Power supply for an intravenous fluid delivery system

Abstract

The present invention relates in one aspect to a power supply for intravenous fluid delivery systems and an infusion fluid warmer for the intravenous fluid delivery systems. The power supply comprises a rechargeable energy storage component for delivery of a primary DC voltage. The power supply comprises a voltage regulator configured to deliver a secondary DC voltage which may exhibit a lower maximum current output than a maximum current output of the primary DC voltage.

Description

[0001] POWER SUPPLY FOR AN INTRAVENOUS FLUID DELIVERY SYSTEM

[0002] The present invention relates in one aspect to a power supply for intravenous fluid delivery systems and an infusion fluid warmer for the intravenous fluid delivery systems. The power supply comprises a rechargeable energy storage component for delivery of a primary DC voltage. The power supply comprises a voltage regulator configured to deliver a secondary DC voltage which may exhibit a lower maximum current output than a maximum current output of the primary DC voltage.

[0003] BACKGROUND OF THE INVENTION

[0004] Intravenous, intraosseous or infusion fluids, such as blood, are commonly used in hospitals. Infusion fluids are also used in the field, for example during patient transportation in disaster areas such as war zones from an accident site to a hospital. The patient may be transported to the hospital in a vehicle such as an ambulance or helicopter.

[0005] The infusion fluid is administrated to the patient during multiple medical procedures and applications. The infusion fluid is typically delivered from an IV fluid bag or IV container into a blood vessel of the patient during the medical procedure. The infusion fluid will often need heating to about the patient’s body temperature because some types of infusion fluids like blood are refrigerated during storage while other types of infusion fluids may be kept at ambient temperatures. However, to prevent hypothermia the infusion fluid should not be infused to the patient directly from storage at typical storage temperatures. Therefore, intravenous fluid delivery systems must be able to warm the infusion fluid to a temperature close to the patient’s temperature to avoid administration of under-heated infusion fluid.

[0006] The infusion fluid warmer comprises a fluid inlet that is coupled to the IV fluid bag and a fluid outlet where appropriately heated infusion fluid flows out and is administered to the patient during operation of the intravenous fluid delivery system.

[0007] Known intravenous fluid delivery systems may comprise several separate devices held in a separate housing and electrically connected through a cable such as a disposable, one-time use, infusion fluid warmer in one housing and a power supply held in another housings.

[0008] US 8,948,581 B2 discloses an intravenous fluid delivery system which comprises a power supply and a warming unit electrically connected via an electric connector and cable. The power supply delivers a regulated voltage to the warming unit through the electric connector and cable. The intravenous fluid delivery system comprises a data communication interface between the power supply and the warming unit through electric connector and cable.

[0009] US 2024 / 0189503 A1 discloses a fluid warming system that comprises a fluid delivery assembly and a drive assembly that are mechanically and electrically connected. A fluid warmer is integrated into the fluid delivery assembly to heat fluid before delivering the latter to a patient.

[0010] US 2017 / 0333630 A1 discloses a fluid warming system that comprises a power supply interface, a control module, a data interface, a power interface and a heat exchanger unit. The fluid warming system delivers intravenous fluid to a patient.

[0011] However, there is a need to provide robust, reliable and cost-efficient solutions to connect the infusion fluid warmer and the power supply of the intravenous fluid delivery system. In that context, the skilled person will appreciate that the intravenous fluid delivery system must be capable of safely operating in extremely challenging environments where various types of contamination such as water, humidity, heat, dust, impact shocks etc. are applied to components of the intravenous fluid delivery system. Hence, there is also a need for intravenous fluid delivery systems that are robust and provide high patient safety even in extremely challenging environments.

[0012] SUMMARY OF THE INVENTION

[0013] A first aspect of the invention relates to a power supply for an intravenous fluid delivery system, comprising:

[0014] - a housing comprising a rechargeable energy storage component such as one or more rechargeable battery cells and / or one or more supercapacitors, wherein the rechargeable energy storage component is configured to supply a primary DC voltage,

[0015] - a DC supply output for delivery of stored power in the rechargeable energy storage component,

[0016] - a voltage regulator, such as a programmable switched-mode DC-DC converter, configured to down-convert the primary DC voltage of the rechargeable energy storage component to a secondary DC voltage e.g. a DC voltage between 3.3 V and 5 V. The power supply comprises:

[0017] - a processing circuit comprising a data communication interface, wherein said processing circuit is configured to extract warmer messages transmitted by an infusion fluid warmer through the data communication interface, wherein the processing circuit further comprises:

[0018] - a controllable switch arrangement configured to electrically connect and disconnect the DC supply output and the primary DC voltage, e.g. by the controllable switch arrangement, and configured to electrically connect and disconnect the DC supply output and the secondary DC voltage e.g. by the controllable switch arrangement.

[0019] The skilled person will understand that the controllable switch arrangement may be controlled by applying an appropriate control voltage to one or more control terminal(s) of the controllable switch arrangement such as one or more gate terminal(s) and / or one or more base terminal(s) of one or more MOSFET(s) and / or IGBT(s) and / HEXFET(s) and / or high-bandgap semiconductors.

[0020] The secondary DC voltage supplied by the voltage regulator may be less than 50 % or less than 33 % of a nominal primary DC voltage. The nominal primary DC voltage may lie between 12 V and 48 V. Additionally, an output resistance of the voltage regulator may be at least 10 times larger, preferably at least 100 times larger, than a nominal output resistance of the energy storage component. The output resistance of the voltage regulator may for example exceed 10 ohm such as larger than 50 ohm. The skilled person will appreciate that the lower secondary DC voltage and / or larger output resistance of the voltage regulator markedly limits the maximum supply current that the infusion fluid warmer can draw through from the DC supply output of the power supply.

[0021] Consequently, e.g. due to the larger output resistance of the voltage regulator, the maximum current output of the secondary DC voltage may be limited to a markedly smaller value than the maximum current output of the primary DC voltage, i.e. supplied by the energy storage component, such as less than 10 % or less than 1 % of the maximum current output of the primary DC voltage. According to certain embodiments of the power supply, the maximum current output of the secondary DC voltage is limited to less than 500 mA such as less than 100 mA.

[0022] The processing circuit of the power supply may be configured to switch the DC supply output from the primary DC voltage to the secondary DC voltage using the control voltage to the one or more control terminal(s) of the controllable switch arrangement in response to a suspected malfunction of the infusion fluid warmer for example as discussed below with reference to the appended drawings.

[0023] One embodiment of the controllable switch arrangement may be configured to electrically disconnect the DC supply output of the power supply from both the primary DC voltage and the secondary DC voltage and electrically connect the DC supply output to ground potential of the power supply or leave the DC supply output in a floating state.

[0024] The processing circuit of the power supply may therefore utilize the voltage regulator to provide a gradual or stepwise supply voltage ramp-up of the infusion fluid warmer at initialization or start-up of the latter. In connection with the start-up of the infusion fluid warmer, the processing circuit of the power supply may be configured to e.g. initially connect the DC supply output to the secondary DC voltage and thereafter monitor the data communication interface for receipt of a valid warmer message from the infusion fluid warmer. The receipt of the valid warmer message in the processing circuit of the power supply provides recognition of the presence of the infusion fluid warmer in the intravenous fluid delivery system. The skilled person will understand that the secondary DC voltage is sufficiently high to enable operation of at least a part of the processing circuit, for example a microprocessor such as a CPU, DSP or microcontroller etc., of the infusion fluid warmer for example as discussed in additional detail below with reference to the appended drawings.

[0025] The valid warmer message preferably comprises an integrity pass state of the infusion fluid warmer. The processing circuit may be configured to maintain the DC voltage output at the secondary DC voltage at least until the valid warmer message has been detected and preferably until the valid warmer message comprises such integrity pass state. In response to the detection of the valid warmer message the processing circuit of the power supply may be configured to respond by disconnecting the secondary DC voltage from the DC voltage output and connect the primary DC voltage to the DC voltage output. This stepwise supply voltage ramp-up of the infusion fluid warmer may be viewed as a safety precautionary action because the high-power primary DC voltage is only connected to the infusion fluid warmer in response to the latter transmits the valid warmer message such as the integrity pass state. The receipt of the integrity pass state further tells the processing circuit of the power supply that the infusion fluid warmer functions correctly. Hence, the processing circuit of the power supply may safely switch the DC output to the primary DC voltage. This stepwise supply voltage ramp-up therefore safeguards the patient against potentially dangerous faults in the infusion fluid warmer at the start-up of the latter such as electrical short circuits of components of the infusion fluid warmer such as a resistive heating element.

[0026] The start-up of the infusion fluid warmer may be carried out by its processing circuit in response to establishment of an electrical connection to the power supply through the power supply input and return supply input of the infusion fluid warmer and detection of the presence of the secondary or primary DC voltage on the power supply input for example as discussed in additional detail below with reference to the appended drawings.

[0027] The data communication interface of the power supply may comprise:

[0028] - an industry-standard communication protocol, such as SPI, IIC, or

[0029] - a proprietary communication protocol such as an asynchronous serial communication protocol. The data communication interface which comprises the proprietary communication protocol may additionally comprise a data detector connected to the DC supply output and configured to extract the warmer messages based on supply current variations on the DC supply output. The latter embodiment enables power line communication by transmitting the warmer messages on a power supply wire between the infusion fluid warmer and power supply for example as discussed in additional detail below with reference to the appended drawings.

