Biological product preservation apparatus and method

Abstract

Biological product preservation apparatus 1 comprising: container unit 100 for preserving biological product; thermal energy store 210 coupled to container unit for managing temperature of said biolog

Description

Technical Field The present disclosure relates to the field of preservation of biological products. For example, the present disclosure may relate to the preservation of body tissue, such as body tissue through which a fluid may be circulated, e.g. with a gaseous oxygen persufflation mixture. Background In some cases, one or more organs may be obtained from a donor patient and such organ(s) may be used in the treatment of a recipient patient. In which case, a surgeon may remove a relevant organ from the patient. The organ is then transferred so that it can be used to treat the recipient patient. During this process, there will be a time period in which the organ is not connected to either patient, and this organ is to be maintained in a suitable state so that it may still be useful in the treatment of the recipient patient. In this time period the organ may have to be transported, such as from one hospital to another. Storage apparatuses have been disclosed which are designed to facilitate this transfer of an organ. For example, GB2592354 discloses apparatuses and methods for the storage and preservation of body tissue. Aspects of the present disclosure seek to provide systems and methods for preservation of biological products. Such systems and methods of the present disclosure may, in some implementations, be used to provide improved preservation of body tissue. Summary Aspects of the disclosure are set out in the independent claims and optional features are set out in the dependent claims. Aspects of the disclosure may be provided in conjunction with each other, and features of one aspect may be applied to other aspects. In an aspect, there is provided a biological product preservation apparatus comprising: a container unit for preserving a biological product; a thermal energy store, wherein the thermal energy store is thermally coupled to the container unit for managing a temperature of a said biological product preserved in the container unit; one or more sensors configured to obtain an indication of a temperature of the thermal energy store; and a controller configured to control operation of the apparatus based on the obtained indication of temperature of the thermal energy store. Embodiments may facilitate controlling a temperature of the container unit using material in the thermal energy store (e.g. material which does not need to come into direct contact with the biological product being preserved). Through temperature monitoring for that energy store, operation of the apparatus may be controlled without requiring a sensor to be provided in close proximity to the biological product in the container unit. This may be particularly advantageous where the container unit is a disposable component and / or the biological product requires high sterility for nearby components. Controlling operation of the apparatus based on the obtained temperature data may comprise determining an indication of a status of: (i) the biological product preserved in the container unit, and / or (ii) the thermal energy store. The controller may be configured to output a status signal comprising an indication of the determined status. Determining an indication of the status of the thermal energy store may comprise determining a status of material in the thermal energy store. Determining the indication of the status may comprise determining an indication of a phase of the material in the thermal energy store. For example, the material in the thermal energy store may be (initially) in one phase state, and the controller may be configured to determine whether this material has changed phase and / or how much of this material has changed phase (e.g. what proportion). For example, the material may initially be a solid, such as ice, and the phase change may comprise the solid, e.g. ice, melting to become a liquid, e.g. water. Determining the indication of the status may comprise determining a proportion of the material in the thermal energy which has changed phase, e.g. determining a proportion of the ice within the thermal energy store which has melted (and is now water). The controller may be configured to predict a time at which material in the thermal energy store should be refreshed based on the obtained indication of temperature of the thermal energy store. For example, the controller may be configured to predict a time at which a threshold amount (e.g. all) of the material within the energy store will have changed phase, e.g. when a threshold amount of ice within the thermal energy store will have melted, e.g. when all of the ice within the thermal energy store will have melted. The controller may be configured to output a prediction signal indicating the predicted time at which the material in the thermal energy store should be refreshed. The predicted time at which the material in the energy store should be refreshed may comprises a time at which a threshold amount of the material in the thermal energy store has changed phase, e.g. when all of the material has changed phase. The material in the thermal energy store may be water-based. The predicted time at which the material in the energy store should be refreshed may comprise a time at which all of the ice in the thermal energy store has melted (or at least when a threshold amount of the ice has melted). For example, the controller may be configured to: (i) predict a time when a threshold amount of the material in the thermal energy store will have changed phase, and (ii) output one or more signals indicative of the predicted time. The apparatus may be configured to display the predicted time, e.g. on a display of the apparatus. The apparatus may be configured to output one or more alerts once within a threshold amount of time from the predicted time (at which the material in the thermal energy store will have changed phase). The one or more sensors may be configured to obtain an indication of temperature at different heights within