Patent Description:
Patient temperature control systems have been introduced to prevent fever in patients in the neuro ICU due to suffering from sub-arachnoid hemorrhage or other neurologic malady such as stroke. Also, such systems have been used to induce mild or moderate hypothermia to improve the outcomes of patients suffering from such maladies as stroke, cardiac arrest, myocardial infarction, traumatic brain injury, and high intracranial pressure. Examples of intravascular heat exchange catheters are disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>,<CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, and <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,.

External patient temperature control systems may be used. Such systems are disclosed in <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>,<CIT>,<CIT>, <CIT>, and <CIT> (collectively, "the external pad patents").

In the present assignee's <CIT>, a heat exchange console that could receive the coils of working fluid loops of both an intravascular heat exchange catheter and an external heat exchange pad was described and patented. In general, in all of the intravascular and external patient temperature control solutions, the temperature of the working fluid flowing through the catheter or pad is regulated by a heat exchange console based on feedback provided by the patient's actual body temperature, typically core body temperature as may be variously measured rectally, esophageally, tympanic car temperature, blood temperature in, e.g., the vena cava, etc. The working fluid temperature is regulated by thermally coupling the working fluid to heating and/or cooling elements in the console.

<CIT> discloses a fluid warming cassette with a stiffening frame structure and an integral handle is provided to support a parenteral fluid container. The fluid container is desirably thin to minimize heat exchange inefficiencies. The frame structure permits the thin fluid container to be inserted into the narrow space between fixed position warming plates of a warming unit. The frame structure has a quadrilateral shape with sides and ends. The fluid container is attached, at its periphery to the sides and ends of the frame structure, within the quadrilateral shape. Part of the frame structure is formed into a handle to assist in both the insertion and removal of the cassette from a warming unit. <CIT> discloses a disposable cassette for an intravascular heat exchange catheter. <CIT> relates to a heat exchange system for patient temperature control with multiple coolant chambers for multiple heat exchange modalities.

<CIT> relates to an apparatus for heating or cooling fluids, particularly physiological fluids such as blood or plasma or fluids, such as dialysis fluid, which are used in the treatment of physiological fluids. Also disclosed are containers in which or through which fluids may be contained or circulated in order to effect heating or cooling.

The invention is defined by independent claim <NUM> and various embodiments are described in dependent claims <NUM>-<NUM>. An apparatus is disclosed that includes a plate assembly having a cassette slot configured to receive a membrane assembly of a cassette, with the membrane assembly being configured for containing working fluid from an intravascular heat exchange catheter or external heat exchange pad or other modality patient heat exchange member. The plate assembly also includes rail receptacles straddling respective sides of the slot and configured for receiving respective side rails of the cassette. At least a first bulge cavity, receptacle or groove is formed inboard of a first one of the rail receptacles. The first bulge cavity has a diameter or width at its widest point that is greater than a width of the slot.

In examples, a second bulge cavity, receptacle or groove is formed inboard of a second one of the rail receptacles. The second cavity may have a diameter or width at its widest point that is greater than a width of the slot. Both bulge cavities join with respective sides of the slot. In certain embodiments, the first and/or second bulge cavity may have a diameter or width at its widest point that is less than a transverse diameter or width of the first or second rail receptacle, and/or greater than a width of the slot.

When die cassette is engaged with the apparatus with the membrane assembly disposed in the slot and the side rails of the cassette disposed in the rail receptacles, a first portion of the membrane, e.g., near an edge of the membrane assembly, that is inboard of a side rail of the cassette can expand into the first bulge cavity when the membrane assembly is filled with working fluid to thereby establish an enlarged fluid passageway along a vertical side edge of the membrane assembly. The first bulge cavity may extend substantially an entire length of the first rail receptacle and may be a circular or semicircular, diamond or other shape.

In another aspect, an apparatus includes a plate assembly which in turn includes a separator plate formed with a first channel on a first side of the separator plate and a second channel on a second side of the separator plate that is opposite the first side. The first channel is configured for receiving refrigerant from a compressor therethrough and the second channel is configured for receiving water or other fluid from a patient heat exchange pad or from a source of water or other fluid other than the pad. A first backing plate abuts the first side of the separator plate and a second backing plate abuts the second side of the separator plate. A cavity borders the first backing plate opposite to the separator plate and is configured for receiving a cassette which is configured for holding working fluid circulating through an intravascular heat exchange catheter.

In some examples, the first and second backing plates abut the first and second sides of the separator plate along the entire or substantially the entire first and second sides of the separator plate with only the first and second channels establishing cavities through which respective fluids may flow. One or both channels may be serpentine-shaped.

