WO1996021485A1

WO1996021485A1 - Heating of physiological fluids

Info

Publication number: WO1996021485A1
Application number: PCT/GB1996/000031
Authority: WO
Inventors: Thomas Gilchrist; Allan Scott
Original assignee: Giltech Limited
Priority date: 1995-01-11
Filing date: 1996-01-10
Publication date: 1996-07-18
Also published as: AU4351596A

Abstract

There is provided an apparatus (1) for warming a physiological fluid, such as blood or a blood product. The apparatus (1) comprises a solid heating body (10) and a heat exchange unit (11) arranged to be engageable with the heating body (10). The apparatus (1) also contains a fluid-tight conduit (19) through which the physiological fluid is carried, the conduit (19) being provided with a pre-formed passageway through the heat exchange unit (11). Heat is passed directly from the heating body (10) (which may be, for example, one or more hot plates (12, 13)) to the heat exchange unit (11) which is desirably disposable. The conduit (19) preferably follows a tortuous path within the apparatus (1), and the temperature of the fluid may be monitored. The apparatus (1) may be portable and may be battery-powered.

Description

"Heating of Physiological Fluids"

The present invention relates to heating of physiological fluids and apparatus therefor.

During medical treatment it is often desirable to heat fluids to be administered to a patient. For example, whole blood and packed cells are commonly stored at a temperature of about 4°C. It is often desirable, however, for blood and blood products to be administered to a patient at approximately normal body temperature. It is generally accepted that even mild hypothermia of a patient may have serious clinical consequences and warming of, for example, transfusion fluids and irrigating fluids to be administered to a patient may therefore be desirable in many cases.

The term "physiological fluid" is used herein to refer to any fluid which may be administered to a patient, for example, blood, a blood product, an irrigating fluid, a fluid containing active ingredients (eg medicaments) or a fluid containing nutrients.

Most known systems for warming physiological fluids use a contra-flowing heat exchange arrangement in which the physiological fluid is circulated through a tube by a pump and is warmed through a wall of the tube by a heated fluid flowing in an opposite direction on the other side of the tube wall. Such devices have the inconvenience of requiring a heating fluid circuit; they can be bulky and inconvenient to move and install.

US Patent 4,532,414 discloses a blood warming device in which a portion of a flexible blood supply conduit is fed through a sinuously-shaped groove in a heating plate. Straight portions of the groove are joined by arcuate portions which must have a relatively large radius to prevent the supply conduit kinking in use and inhibiting blood flow. It is not always easy to position the flexible supply conduit in the groove without it kinking or deforming. Furthermore, only a relatively small proportion of the area of the heating plate is in contact with the supply conduit and heat transfer efficiency is thus relatively small. Indeed, this document suggests using two or more such units in cascade or series where fluid must be transferred at a very rapid rate.

According to a first aspect, the present invention provides apparatus for heating a physiological fluid, said apparatus comprising a solid heating body, an electrical heating element coupled to the heating body and a heat exchange unit arranged so as to be engageable with the heating body and comprising a fluid-tight conduit for passage therethrough of the physiological fluid, the conduit being provided by a preformed fixed passageway through the heat exchange unit.

In use of the apparatus, the physiological fluid to be warmed passes through the conduit of the heat exchange unit. The heat exchange unit is preferably arranged in direct contact with the heating body to which heat energy is supplied by the electrical heating element.

The heating body may be provided in the form of one or more heating plates. The or at least one of the heating plates may be substantially planar and may be substantially flat. Preferably, the heating body comprises a pair of heating plates between which the heat exchange unit may be received; the heating plates may be separable to facilitate insertion and/or removal of the heat exchange unit.

The heat exchange unit is preferably easy to handle. It is preferably removable from the apparatus and may be provided as a disposable unit. It may be substantially rigid and may be substantially planar.

The conduit of the heat exchange unit may be provided in the form of a tortuous passageway. It may comprise a plurality of conduit portions in the form of substantially straight pipes arranged transversely to each other. An end of one conduit portion may be connected to an adjacent end of an adjacent conduit portion by a fluid tight end cap. The end cap may connect adjacent ends of adjacent first and second conduit portions and connect adjacent ends of adjacent third and fourth conduit portions. The end cap may fix the conduit portions transversely in relation to each other. Preferably, a pair of end caps are provided and are arranged such that opposite ends of each conduit portion are connected to respective first and second end caps.

The conduit portions may be substantially parallel. Side walls of adjacent conduit portions may touch each other.

The conduit portions may be provided in aluminium. Anodised or non-anodised aluminium may be used. The or each end cap may be provided in plastics material, for example polycarbonate, which may be machined.