[0030] Furthermore, the data communication interface may provide cost reductions of the infusion fluid warmer because certain components, and generally intelligence, of the intravenous fluid delivery system can be moved from the infusion fluid warmer, which is typically a disposable, single-use device, to the power supply. The cost reductions of the infusion fluid warmer may be achieved by eliminating visual and / or audio indicators from the infusion fluid warmer

[0031] Each of the warmer messages may comprise one or more data packet(s) and each of the supply messages may comprise one or more data packet(s). Each of the data packets may comprise one or more predetermine fields such a payload field, that e.g. comprises respective values of the one or more operational parameters, an error- detection code, an error-correction code, a header etc. A length of at least some of the one or more data packets may lie between 32 bits and 128 bits. The data communication interface may comprise a serial communication protocol with a data speed between 0.5 kbit / s and 100 kbit / s. Hence, the validity of a warmer message may be determined by the processing circuit of the power supply by reading the errordetection code and / or error-correction code. Likewise, the validity of a supply message may be checked by the processing circuit of the infusion fluid warmer by reading the error-detection code and / or error-correction code.

[0032] According to one embodiment of the power supply, the processing circuit is configured to:

[0033] - initializing the power supply e.g. by loading one or more software components from a non-volatile memory of the power supply,

[0034] - set the DC supply output to the secondary DC voltage by the controllable switch arrangement,

[0035] - monitor the data communication interface for the warmer messages,

[0036] - detect a valid warmer message comprising an integrity pass state of the infusion fluid warmer or integrity fail state of the infusion fluid warmer,

[0037] - respond to the integrity pass state by disconnecting the secondary DC voltage from the DC supply output and connect the primary DC voltage to the DC supply output by the controllable switch arrangement;

[0038] - respond to the integrity fail state by maintaining the secondary DC voltage at the DC supply output and continue to monitor the data communication interface for the warmer messages.

[0039] According to this embodiment, the processing circuit may per default set the DC supply output to the secondary DC voltage in connection with the initialization of the power supply and subsequently monitor the data communication interface for receipt of the integrity pass state before connecting the primary DC voltage to the DC supply output. The receipt of the valid warmer message with the integrity pass state from the infusion fluid warmer tells the power supply that the supply voltage to the infusion fluid warmer can safely be switched to the primary DC voltage. The infusion fluid warmer may respond to the on-set of the primary DC voltage at the power supply input of the fluid warmer by commencing normal operation for example as discussed in additional detail below with reference to the appended drawings. According to one embodiment of the power supply, the processing circuit is configured to:

[0040] - monitor the data communication interface for receipt of warmer messages transmitted by the infusion fluid warmer during normal operation thereof,

[0041] - disconnect the primary DC voltage from the DC supply output by control of the first controllable switch arrangement in response to a failure to receive a valid warmer message within a predetermined time period,

[0042] - connect the secondary DC voltage of the voltage regulator to the DC supply output by control of the first controllable switch arrangement. According to this embodiment, the power supply may switch the DC supply output to the secondary DC voltage during normal operation in case of suspected malfunction of the infusion fluid warmer.

[0043] The data communication interface of the power supply may be bidirectional to allow the processing circuit of the power supply to transmit supply messages to the infusion fluid warmer through data communication interface. According to this embodiment, the processing circuit is configured to:

[0044] - generate and transmit supply messages to the infusion fluid warmer through the data communication interface, wherein the supply messages may comprise settings of one or more operational parameters of the infusion fluid warmer. The commands of the processing circuit of the power supply may alternatively, or additionally, comprise requests for transmission of respective values of one or more operational parameters of the infusion fluid warmer such as infusion fluid temperature, instantaneous power dissipation or accumulated power dissipation in a heating element, incoming power or current at a power supply input of the fluid warmer etc.

[0045] One embodiment of the power supply comprises one or more visual indicators such as an alphanumeric display and / or graphics display mounted to the housing, and wherein the processing circuit is configured to:

[0046] - repeatedly measure power values delivered through the DC supply output to the infusion fluid warmer,

[0047] - repeatedly detect, in the received warmer messages, power dissipation values of the resistive heating element corresponding to the measured power values,

[0048] - repeatedly display the measured power values delivered through the DC supply output on the one or more visual indicators; and - optionally display the corresponding power dissipation values of the resistive heating element on the one or more visual indicators. The processing circuit may additionally be configured to:

[0049] - repeatedly compare the measured power values delivered through the DC supply output with the corresponding heating element power dissipation values,

[0050] - disconnect the DC supply output from the energy storage component, e.g. by the controllable switch arrangement, if the measured power value and the corresponding power dissipation value of the heating element differs by more than a preset power limit.

[0051] One embodiment of the power supply comprises an interconnect cable which is configured to establish electrical and mechanical connection between the power supply and the infusion fluid warmer. The interconnect cable may comprise a proximal end attached to the housing of the power supply for example fixedly attached. The interconnect cable may further comprise:

[0052] - a first wire electrically connected to the DC supply output, e.g. via a first terminal of the power supply, and a second wire connected to a return supply voltage e.g. ground,

[0053] - at least one third wire connectable to the data communication interface. A distal end of said interconnect cable may comprise a releasable connector which comprises a first pin connected to the first wire, a second pin connected to the second wire and a third pin connected to the at least one third data wire.

[0054] The skilled person will appreciate that the construction of the interconnect cable is configured to support a data communication interface that comprises an industrystandard communication protocol such as SPI, IIC by virtue of the at least one third data wire which may be utilized for transmission of the warmer messages and / or supply messages. The first wire and the second wire are utilized for transfer of power to the infusion fluid warmer. The skilled person will understand that the first wire and the second wire of the interconnect cable must be dimensioned to transfer large amounts of power, e.g. exceeding 100 W or 200 W, from the power supply to the infusion fluid warmer and hence possess a relatively small resistance e.g. less than 1 ohm or less than 0.1 ohm.

[0055] A second aspect of the invention relates to an infusion fluid warmer comprising a housing comprising a fluid inlet and a fluid outlet and a fluid channel extending between the fluid inlet and a fluid outlet, a power supply input and return supply input connectable to a power supply wire and a return supply wire, respectively, of an interconnect cable, a heating element thermally coupled to the fluid channel and configured to deliver heat to infusion fluid in the fluid channel. The infusion fluid warmer comprises a processing circuit comprising a data communication interface, wherein said processing circuit is configured to:

[0056] -- repeatedly generate and transmit warmer messages through the data communication interface to an external device such as the above-disclosed power supply.

[0057] According to one embodiment of the infusion fluid warmer, the processing circuit is configured to:

[0058] - repeatedly determine warmer data which comprises respective values of one or more operational parameters of the infusion fluid warmer,

[0059] - write the warmer data to the warmer messages before the transmission to the external device such as the power supply.

[0060] The one or more operational parameters of the infusion fluid warmer may comprise one of more of:

[0061] - power dissipation in the resistive heating element,

[0062] - power received at the power supply input,

[0063] - a resistance of the heating element,

[0064] - a temperature of the heating element,

[0065] - a flow rate of the infusion fluid in the fluid channel; and

[0066] - a temperature of the infusion fluid,

[0067] - a result of an integrity test of the infusion fluid warmer.

[0068] According to certain embodiments of the infusion fluid warmer, the processing circuit is configured to:

[0069] - perform an integrity test of the infusion fluid warmer during an initialization sequence, wherein the integrity test comprises comparisons between the respective values of the one or more operational parameters and corresponding target values,

[0070] - generate a warmer message comprising an integrity pass state or an integrity fail state based on a result of the integrity test,

[0071] - transmit the warmer message comprising the integrity pass state or integrity fail state through the data communication interface. The processing circuit of the infusion fluid warmer may be configured to transmit the integrity pass message or the integrity fail message to the power supply, e.g. depending on outcomes of self-tests carried out by the processing circuit, at regular time intervals for example at a time interval between 100 ms and 500 ms. This enables the processing circuit of the power supply to during normal operation regularly check that the infusion fluid warmer is operating correctly.

[0072] One embodiment of the infusion fluid warmer comprises a detachable externally accessible electrical connector, such as a plug or a socket, arranged on, or in, the housing. The electrical connector comprises at least:

[0073] - a first pin connected to the power supply input and a second pin connected to the return supply input; and optionally a third pin connected to the data communication interface. The infusion fluid warmer may therefore be detached from the power supply after use and disposed of or possibly recycled.

[0074] A third aspect of the invention relates to an intravenous fluid delivery system which comprises the power supply according to any of the above-disclosed embodiments thereof and the infusion fluid warmer according to any of the above-disclosed embodiments thereof. The intravenous fluid delivery system may additionally comprise an interconnect cable comprising:

[0075] - a first conductor, such as a power supply wire, and a second conductor such as power return wire, e.g. shield, and optionally a third conductor such as a data wire; and

[0076] - a distal detachable connector mating to the detachable externally accessible electrical connector of the infusion fluid warmer.

[0077] BRIEF DESCRIPTION OF THE DRAWINGS

[0078] The appended drawings illustrate the design and utility of embodiments of the nfusion fluid warmer, power supply and intravenous fluid delivery system in which similar elements are referred to by common reference numerals. These drawings are not necessarily drawn to scale. To better appreciate how the above-recited and other advantages and objects are obtained, a more particular description of the embodiments will be rendered, which are illustrated in the accompanying drawings. These drawings depict only typical embodiments and are not therefore to be considered limiting of the scope of the appended patent claims.

[0079] FIG. 1 shows a schematic block diagram of an intravenous fluid delivery system in accordance with embodiments of the invention,

[0080] FIG. 2 shows a schematic block diagram of a first embodiment of an infusion fluid warmer of the intravenous fluid delivery system,

[0081] FIG. 3 shows a schematic block diagram of a second embodiment of an infusion fluid warmer of the intravenous fluid delivery system,

[0082] FIG. 4 shows a schematic block diagram of a first exemplary embodiment of a power supply of the intravenous fluid delivery system,

[0083] FIG. 5 shows a schematic block diagram of a second exemplary embodiment of a power supply of the intravenous fluid delivery system,

[0084] FIG. 6 is a flowchart of control steps carried out by a processing circuit of the power supply of the intravenous fluid delivery system,

[0085] FIG. 7 is a flowchart of control steps carried out by a processing circuit of the infusion fluid warmer of the intravenous fluid delivery system; and

[0086] FIG. 8 is a schematic illustration of a multi-step supply voltage ramp-up of the infusion fluid warmer according to an exemplary embodiment of the intravenous fluid delivery system.