With this structure, refrigerant in the first channel can exchange heat with fluid in a cassette disposed in the cavity. Likewise, refrigerant in the first channel can exchange heat across the separator plate with fluid in the second channel. Moreover, fluid in the second channel can exchange heat across the separator plate and the first backing plate with fluid in a cassette disposed in the cavity. Refrigerant flow through the first channel may be established to maintain some liquid phase throughout traversal of refrigerant through the first channel. In certain embodiments, other plate assemblies are contemplated which may have one or more channels configured for receiving water or other fluid from a patient heat exchange pad or from another source of water or other fluid (e.g., which has been cooled or heated), where the fluid or water in the channel can exchange heat with fluid in a cassette disposed in the plate assembly.

In another aspect, a heat exchange system to exchange heat with working fluid from an intravascular heat exchange catheter or from an external heat exchange pad or other modality patient heat exchange member includes at least one compressor configured to circulate refrigerant through the system to exchange heat with the working fluid. At least one duct or tube or port is configured for receiving exhaust heat from the compressor and directing the exhaust heat onto a patient.

In certain embodiments, a heat exchange system to exchange heat with working fluid from an intravascular heat exchange catheter or from an external heat exchange pad or other modality patient heat exchange member may include a plate assembly having one or more channels. A channel may be configured for receiving refrigerant therethrough, where refrigerant flow through a channel is established or adjusted to maintain at least some liquid phase throughout traversal of refrigerant through the channel or cold plate and the refrigerant exchanges heat with the working fluid.

The details of the various embodiments described herein, both as to structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which:.

Referring initially to <FIG>, in accordance with present principles, a system <NUM> may include an intravascular heat exchange catheter <NUM> controlled by a control system <NUM> to control patient temperature, e.g., to prevent the patient <NUM> from becoming febrile or to induce therapeutic hypothermia in the patient <NUM>. In the catheter, working fluid or coolant such as but not limited to saline circulates (typically under the influence of a pump "P" in the control system) in a closed loop from the control system <NUM>, through a fluid supply line L1, through the catheter <NUM>, and back to the system <NUM> through a fluid return line L2, such that no working fluid or coolant enters the body. Any of the catheters disclosed above or in the following U. patents may be used, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, The catheter <NUM> may be placed in the venous system, e.g., in the superior or inferior vena cava.

Instead of or in addition to the catheter <NUM>, the system <NUM> may include one or more pads <NUM> that are positioned against the external skin of the patient <NUM> (only one pad <NUM> shown for clarity). The pad <NUM> may be, without limitation, any one of the pads disclosed in the external pad patents referenced above. The temperature of the pad <NUM> can be controlled by the control system <NUM> to exchange heat with the patient <NUM>, including to induce therapeutic mild or moderate hypothermia in the patient in response to the patient presenting with, e.g., cardiac arrest, myocardial infarction, stroke, high intracranial pressure, traumatic brain injury, or other malady the effects of which can be ameliorated by hypothermia. The pad <NUM> may receive working fluid from the system <NUM> through a fluid supply line L3, and return working fluid to the system <NUM> through a fluid return line L4.

The control system <NUM> may include one or more microprocessors <NUM> receiving target and patient temperatures as input and controlling, among other things, the pump "P" and a refrigerant compressor <NUM> and/or a bypass valve <NUM> that can be opened to permit refrigerant to bypass a condenser. The refrigerant circulates through a heat exchanger within the control system <NUM> and described further below. The processor <NUM> may access instructions on a computer memory <NUM> to configure the processor <NUM> to execute logic discussed below. The computer memory <NUM> may be, e.g., disk-based or solid-state storage.

Warm exhaust air from the compressor <NUM> or fan may be directed through a duct <NUM> to warm the patient <NUM>. While <FIG> shows that the duct <NUM> has an open end adjacent the patient, it is to be understood that the duct <NUM> may direct air into a blanket, tent or other covering that partially or complete encloses the patient.

In other embodiments, heat generated by the system <NUM>, e.g., by the compressor or any other component of the system, may be transferred or directed to the surface of a patient to warm the patient before, after or while the patient is being cooled with a heat exchange catheter or pad.

<FIG> also shows that in the absence of refrigerant for the compressor <NUM> or in the absence of electrical power or other reason for not being able to circulate refrigerant through the system to cool the working fluid to the catheter <NUM>, if it is desired to nevertheless cool the working fluid to the catheter <NUM> a source <NUM> such as a cold water bath can be connected to the pad fluid lines L3 and L4 for providing cold fluid to the system to cool the catheter working fluid. Details are discussed further below.

<FIG> shows a portion of an example heat exchanger in the control system <NUM> which includes at least two cold plates <NUM>, <NUM> defining a cassette slot <NUM> between them. In one embodiment, the width "W" of the slot <NUM> is less than forty mils (<NUM>), and may be between twenty nine mils and thirty one mils (<NUM>,<NUM>-<NUM>,<NUM>). In other embodiments, the slot is between <NUM>" - <NUM>" mils (<NUM>-<NUM>).