Clamping means may be provided to clamp the heat exchange unit to the heating body or between the heating plates. The clamping means may encourage a large surface area of contact between the heat exchange unit and the heating body. The clamping means may be resilient and/or may be provided by one or more releasable fasteners.

Preferably, the temperature of the heating body and/or the temperature of the physiological fluid is electronically monitored, and subsequently controlled. The apparatus may be provided with one or more of the following: a temperature indicator; a high temperature alarm, a low temperature alarm and a high temperature cut out which may require manual resetting when tripped. Desirably the apparatus heats the fluid to approximately body temperature.

The heating body may be heated by one or more electrical strip elements; these may be rubber strip elements. The apparatus may be arranged to operate from any desirable electrical power source, for example 240 volts alternating current, or 12 volts direct current. The apparatus may be portable and powered from a portable battery, which is preferably rechargeable.

According to a second aspect, the present invention provides a method of heating a physiological fluid in which method the physiological fluid passes through a preformed fixed passageway in a heat exchange unit and the heat exchange unit is arranged in contact with a solid heating body to which heat energy is supplied by a heating element. The preformed fixed passageway forms a fluid-tight conduit for the fluid. The heat energy is usually supplied by an electrical heating element.

The second aspect of the invention may incorporate one or more features described with reference to the first aspect.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings of which:

Fig. 1 is a schematic diagram showing an apparatus in accordance with the invention incorporated in a drip supply;

Fig. 2 is a perspective view of one embodiment of the apparatus according to the invention;

Fig. 3 is a perspective view of a heater unit which forms a part of the apparatus; and

Fig. 4 is an elevation of the heat exchange unit which forms a part of the apparatus.

Figure 1 shows heating apparatus 1 in accordance with the invention incorporated into a drip system. A pair of bags 2 containing a physiological fluid to be administered to a patient are suspended from bag spikes in a conventional way. The bags 2 may release the fluid under gravity or one or more of them may be squeezed to cause the fluid to be expelled.

Fluid released from each of the bags 2 passes into a drip chamber 3 and subsequently into the heating apparatus 1 where it is warmed to a desired temperature before passing through a filter 4 and subsequently being administered to a patient (not shown) .

Various parts of passageways through which the physiological fluid flows from the bags 2 to the patient are supported by means of clamps 5 and roller clamps 6 and connected by luer connections 7.

Sample dimensions are shown in Fig. 1. Each of the heater tails and filter tails are approximately 200 mm long.

The heating apparatus 1 (an embodiment of which is illustrated in Fig. 2) comprises a heater unit 1C (for example as illustrated in Figs. 2 and 3) and a heat exchange unit 11 (for example as illustrated in Figs. 2 and 4) .

Fig. 2 shows an apparatus accordingly to the invention which is indicated generally as 1. In the embodiment illustrated apparatus 1 is in the form of a hinged box consisting of a first portion 29 and a second portion 30 connected by hinge 24.

Apparatus 1 has a two part heater unit 10 comprising two substantially planar heating plates 12, 13 located in the first and second portions 29, 30 respectively. Heating plates 12, 13 are designed to accommodate a heat exchange unit 11 so that heating surfaces 14, 15 maintain good contact with unit 11. Contact between the (substantially planar) heating surfaces 14, 15 and unit 11 permits transfer of heat from surfaces 14 , 15 to unit 11, the heat then being transferred to the physiological fluid to be heated. Heat exchange unit 11 may be removed from apparatus 1, and optionally unit 11 is disposable.

Heating plates 12, 13 (and the surfaces 14, 15) are heated by means of rubber strip exchange electrical heating elements 31, 32 which are shown surrounding the edge of plates 12, 13 respectively. Elements 31, 32 are connected by cable 27 to control unit 8 and then to a power supply (not shown) . Control unit 8 may be a transformer to obtain a power source of the required voltage/ampage and/or may be a time control unit.

Heat exchange unit 11 is a rigid, substantially planar, unit. Within unit 11 is a tortuous conduit through which the fluid is directed, during the warming process. Generally unit 11 will contain numerous parallel pipes (not shown) which are connected in series by connecting portions within first and second end caps 20, 21. Inlet 25 and outlet 26 are shown in the heat exchange unit 11 and these are located at each end of a circuitous conduit (not illustrated) contained within unit 11. The physiological fluid to be heated enters through inlet 25, travels through the conduit (not shown) , being passed down each pipe 19 in turn and is expelled through outlet 26 at a temperature suitable for administration to a patient. The apparatus may contain one or more temperature detectors to monitor the delivery temperature of the physiological fluid and to set off an alarm, optionally also switching the heating elements up or down, or on or off. Inlet 25 and outlet 26 may comprise connectors (not shown), for example standard luer connectors, to enable delivery of the fluid from its storage container and transport of the heated fluid to the patient optionally via other medical apparatus (not shown) .

