flexible container 150 is thusbalanced by compression forces arising inside the surface layer 132, along atangential direction of the surface layer 132. Thus the inner core of the supportingisolating element 130 will be effectively protected from pressure exerted by theflexible container 150 on the supporting isolating element 130. 13 The gap 113 formed between the inner surface of the core element 112 andthe outer surface of the supporting isolating element 1í_3_fi4110 is relatively narrow. lnthe embodiment, the gap 113 is 1.0 mm. The gap 113 may, however, be smaller andlarger than 1.0 mm. For example, the gap 113 may be within the interval of 0.5-5mm. Alternatively, the gap 113 may be within the interval of 0.5-1.5 mm. The width ofthe gap 113 should be enough for the bag 150 to be able to house the first fluid. Thegap 113 should not be too large, as it increases the cross sectional area for the fluidflow. As said cross sectional area extends inwards from the inner surface of the coreelement 112, an increase of this extension will result in an increased volume of fluidbeing transported in the bag 150 relatively far away from the core element 112. Thismay decrease the efficiency of the heat conduction process.

The heat exchanger 100 operates by exchanging heat between the first fluidand the second fluid by heat conduction. The first fluid is present within the flexiblecontainer 150. The first fluid is arranged to continuously circulate so that the fluidwithin the flexible container 150 is continuously replaced by new fluid. ln case theflexible bag is disposed inside the gap 113 formed between the inner surface of thecore element 112 and an outer surface of the supporting isolating element fglíí4ij0,the heat exchange between the first fluid and the heat exchanger 100 will occur atthe contact area between a side of the flexible container 150 and the inner surface ofthe core element 112. The core element 112 exchanges heat with the second fluidvia its outer surface being in contact with the heat exchanging element 120. ln the embodiment, the flexible container 150 is a bag. The bag 150according to the embodiment is shown in Fig. 2 and Fig 3a and b respectively. Thebag 150 has a main body 152. The main body 152 comprises an inner flexible layer154a and an outer flexible layer 154b overlapping each other. The inner flexible layer154a and the outer flexible layer 154b are sealed together to allow a fluid to becontained in-between the layers. ln the embodiment, the fluid will be the first fluid.One or more inlets 156 are arranged on the main body for inputting a fluid into thebag 150. One or more outlets 158 are arranged on the main body for outputting afluid from the bag 150.

The inner layer 154a and the outer layer 154b are shaped as an annulussector such that the main body 152, when folded, may fit inside the gap 113 betweenthe conically shaped core element 112 and the supporting isolating body 130.

The inner flexible layer 154a and the outer flexible layer 154b comprises aflexible polymeric material. Such a polymeric material may be for example 14 polyethylene, polypropylene, polyvinyl chloride. lt may be advantageous that the inner flexible layer 154a and the outerflexible layer 154b are flexible enough to be able to follow and fill the gap 113. At thesame time, it may be advantageous that the inner flexible layer and the outer flexiblelayer are not too elastic, as that may risk unwanted expansion of the bag inside, andpotentially even outside of, the gap 113 when the fluid is being pressurized. Thus,according to the embodiment, an in-plane Young's modulus of the inner flexible layer154a and the outer flexible layer 154b is higher than 100 l\/lPa.

The inner layer 154a and the outer layer 154b have different opacity. Thisallows for a user, such as medical personnel, to more easily mount the bag insidethe heat exchanger 100 with the correct side facing the core element 112.

One of the layers 154a,154b of the bag 150 contains a surface configured toreflect IR radiation. This allows for detecting the temperature of the fluid within thebag using infrared detection. ln another embodiment shown in Fig 4a and b, the bag 650 comprises twoinlets 656 and two outlets 658. This may allow for one bag to be fluidly connected toa body heat exchanging arrangement comprising two separate heat exchangingelements. ln such a case, only one conical heat exchanger is required. ln yet another embodiment shown in Fig 5a-b, The bag 750 comprises aninner barrier leaving an opening at one of its ends to allow fluid to pass the innerbarrier thus forming a flow path within the bag. The the flow path comprises at leasttwo portions essentially parallel with each other. ln yet another embodiment shown in Fig 6a-b, the bag 850 comprises aninner barrier 890, two inlets 856 and two outlets 858 arranged such as to form twoflow paths within the bag 850. Each of the two flow paths are fluidly connected to itsown inlet and its own outlet.

Figure 7 shows a schematical view of a system 200 for hypothermiatreatment of a patient 202 according to an embodiment.

The system 200 comprises a conical heat exchanger 100 according to theembodiment disclosed hereinabove. Alternatively, the system 200 may comprise anannular heat exchanger according to another embodiment of the inventive conceptas defined by the claims. Such an annular heat exchanger could be for example acylindrical heat exchanger.

The system 200 further comprises a bag 150 according to any one of theembodiment disclosed hereinabove. Alternatively, the system 200 may comprise a bag according to another embodiment of the inventive concept as defined by theclaims. The bag may be fitted into the gap 113 of the conical heat exchanger 100.