In a specific example the width "W" may be thirty mils. As further detailed below, the slot <NUM> may establish a coolant chamber to receive a heat exchange member such as but not limited to a cassette through which working fluid from an intravascular heat exchange catheter, external heat exchange pad or external cooling pad or other modality patient heat exchange member flows, Because heat exchange is effected through the walls of the heat exchange member, the working fluid from the catheter or pad does not contact any surface or fluid in the heat exchanger of the control system <NUM> outside the walls of the heat exchange member. In this way, the working fluid, typically saline in non-limiting examples, circulating through the intravascular catheter or pad can remain sterile. Accordingly, attention will first focus on the coolant chamber established by the slot <NUM>.

The cold plates <NUM>, <NUM> may be made of metal, or other thermally conductive materials, and can be rectilinear as shown and indeed may be nearly square. The cold plates <NUM>, <NUM> may abut each other along left and right side walls <NUM>, with elongated vertical cassette frame receptacles R1 and R2 being located immediately inboard of the respective side walls <NUM> and with the slot <NUM> extending between the walls <NUM> and terminating at the receptacles R1, R2 as shown. The frame receptacles R1, R2 may be wider than the slot <NUM>. In the example shown, refrigerant inlet and outlet tubes <NUM>, <NUM> extend through at least one of the cold plates <NUM> to communicate refrigerant from the compressor <NUM> into a refrigerant passageway in the cold plate, which establishes a second coolant chamber in addition to (and in thermal contact with) the first coolant chamber established by the slot <NUM>. Each cold plate may have its own refrigerant inlet and outlet tubes, or each cold plate may have either an inlet or an outlet, e.g., where refrigerant passageways of the cold plates are in fluid communication with one another, or, in the embodiment shown, only one cold plate may be formed with refrigerant inlet and outlet tubes and the other cold plate either thermally coupled to the cold plate in which the refrigerant flows and/or receiving refrigerant from the other cold plate through passageways formed through one or both of the side walls <NUM>.

In one example, pad working fluid inlet and outlets Pin and Pout may also be formed in at least one of the cold plates as shown. As discussed in greater detail below, working fluid from the pad <NUM> or from the cold fluid source <NUM> via lines L3 and L4, or other lines, may be ported into the pad working fluid inlet and outlets Pin and Pout to exchange heat with the refrigerant or in some cases with the working fluid from the catheter flowing through the cold plates. Also, to provide for warming working fluid, one or more electric heaters <NUM> may be mounted on one or both of the cold plates to heat the cold plates. Alternatively to warm the cold plates, the bypass valve <NUM> (<FIG>) may be opened to allow hot gaseous refrigerant from the compressor to bypass the condenser as the gaseous refrigerant circulates through the system.

<FIG> shows details of an example cold plate <NUM> looking at the inner surface in transparency, it being understood that the inner surface typically is metal and that the serpentine refrigerant passageway <NUM> shown in <FIG> typically would not be visible to the human eye. In any case, the example refrigerant passageway that fluidly connects the refrigerant inlet <NUM> to the refrigerant outlet <NUM> may be serpentine-shaped as shown, or may be some other shape or pattern such as a herringbone pattern, a wave pattern, or a winding, tortuous, or sinuous pattern or a configuration having one or more curves, turns and/or bends, etc..

<FIG> shows an example working fluid cassette <NUM> according to present principles. The cassette <NUM> is configured to fit snugly into the slot <NUM> and cassette frame receptacles R1, R2 defined between the cold plates <NUM>, <NUM>. Working fluid such as saline from a patient-engageable heat exchange member such as the catheter <NUM> or external pad flows through the cassette <NUM> in operation, with the working fluid exchanging heat with the refrigerant in the cold plates. In example embodiments, the cassette <NUM> is a low cost single-use disposable item that can contain, e.g., sterile saline which circulates through the catheter <NUM> or an external pad. The cassette may be placed by a medical caregiver in the slot <NUM> between the cold plates <NUM>, <NUM> and the membrane portion which defines a space or working fluid chamber through which the example saline flows inflates when the working fluid flows through it, achieving thermal contact with the cold plates <NUM>, <NUM>.