the thermal energy store. The controller may be configured to determine a proportion of the material within the thermal energy store which has changed phase based on temperature data associated with different heights within the thermal energy store. The controller may be configured to determine a change of phase has occurred based on a value of the temperature and / or a rate of change of the temperature. For example, the controller may be configured to determine a change of phase has occurred in response to detecting a rate of change of temperature at above a threshold amount. The controller may be configured to control operation of the apparatus based on a rate of change of temperature in the thermal energy store. The controller may be configured to determine a phase change event has occurred in the thermal energy store based on the rate of change of temperature. The controller may be configured to output an alert in response to determining that a threshold amount of the material stored in the thermal energy store has changed phase. The alert may comprise an indication of the time up to the predicted time at which all of the material will have changed phase, e.g. when all ice will have melted. The apparatus may output alert(s) at selected times before the predicted time. The controller may be configured to control operation of the apparatus based on temperature data obtained from each of the sensors (e.g. which are at different heights within the thermal energy store). The controller may be configured to determine an extent of phase changing having occurred for material in the thermal energy store based on a difference in obtained temperature data from the different sensors (e.g. temperature values for the different sensors and / or rate of change values for the temperature values from the different sensors). The controller may be configured to determine an indication of a temperature of body tissue preserved in the container unit based on the obtained temperature data. The biological product may comprise any suitable product to be used in a medical scenario. For example, the biological product may comprise a product which is to be used to facilitate treatment of a patient. Such a product may be in the form of body tissue, e.g. artificial or real. For example, the body tissue may comprise an organ (e.g. a human or animal organ). Additionally, or alternatively, the biological product could comprise another substance for facilitating treatment of a patient, such as replacement blood or other bodily fluids, or a suitable medicine (e.g. a drug, a vaccine or other composition to be applied to the patient to be treated). Embodiments may find particular utility for the preservation of biological products which would benefit from (or require) their temperature to be tightly controlled prior to use. For example, this may reduce the likelihood of the product deteriorating during the period in which it is being preserved (i.e. prior to its subsequent use for treating a patient). The apparatus is configured to preserve the biological product. Preservation of the biological product may comprise retaining the biological product in an environment whose temperature is controlled. For instance, the controller may be configured to manage a temperature of the biological product, thereby to provide preservation of said product. Preservation of the product may comprise retaining the product in selected conditions for the local environment to that product, such as retaining the local temperature to the product within a selected temperature range. The apparatus may be configured to preserve the product whether the apparatus is stationary or moving. For example, the product may be stored in the apparatus and / or transported within the apparatus. In other words, the apparatus may be portable, e.g. to facilitate transport of the apparatus (and said product therein). During either storage or transportation, the apparatus may be configured to provide preservation (e.g. thermal management) of the product. The container unit may be configured to preserve the body tissue in preservation liquid. For example, one or more walls of the container unit may define an internal volume which is filled with preservation liquid. The biological product, e.g. the body tissue, may be preserved in the preservation liquid within the container unit. For example, this may further facilitate preservation of the product. The apparatus may comprise a fluid delivery system configured to circulate fluid to the product preserved in the container unit. The fluid delivery system may be configured to supply a gas to the product, e.g. to supply a gas to the body tissue. The apparatus may be a persufflation apparatus and the fluid delivery system may comprise a persufflation gas supply system configured to supply persufflation gas to the body tissue in the container unit. For example, the apparatus may be configured to deliver persufflation gas to body tissue in the preservation liquid in the container unit. A thermal transfer path may be defined between the thermal energy store and the container unit. The thermal transfer path may couple at least one surface of the container unit to at least one surface of the thermal energy store. A portion of the thermal transfer path may be provided by material of a base unit (which houses the container unit). The base unit may comprise a volume of material arranged to provide a thermal energy conduit (e.g. along which thermal conduction is preferable to its surrounding material). The thermal energy conduit may extend from the thermal energy store towards the container unit (e.g. to a container unit receiving portion of the base unit). The controller may be configured to determine a phase of the material in the thermal energy store, and / or to determine when a phase change event has occurred for the material in the thermal energy store. The controller may be configured to predict when the material in the thermal energy store has all changed phase, e.g. melted. The controller may be configured to output a signal containing the predicted melt time. The thermal energy store may comprise a housing for storing material to thermally couple with (preservation liquid in) the