The system 200 further comprises a patient cooling element 210, and tubing204 arranged to fluidly connect the bag 150 and the patient cooling element 210 viathe inlets 156 and outlets 158 of the bag. This allows for the first fluid to circulatebetween the bag 150 and the patient cooling element 210 for cooling the patient 202.

The system 200 further comprises a sealed cabinet 230 enclosing the heatexchanging element 110 and wherein the heat exchanging core 112 constitutes aportion of the cabinet wall. ln the embodiment shown in Fig. 7, the system 200 is adapted forhypothermia treatment via a nasal cavity 220 of the patient 202. The patient coolingelement 210 comprises a first bal|oon catheter 212a adapted to be introducedthrough a first nostril into the nasal cavity 210 and a second bal|oon catheter 212badapted to be introduced through a second nostril into the nasal cavity 220.

The system 200 further comprises an IR sensor 140 arranged to measure thetemperature of the fluid within the bag 150. The IR sensor 140 is used to providefeedback for temperature control. The IR sensor 140 is arranged to measure theinfrared radiation emitted by the bag 150. This is based on the emitted infraredradiation being dependent on the temperature of the emitting material, i.e. the bag150.

The system 200 further comprises a control unit arranged to control thetemperature of the first fluid. The control unit uses data from the IR sensor 140 asinput. The temperature is determined from an analysis of the data from the IR sensor140. ln the embodiment, the analysis is carried out by the control unit. Alternatively,the analysis may be carried out by the IR sensor 140. The control unit is arranged tocontrol the temperature of the first fluid using the temperature reading determinedfrom an analysis of the data from the IR sensor 140 as input.

The system 200 further comprises a temperature regulating unit arranged toregulate the temperature of the first fluid. The temperature regulating unit comprisesa cooling unit. ln the embodiment, the cooling unit is a cooling machine (i.e. arefrigerator) operating by initiating heat exchange between a warm and a cold sideby a refrigeration cycle. Alternatively, or additionally, the temperature regulation unitmay be a Peltier element utilizing thermoelectric cooling. The temperature regulatingunit may further comprise a heating unit. Such a heating unit may for example bebased on electrical resistive heating. 16 ln the embodiment, the heat exchanging element 120 is f|uidly connected tothe temperature regulating unit, such as to allow the second fluid to circulatebetween the heat exchanging unit and the heat exchanging element 120. Thecirculation is realized by actively pumping the second fluid. Pumping is carried out bya pump unit being f|uidly connected to the heat exchanging unit and the temperatureregulating unit in series.

As can be seen in the embodiment shown in Fig. 7, the system 200 has onlyone conical heat exchanger. For such a system, an embodiment of the bagcomprising two inlets and two out|ets can be used. This allows for the bag to bef|uidly connected to both the first ba||oon catheter and the second ba||oon catheter.

Alternatively, the system may comprise more than one conical heatexchanger. An example embodiment showing such an arrangement is shown in Fig.8 showing a system 300 comprising a first conical heat exchanger 100a and asecond conical heat exchanger 100b. ln the embodiment, a first heat exchanger core110a and a second heat exchanger core 110b are enclosed by the sealed cabinet330. The first heat exchanger core 110a and the second heat exchanger core 110bcomprises two separate portions on the cabinet wall. ln the embodiment, the firstheat exchanger core and the second heat exchanger core 110b are arrangedopposed to each other as shown in Fig. 8. ln such a case, a first bag 150a and asecond bag 150b, each comprising one inlet 156a,156b and one outlet 158a,158b,can be used. This allows for each ba||oon catheter to be f|uidly connected to its ownconical heat exchanger. Specifically, for the system 300, the first ba||oon catheter312a is f|uidly connected via tubing 304a to the inlet 156a and outlet 158a of the firstbag 150a residing inside the gap of the first conical heat exchanger 100a. ln thesame way, the second ba||oon catheter 312b is f|uidly connected via tubing 304b tothe inlet 156b and outlet 158b of the second bag 150b residing inside the gap of thesecond conical heat exchanger 100b. This arrangement may allow a more efficientand reliable cooling.

The embodiments herein are not limited to the above described examples.Various alternatives, modifications and equivalents may be used. For example, oneor more cylindrical heat exchangers using cylindrically shaped core elements may beused in the system. This disclosure should therefore not be limited to the specificform set forth herein. This disclosure is limited only by the appended claims andother embodiments than the mentioned above are equally possible within the scopeof the claims.