In the example shown, the cassette <NUM> includes a frame <NUM> defining a periphery and a preferably rectilinear opening bounded as shown on at least three sides by the periphery of the frame. In the non-limiting example shown, the frame includes an elongated parallelepiped-shaped top rail <NUM> and elongated parallelepiped-shaped left and right side rails <NUM> parallel to each other and perpendicular to the top rail <NUM>. The example frame <NUM> may have a metal strip or bottom rail <NUM> opposite the top rail and connected to the left and right side rails <NUM> to support the membrane and facilitate placing the membrane in biaxial tension. In any case, the example frame <NUM> is rectilinear and is configured for being closely received between the two cold plates <NUM>, <NUM>, with the side rails <NUM> slidably engageable with the frame receptacles R1, R2 between the cold plates <NUM>, <NUM> and with the below-described membrane assembly passed through the slot <NUM> to be in close juxtaposition with the refrigerant channels in the cold plates. In certain variations, the receptacles R1, R2 may be keyed or each have a different shape which corresponds to the shapes or configuration of the side rails of the cassette. This would help ensure that the cassette is inserted into the slots and receptacles in the correct orientation, providing guidance to a user.

In <FIG>, the frame, in the example shown, the top rail <NUM> thereof, is formed with a fluid inlet <NUM> in which an inlet tube <NUM> has been disposed and a fluid outlet <NUM> in which an outlet tube <NUM> has been disposed. Both the inlet and outlet establish respective fluid passageways through the frame into the opening. The inlet and outlet tubes <NUM>, <NUM> may be engaged with the fluid return and supply lines L1, L2 that are associated with the catheter <NUM>. One or both tubes <NUM>, <NUM> may terminate at just below the top rail <NUM> (<FIG>), be flush with the bottom of the top rail, or they may extend any desired length down to the bottom of the assembly, i.e., one or both tubes <NUM>, <NUM> may extend almost the entire length of the left and right side rails <NUM>, ending just above the below-described bottom seam of the membrane assembly. In certain embodiments, the inlet and outlet tubes may extend a length sufficient to allow the tubes to engage features or components in or on the cold plates, e.g., at least a portion or end segment of the tubes may rest in grooves or steps located in or on an inner wall or face of the cold plate. The inlet and outlet tubes may be positioned such that they mate or are in line with bulge cavities in the cold plates. This orientation may help minimize or prevent the membrane assembly from bulging outwards in an uncontrolled or less controlled manner, which could result in a rupture. In certain embodiments, the inlet and outlet tubes <NUM>, <NUM> or separate inlet and outlet tubes may be engaged with the fluid return and supply lines L3, L4 that are associated with the external pad.

Indeed, a membrane assembly <NUM>, e.g., a polymeric membrane assembly, is connected to the frame <NUM>, blocking the opening that is bounded on four sides by the frame as shown. The membrane assembly <NUM> includes a first membrane <NUM> that is parallel to and closely spaced from a second membrane <NUM>, leaving a space therebetween which establishes a working fluid chamber. The fluid inlet <NUM> and fluid outlet <NUM> communicate with the space between the membranes <NUM>,<NUM>. At least one and preferably both of the membranes <NUM>, <NUM> are disposed in tension in the opening. The space between the membranes is expandable when filled with working fluid.

In one example, each membrane is no more than two mils (<NUM>) thick and more preferably is between one mil and three mils in thickness (<NUM> - <NUM>), inclusive. In certain embodiments, each membrane may be between one mil and five mils in thickness (<NUM> - <NUM>) The example membranes <NUM>,<NUM> are co-extensive with the opening and like the opening are more or less square, with the length of top and bottom edges of the example membranes being approximately equal (within ± <NUM>% and more preferably within ±<NUM>%) of the lengths of the left and right edges of the membranes. In other embodiments instead of a square (<NUM>:<NUM>) aspect ratio, an aspect ratio of up to <NUM>:<NUM> may be used. The working fluid chamber between the membranes is also rectilinear and in certain embodiments no obstructions exist between the membranes, meaning the working fluid chamber is a complete rectilinear, more or less square chamber.

Owing to the thinness of the membranes <NUM>, <NUM> and the closeness of the cold plates <NUM>, <NUM> to each other and to the membrane assembly between them when the cassette is engaged with the cold plates, the system shown in the figures affords low impedance of heat transfer between the refrigerant circulating in the cold plates and the working fluid circulating between the membranes <NUM>, <NUM>. The working fluid chamber between the membranes inflates due to backpressure generated by working fluid flow, eliminating or reducing the need for a moving mechanism in the cold plates. Moreover, the narrow slot <NUM> between the two cold plates provides better heat transfer by reducing the conductive path length between the cold plates and the working fluid. The frame allows for ease of handling, such as insertion and removal of the cassette with/from the cold plates.