In apparatus 1 illustrated in Fig. 2 spring clips 9 are shown on the outside of lower portion 30 to hold faces 15, 16 of heater plates 13, 14 snugly against each heat exchange surface of unit 11. Also illustrated is an abnormal temperature indicator light 33 which is lit when the temperature of the physiological fluid falls outside an acceptable range.

The heater unit 10 of Fig. 3 has a heating body in the form of a pair of electrically heated heating plates 12, 13 each of which has a substantially planar heating surface 14, 15. In use of the apparatus, the heat exchange unit 11 is inserted and maintained between the heating surfaces 14, 15. The heating plates are maintained within a heating box 22. Each heating surface 14, 15 is heated in use by a respective 500 watt rubber strip electrical heated element (not shown) , one attached to each heating plate 12, 13.

The heating plates 12, 13 are resiliently separable to facilitate insertion and removal of the heat exchange unit 11. In the heater unit 10 of Fig. 3 six guiding pegs 16 pass through each heating plate 12, 13 to guide their relative movement. Resilient means in the form of six springs 17, one positioned about each guiding peg 16 bias the heating plates 12, 13 resiliently together.

Clamping means is also provided by a pair of two half- turn screws 18 provided on a rear side of the heater unit. In use, the screws 18 are tightened to clamp the heat exchange unit 11 in direct contact between the heating surfaces 14, 15 and to encourage a maximum possible surface area of contact.

The heat exchange unit 11 illustrated in Fig. 4 is provided as a preformed rigid, substantially planar, disposable unit. It has fourteen substantially parallel conduit portions provided by pipes 19 of circular cross section (not all of which are shown) . In this embodiment, the heat exchange unit 11 is 320mm long; each pipe 19 has a wall thickness of 1mm, a cross-sectional area of 18mm² and is provided in anodised aluminium.

Respective first and second end caps 20, 21 fluidly connect respective ends of adjacent pipes 19 to form a tortuous passageway through the heat exchange unit 11 and to form a fluid tight conduit for passage therethrough of the physiological fluid. Each of the end caps 20, 21 is made of machined polycarbonate and is substantially rigid.

The end caps 20, 21 retain each of the conduit portions 19 in a fixed relationship to each other. This facilitates handling of the unit 11 which may be easily inserted between the heating surfaces 14, 15 of the heater unit 10 and easily removed after use. Arcuate portions 23 in the end caps 20, 21 fluidly connect adjacent ends of adjacent pipes 19. The arcuate portions have relatively small radii permitting a compact construction in which sides of adjacent pipes 19 touch each other.

The heating unit 10 may be free standing or it may fit on to a standard' blood transfusion pole.

Improvements and modifications may be made without departing from the scope of the invention.

Claims

1. An apparatus for heating a physiological fluid, said apparatus comprising a solid heating body, an electrical heating element coupled to the heating body and a heat exchange unit arranged so as to be engageable with the heating body, said heat exchange unit comprising a fluid-tight conduit provided by a preformed fixed passageway through the heat exchange unit for passage of the physiological fluid.

2. An apparatus as claimed in Claim 1, wherein said heat exchange unit is removable from the apparatus.

3. An apparatus as claimed in Claim 2 wherein said heat exchange unit is disposable.

4. An apparatus as claimed in any one of Claims 1 to 3 wherein the conduit of the heat exchange unit is in the form of a tortuous passageway.

5. An apparatus as claimed in any one of Claims 1 to 4 wherein the conduit of the heat exchange unit is formed from a number of substantially parallel pipes connected in series via fluid tight end caps.

6. An apparatus as claimed in any one of Claims 1 to 5 wherein the temperature of the physiological fluid is electronically monitored and/or is controlled.

7. An apparatus as claimed in any one of Claims 1 to 6 heated by electrical strip elements.

8. An apparatus as claimed in any one of Claims 1 to 7 wherein the heating body comprises a pair of heating plates between which the heat exchange unit is received and maintained in contact with the heating surfaces of the heating plates.

9. An apparatus as claimed in any one of Claims 1 to 8 which is portable.

10. A method of heating a physiological fluid, said method comprising passing said fluid through a preformed fixed passageway within a heat exchange unit, the heat exchange unit being arranged in contact with a solid heating body to which heat energy is supplied by a heating element.