Claims (25)

17 CLA|I\/IS

1. Annular heat exchanger Qíšgfior use in hypothermia treatment,the annular heat exchanger being arranged for exchanging heat with a firstfluid contained within a flexible containernlmišgíi, the annular heat exchangercomprising:a heat exchanging core íllfglcomprising:an annularly shaped core element_gj_f_f_2_}_;a heat exchanging element l 12th arranged in contact with an outer surface of said core element; a supporting isolating element Qgšgimountable inside of the annularlyshaped core element such that a gap ijjåluis formed between an inner surface ofthe core element and an outer surface of the supporting isolating element to allowfitting the flexible container within the gap, wherein heat is exchanged between the first fluid contained within the flexiblecontainer and a second fluid contained within the heat exchanging element.

2. The annular heat exchanger according to claim 1, wherein the heatexchanging element is a tube formed as a coil.

3. The annular heat exchanger according to claim 1 or 2, wherein the heatexchanging element is attached to the outer surface of said core element.

4. The annular heat exchanger according to any one of claim 1-3, wherein thegap is within the interval 0.5-5 mm.

5. The annular heat exchanger according to any one of claim 1-3, wherein thegap is within the interval within 0.5-1.5 mm.

6. The annular heat exchanger according to any one of the preceding claims, wherein the supporting isolating element comprises a temperature isolating material.

7. The annular heat exchanger according to any one of the preceding claims, wherein the supporting isolating element comprises a polymeric foam material. |2O 18

8. The annular heat exchanger according to any one of the preceding claims,wherein the supporting isolating element, along the side facing the inner side of theannularly shaped core element, comprises a surface layer, said surface layer comprising a material which is harder than the materialpresent inside the surface layer.

9. The annular heat exchanger according to any one of the preceding claims,wherein the annular heat exchanger is a conical heat exchanger and the annularlyshaped core element being a conically shaped core element.

10. The annular heat exchanger according to claim 9, wherein the conicallyshaped core element forms a frustum with its larger end open.

11. The annular heat exchanger according to claim 9 or 10, wherein the conically shaped core element has an aperture in the interval 10-45°.

12. Use of the annular heat exchanger according to any one of claim 1-11 forhypothermia treatment.

13. A bag ítšfš) for use as a flexible container in the annular heat exchangeraccording to any one of the claims 1-11, the bag comprising:a main body (1521 comprising: an inner flexible layer íjäßígggfland an outer flexible layer ílëgtgloverlapping each other, the inner flexible layer and the outer flexible layer being sealedtogether to allow a fluid to be contained in-between the layers,one or more inlets gjßfijmfor inputting a fluid into the bag,one or more outlets gfljwšíšjwfor outputting a fluid from the bag.

14. The bag according to claim 13, wherein the inner flexible layer and theouter flexible layer comprises a flexible polymeric material.

15. The bag according to claim 13-14, wherein with an in-plane Young”smodulus of the inner flexible layer and the outer flexible layer is higher than 100l\/lPa. 19

16. The bag according to any one of claim 13-15, further comprising at leastone inner barrier gïšiügïëëüi leaving an opening at one of its ends to allow fluid topass the inner barrier thus forming a flow path within the bag, wherein the flow pathcomprises at least two portions essentially parallel with each other.

17. The bag according to any one of claim 13-15, comprising two inletsfåfißßštšl and two outlets fßšêgšâåi.

18. The bag according to claim 17, further comprising at least one innerbarrier arranged such as to form two flow paths within the bag, wherein the two flowpaths are essentially parallel with each other, and wherein each flow path is fluidlyconnected to its own inlet and its own outlet.

19. The bag according to any one of claim 13-18 wherein the inner layer and the outer layer have different opacity.

20. The bag according to any one of claim 13-19 wherein one of the layers ofthe bag comprises a surface configured to reflect IR radiation.

21. The bag according to any one of claim 13-20, wherein the inner layer andthe outer layer being shaped as an annulus sector such that the main body, whenfolded, fit inside the gap between the conically shaped core element and thesupporting isolating body.

22. A system for hypothermia treatment of a patient, the system comprising: An annular heat exchanger according to any one of claim 1-11, a bag according to any one of claim 13-21, wherein the bag is fitted into thegap of the annular heat exchanger, a patient cooling elementflígfi, and tubing (2ü4,íšü4a,3í?=4t:-§ arranged to fluidly connect the bag and the patientcooling element via the inlets and outlets of the bag, such that the fluid is allowed tocirculate between the bag and the patient cooling element for cooling the patient.

23. The system according to claim 22, wherein the system is adapted forhypothermia treatment via a nasal cavity of the patient, the patient cooling elementcomprising a first balloon catheter 121 2:a. 312.59 adapted to be introduced through afirst nostril into the nasal cavity íggmüjmand a second balloon catheter íâtâbßftâbtadapted to be introduced through a second nostril into the nasal cavity.

24. The system according to claim 22 or 23, further comprising a sealedcabinet 52363303 enclosing the heat exchanging element and wherein the heatexchanging core constitutes a portion of the cabinet wall.

25. The system according to any one of claim 22-24, further comprising an IRsensor (1493 arranged to measure the temperature of the fluid within the bag.