With respect to the example working fluid chamber between the membranes <NUM>, <NUM> having a width-to-length aspect ratio near <NUM>:<NUM> (i.e., square or nearly so), the amount of backpressure required to induce working fluid flow through heat exchanger is reduced compared to a less square configuration. This reduces the amount of work that a working fluid pump must perform, which is desirable for two reasons. One, since the pump may be disposable, lower performance requirements translate into a lower cost disposable and quieter system. For instance, peristaltic roller pumps offer quiet operation and a low-cost disposable element, but operate most efficiently when only modest pressures are required. Two, lowering the working fluid pump work reduces the amount of heat transferred into the working fluid by the pump itself. Also, a low width/length aspect ratio results in slower working fluid velocity which reduces the amount of mixing, but this otherwise desirable (from a heat exchange standpoint) effect is negligible in the present example system since the Reynolds numbers are typically < <NUM>, suggesting a laminar flow regime. Furthermore, a low width/length aspect ratio significantly reduces the number of bends (or "corners") in the fluid flow path. These bends are areas of mixing for the fluid which promotes heat transfer. Without them, a fluid boundary layer builds up. However, this effect is offset herein by maintaining a narrow slot between the cold plates. This way the primary heat transfer mechanism is by conduction, but the conduction path length (and therefore boundary layer) is small, resulting in a relatively high rate of heat transfer.

In certain embodiments, the surface of the cold plate facing the cassette membrane may be coated with a non-stick ("release"), and/or hydrophobic coating to aid in the removal of the cassette after use. Removal may be difficult in some instances due to backpressure from the saline fluid flow pressing the heat exchange membrane against the cold plate surface for an entire duration of use (e.g., up to <NUM> days), resulting in the membrane sticking to the cold plate. The large surface area may result in high forces which may be difficult for the user to overcome. Additionally, a thin film of water may exist between the membrane and cold plate surface (due to leakage, condensation), resulting in an additional capillary force which in some cases can be difficult to overcome and can result in damage to the cassette or cold plate, making extraction difficult. The non-stick and/or hydrophobic coating mitigates this by minimizing the capillary force. Additionally this water film may dry out completely, potentially resulting in van der Waals adhesion. The non-stick aspect of the coating prevents this from happening. Fluoropolymer coatings provide both hydrophobic and release (non-stick) characteristics, and may be utilized along with other non-stick and/or hydrophobic materials or coatings.

In certain examples, the membranes <NUM>, <NUM> are stretched under tension during assembly to the frame, preferably biaxially (i.e., in tension between the top and bottom rails <NUM>, <NUM> and also in tension between the left and right side rails <NUM>). This tension can be maintained over the shelf life of the product. Pretensioning minimizes wrinkles in material, which is beneficial because wrinkles can impede working fluid flow and create air gaps which reduce heat transfer between the working fluid and cold plates. Wrinkles can also complicate insertion of the membrane assembly into the narrow slot <NUM>.

To establish pre-tensioning of the membranes, the frame may be made in halves and posts, such as threaded fasteners, can extend transversely to one half of the frame, with the membranes <NUM>, <NUM> being stretched over the posts and holes made in the membranes to receive the posts. The other half of the frame is then positioned to sandwich a rectilinear border portion of the membrane assembly between the frame halves, and a closure such as respective nuts engaged with the posts to hold the frame halves together with the membrane assembly field in tension between the frame halves. Optionally a post, e.g., a post that uses a press fit, may be located in one or more frames to hold the frame halves together. The post may be made of plastic or other suitable material. <FIG> shows that the working fluid chamber is closed off at the bottom by a bottom seam 74A of the membrane assembly, which is part of the border portion. In addition to applying tension to avoid wrinkling during use, additional posts may be used to avoid wrinkling during the welding process, improving the quality of the weld joints.

In the border portion, at least one and preferably more layers of polymer film may be used to reinforce the membranes <NUM>, <NUM> to establish welded seams through which (at the sides of the membrane assembly) the post holes are formed, allowing for easier fabrication. By placing reinforcing layers on the border portion only, the central "window" of the membrane assembly consists only of a single thin layer membrane 'between the working fluid and one of the cold plates <NUM>, <NUM> to minimize impeding heat transfer. A die-cut reinforcement layer may be used which reinforces the entire perimeter with one piece of material.

In some examples, the polymer membranes <NUM>, <NUM> are highly stretchable, at least greater than <NUM>% elongation. This allows the membranes to change from the empty flat state shown in <FIG> to an inflated shape (within the slot <NUM> between the cold plates) without wrinkling. It also allows the membranes to easily conform to features on the faces of the cold plates.