container unit via the thermal transfer path. For example, the thermal energy store may store a material capable of being used to cool the container unit (and the biological product preserved therein). The apparatus may be arranged to facilitate replacement of the material stored in the housing. The housing may be removable. For example, the housing of the thermal energy store may be removed from the apparatus to permit replacement of the material therein. The thermal energy store may comprise a removable drawer, e.g. to enable material therein to be replaced. The material may comprise a phase change material, e.g. the thermal energy store may be configured to receive a phase change material. The phase change material may be selected to have a phase change temperature within a threshold temperature range of an intended temperature for the biological product. In other words, the phase change material may be selected to facilitate latent heat absorption when being used for managing the temperature of the biological product. In other words, the phase change material may be selected so that it will change phase during operation of the apparatus to preserve the product. For example, ice may be used, e.g. with that ice melting during use. The apparatus may comprise a base unit. The base unit may comprise the thermal energy store and a container unit receiving portion arranged to receive the container unit. The base unit may comprise one or more sensors which are used by the controller to control operation of the apparatus. The thermal transfer path may comprise one or more thermal conduits within the base unit which thermally couple the thermal energy store to the container unit receiving portion. For example, the thermal conduit(s) may provide a preferential thermal conduction path (e.g. which is more thermally conductive than their surrounding / neighbouring volumes of material). The container unit may comprise a storage region for holding a liquid in which a biological product is to be preserved. The apparatus may also comprise an agitator configured to agitate liquid disposed in the storage region of the container unit. The agitator may be configured to distribute thermal energy throughout the preservation liquid in the container unit. For example, the agitator may be configured to inhibit thermal stratification occurring within the preservation liquid in the container unit. The agitator may be part of the container unit. The agitator may comprise at least one agitator port configured to deliver a fluid, e.g. a gas, to the storage region of the container unit to agitate the liquid therein. The agitator may be configured to deliver a fluid to the preservation liquid to agitate the preservation liquid, wherein that fluid is a fluid which is to be circulated to body tissue preserved in the container unit. For example, the apparatus may be configured to deliver a gas, such as a persufflation gas, to the body tissue, and the agitator may be configured to deliver gas, e.g. persufflation gas, to the preservation liquid in the container unit for agitation thereof, e.g. at least some of the persufflation gas which would otherwise be delivered to the product (e.g. body tissue) may be diverted into the preservation liquid to provide agitation thereof (e.g. through the agitator port). In other words, the agitator may be configured to deliver (persufflation) gas to the preservation liquid in the storage region. The agitator may be configured to bubble (persufflation) gas up through the preservation liquid in the storage region. The agitator may be coupled to the (persufflation) gas supply system to receive persufflation gas therefrom. The container unit may comprise an agitator conduit coupling an inlet port (for connecting to receive fluid, e.g. persufflation gas, to be circulated to the body tissue) to the agitator port. A passageway may extend between the inlet port and the outlet port (for coupling to the body tissue), and wherein the agitator conduit may be coupled to the passageway, e.g. to receive some of the gas which would otherwise travel through the outlet port towards the body tissue (for using that gas to agitate the preservation liquid). The agitator port may be in a lower portion of the storage region. The agitator port may be in a base of the storage region. The container unit may comprise a passageway which couples the inlet port to the outlet port. Said passageway may be external to the storage region of the container unit. The container unit may comprise a liquid region within the passageway. For example, the container unit may comprise a humidifier (e.g. which contains the liquid region) to humidify gas to be delivered to the body tissue (e.g. before that gas passes out through the outlet port towards the body tissue). The humidifier may be external to the internal volume of the container unit, e.g. on an exterior wall of the container unit. The container unit may be configured to bubble persufflation gas through liquid in the liquid region, e.g. thereby to humidify the persufflation gas, before that persufflation gas is delivered to the body tissue (e.g. for persufflation thereof). The apparatus may comprise an obstruction member within the storage region of the container unit. The obstruction member may be configured to inhibit excess movement of the body tissue within the storage region. The obstruction may provide ballast to reduce a volume of preservation liquid within the storage region. The obstruction member may comprise a plurality of apertures sized to permit movement of liquid therethrough but to inhibit movement of the body tissue therethrough. For example, the apertures may be configured to permit sloshing of liquid therethrough, but to inhibit movement of the body tissue (e.g. by more than a threshold amount). The obstruction member may comprise one or more flanges configured to contact at least one wall of the container unit. The flanges may surround a main portion of the obstruction member, and the main portion may define an internal region in which the body tissue to be preserved is retained. The obstruction member may be configured to retain the body tissue within said internal region. The obstruction member may be