[0087] DETAILED DESCRIPTION OF THE DRAWINGS

[0088] The skilled person will understand that the accompanying drawings are schematic and simplified for clarity and may in some instances merely show details which are essential to the understanding of the exemplary embodiments of the corresponding intravenous fluid delivery systems while other details have been left out.

[0089] FIG. 1 shows a schematic drawing of an intravenous fluid delivery system 1 which comprises an infusion fluid warmer 100, an interconnect cable 50 and a power supply 20. The infusion fluid warmer 100 and the power supply 20 comprises their respective housings 101, 21 and are electrically and physically connected through an interconnect cable 50 during normal operation of the system 1. A distal end of the interconnect cable 50 may comprise a releasable or detachable connector 106. The releasable connector 106 may comprise a plug mounted to the distal end of the interconnect cable 50. The releasable connector 106 is configured to mate with an externally accessible socket 108 which is arranged on, or inside, a housing 101 of the infusion fluid warmer 100. A proximate end of the interconnect cable 50 may be fixedly or detachably connected to the housing 21 of the power supply 20 by a suitable electrical connector in the latter case (not shown). The interconnect cable 50 comprises power supply wire 54 and a return supply wire 52 for delivery of power from the power supply 20 to the infusion fluid warmer 100. The interconnect cable 50 may have a power rating of more than 100 W.

[0090] The skilled person will appreciate that the infusion fluid warmer 100 may be a disposable, single-use device, e.g. due to patient safety concerns, while the power supply 20 may be reused for numerous infusion fluid treatment session or events.

[0091] The power supply 20 may comprise an AC voltage inlet 32 that may accept ordinary line voltages between 100 V and 230 V from an AC cable 23. The power supply 20 may additionally, or alternatively, comprise a DC supply input 72 which may be releasably connected to an external DC charger 70. The power supply 20 is configured to draw power from the AC voltage input 32 or from the DC supply input 72 and use the power to charge a rechargeable energy storage component (not shown) arranged inside the housing 21 as described in further detail below.

[0092] The housing 21 of the power supply 20 may comprise an elastomeric compound for example manufactured by injection moulding or other manufacturing techniques. The housing 21 may comprise an interior space in which components of the power supply

[0093] 20 such as the rechargeable energy storage component 28 are arranged. The housing

[0094] 21 may be sealed to protect the interior of the housing 21 from pollutants in the external environment such as moisture, liquids, dust etc. The housing 21 may comprise an opening 30 or hook for fixing the housing 21 to a. IV bag stand or pole (not shown) or similar support structure during operation of the system 1. The power supply 20 may comprise one or more visual indicators, such as LEDs 24 and / or an alphanumeric display and / or graphics display 22, that may be mounted on the housing 21 and preferably readily visible to an operator of the system 1. The power supply 20 may additionally, or alternatively, comprise an audio indicator such as a loudspeaker 25 and / or a buzzer or vibrator (not shown) that both may be mounted in the housing 21. Various features and functions of visual, audio and buzzer indicators are discussed below in additional detail.

[0095] The infusion fluid warmer 100 comprises a housing 101 which comprises a fluid inlet 102 and a fluid outlet 104. The infusion fluid warmer 100 comprises a fluid channel 109 (FIG. 3) extending between the fluid inlet 102 and the fluid outlet 104 such that infusion fluid passes from the fluid inlet 102 to the fluid outlet 104. During normal operation of the fluid warmer 1 , an intravenous fluid flows from an IV bag, e.g. by gravitational pull, to the fluid inlet 102 and further through the fluid channel 109 to the fluid outlet 104. The intravenous fluid is preferably heated to a target temperature range or a specific target temperature by a heating element to make the intravenous fluid suitable for intravenous administration to patients. The target temperature range of the intravenous fluid may for example lie between 39 degrees Celsius and 42 degrees Celsius. The skilled person will appreciate that the temperature of the intravenous fluid at the fluid inlet 102 may be significantly lower than the target temperature at the fluid outlet 104. The infusion fluid warmer 100 may comprise a strap 110 or similar means to fix the infusion fluid warmer 100 to the patient during intravenous administration of the infusion fluid during a treatment event or session.

[0096] The infusion fluid warmer 100 comprises an externally accessible electrical connector 108, such as a plug or a socket, arranged on, or in, the housing 101 as discussed in detail below. The externally accessible electrical connector 108 may be detachably coupled to the mating connector 106 of the interconnect cable 50. In this manner, the infusion fluid warmer 100 may be released from the battery pack 20 and interconnect cable 50 after termination of a treatment session or fluid delivery event. The infusion fluid warmer 100 may subsequently be disposed of in an appropriate manner. The housing 101 may comprise one or more visual and / or audio indicators 112. The audio indicator(s) may be configured to notify a system operator, e.g. medical professional, about various suspected malfunctions of the intravenous fluid delivery system for example malfunctions in the infusion fluid warmer and / or power supply.

[0097] The infusion fluid warmer 100 and battery pack 20 comprise respective data communication interfaces that are configured to exchange various kind of warmer messages and / or supply messages associated with the infusion fluid warmer 100 and / or power supply 20, respectively, through the power supply wire 54 of the interconnect cable 50 as discussed in detail below. The respective data communication interfaces may be unidirectional data interfaces or bidirectional data interfaces.

[0098] FIG. 2 shows a simplified schematic drawing of the infusion fluid warmer 100 according to first exemplary embodiments thereof. The infusion fluid warmer 100 comprises the housing 101 which may comprise an elastomeric compound for example manufactured by injection moulding or other manufacturing techniques. The housing 101 may comprise an interior space in which components of the infusion fluid warmer 100, such as the resistive heating element, processing circuit, various support structures etc, are arranged. The housing 101 may sealed to protect the interior of the housing 101 from pollutants in the external environment such as moisture, liquids, dust etc.

[0099] The infusion fluid warmer 100 comprises the fluid channel 109 which extends between the fluid inlet 102 and fluid outlet 104. The housing 101 may comprise a proximal fluid connector 122 coupled to the fluid inlet 102. The proximal fluid connector 122 may comprise a barbed fitting, configured to provide a leak tight connection to a fluid source tube (not shown). The fluid source tube may provide a fluid flow path from the IV bag or IV container to the proximal fluid connector 122. The housing 101 may further comprise a distal fluid connector 124, such as a barbed fitting, configured to provide a leak tight connection to a fluid delivery tube (not shown). The fluid delivery tube provides a fluid flow path from the fluid outlet 104 to the patient. During normal operation of the fluid warmer 100 the intravenous fluid flows from the IV bag to the fluid inlet 102 and further through the fluid channel 109 to the fluid outlet 104. The intravenous fluid is heated during its flow through the fluid channel to the target temperature or temperature range by a resistive heating element which may comprise one or more resistive segments 130, 132, 134, 136. An optional temperature sensor 135 may be arranged in the fluid channel 109 at the fluid inlet 102 or at the fluid outlet 102 or temperature sensors may be arranged both at the fluid inlet 102 and fluid outlet 104. The temperature sensor 138 or temperature sensors is / are configured to measure the respective temperatures of the intravenous fluid at the fluid inlet 102 and / or the fluid outlet 104.

[0100] The fluid warmer 100 comprises a power supply input 126 and return supply input 128, such as ground connection of electric circuitry of the warmer 100. The power supply input 126 and return supply input 128 are connectable to the power supply wire 54 and a return supply wire 52 of the interconnect cable 50, respectively, as discussed above. The power supply input 126 and return supply input 128 may be connected to respective pins of the above-discussed externally accessible electrical connector 108 to provide a releasable coupling between the infusion fluid warmer 100 and the interconnect cable 50.

[0101] The power supply input 126 is connected to a voltage supply grid 144 of the infusion fluid warmer 100 and distributes DC operating voltage and current to electric circuitry of the infusion fluid warmer 100. The DC operating voltage is controlled by the power supply 20 and may lie between 12 V and 48 V such as between 18 V and 30 V. The peak power drawn from the voltage supply grid 144 during normal operation, where infusion fluid is heated to the target temperature or temperature range, may lie between 100 W and 800 W. Most of the power drawn from the voltage supply grid 144 is dissipated in the resistive heating element during fluid heating. The skilled person will understand that power consumption of the infusion fluid warmer 100 may be significantly lower when the infusion fluid warmer 100 is idling or initializing, e.g. running an initialization or start-up sequence, because the power dissipation in the resistive heating element is largely eliminated during the initialization or start-up sequence.

[0102] The infusion fluid warmer 100 may comprise a DC voltage converter 116, such as a DC-DC switched mode converter or a linear voltage regulator, that is configured to step-down the DC voltage on the power supply input 126. This step-down of the DC voltage may be required because certain active or passive components of the infusion fluid warmer 100 may require lower DC supply voltages than the DC voltage at the power supply input 126. The DC voltage converter 116 may for example be configured to deliver a DC output voltage between 3.0 V and 5.0 V.