Additionally, the membranes may be made of a material which can also be made into tubing. Tubes such as the inlet and outlet tubes <NUM>, <NUM> shown in <FIG> can then be thermally welded (e.g., using RF sealing) to the membranes, which is more reliable and quicker than adhesive bonding. The membranes <NUM>, <NUM> need not provide their own lateral support because the cold plates <NUM>, <NUM> and frame <NUM> provide the support for the inflated membrane assembly, allowing it to withstand the pressure generated as a result of working fluid flowing through between the membranes. Structural features such as raised bumps, concavities, raised ribs, and so on may be located on the cold plates to optimize heat transfer. For example, the face of the cold plate, may be corrugated or include features (cut out or raised) that provide an increased surface area and increase or optimize heat exchange or transfer between the membranes and the cold plates. The features may have different shapes or patterns, e.g., a serpentine, winding, tortuous, or sinuous pattern or shape, or may include a configuration having one or more curves, turns and/or bends. This can be economically advantageous because the cold plates may be reusable components. Manifolds can be cut into the cold plates to even out the distribution of saline flow.

Having described an example non-limiting thermal exchange combination of structure between the heat exchanger in the control system <NUM> and the sterile working fluid in the intravascular temperature control catheter <NUM> or pad <NUM>, attention is now directed to <FIG>, which shows an example embodiment of additional coolant chambers in the cold plates by which to effect heat exchange with working fluid, including non-sterile working fluid, from the external heat exchange pad <NUM>. Note that the plate structures shown in <FIG> preferably are metal or other material with high heat conductivity.

As shown, the cold plates <NUM>, <NUM> may be multi-plate assemblies defining multiple fluid chambers, although in the discussion below they are referred to generally as "plates" <NUM> and <NUM>. In the non-limiting example shown, the refrigerant inlet and outlet tubes <NUM>,<NUM> extend through an outer wall <NUM> and a separator wall <NUM> of the cold plate <NUM> to communicate refrigerant from the compressor <NUM> into the refrigerant passageway in the cold plate, which establishes a refrigerant chamber <NUM> that is bounded by the separator wall <NUM> and an inner wall <NUM>. On the other side of the inner wall <NUM> is the working fluid cassette slot <NUM>. As stated earlier, each cold plate may have its own refrigerant inlet and/or outlet tubes, or only one cold plate may be formed with refrigerant inlet and outlet tubes and the other cold plate either thermally coupled to the cold plate in which the refrigerant flows and/or receiving refrigerant from the other cold plate through passageways formed between the cold plates. In the example shown, the cold plates <NUM>, <NUM> are thermally coupled through the side walls <NUM> (<FIG>), a common bottom wall <NUM> (<FIG>), and through the uninterrupted portions of a top wall <NUM> in which the slot <NUM> is formed.

In some examples, the cold plates <NUM>, <NUM> are mirror image structures of each other. In the example of <FIG>, the refrigerant chamber <NUM> in the left-hand cold plate (<NUM>) is in fluid communication through refrigerant supply and return passageways <NUM>, <NUM> with a refrigerant chamber <NUM> in the right-hand cold plate <NUM>. Thus, the refrigerant chambers of the cold plates straddle the cassette slot <NUM> and are separated therefrom by respective inner walls <NUM>, with refrigerant flowing serially through the left and right refrigerant chambers <NUM>, <NUM>, first from the refrigerant inlet tube <NUM> into the left refrigerant chamber <NUM>, then through the refrigerant supply passageway <NUM>, the right hand refrigerant chamber <NUM>, back through the refrigerant return passageway <NUM>, and out the refrigerant outlet tube <NUM>. This increases the refrigerant fluid flow rate through the refrigerant chambers <NUM>, <NUM>, when two refrigerant chambers are provided as in the example shown.

In contrast, pad working fluid channel fluid flow may be plumbed in parallel to left and right pad fluid chambers <NUM>, <NUM>, which straddle the refrigerant chambers as shown and are separated therefrom by respective separator walls <NUM>. In the non-limiting example shown, fluid from the external pad flows through the pad working fluid inlet Pin into an inlet plenum <NUM> formed in the bottom wall <NUM>. The fluid flows in parallel through inlet ports <NUM>, <NUM> into left and right pad working fluid chambers <NUM>, <NUM>. The fluid exits the pad working fluid chambers through an upper plenum <NUM><NUM> formed in the top plate <NUM> and out of the working fluid outlet Pout back to the external pad. This example parallel fluid flow reduces backpressure in the pad working fluid system.

Note that the above-described series fluid flow through the refrigerant chambers and parallel flow through the pad working fluid chambers is exemplary only, and is not limiting. Thus, fluid flow through the pad working fluid chambers may be in series and/or fluid flow through the refrigerant chambers may be parallel. Note further that the particular example plumbing arrangements illustrated and described are but one example of plumbing fluid through the multi-chamber cold plates <NUM>, <NUM>.