resilient. The agitator may be coupled to a surface of the container unit. At least one surface of the container unit receiving portion may be arranged to thermally couple the thermal energy store to a corresponding surface of the container unit. The agitator may be located adjacent to said corresponding surface of the container unit, e.g. the agitator port may be located proximal / adjacent to said surface of the container unit. The base unit may comprise a container unit receiving portion arranged to receive said container unit. At least one surface of the container unit receiving portion may be configured to thermally couple the container unit to a thermal management system for managing a temperature of the preservation liquid in the storage region. The agitator port may be disposed adjacent to said at least one surface of the container unit receiving portion. The agitator may comprise a fluid mover. For example, the agitator port may be located in a lower portion of the storage region in the container unit. The container unit is configured for delivering persufflation gas to the preservation liquid in the internal volume of the container unit, e.g. to bubble the persufflation gas through the preservation liquid. The container unit may be configured to deliver the persufflation gas into a lower region of the preservation liquid and to bubble this up through the preservation liquid. In an aspect, there is provided a base unit for a biological product preservation apparatus, the base unit comprising: a container unit receiving portion arranged to receive a container unit for preserving a biological product; a thermal energy store, wherein the thermal energy store is thermally coupled to the container unit receiving portion for managing a temperature of a said biological product preserved in a said container unit; one or more sensors configured to obtain an indication of a temperature of the thermal energy store; and a controller configured to control operation of the apparatus based on the obtained indication of temperature of the thermal energy store. In an aspect, there is provided a method of preserving a biological product, the method comprising: preserving a biological product in a container unit of a biological product preservation apparatus, wherein the container unit is thermally coupled to a thermal energy store for managing a temperature of the biological product preserved in the container unit; obtaining an indication of a temperature of the thermal energy store; and controlling operation of the apparatus based on the obtained indication of temperature of the thermal energy store. Aspects of the present disclosure may comprise one or more computer program products comprising computer program instructions configured to program a controller to control operation of a biological product preservation apparatus to implement any of the methods disclosed herein. Figures Some examples of the present disclosure will now be described, by way of example only, with reference to the figures, in which: Fig. 1 is a schematic diagram of a biological product preservation apparatus. Fig. 2 is a schematic diagram of a biological product preservation apparatus. Fig. 3 is a schematic diagram of a container unit for a biological product preservation apparatus. In the drawings like reference numerals are used to indicate like elements. Specific Description Embodiments of the present disclosure are directed to apparatuses and methods for preserving a biological product. For this, the product is preserved in a container unit that is thermally coupled to a thermal energy store. The thermal energy store may house material which is used for managing a temperature of the container unit. For example, the thermal energy store may store ice, and this store of ice may be thermally coupled to the container unit to keep the container unit at a relatively cool temperature. One or more sensors are included for measuring a temperature of the thermal energy store, and the apparatus may be controlled based on this thermal energy store temperature data. This sensor data may be used to determine a status of the material in the thermal energy store, e.g. to determine if the material therein needs refreshing. This sensor data may be used to infer one or more properties of the biological product being preserved and / or of other operating conditions of the apparatus itself. By providing the sensor(s) in a location which does not come into contact with the biological product, these sensors may be re-used for preservation of multiple products, as well as retaining the sensors in a sterile form after each use. Embodiments may find particular utility in the field of preservation and storage of body tissue, such as organs. Likewise, embodiments may find particular utility as part of a persufflation system for delivering persufflation gas to the body tissue being preserved. A first example of a biological product preservation apparatus 1 will now be described with reference to Fig. 1. The Biological Product Preservation Apparatus of Fig. 1 The biological product preservation apparatus 1 includes a container unit 100 and a base unit 200. The container unit 100 includes a storage region for preserving the biological product. In the example of Fig. 1, the biological product is body tissue 10, such as an organ. The base unit 200 comprises a thermal energy store 210, a container unit receiving portion 227 and a controller 250. The base unit 200 includes a thermal energy store housing 221, as well as thermal connector 223. A thermal transfer path is defined between the thermal energy store 210 and the container unit receiving portion 227, e.g. from the thermal energy store 210, through the housing 221, the thermal connector 233, and to the container unit receiving portion 227 (or in reverse). Thermal transfer may then occur between the container unit receiving portion 227 and the container unit 100 (e.g. via air gap 230). The base unit 200 also includes a container unit transfer sensor 255. As shown in Fig. 1, the container unit 100 is inserted into the base unit 200 (into the container unit receiving portion 227). There may be an air gap 230 between at least some portions of the container