[0103] The fluid warmer 100 comprises a processing circuit that may comprise a software programmable microprocessor 140 or DSP configured to control hardware components of the infusion fluid warmer 100, e.g. the resistive heating element, by executing various software components. A DC supply voltage input VDD of the software programmable microprocessor 140 may be energized by the above-discussed DC output voltage of the DC voltage converter 116. The infusion fluid warmer 100 comprises the resistive heating element that may comprise one or more individually controllable resistive segments such as schematically illustrated resistive segments 130, 132, 134, 136. The resistive heating element is thermally coupled to the fluid channel 109 such that power dissipated in the resistive heating element heat is thermally conducted to the fluid channel 109 and to the infusion, e.g. intravenous, fluid flowing therein. The single resistive segment or each of the plurality of individually controllable resistive segments 130, 132, 134, 136 is preferably electrically connected to the power supply line 144 through respective controllable switches s1 , s2, s3, s4. The processing circuit 140 may be configured to control the power dissipation in the resistive heating element by switching each of the one or more controllable semiconductor switches s1, s2, s3, s4 between respective conducting and nonconducting states. The skilled person will understand that each of the one or more controllable semiconductor switches s1, s2, s3, s4 may switched between conducting and non-conducting states by configuring the control circuit to apply an appropriate control voltage to a control terminal of the switch such as to a gate terminal or a base terminal of a MOSFET or an IGBT, respectively. The switching of the one or more controllable semiconductor switches s1, s2, s3, s4 may result in the generation of one or more drive voltages across the heating element e.g. separate drive voltages for the resistive segments 130, 132, 134, 136 and thereby generate power dissipation. Each of the drive voltages may comprise any of a sinusoidal waveform, a switched voltage waveform such as PWM, PDM waveform etc.

[0104] One embodiment of the fluid warmer 100 comprises a heat exchanger (not shown) which preferably comprises a highly thermally conductive material such as metal such as aluminium, sliver or copper. The heat exchanger may be interposed between the resistive heating element and the fluid channel 109. An electrically insulating and thermally conductive layer may be inserted between the heating exchanger and the fluid channel 109

[0105] One embodiment of the fluid warmer 100 comprises a support structure 138 for the resistive heating element. The support structure 138 may comprise various types of carrier substrates such as a printed circuit board (PCB) or ceramics substrate. The support structure 138 may comprise the resistive heating element e.g. formed as a plurality of separate resistors soldered to a surface of the carrier substrate. The surface of the carrier substrate may for example comprise a surface facing the fluid channel and an opposing surface facing away from the fluid channel. The heat exchanger may be interposed between an upper surface of the carrier substrate which faces the fluid channel and the fluid channel 109. In this embodiment, a lower surface of the heat exchanger may define an upper section of the fluid channel 109. According to another embodiment of the fluid warmer 100 the support structure 138 and the resistive heating element are formed as a single integrally formed structure such a printed circuit board wherein the resistive heating element comprises a plurality of electrical traces of the PCB. The skilled person will understand that various electrical circuits and components of the infusion fluid warmer 100 may be attached to the printed circuit board such as the microprocessor 40, the DC voltage converter 116 etc.

[0106] The processing circuit of the infusion fluid warmer 100 is configured to generate different types of warmer data which may comprise respective values of one or more operational parameters of the infusion fluid warmer 100. The respective values of the one or more operational parameters may be collected by the processing circuit in connection with the start-up / initialization sequence of the infusion fluid warmer 100 e.g. before normal operation is commenced or at least before power the resistive heating element is activated to heat infusion fluid. The respective values of the one or more operational parameters may be compared by the processing circuit to respective target values to determine the integrity of the infusion fluid warmer 100 as discussed in further detail below.

[0107] The respective values of the one or more operational parameters may additionally, or alternatively, be collected by the processing circuit during normal operation of the infusion fluid warmer 100. The processing circuit may be configured to repeatedly determine the respective values of the one or more, i.e. at least one, operational parameter and repeatedly transmit warmer messages that comprise the respective values of the one or more operational parameters to the power supply 20 through the data communication interface.

[0108] The one or more operational parameters may comprise one or more of:

[0109] - power dissipation in the resistive heating element such as instantaneous or accumulated power dissipation in the heating element,

[0110] - power or current received at the power supply input 126,

[0111] - a resistance of the heating element,

[0112] - a temperature of the heating element,

[0113] - a flow rate of infusion fluid in the fluid channel 109; and

[0114] - a temperature of the infusion fluid at the fluid inlet 102 and / or at the fluid outlet 104,

[0115] - power dissipated in the resistive heating element,

[0116] - an integrity status, such as a pass state or fail state, of the infusion fluid warmer 100. In one embodiment of the infusion fluid warmer 100, the processing circuit thereof is configured to execute the initialization sequence in response to the presence of DC voltage at the power supply input 126 e.g. the primary DC voltage or secondary DC voltage delivered by the power supply 20 in an autonomous manner. The initialization sequence may comprise a self-test carried out by the microprocessor 140. The processing circuit may thereafter start transmission of the warmer messages in an autonomous manner, i.e. without awaiting messages or commands from the power supply 20. The processing circuit may for example automatically execute the initialization sequence of the infusion fluid warmer 100 in response to the onset of an appropriate DC voltage on the DC supply voltage input VDD of the microprocessor 140. The processing circuit may be configured to determine, during the initialization process, the respective value(s) of one or more operational parameters that is / are indicative of the integrity of one or more components of the infusion fluid warmer. According to one such embodiment, the processing circuit is configured to determine a resistance of the heating element and compare that resistance with a predetermined target value of the resistance of the heating element.

[0117] The processing circuit may be configured to generate and transmit a warmer message comprising an integrity pass state or an integrity fail state to the external power supply 20, indicative of the integrity of the heating element and / or the integrity of any other or additional electrical component of the infusion fluid warmer, based on an outcome of the comparison. The warmer message which comprises the integrity pass state or integrity fail state may be transmitted as a first message after the initialization sequence of the infusion fluid warmer 100 is completed. The processing circuit of the power supply 20 may be configured to respond to the integrity pass state or integrity fail state in an appropriate manner to safeguard patient safety as discussed in additional detail below.

[0118] The one or more operational parameters may comprise integrity checks of certain circuits and / or functions and / or components of the fluid warmer 100 such as the resistive heating element, the data communication interface etc. The microprocessor 140 may for example be configured, e.g. programmed, to read the values of the one or more operational parameters through a data input port P1 or through an analogue input port of the microprocessor 140. The microprocessor 140 may for example measure the supply current from a current measurement circuit 114 or current sensor 114. An input port P1 of the microprocessor 140 may be connected to the current sensor 114 for repeatedly reading supply current values and calculate a corresponding power consumption of the infusion fluid warmer. The microprocessor 140 may for example measure the temperature of the intravenous fluid at the fluid inlet 102 by reading the temperature (T1) from the temperature sensor 138 for example using the input port P1 of the microprocessor 140 or another input port.

[0119] The processing circuit of the infusion fluid warmer 100 comprises a data communication interface which may comprise an industry-standard serial communication interface such as an IIC or SPI interface or a proprietary data communication interface such as a serial proprietary data communication interface. The data communication interface may comprise an asynchronous serial communication protocol or a synchronous serial communication protocol. The data communication interface may be operating in accordance with a proprietary asynchronous communication protocol. One embodiment of the data communication interface comprises a supply current modulator 142.

[0120] The microprocessor 140 may comprise a protocol handler of the data communication interface e.g. integrated as a software component or a mix of a software component and dedicated digital circuitry externally to the microprocessor 140. An output of the supply current modulator 142 is connected to the voltage supply grid 144 and therethrough connected to the power supply input 126. An input of the supply current modulator 142 is connected to an output port, DATA, of the microprocessor 140.

[0121] The microprocessor 140 generates the warmer data in accordance with the data communication protocol and transmits the warmer messages to the input of the supply current modulator 142. The supply current modulator 142 is configured to modulate, e.g. superimpose, the supply current flowing through the power supply input 126 in accordance with the warmer messages such that the warmer messages are embedded in, or represented by, the supply current variations. The latter are detected by a data detector, e.g. data demodulator, of the power supply 20 as discussed in additional detail below. The skilled person will understand that the supply current comprises a superposition of the DC supply current and current, preferably small, variations caused by the warmer messages.

[0122] The supply current modulator 142 may comprise a controllable current source (not shown) electrically connected to the power supply input 126 or a controllable resistance (not shown) electrically connected to the power supply input 126. The controllable current source or the controllable resistance is configured to draw a variable current from the power supply input 126 in accordance with the warmer messages e.g. embed or superimpose the warmer messages in the variable current.

[0123] In one embodiment of the infusion fluid warmer 100, the controllable resistance comprises least a part of the heating element such as a resistive segment, e.g. one or more of the resistive segments 130, 132, 134, 136, of the resistive heating element.

[0124] The latter embodiment accordingly utilizes the resistive heating element for two distinct purposes and thus eliminates additional resistors to implement the controllable resistance

[0125] The data communication interface of the infusion fluid warmer 100 may be configured to apply data encoding methodologies of the warmer messages. One embodiment of the proprietary data communication interface is configured to superimpose the supply current onto the power supply input 126 by pulse width modulation where different pulse lengths indicate bit values of the warmer messages such that e.g. a short or first pulse represents logic “1” and a second and long pulse represents logic “0”, wherein the first and second pulse lengths are different, e.g. short pulse and long pulse.

[0126] In another embodiment, the proprietary data communication interface is configured to encode the warmer messages by a multi-tone, e.g. two-tone, modulation, wherein bit values of the warmer messages are encoded by different tone frequencies. For example, logic “1” may be encoded as a 1 kHz tone and logic “0” encoded as a 2 kHz tone or vice versa etc.

[0127] At least a part of the warmer messages may comprise one or more data packets. The data packets may for example be structured according to the proprietary communication protocol. The warmer messages may be transmitted to the power supply 20 through the proprietary, e.g. serial, data communication interface. Each data packet may comprise one or more predefined data fields such a payload field, that e.g. comprises values of the at least one operational parameter and / or messages, an errordetection code field, a header field etc. Each data packet may have a length between 32 bits and 128 bits. A bit rate of the proprietary data communication interface may lie between 1 kbit / s and 100 kbit / s.