Indeed, <FIG> shows a system similar to the one shown in <FIG>, except that fluid flow through the refrigerant chambers is in parallel. Both refrigerant chambers may communicate with a refrigerant inlet plenum <NUM> through which refrigerant flows into each refrigerant chamber <NUM>, <NUM> in parallel. Also, both refrigerant chambers may communicate with a refrigerant outlet plenum <NUM> through which refrigerant flows out of each refrigerant chamber <NUM>, <NUM> in parallel back to the compressor.

It may now be appreciated that in the intravascular heat exchange mode, working fluid from the catheter <NUM> flowing through the cassette <NUM> which is disposed in the slot <NUM> exchanges heat with the refrigerant in the refrigerant chambers <NUM>, <NUM> through the respective inner walls <NUM>. The catheter working fluid comes into contact with no portion of the cold plate heat exchanger, owing to it flowing through the cassette <NUM>. In this way, the catheter working fluid retains its sterility and is enclosed in a closed fluid circuit for withstanding circulation fluid pressures of, e.g., up to seventy pounds per square inch (<NUM> kPa).

On the other hand, since pad working fluid is separated from the patient by an external pad, it may not require sterility, in which case the pad working fluid may contact the separator plates <NUM> directly in the cold plates <NUM>,<NUM> to exchange heat with the refrigerant in the refrigerant chambers <NUM>, <NUM>.

<FIG> shows an alternate cold plate assembly <NUM> having a cassette slot <NUM>' and rail receptacles R1' and R2' straddling the slot <NUM>' for receiving the side rails of the cassette <NUM>, with the receptacles and slot being substantially the same in configuration and function as the counterparts shown in <FIG>. However, unlike <FIG>, <FIG> shows that inboard of each receptacle R1,' R2', the cold plate assembly <NUM> is formed with respective bulge or expansion cavities <NUM> receptacles or grooves that may extend substantially the entire length of the side rail receptacles (give or take a few millimeters). In the embodiment, each bulge cavity <NUM> may be circular or semicircular-shaped (although other shapes may be used). The bulge cavity may be defined between the cold plates <NUM>', <NUM>'. Cold plates <NUM>' and/or <NUM>' may have a cavity or groove formed on its inner wall. The cavity or groove may be separated or spaced apart from the side rail receptacle, e.g., by a landing or other segment of the cold plate, such that the bulge cavity is separated or spaced apart from the side rail receptacle. This may help minimize or prevent expansion of the membrane assembly into the side rail receptacles when the membrane is filled with working fluid. The bulge cavity joins or connects to the slot <NUM>', e.g., a semicircular shaped bulge cavity may join the slot <NUM>', at the apex of the semi-circle. As shown in <FIG>, each bulge cavity <NUM> may have a width W or diameter at its widest point (e.g., the diameter of a circle or semi-circle) that is less than the transverse diameter or width W2 of the rail receptacle but greater than the width W3 of the slot <NUM>'. In other embodiments, the bulge cavity may be immediately inboard of a rail receptacle.

With this structure, when the cassette <NUM> is engaged with the cold plate assembly <NUM> with the membrane assembly <NUM> disposed in the slot <NUM>' and the rails of the cassette disposed in the rail receptacles R1', R2', portions of the membrane assembly, e.g., portions that are near the edges of the membrane assembly <NUM> and that are inboard of the side rails of the cassette, can expand into the bulge cavities <NUM> when the membrane assembly <NUM> is filled with working fluid. This establishes enlarged fluid supply and return passageways along the vertical side edges of the membrane assembly <NUM>. In this way, working fluid entering the top of the cassette <NUM> along one of the side rails flows mostly down the fluid supply passageway of the portion of the membrane assembly that has expanded within the bulge cavity. The fluid supply tube on the cassette <NUM> may be positioned such that it is concentric with or in line with the bulge cavity. Portions of the supply fluid progressively emerge as the fluid flows down the supply passageway from the fluid supply passageway, flowing across the membrane assembly to the fluid return passageway that is established by the portion of the membrane assembly that has expanded within the bulge cavity <NUM> immediately adjacent the fluid return tube on the cassette <NUM>.

<FIG> illustrates an alternate cold plate <NUM> that is substantially identical in configuration and operation to the cold plates shown in <FIG>, with the following exceptions. A separator plate <NUM> may have channels <NUM>, <NUM> (that may be configured like the serpentine channel <NUM> shown in <FIG> or configured in another pattern or shape, e.g. having one or more curves, turns and/or bends) formed in each of its respective side surfaces. Like the other cold plate structures shown and discussed herein, the separator plate <NUM> is highly thermally conductive and may be made of metal or an appropriate thermoplastic or other heat-transmitting material.