unit 100 and the wall(s) which define the container unit receiving portion 227. Although not shown in Fig. 1, the apparatus 1 may include an energy storage device, such as a battery. Likewise, the apparatus 1 will include a lid which seals the container unit 100 and also the base unit 200, but for simplicity, this is not shown in Fig. 1. The container unit 100 comprises one or more walls which define an internal storage volume for the container unit 100. The body tissue 10 is disposed in the internal storage volume of the container unit 100. The container unit receiving portion 227 of the base unit 200 comprises one or more walls which surround an open volume for receiving the container unit 100. With the container unit 100 received in the container unit receiving portion 227 of the base unit 200 (as shown in Fig. 1), the one or more walls of the container unit 100 will be held in close proximity to the one or more walls of the container unit receiving portion 227. These may be separated by the air gap 230. For example, the walls of the container unit 100 may run parallel to the corresponding walls of the container unit receiving portion 227 (e.g. or at least approximately parallel). The container unit 100 may be a consumable product. For instance, it may be a single-use component. As will be appreciated, for the preservation of biological products, such as body tissue 10, any components which come into contact with that body tissue 10 may need to be discarded after use. The container unit 100 may be arranged to preserve the body tissue 10 in the internal volume so as to permit multiple uses of the base unit 200, e.g. with different subsequent container units. The thermal energy store 210 provides a volume for holding material for storing thermal energy. The thermal energy store 210 may comprise an internal volume for receiving such material. The base unit 200 may have a corresponding recess in which the thermal energy store 210 is received. At least a portion of the thermal energy store 210 may be removable from the base unit 200. For example, the thermal energy store 210 may comprise a drawer which can hold material in its internal volume. The drawer may be removable from the base unit 200 to permit replacement of the material in its internal volume. While numerous different materials could be used within the thermal energy store 210, ice may be particularly beneficial due to its abundance in medical settings, and also due to its melting temperature being close to desired preservation temperatures for many biological products. In use, the thermal energy store 210 may be filled with the material, e.g. filled with ice. At least a portion of the base unit 200 which surrounds the thermal energy store 210 may be provided by housing 221. The housing 221 may comprise one or more walls which define the internal volume into which the thermal energy store 210 is provided. For example, where the thermal energy store 210 is provided by a drawer, the housing 221 may provide at least some of the walls which surround the space into which the thermal energy store 210 may be slid. A thermal transfer path of the base unit 200 is defined which thermally couples the housing 221 to the container unit receiving portion 227 (and thus which couples the thermal energy store 210 to the container unit 100). The thermal transfer path may be provided by a separate material to the rest of the base unit 200. For example, the thermal transfer path may be formed of a material with high thermal conductivity, such as aluminium. The thermal transfer path may provide a preferential flow path for thermal energy to and / or from the container unit receiving portion 227 and the housing 221. For example, the thermal transfer path may be provided by a volume of material which is more thermally conductive than the adjacent / neighbouring material. For this, for example, the portions of the thermal transfer path may be formed from material(s) which is of higher thermal conductivity than the material surrounding those portions. The container unit receiving portion 227 may comprise one or more walls of material which form part of the thermal transfer path. For example, the majority, e.g. all, of the container unit receiving portion 227 may form part of the thermal transfer path. For example, the same material which provides the housing 221 may provide the wall(s) of the container unit receiving portion 227. In other words, with the container unit 100 received in the container unit receiving portion 227, the container unit 100 may be at least partially surrounded by material which provides the thermal transfer path, e.g. substantially completely surrounded. The thermal connector 223 may be connected to both the housing 221 and the container unit receiving portion 227. For example, a continuous piece of material may extend from the housing 221 to the container unit receiving portion 227, and that piece of material may provide the thermal connector 223. The thermal transfer path may be formed of more thermally conductive material than the portions of the base unit 200 which are adjacent to this thermal transfer path. At least one sensor may be provided in the thermal energy store 210. In Fig. 1, this is shown as the first sensor 251. The first sensor 251 may be coupled to one of the walls of the housing 221. For example, the first sensor 251 may be located on an inside wall of the thermal energy store 210 (e.g. on an inside wall of the housing 221). The first sensor 251 may be located proximal to, e.g. adjacent and / or in contact with, material in the thermal energy store 210. The first sensor 251 is coupled to the controller 250. This coupling is shown by the dashed lines in Fig. 1. The base unit 200 is configured to receive the container unit 100 in the container unit receiving portion 227 and to hold the container unit 100 within thermal transfer range of the container unit receiving portion 227, e.g. in close proximity to each other. Likewise, the base unit 200 is configured to receive the thermal energy store 210 within the housing 221 and to hold the thermal energy store 210 within thermal transfer range of the housing 221, e.g. in close proximity to each other and / or even in contact