[0128] According to one embodiment of the infusion fluid warmer 100, the data communication interface is unidirectional such that warmer messages may be transmitted from the infusion fluid warmer 100 to the external device, such as the power supply 20, using the above-discussed data communication methodology wherein the warmer messages is modulating the supply current. Another embodiment of the infusion fluid warmer 100 comprises a bidirectional data communication interface which, in addition to the transmission of warmer messages via the power supply input, is configured to detect, e.g. demodulate, supply messages transmitted by an external device, such as the power supply 20, to the power supply input 126 of the infusion fluid warmer 100. The latter embodiment may comprise a dedicated data demodulator circuit (not shown) connected to the power supply input 126.

[0129] The target temperature range of the intravenous fluid may for example lie from 39 degrees Celsius to 42 degrees Celsius. The skilled person will appreciate that the temperature of the intravenous fluid at the fluid inlet 6 may be significantly lower than the lower limit of the target temperature range for example less than room temperature for the reasons discussed above. The fluid channel 109 may comprise a straight central section or meandering central section, channel or conduit extending through the housing 101 to direct the flow of intravenous fluid from the fluid inlet 102 to the fluid outlet 104. In some embodiments, the straight central section comprises a rectangular cross-sectional shape with a width to height ratio larger than 50. These dimensions lead to efficient thermal coupling of thermal power or energy to the intravenous fluid due to a large contact area between walls of the heat exchanger and the intravenous fluid. Where the fluid channel 109 comprises a meandering section, it may comprise a width wise channel shape or pattern extending orthogonally to the flow of intravenous fluid at the fluid inlet and fluid outlet 102, 104.

[0130] FIG. 3 shows a simplified schematic drawing of an infusion fluid warmer 100a according to a second exemplary embodiment thereof. The circuits, features and functions of the second embodiment of the infusion fluid warmer 100a are generally identical to those of the first embodiment 100 discussed above, unless otherwise stated, and will accordingly not be discussed here for the purpose of brevity. One difference between the second embodiment of the infusion fluid warmer 100a and the first embodiment of the infusion fluid warmer 100 is that warmer messages and / or supply messages are not superimposed on the power supply input 126 of the second embodiment of the infusion fluid warmer 100a. The data communication interface of the second embodiment 100a comprises one or two dedicated data wires and optionally a clock line. Therefore, the supply current modulator 142 of the first embodiment 100 may be eliminated.

[0131] The data communication interface of the second embodiment 100a may comprise an industry-standard serial interface such as an IIC or SPI interface or alternatively comprise a proprietary serial data communication interface. The skilled person will understand that such an industry-standard serial communication interface may be integrally formed with the microprocessor 140. The skilled person will understand that each of the industry-standard serial interface and proprietary serial communication interface may comprise an asynchronous communication protocol or a synchronous communication protocol. The asynchronous industry-standard communication interface may comprise a single data line and the asynchronous proprietary communication interface likewise. The data communication interface of the second embodiment 100a comprises a serial data output terminal 127 and a clock output terminal 125. The serial data output terminal 127 and clock output terminal 125 may be connected to respective pins of an externally accessible connector such as a socket (not shown) which is arranged on, or inside, the housing 101 of the infusion fluid warmer 100a. The power supply input 126 may be connected to a third pin of the externally accessible connector.

[0132] The interconnect cable 50 where mating to the second embodiment of the infusion fluid warmer 100a may correspondingly comprise a dedicated supply wire, preferably with large cross-sectional area and small resistance to conduct power larger than 100 W to the infusion fluid warmer 100a. The interconnect cable 50 may further comprise one or two physically separate data wires to support the above-mentioned embodiment of the data communication interface with separate data line(s), with smaller physical dimensions such as smaller cross-sectional areas

[0133] FIG. 4 shows a schematic block diagram of an exemplary embodiment of the power supply 20 of the intravenous fluid delivery system 1. The power supply 20 comprises the housing 21 that comprises the rechargeable energy storage component 28 that may comprise one or more rechargeable battery cells 30a - 30d and / or one or more supercapacitors etc. The rechargeable energy storage component 28 delivers a primary DC voltage at power node 34 and supplies power from the one or more rechargeable batteries 30a - 30d and / or one or more supercapacitors to certain components of the power supply. The skilled person will appreciate that the rechargeable energy storage component 28 may be configured to deliver a primary DC voltage between 12 V and 48 V at the power node 34 depending inter alia on factors such as the type and number of rechargeable battery cells 30a - 30d, energy storage capacity, target maximum power delivery capacity etc. The housing 21 may be sealed to protect the rechargeable energy storage component 28 and other components inside the housing 21 against shock impacts, environmental dust and moisture etc. of the external environment. The power supply housing 21 may be a separate component from the housing 101 of the fluid warmer 100. The power supply 20 comprises a DC supply output 56 and return supply, such as a ground connection, for delivery of stored energy in the rechargeable energy storage component 28 to the infusion fluid warmer 100 through the power supply wire 54 and return supply wire 52 of the interconnect cable 50 as discussed above.

[0134] The power supply 20 comprises an AC connector 32 that may be releasably connected to the AC line voltage, e.g. 110 - 230 V @50 Hz - 60 Hz. The power supply 20 may comprise an AC / DC converter 24 to convert the AC line voltage to a suitable DC voltage at an output of the AC / DC converter. The power supply 20 comprises a charge control circuit 26 that has an input connected to the DC voltage at the output of the AC / DC converter. The microprocessor 40 is configured to control the charging of the rechargeable energy storage component 28, e.g. the rechargeable batteries 30a- 30d, by controlling power delivery by the charge control circuit 26 to the rechargeable energy storage component via a power conductor 27. An output port P2 of the microprocessor 40 may be connected to a power control input 29 of the charge control circuit 28. Various types of charge control circuit 26 may be used for example depending on chemistry of the one or more rechargeable battery cells 30a - 30d of the rechargeable energy storage component 28. The charge control circuit 26 may for example comprise a constant current and constant voltage circuit for e.g. charging Li- Ion battery cells.

[0135] The power supply 20 comprises a processing circuit which may comprise a software programmable microprocessor 40 or DSP configured to control hardware circuits of the power supply 20, such as the charge control circuit 26, by executing various software components. A DC supply voltage input VDD of the software programmable microprocessor 40 (“microprocessor 40”) may connected to, and energized by, a stepdown DC voltage converter 36. The DC supply voltage input VDD of the microprocessor 40 is connected to an output of the step-down DC voltage converter 36 by a suitable conductor 48 such as a wire or trace of a printed circuit board (not shown). The step-down DC voltage converter 36 may be configured to generate a DC output voltage based on the primary DC voltage at the power node 34 of the rechargeable energy storage component 28. The DC output voltage is lower than the primary DC voltage such as between 3.0 and 5.0 V when the primary DC voltage is between 12 V and 48 V.

[0136] The power supply 20 comprises a data communication interface electrically connected to the DC supply output 56. The communication interface is configured to receive and detect, such as extract, data transmitted from an external device on the DC supply output 56, such as the warmer messages transmitted by the infusion fluid warmer 100 as discussed above. The data communication interface is compatible with the data communication interface of the infusion fluid warmer 100 as discussed above.

[0137] Consequently, the data communication interface of the power supply 20 may comprise an industry-standard serial communication interface such as an IIC or SPI interface or the proprietary data communication interface operating in accordance with the proprietary communication protocol discussed above. The data communication interface is configured to receive and detect, e.g. extract, the warmer messages transmitted by the infusion fluid warmer 20 based on supply current variations on the DC supply output 56. The data communication interface may comprise a data detector 42, such as a data demodulator, connected to the DC supply output 56. An input of the data detector 42 may be connected to the DC supply output 56. An output of the data detector 42 may be connected to an analog input port of the microprocessor 40 or a digital input port DATA of the microprocessor 40.

[0138] The data detector 42 may comprise a sense resistor (not shown) connected in series with the DC supply output 56 such as between the controllable switch 60 and the DC supply output 56. The data detector 42 may be configured to sense the supply current variations by measuring a voltage drop across the sense resistor.

[0139] The data communication interface may comprise a frequency detector such as a Fast- Fourier Transform (FFT) based detector. The microprocessor 40 may be configured to perform FFT analysis of the output of the data detector 42 to detect, e.g. demodulate, the previously discussed tones of the multi-tone, e.g. two-tone, modulation of the warmer messages carried out by the data communication interface of the infusion fluid warmer 100. The microprocessor 40 may in the alternative comprise one or more bandpass filters configured to detect the multi-tones of the warmer messages. In both embodiments, the microprocessor 40 may comprise a software component configured to carry out the detection of the multi-tone encoded warmer messages transmitted by the warmer. This software component may accordingly form part of the data communication interface of the power supply 20.

[0140] The processing circuit preferably comprises a controllable switch arrangement 60, that may comprise one or more semiconductor switches such as one or more MOSFETs, HEXFETs and IGBTs, electrically connectable between the rechargeable energy storage component 28 and the DC supply output 56. The primary DC voltage at power node 34 is connected to a first input 59 of the controllable switch arrangement 60. The processing circuit is configured to selectively connect and disconnect the primary DC voltage of the energy storage component 28 from the DC supply output 56 by controlling a state, i.e. a conducting state and a non-conducting state, of the controllable switch arrangement 60.