Left and right backing plates <NUM>, <NUM> can abut the left and right sides of the separator plate <NUM> along the entire sides of the separator plate with only the channels <NUM>, <NUM> establishing cavities through which the respective fluids may flow. (An exploded view of <NUM> is shown in <FIG>). Thus, refrigerant may flow through the left channel <NUM> between the separator plate <NUM> and the left backing plate <NUM> and water from the lines L3, L4 in <FIG>, e.g., from a patient heat exchange pad or from a source of water other than the pad, such as a water reservoir which may act as a thermal storage unit, may flow between the separator plate <NUM> and the right backing plate <NUM> through the right channel <NUM>. In this configuration, the cassette slot <NUM>' may be located on the side of the left backing plate <NUM> that is opposite the separator plate <NUM> as shown. With this structure, not only can the refrigerant exchange heat with either sterile catheter <NUM> saline in the cassette or non-sterile fluid from the pad <NUM>, or optionally pad fluid in a cassette, but furthermore in the event that refrigerant is not available or battery power only is available (hence the compressor <NUM> is effectively offline), water from the cold fluid source <NUM> (shown in <FIG>) or a water reservoir (e.g., where the water was previously cooled by the compressor) may be ported to the right channel <NUM> to provide some heat exchange across the separator plate <NUM> and left backing plate <NUM> with the cassette <NUM> in the slot <NUM>'.

The certain embodiments, various cold assemblies described herein may be assembled by brazing the plates together, e.g., in an oven, and/or e.g. by vacuum brazing. The plates may also or alternatively be connected by mechanical fasteners and sealed with o-rings, and/or a gasket may be utilized.

If desired, the refrigerant may be allowed to warm to heat the present cold plates when, for example, target temperature is reached, to avoid over-cooling the patient and/or to run a system pump backwards to shorten x-probe equalization stops. Moreover, refrigerant flow may be established or adjusted to maintain at least some liquid phase of the refrigerant throughout the entire period of time, substantially the entire period of time or part of the time that the refrigerant flows or traverses through the passageway of the cold plate, to promote heat exchange, wherein the refrigerant may exchange heat with working fluid from the intravascular heat exchange catheter and/or the external heat exchange pad.

As discussed above, using the duct <NUM> in <FIG> the patient <NUM> may be externally warmed for comfort by the exhaust heat from the compressor <NUM> during internal cooling or to re-warm the patient after cooling. In certain embodiments, heat generated by the system <NUM>, e.g., by the compressor or any other component of the system, may be transferred or directed onto the surface of a patient to warm the patient before, after or while the patient is cooled with a heat exchange catheter or pad, e.g., to prevent or reduce shivering. In certain variations, heat may be directed onto the patient via a Bairhugger or other hot air blanket or tent used in hospitals to help keep the patient's skin warm. Other mechanisms or ways to warm a patient include but are not limited to: placing or including an electric heating element inside a pad; warming a patient with a radiant heating lamp; directing warm air from a fan on the console or system, which is removing heat from the compressor, onto or toward the surface of a patient; and providing or including a third fluid circuit containing a warming fluid in the system.

While the various embodiments of the COLD PLATE DESIGN IN HEAT EXCHANGER FOR INTRAVASCULAR TEMPERATURE MANAGEMENT CATHETER AND/OR HEAT EXCHANGE PAD are herein shown and described in detail, the scope of the present invention is to be limited by nothing other than the appended claims. Components included in one embodiment can be used in other embodiments in any appropriate combination.

Claim 1:
An apparatus comprising:
a cassette (<NUM>) comprising a membrane assembly (<NUM>) and side rails (<NUM>);
a plate assembly (<NUM>, <NUM>, <NUM>) comprising at least two thermally conductive plates (<NUM>, <NUM>) defining a cassette slot (<NUM>') between the plates, the plate assembly configured to receive the membrane assembly (<NUM>) of the cassette (<NUM>) and exchange heat therewith, with the membrane assembly being configured for containing working fluid from an intravascular heat exchange catheter (<NUM>) or heat exchange pad (<NUM>), the plate assembly (<NUM>, <NUM>, <NUM>) also including rail receptacles (R1', R2') straddling respective sides of the slot and configured for receiving the respective side rails (<NUM>) of the cassette, wherein
at least a first cavity (<NUM>) is formed inboard of a first one of the rail receptacles (R1'), the first cavity having a width (W) at its widest point that is greater than a width (W3) of the slot (<NUM>'), wherein when the cassette (<NUM>) is engaged with the apparatus with the membrane assembly (<NUM>) disposed in the slot (<NUM>') and the side rails (<NUM>) of the cassette (<NUM>) disposed in the rail receptacles (R1', R2'), a first portion of a membrane of the membrane assembly that is inboard of a side rail of the cassette can expand into the first cavity when the membrane assembly (<NUM>) is filled with working fluid to thereby establish an enlarged fluid passageway along a vertical side edge of the membrane assembly.