with each other. The container unit receiving portion 227 is configured to thermally couple to the container unit 100. That is, the container unit 100 and container unit receiving portion 227 are configured to exchange thermal energy therebetween. For example, in the event that the container unit 100 is hotter than the container unit receiving portion 227, the container unit 100 may radiate heat to the container unit receiving portion 227, and vice-versa. In other words, the container unit receiving portion 227 is arranged to thermally couple with the container unit 100 for adjusting a temperature thereof (and thus for managing a temperature of the body tissue 10 preserved in the container unit 100). Likewise, the housing 221 is configured to thermally couple to the thermally energy store. That is, the thermal energy store 210 and the housing 221 are configured to exchange thermal energy therebetween. For example, in the event that the thermal energy store 210 is hotter than the housing 221, the thermal energy store 210 may conduct and / or radiate heat to the housing 221, and vice-versa. In other words, the thermal energy store 210 is arranged to thermally couple with the housing 221 for adjusting a temperature thereof. As such, a thermal transfer path may be defined between the material in the thermal energy store 210 (e.g. the ice) and the biological product in the container unit 100 (e.g. the body tissue 10). The material in the thermal energy store 210 may be used for heating or cooling the container unit 100 (e.g. for two-way transfer). That is, thermal energy may be transferred along the thermal transfer path from the container unit 100 to the thermal energy store 210 or along the thermal transfer path from the thermal energy store 210 to the container unit 100. That is, thermal energy may be permitted to flow along the thermal transfer path (e.g. between the biological product in the container unit 100 and the material in the thermal energy store 210). The apparatus 1 is configured to permit two-way flow of thermal energy along this thermal transfer path. In the example of Fig. 1, control of the flow of the thermal energy may be entirely passive. As such, in the event that the container unit 100 is at a greater temperature than the material in the thermal energy store 210, heat may flow along the thermal transfer path towards the thermal energy store 210 (and vice-versa). In other words, the apparatus 1 is configured to provide closed loop thermal transfer between the thermal energy store 210 and the container unit 100. As will now be described in more detail, the apparatus 1 may be controlled by the controller 250 based on the data obtained from the first sensor 251. Control of the apparatus based on sensor data As described above, the apparatus 1 is configured to facilitate transfer of thermal energy between the thermal energy store 210 and the biological product in the container unit 100. Heat will flow along the thermal transfer path from the hotter region (one of the container unit 100 or the thermal energy store 210) to the cooler region (the other of the container unit 100 or the thermal energy store 210). The controller 250 is configured to monitor the status of the thermal energy store 210 to ensure that the apparatus will permit this desired transfer of thermal energy. This transfer of thermal energy will influence a temperature of the biological product preserved in the container unit 100. In the following example, the scenario for this is that the body tissue 10 in the container unit 100 is to be kept at a relatively cool temperature (e.g. somewhere between 4 and 12 degrees Celsius), and the thermal energy store 210 initially stores a material which is colder than this temperature. In this case, thermal energy will predominantly be transferred from the container unit 100 along the thermal transfer path to the thermal energy store 210 (e.g. to the material therein). In other words, the container unit 100 will be at an elevated temperature which acts to heat the thermal energy store 210. The material for the thermal energy store will be chosen to have a phase change temperature at a value close to that of the intended temperature for the container unit. Where this material is to be at a lower temperature than the container unit, the phase change temperature should be below the intended temperature for the container unit. Heat transferred from the container unit 100 to the thermal energy store 210 may then be absorbed by the material in the thermal energy store 210 as latent heat (for changing the phase of that material), as well as for heating the mixture of material (before / afterthat phase change event has occurred). In this example, the material will be ice (e.g. with a melting temperature of approximately zero degrees Celsius). The use of ice in such scenarios may be beneficial as the melting temperature of ice may be relatively close to the desired temperature range for the container unit 100, and so at least initially, a large amount of energy may be absorbed without a significant increase in temperature due to the latent heat transition from ice to water. Ice is also typically abundant in medical settings. The present inventors have identified that improved preservation of biological products in the container unit, e.g. improved preservation of body tissue, may be obtained through monitoring the contents of the thermal energy store 210, and in particular by monitoring the thermal storage capacity of the thermal energy store 210 (of the material in the thermal energy store 210). For this, the controller 250 may be configured to determine a phase of the material in the thermal energy store 210. This may comprise determining a proportion of the material which is in that phase. The controller 250 may also be configured to predict an estimated time at which all of the material in the thermal energy store 210 will have changed phase. In the example of Fig. 1, one sensor (the first sensor 251) is provided in the thermal energy store 210. The first sensor 251 is part of the base unit 200. The first sensor 251 is coupled to the thermal energy store 210 in the base unit 200, such as being in, or attached to, a wall of the housing 