[0141] The state of the controllable switch arrangement 60 may be carried out via one or more control terminal(s) 62 of the controllable switch arrangement 60. The control terminal 62 may be connected to one or more base or gate terminals of the one or more semiconductor switches. A microprocessor 40 of the processing circuit may be configured to control the state of the controllable switch arrangement 60. This control of the state of the controllable switch arrangement 60 may for example be carried out via an output port P1 of the microprocessor 40 which port P1 is connected to the control terminal 62. The microprocessor 40 is accordingly configured to disconnect the energy storage component 28, and hence the primary DC voltage, from the DC supply output 56 by the controllable switch arrangement 60. Thereby, effectively interrupt the supply of power from the power supply 20 to the infusion fluid warmer 100.

[0142] According to some embodiments of the power supply 20, the processing circuit is configured to connect the DC supply output 56 to a lower secondary DC voltage after the primary DC voltage has been disconnected from DC supply output 56 as discussed below.

[0143] According to one embodiment of the power supply 20, the processing circuit is configured to monitor the warmer messages received from the infusion fluid warmer 100 during normal operation thereof. The processing circuit is further configured to disconnect the energy storage component 28, from the DC supply output 56 if the infusion fluid warmer 100 appears to be defective. In one such embodiment, the microprocessor 40 monitors the data communication interface for a predetermined time period. If the microprocessor 40 fails to detect a valid warmer message, such as the message comprising the integrity pass state or integrity fail state, within the predetermined time period, the microprocessor 40 disconnects the energy storage component 28 from the DC supply output 56 by controlling the controllable switch arrangement 60. On the other hand, if the microprocessor 40 detects valid warmer message, such as the message comprising the integrity pass state or integrity fail state, within the predetermined time period, the processing circuit continues to supply power to the infusion fluid warmer 100 and normal operation is maintained.

[0144] One embodiment of the processing circuit of the power supply 20 comprises a bidirectional data communication interface which, in addition to the receipt and detection, e.g. demodulation, of the warmer messages is configured to transmit supply messages to the infusion fluid warmer 100 through the data communication interface. According to one such embodiment, the power supply 20 is configured to transmit the supply messages through the DC supply output 56 to provide bidirectional power line communication with the infusion fluid warmer. The supply messages may comprise commands to the infusion fluid warmer 100 to read and transmit specific values of the one or more operational parameters of the infusion fluid warmer 100 to the power supply 20 through the bidirectional data communication interface such as fluid temperature, instantaneous or accumulated power dissipation in the heating element, power or current at the power supply input of the fluid warmer etc.

[0145] The power supply 20 may transmit various data associated with the operational parameters of the power supply 20 to the microprocessor 140 of the infusion fluid warmer 100 through the bidirectional data communication interface such as the number of rechargeable battery cells 30a - 30d and / or supercapacitors. The operational parameters of the power supply 20 may comprise individual maximum current outputs of the rechargeable battery cells 30a - 30d and / or supercapacitors or their combined the maximum current output. These embodiments could enhance flexibility of the intravenous fluid delivery system 1 by allowing the infusion fluid warmer 100 to cooperate with different types of power supplies and adjust its operational parameters according to the specific type of connected power supply. The operational parameters of the power supply 20 may comprise a charge state, e.g. expressed from 0 to 100 %, of the energy storage component and / or a temperature of the energy storage component. The charge state may be helpful for the infusion fluid warmer 100 to adapt its operation, e.g. power consumption, to the charge state for example by reducing the power consumption of the infusion fluid warmer 100 if the charge state of the energy storage component is below a certain threshold.

[0146] The processing circuit may comprise a voltage regulator 36, such as a programmable switched-mode DC-DC converter. The voltage regulator 36 is connected to the power node 34 and configured to down-convert the primary DC voltage to a secondary DC voltage VDD at output VDD. As mentioned above, the primary DC voltage typically lies between 12 V and 48 V which is an unacceptable high supply voltage for certain active circuits of the power supply 20 such as the microprocessor 40. The secondary DC voltage 44 is therefore connected for example to the power supply input 41 of the microprocessor 40. The secondary DC voltage 44 may lie between 3.0 V and 5.0 V. An output resistance of the voltage regulator 36 is preferably much larger than the output resistance of the energy storage component 28 for example larger than 10 ohm such as larger than 50 ohm. The output resistance of the voltage regulator 36 may be intrinsic to the voltage regulator and / or implemented by a resistor (not shown) connected in series with the secondary DC voltage. An output terminal 63 of the controllable switch arrangement 60 is connected to the DC supply output 56 such that the output terminal 63 either conducts the primary DC voltage or the secondary DC voltage to the DC supply output 56 depending on the state of the controllable switch arrangement 60. Hence, the voltage at the DC supply output 56 can be switched between the primary DC voltage, generated by the energy storage component 28, and the secondary DC voltage VDD generated by the voltage regulator 36.

[0147] The voltage regulator 36 may be configured to provide gradual supply voltage start-up of the power supply voltage to the infusion fluid warmer 100 according to certain embodiments of the power supply 20. According to one such embodiment, the secondary DC voltage VDD is connected to a second input 58 of the controllable switch arrangement 60 such that the microprocessor 40 can connect the secondary DC voltage to the DC supply output 56 instead of the primary DC voltage by selecting the appropriate state of the controllable switch arrangement 60.

[0148] This control over the voltage at the DC supply output 56 is utilized in one embodiment of the power supply 20 to provide a multi-step supply voltage ramp-up of the infusion fluid warmer 100 controlled by the power supply 20. This approach is beneficial because it provides additional patient safety against possible hazardous defects in the infusion fluid warmer 100 at start-up. This is achieved because defects like short- circuits to the DC supply grid 144 of the infusion fluid warmer 100, for example through a defective heating element and / or switches s1, s2, s3, s4, will draw much less power from the secondary DC voltage than from the primary DC voltage. The skilled person will understand that the primary DC voltage is higher than the secondary DC voltage. Furthermore, and importantly, the output impedance of the energy storage component 28 is preferably much smaller than an output impedance of the programmable voltage regulator 36. When the output impedance of the programmable voltage regulator 36 is much higher, e.g. at least ten times higher, than the output impedance of the energy storage component 28 short-circuit induced hazardous defects in the infusion fluid warmer 100 could lead to overheating of the housing 101 of warmer 100 and / or overheating of the infusion fluid. Hence, the multi-step supply voltage ramp-up offers important patient safety advantages in view of the often physical contact between the fluid warmer 100 and the patient during administration of the intravenous fluid.

[0149] The alphanumeric display 22 of the power supply 20 may in one embodiment be configured to provide an operator of the intravenous fluid delivery system 1, such as a medical doctor, a nurse or emergency individual etc., with an intuitive evaluation tool which indicates whether the intravenous fluid delivery system 1 functions correctly. According to the latter embodiment of the power supply, and corresponding intravenous fluid delivery system 1 , the power supply 20 and the infusion fluid warmer 100, the alphanumeric display 22 of the power supply 20 is configured to provide an operator of the intravenous fluid delivery system 1, such as a medical doctor, a nurse or emergency individual, with an intuitive support tool to evaluate whether or not the intravenous fluid delivery system 1 functions correctly.

[0150] According to this embodiment of the system 1 , the processing circuit of the power supply 20 is configured to repeatedly measure the power delivered through the DC supply output 56 to the infusion fluid warmer 100. The processing circuit of the infusion fluid warmer 100 is configured to repeatedly measure the corresponding power consumption of the heating element, and optionally of the entire warmer 100, using a second current sensor 117. The processing circuit of infusion fluid warmer 100 is further configured to repeatedly transmit the corresponding power consumptions to the power supply 20 through the data communication inface. The processing circuit of the power supply 20 monitors the data communication interface of the power supply 20 and repeatably reads the power consumptions received from the infusion fluid warmer 100 through the data communication interface. ‘

[0151] The processing circuit of the power supply 20 is further configured to repeatedly display the measured power flowing through the DC supply output 56 of the power supply 20 on the alphanumeric display 22. The processing circuit of the power supply 20 may optionally be further configured to display the corresponding power consumption values of the infusion fluid warmer 100 on the alphanumeric display 22. This visual display of the power delivery of the power supply in connection with infusion fluid heating is a useful tool for the system operator because the operator typically possesses a priori knowledge of the approximate power consumption of the infusion fluid warmer to be expected during a certain set of operating conditions of the intravenous fluid delivery system 1.

[0152] For example, when the infusion fluid warmer 100 is heating infusion fluid of a certain inlet temperature, outlet temperature and flowrate, the operator knows from experience that the power dissipation approximately should lie between certain upper and lower power limits e.g. 100 W and 800 W. Hence, if the power dissipation displayed on the alphanumeric display 22 deviates from the upper and lower power limits, this may indicate a system failure or malfunction. The system operator may in response check components, electrical connections and fluid connections of the intravenous fluid delivery system 1 to identify the cause of the suspected malfunction take corrective action(s).

[0153] An exemplary malfunction of the intravenous fluid delivery system 1 could be an interruption of the supply of infusion fluid from the IV container to the fluid inlet 102 of the infusion fluid warmer 100. The interruption of the supply of infusion fluid may be caused by an obstruction in / on the fluid tube or a disconnection of the fluid tube coupled to the fluid inlet 102. In the latter situation, the processing circuit of the infusion fluid warmer 100 may be configured to reduce the power supply to the resistive heating element to a small value, e.g. below 10 W or 1 W, because heating energy is not needed to reach the target temperature of a small amount of infusion fluid staying in the fluid channel under these circumstances. According one embodiment, the processing circuit of the power supply 20 is additionally configured to compare the measured power through the DC supply output 56 with the corresponding power consumption of the fluid heater 100 as measured by the processor of the infusion fluid warmer and transmitted to the power supply 20 in form of warmer messages. The processing circuit of the power supply 20 is configured to disconnect the DC supply output 56 for example using the controllable switch arrangement 60 if the measured power at the DC supply output 56 and the corresponding power dissipation in the infusion fluid warmer differs by more than a preset power threshold. The processing circuit of the power supply 20 is configured to repeatedly read power dissipation values of the infusion fluid warmer 100 as transmitted by the processing circuit of the infusion fluid warmer. A major or dominant portion of the power consumption of the infusion fluid warmer 100 is used for power dissipation in the heating element(s) during normal operation of the infusion fluid warmer 100 where the latter heats the infusion fluid flowing through the fluid channel 109.