221. This may be of particular utility where the container unit 100 is a consumable product. As such, the relevant sensor electronics may be capable of operating repeatedly with subsequent consumables. This may also simplify the design of the container unit 100. The first sensor 251 may comprise a temperature sensor. The first sensor 251 is configured to obtain an indication of a temperature of the thermal energy store 210. The first sensor 251 is located at a certain height within the thermal energy store 210. That is, the first sensor 251 may be located at a height somewhere between a bottom and a top of the thermal energy store 210. The first sensor 251 is configured to obtain an indication of a temperature at its height within the thermal energy store 210, e.g. to obtain an indication of a temperature of the material within the thermal energy store 210 at that height. In other words, the apparatus 1 is configured to obtain an indication of the temperature of the material in the thermal energy store 210 at a selected height within the thermal energy store 210 (e.g. using the first sensor 251). In the example of Fig. 1, only one sensor is shown (at one height), but in other examples such as Fig. 2 as will be described below, a plurality of sensors may be included, and these sensors may be at different heights within the thermal energy store 210. The controller 250 may be configured to determine a thermal energy storage capacity of the thermal energy store 210 based on the data obtained from the thermal energy store 210. In particular, the controller 250 may be configured to determine a phase of the material in the thermal energy store 210, and / or a proportion of the material within the thermal energy store 210 in each phase. For the case of initially storing ice in the thermal energy store 210, the controller 250 may be configured to obtain an indication of an amount of melted ice within the thermal energy store 210. For temperature data obtained from the first sensor 251 within the thermal energy store 210, the controller 250 may be configured to determine whether or not the material adjacent to that sensor remains ice or if it has melted (to become water). Based on the timing for when this melting occurs and the height of the first sensor 251 within the thermal energy store 210, the controller 250 may be configured to predict when all of the ice in the thermal energy store 210 will have melted. For this, the controller 250 is configured to determine whether or not ice has melted based upon a value of the temperature and / or a rate of change in temperature values. For instance, at temperatures substantially below zero degrees Celsius, it may be determined that the ice has not melted, and at temperatures substantially above zero degrees Celsius, it may be determined that the ice has melted. For temperatures at or close to zero degrees Celsius, the controller 250 may be configured to determine whether the ice has melted based at least in part on a rate of change of temperature values. In particular, the controller 250 may be configured to determine that the ice has melted in response to detecting an increase in the rate of temperature change (versus time). In other words, in the event that the temperature begins to increase and / or to increase at an elevated rate (from a value at approximately zero degrees Celsius), the controller 250 may infer that melting has occurred. The controller 250 may be configured to monitor the temperature value from the first sensor 251, which is at a selected height within the thermal energy store 210, and to determine how high within the thermal energy store 210 the melted ice has reached based on data obtained from the first sensor 251 as well as an amount of elapsed time. In an initial state, the thermal energy store 210 may be filled with ice. As this ice begins to melt, water will accumulate at the bottom, and the remaining ice will begin to float upon that water. As such, water will fill up at the bottom pushing the ice upwards. Typically, the last ice to melt will be at the top of the thermal energy store 210, as it will have been continually pushed higher up due to rising water levels within the thermal energy store 210. The controller 250 is configured to monitor the obtained temperature data from the first sensor 251. The controller 250 may be configured to determine that ice at the height of the first sensor 251 within the thermal energy store 210 has melted in response to a change in the rate of increase of temperature within the thermal energy store 210 exceeding a threshold amount. The controller 250 may monitor an amount of time elapsed (e.g. since the ice was initially provided in the thermal energy store 210). The controller 250 may be configured to determine a proportion of the ice which has melted within the thermal energy store 210 based on the height at which the first sensor 251 is located (i.e. the height at which the meltwater has reached within the thermal energy store 210). For example, the controller 250 may be configured to determine a percentage amount of ice remaining, e.g. based on stored data indicative of the expected final height for the meltwater within the thermal energy store 210 and the height of the first sensor 251. In response to determining that the ice next to the first sensor 251 has melted, the controller 250 may also obtain an indication of an amount of time elapsed for this melting to have occurred. The controller 250 may be configured to predict when all the ice will have melted based on the rate of progression of ice melt within the thermal energy store 210. For example, the controller 250 may be configured to determine a proportion of the amount of melted ice within the thermal energy store 210. Based on this proportion and the amount of time taken since the ice was initially put within the thermal energy store 210, the controller 250 may be configured to predict when all of the ice will melt. The controller 250 may be configured to control operation of the apparatus 1 based on the predicted melt time for the ice. The apparatus 1 may comprise a display screen or GUI. The controller 250 may be configured to display an indication of the predicted melt time on