[0154] Therefore, the power through the DC supply output 56 and the corresponding heating element power dissipation, measured by the second current sensor 117, should match within a preset power limit. The preset power limit may correspond to a deviation of more than 10 % between the power delivered by the power supply 20 through the DC supply output 56 and the corresponding heating element power dissipation. If the deviation is above the preset power limit that may indicate an electrical malfunction in the infusion fluid warmer 100 such as short-circuit(s). In that situation, the processing circuit of the power supply may be configured to disconnect the DC supply output 56 from the energy storage component 28 and thereby interrupt power supply to the infusion fluid warmer 100 providing improved patient safety.

[0155] FIG. 6 is flowchart of control steps carried out by the processing circuit of the power supply 20 of the intravenous fluid delivery system 1. FIG. 7 is flowchart of corresponding control steps carried out by the processing circuit of the infusion fluid warmer 100 of the intravenous fluid delivery system 1. The flowcharts show the abovediscussed embodiment of the system 1 that inter alia comprises the multi-step supply voltage ramp-up.

[0156] In step 600 the processing circuit of the power supply 20 initializes the power supply 20 for example comprising loading software components from a non-volatile memory in the memory of the microprocessor 40 (FIG. 4). The processing circuit may additionally check whether one or more hardware components of the power supply 20, such as the heating element, functions correctly.

[0157] In step 610 the processing circuit of the power supply 20 sets the voltage at the DC supply output 56 to the secondary DC voltage, e.g. between 3.0 V and 5 V, by switching the output terminal of the controllable switch arrangement 60 to the lower DC supply voltage VDD. The on-set of the secondary DC voltage starts the start- up / initialization sequence of the processing circuit of the infusion fluid warmer 100 as discussed below.

[0158] In step 620 the processing circuit of the power supply 20 monitors the data communication interface for receipt of a valid warmer message such as the previously discussed integrity pass message or integrity fail message which may be transmitted through the power supply wire and return supply wire, respectively, of the interconnect cable as discussed above. The valid warmer message means a message that complies with the data communication protocol of the respective data communication interfaces of the power supply 20 and infusion fluid warmer 100. In response to detection of such valid warmer message, the processing circuit of the power supply 20 proceeds to step 630. If the processing circuit of the power supply 20 on the other hand fails to detect the valid warmer message the processing circuit maintains the secondary DC voltage at the supply output 56 and returns to step 620 and keeps monitoring the data communication interface.

[0159] In step 630 the processing circuit of the power supply 20 may switch the voltage at the DC supply output 56 from the secondary DC voltage to the primary DC voltage by the controllable switch arrangement 60 in response to receipt of the valid warmer message. The latter indicates at least that the infusion fluid warmer 100 appears to function correctly. In alternative embodiments of the power supply 20 its processing circuit maintains the secondary DC voltage DC supply output 56 while continuing to monitor the data communication interface for receipt of the integrity pass state or integrity fail state before the DC supply output 56 is switched to the primary DC voltage. The processing circuit may additionally or alternatively maintain the secondary DC voltage on DC supply output 56 until receipt of value(s) of the one or more operational parameters of the infusion fluid warmer 100 such as temperature of the heating element, power dissipation in the heating element, fluid temperature in the fluid channel etc. When the processing circuit of the power supply 20 receives the integrity pass state the processing circuit of the power supply 20 jumps to step 640 in response. On the other hand, if the processing circuit of the power supply 20 receives the integrity fail state the processing circuit preferably responds by jumping back to step 620.

[0160] In step 640 the processing circuit of the power supply 20 responds to the receipt of the integrity pass message by switching the voltage at the DC supply output 56 from the secondary DC voltage to the primary DC voltage by the controllable switch arrangement 60. This switching the voltage at the DC supply output 56 from the secondary DC voltage to the primary DC voltage is illustrated on FIG. 8 at time instant t3 where the voltage at the DC supply output 56 switches from the secondary DC voltage to the primary DC voltage. Thereafter, the processing circuit of the power supply 20 jumps to step 650.

[0161] In step 650 the infusion fluid warmer 100 resides in normal operation mode in response to the on-set of the primary DC voltage at the supply input 126 of the infusion fluid warmer 100. The processing circuit of the power supply 20 again monitors the data communication interface for receipt of the warmer messages repeatedly transmitted by the infusion fluid warmer 100 as response to the presence of the primary DC voltage on the power supply input 126. These warmer messages may inter alia comprise the same integrity pass state or fail state discussed above and / or the values of the one or more the operational parameters of the infusion fluid warmer 100.

[0162] If the processing circuit of the power supply 20 receives the warmer message processing circuit of the power supply 20 jumps to step 660. On the other hand, if the processing circuit of the power supply 20 fails to receive the warmer message, preferably within a predetermined time window, the processing circuit may disconnect the primary DC voltage from the DC supply output 56 by the controllable switch arrangement 60. The processing circuit of the power supply 20 may thereafter connect the DC supply output 56 to the lower DC supply voltage VDD and jump back to step 620. The jump back to step 620 is motivated by the lack of warmer messages which may indicate a possible malfunction / error of the infusion fluid warmer 100.

[0163] In step 660 the processing circuit of the power supply 20 may repeatedly detect the power flowing through the DC supply output 56 and determine whether the detected power at certain time instants is within the predetermined power limits discussed above in view of the expected power consumption of the infusion fluid warmer 100. The processing circuit of the power supply 20 may estimate the expected power consumption of the infusion fluid warmer 100 by evaluating appropriate operational parameter value(s) transmitted by the infusion fluid warmer 100 in step 650. For example, if the operational parameters indicate an off state of the heating element and the power consumption is high, that situation may indicate a fault, such as a short- circuit, in the infusion fluid warmer 100. If such a fault situation in the infusion fluid warmer 100 is suspected, the processing circuit of the power supply 20 may respond by disconnecting the primary DC voltage from the DC supply output 56 and instead connect the DC supply output 56 to the lower DC supply voltage VDD by the controllable switch arrangement 60 and finally jump back to step 620.

[0164] On the other hand, if the processing circuit of the power supply 20 determines that the detected power is within the predetermined power limits the processing circuit jumps back to step 650 and awaits the next warmer message from the infusion fluid warmer 100.

[0165] In step 700 (FIG. 7), the processing circuit of the infusion fluid warmer 100 is non- operational and awaits an appropriate DC supply voltage, e.g. above a preset threshold such as 3.3 V, at the power supply input 126. The skilled person will understand that an ’’appropriate DC supply voltage” in the present context means a DC voltage sufficiently high to enable operation of the microprocessor 140 (FIG. 4). When the appropriate DC supply voltage at the power supply input 126 is reached, the processing circuit responds by jumping to step 710. In step 710, the processing circuit of the infusion fluid warmer 100 executes the start-up / initialization sequence of the infusion fluid warmer 100 at time instant t1 indicated on FIG. 8. The processing circuit may for example use the autonomous start-up sequence discussed above. The processing circuit of the infusion fluid warmer 100 may turn off the heating element to eliminate power dissipation therein and thereafter jump to step 720.

[0166] In step 720, the processing circuit of the infusion fluid warmer 100 carries out various integrity tests of the components and circuits of the infusion fluid warmer 100 such as the resistive segments 130-134 and associated switches 130a-130d etc. The processing circuit may further check that the voltage on the power supply input 126 is set to the secondary DC voltage. If the integrity test of the components and circuits is passed the processing circuit jumps to step 730. Otherwise, the processing circuit jumps back to repeat step 720. In step 730 the processing circuit transmits a valid warmer message for example comprising to the power supply 20 through the data communication interface with the result of the integrity tests of step 720. The valid warmer message may for example be transmitted through the power supply wire and return supply wire, respectively, of the interconnect cable, as discussed above.

[0167] This transmittal of the valid warmer message is illustrated on FIG. 8 at time instant t2. The integrity pass message may be transmitted to the power supply 20 while the DC supply output 56 is set to the secondary DC voltage in embodiments that comprise the multi-step supply voltage ramp-up as illustrated on FIG. 8. The processing circuit may transmit a further warmer message that comprises a command to the power supply 20 to switch to the primary DC voltage or the power supply 20 may be configured to automatically switch to the primary DC voltage in step 740 as response to the receipt of the valid warmer message as discussed above.

[0168] Nevertheless, the processing circuit of the infusion flid warmer 100 may be configured to carry out similar integrity tests of the components of the infusion fluid warmer 100 even without the optional multi-step supply voltage ramp-up. In the latter embodiment, the processing circuit of the power supply 20 initializes the DC supply output 56 to the primary DC voltage. In both instances the processing circuit of the infusion fluid warmer 100 may be configured to generate and transmit the valid warmer message after completion of the start-up / initialization sequence of the infusion fluid warmer 100 and preferably at least before the heating element commence heating of the infusion fluid.

[0169] The processing circuit of the infusion fluid warmer 100 may additionally, or alternatively, be configured to repeatably generate and transmit warmer messages that comprise other operational parameters of the infusion fluid warmer 100 after completion of the start-up / initialization sequence and before the heating element is activated. The skilled person will understand that the latter timing, i.e. transmittal of the warmer messages comprising other operational parameters, before the heating element is activated, is advantageous because supply noise on the power supply input 126 of the infusion fluid warmer 100 is relatively low compared to the supply noise during active operation of the heating element.

[0170] The supply noise is inter alia caused by the alternatingly switching on and off of the heating element, e.g. the resistive segments 130a-d thereof, that is / are connected to the power supply input 126 for example through the voltage supply grid 144. In step 750 the infusion fluid warmer 100 enters the normal operation mode. The processing circuit of the infusion fluid warmer 100 may repeatedly carry out the above- mentioned integrity tests and transmits corresponding integrity pass or fail messages to the power supply 20 to allow the processing circuit of the latter to verify correct functionality of the infusion fluid warmer 100.

[0171] In step 760 the processing circuit initiates a control loop that continuously adjusts power dissipation in the heating element such that the target temperature of the infusion fluid is reached and maintained within the previously described target temperature range or specific target temperature. The control loop may comprise a PID controller that alternatingly turn on and turn off the power dissipation in the resistive heating element.

[0172] In step 770 the processing circuit of the infusion fluid warmer 100 may repeatably generate and transmit various types of warmer messages and these may include one or more of the previously discussed operational parameter values of the fluid warmer 100 such as its status. The processing circuit may for example determine the power consumed by the fluid warmer, i.e. power flowing through the power supply input 126, by reading the current sensor 114 and read the corresponding DC voltage on the power supply input 126. When the repeated integrity tests of the processing circuit of the infusion fluid warmer 100 are passed (Y), the processing circuit of the infusion fluid warmer 100 may jump back to step 750 and continue to heat the resistive heating element in the heating element control loop. If the integrity test fails (N) at a certain point in time, the processing circuit of the of the infusion fluid warmer 100 may generate and transmit a warmer message to the power supply 20 indicating the failed integrity test. In response, the processing circuit of the power supply 20 may disconnect the primary DC voltage from the DC supply output 56 and connect the DC supply output 56 to the lower DC supply voltage VDD.

[0173] The processing circuit of the infusion fluid warmer 100 may thereafter jump back to step 720 wherein the processing circuit carries out various integrity tests of the components and circuits of the infusion fluid warmer 100. Consequently, the processing circuit of the infusion fluid warmer 100 resides in a failure state or mode where the heating element is deactivated. If the cause of the failed integrity test is eliminated, for example by manual intervention of the system operator, the processing circuit of the infusion fluid warmer 100 may respond by generating and transmitting a warmer message which comprises an integrity pass state to the power supply 20 which may respond by switching the DC supply output 56 from the secondary DC voltage to the primary DC voltage and normal system operation resumed.

Claims

37CLAIMS1. A power supply for an intravenous fluid delivery system, comprising:- a housing comprising a rechargeable energy storage component such as one or more rechargeable battery cells and / or one or more supercapacitors, wherein the rechargeable energy storage component is configured to supply a primary DC voltage,- a DC supply output for delivery of stored power in the rechargeable energy storage component,-- a voltage regulator, such as a programmable switched-mode DC-DC converter, configured to down-convert the primary DC voltage of the rechargeable energy storage component to a secondary DC voltage e.g. a DC voltage between 3.3 V and 5 V; and- a processing circuit comprising a data communication interface, wherein said processing circuit is configured to extract warmer messages transmitted by an infusion fluid warmer through the data communication interface, wherein the processing circuit further comprises:- a controllable switch arrangement configured to electrically connect and disconnect the DC supply output and the primary DC voltage and configured to electrically connect and disconnect the DC supply output and the secondary DC voltage.

2. A power supply for an intravenous fluid delivery system according to claim 1, wherein an output resistance of the voltage regulator is at least 10 times larger, preferably at least 100 times larger, than a nominal output resistance of the energy storage component for example larger than 10 ohm such as larger than 50 ohm.

3. A power supply for an intravenous fluid delivery system according to claim 1, wherein the data communication interface comprises:- an industry-standard communication protocol, such as SPI, IIC, or- a proprietary communication protocol such as an asynchronous serial communication protocol.

4. A power supply for an intravenous fluid delivery system according to claim 3, wherein the data communication interface comprises the proprietary communication protocol and- a data detector connected to the DC supply output and configured to extract the warmer messages based on supply current variations on the DC supply output.

385. A power supply for an intravenous fluid delivery system according to claim 4, wherein the data detector comprises a frequency detector such as a Fast-Fourier Transform based detector and / or one of more bandpass filter based detectors.

6. A power supply for an intravenous fluid delivery system according to any of the preceding claims, wherein the processing circuit is configured to:- initializing the power supply e.g. by loading one or more software components from a non-volatile memory of the power supply,- set the DC supply output to the secondary DC voltage by the controllable switch arrangement,- monitor the data communication interface for the warmer messages,- detect a valid warmer message comprising an integrity pass state of the infusion fluid warmer or integrity fail state of the infusion fluid warmer,- respond to the integrity pass state by disconnecting the secondary DC voltage from the DC supply output and connect the primary DC voltage output to the DC supply output by the controllable switch arrangement; and- respond to the integrity fail state by maintaining the secondary DC voltage at the DC supply output and continue to monitor the data communication interface for the warmer messages.

7. A power supply for an intravenous fluid delivery system according to any of claims 1- 6, wherein said processing circuit is configured to:- monitor the data communication interface for receipt of warmer messages transmitted by the infusion fluid warmer during normal operation thereof,- disconnect the primary DC voltage from the DC supply output by control of the first controllable switch arrangement in response to a failure to receive a valid warmer message within a predetermined time period,- connect the secondary DC voltage to the DC supply output by control of the first controllable switch arrangement.

8. A power supply for an intravenous fluid delivery system according to any of the preceding claims, wherein the data communication interface is bidirectional and wherein the processing circuit is configured to:- generate and transmit supply messages to the infusion fluid warmer through the data communication interface, wherein the supply messages may comprise settings of oneor more operational parameters of the infusion fluid warmer and / or requests for transmission of respective values of one or more operational parameters of the infusion fluid warmer such as fluid temperature, instantaneous power dissipation or accumulated power dissipation in the heating element, incoming power or current at a power supply input of the fluid warmer etc.

9. A power supply for an intravenous fluid delivery system according to any of the preceding claims, comprising one or more visual indicators, such as an alphanumeric display and / or or graphics display, mounted to the housing, and wherein the processing circuit is configured to:- repeatedly measure power values delivered through the DC supply output to the infusion fluid warmer,- repeatedly detect, in the received warmer messages, power dissipation values of the resistive heating element corresponding to the measured power values,- repeatedly display the measured power values delivered through the DC supply output on the one or more visual indicators; and- optionally display the corresponding power dissipation values of the resistive heating element on the one or more visual indicators.

10. A power supply for an intravenous fluid delivery system according to claim 9, wherein the processing circuit is configured to:- repeatedly compare the measured power values delivered through the DC supply output with the corresponding heating element power dissipation values,- disconnect the DC supply output from the energy storage component if a measured power value and a corresponding power dissipation value of the heating element differs by more than a preset power limit.

11. A power supply for an intravenous fluid delivery system according to any of the preceding claims, comprising an interconnect cable comprising:- a proximal end attached to the housing,- a first wire electrically connected to the DC supply output, e.g. via a first terminal of the power supply, and a second wire connected to a return supply voltage,- at least one third wire connectable to the data communication interface; and wherein a distal end of said interconnect cable optionally comprises a releasable connector which comprises a first pin connected to the first wire, a second pinconnected to the second wire and a third pin connected to the at least one third data wire.

12. An infusion fluid warmer comprising a housing comprising a fluid inlet and a fluid outlet and a fluid channel extending between the fluid inlet and the fluid outlet, a power supply input and return supply input connectable to a power supply wire and a return supply wire, respectively, of an interconnect cable, a heating element thermally coupled to the fluid channel and configured to deliver heat to infusion fluid in the fluid channel, a processing circuit comprising a data communication interface, wherein said processing circuit is configured to:-- repeatedly generate and transmit warmer messages through the data communication interface to a power supply.

13. An infusion fluid warmer according to claim 12, wherein the processing circuit is configured to:- repeatedly determine warmer data which comprises respective values of one or more operational parameters of the infusion fluid warmer,- write the warmer data to the warmer messages before the transmission to the power supply.

14. An infusion fluid warmer according to claim 13, wherein the one or more operational parameters comprises one of more of:- power dissipation in the resistive heating element,- power received at the power supply input,- a resistance of the heating element,- a temperature of the heating element,- a flow rate of the infusion fluid in the fluid channel,- a temperature of the infusion fluid,- a result of an integrity test of the infusion fluid warmer.

15. An infusion fluid warmer according to any of claims 12 to 14, wherein the processing circuit is configured to:- perform an integrity test of the infusion fluid warmer during an initialization sequence,wherein the integrity test comprises comparisons between the respective values of the one or more operational parameters and corresponding target values,- generate a warmer message comprising an integrity pass state or an integrity fail state based on a result of the integrity test,- transmit the warmer message comprising the integrity pass state or integrity fail state through the data communication interface e.g. to an external power supply according to any of claims 1 -11.

16. An infusion fluid warmer according to any of claims 12 to 15, comprising a detachable externally accessible electrical connector, such as a plug or a socket, arranged on, or in, the housing, wherein said electrical connector comprises at least:- a first pin connected to the power supply input and a second pin connected to the return supply input; and optionally a third pin connected to the data communication interface.

17. An intravenous fluid delivery system, comprising: a power supply according to any of claims 1 -11 , an infusion fluid warmer according to any of claims 12 -16; and an interconnect cable comprising:- a first conductor, such as a power supply wire, and a second conductor such as power return wire, e.g. shield, and optionally a third conductor such as a data wire; and- a distal detachable connector mating to a detachable externally accessible electrical connector of the infusion fluid warmer.

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