the display screen / GUI. For example, this may enable an operator of the apparatus 1 to have an idea of when they should replace the ice within the thermal energy store 210. The apparatus 1 may also be configured to output one or more alerts associated with the melt time. For example, the apparatus 1 may be configured to output an alert which is still a relatively long period of time away from the predicted melt time. This may be an hour or more before the predicted melting event occurs. The apparatus 1 may be configured to output an alert at a closer time to the predicted melt time and / or to output an alert in response to determining that all ice has melted within the thermal energy store 210. The alert(s) may comprise an indication that the ice within the thermal energy store 210 is to be refreshed. By monitoring the contents of the thermal energy store 210, the controller 250 may inform an operator of the apparatus 1 as to when they should be replacing the ice within the thermal energy store 210. In so doing, the material in the thermal energy store 210 (e.g. ice) may be refreshed at suitable intervals, so that this material may provide the desired temperature managing effect for the container unit 100 (and the biological product therein). Operation of the Apparatus In operation, the thermal energy store 210 is filled with material (in this example ice) and the container unit 100 containing the biological product is inserted into the container unit receiving portion 227 of the base unit 200. As such, the biological product in the container unit 100 is thermally coupled to the ice in the thermal energy store 210 (via the previously described thermal transfer path). In this example, the thermal energy store 210 contains material at a lower temperature than the container unit 100, and so the thermal coupling therebetween acts to heat up the thermal energy store 210 (and cool the container unit 100). The controller 250 monitors the temperature data from the first sensor 251, as well as the amount of time elapsed since the thermal energy store 210 was filled with ice. The controller 250 determines that the material adjacent the first sensor 251 has melted in response to a rate of temperature increase for the temperature data from the first sensor 251 exceeding a threshold value. At which point, the controller 250 also predicts a time at which all of the ice will have melted based on the amount of time elapsed and the relative height of the first sensor 251 within the thermal energy store 210. This predicted complete melt time may be displayed on a display of the apparatus 1 and / or one or more alerts may be output which indicate this predicted melt time. A user of the apparatus 1 may then refresh the material within the thermal energy store 210 at a suitable time. That is, they may discard the water (and any remaining ice) in there, and replace it with new ice, and the monitoring process will start again. This approach may help to ensure that the material in the thermal energy store 210 has a suitable thermal capacity for managing a temperature of the container unit 100. Another example of a biological product preservation apparatus 1 will now be described with reference to Fig. 2. Biological product preservation apparatus of Fig. 2 The apparatus 1 of Fig. 2 is similar to that of Fig. 1, and so repeat components shall not be described again here. As with the apparatus 1 of Fig. 1, for the apparatus 1 of Fig. 2, a thermal transfer path is defined between the thermal energy store 210 and the container unit 100. The apparatus 1 of Fig. 2 also includes additional features and functionality to facilitate improved preservation of biological products. For instance, the apparatus 1 of Fig. 2 is configured for preserving body tissue 10 and for circulating fluid through that body tissue 10 for improved preservation of the body tissue 10. In particular, the apparatus 1 may be configured to provide persufflation of body tissue 10 preserved in the container unit 100. That body tissue 10 may also be preserved within a pool of preservation liquid 110. For this, and as shown in Fig. 2, the apparatus 1 may include a persufflation gas store 240, a gas delivery, an inlet connection 141, tubing 142, an outlet connection 143, a gas receiving line 243 and a gas outlet 244. The container unit 100 may also hold preservation liguid 110. The apparatus 1 of Fig. 2 also includes one or more additional sensors to those shown in Fig. 1. As shown, these may include the first sensor 251, second sensor 252, third sensor 253 ambient sensor 256, a container unit receiving portion sensor 257 and / or an air gap sensor 259. These additional sensors / components may enable further control of the apparatus to that described in relation to Fig. 1. Each of these different aspects of the apparatus 1 of Fig. 2 will now be described in turn in more detail. Preservation of body tissue As already mentioned, the apparatus 1 may be configured to preserve a biological product in the form of body tissue 10, such as a replacement organ. For this, it may be beneficial to preserve the body tissue 10 in a preservation liquid 110. One or more walls of the container unit 100 define an internal volume arranged to receive preservation liquid 110 in which the body tissue 10 is to be preserved. As shown in Fig. 2, the body tissue 10 may be at least partially submerged within the preservation liquid 110 in the container unit 100. The body tissue 10 may float in the preservation liquid 110 in the container unit 100. As with the apparatus 1 of Fig. 1, one or more external surfaces of the container unit 100 are configured to couple thermally with the material of the container unit receiving portion 227. This forms part of a thermal coupling between the container unit 100 and the thermal energy store 210. In addition to the radiative thermal transfer between the container unit receiving portion 227 and the wall(s) of the container unit 100, thermal energy will be thermally transferred (e.g. conductively) between the wall(s) of the container unit 100 and the preservation liquid 110 stored in the internal volume of the container unit 100. In turn, thermal energy may be transferred (e.g. conductively) between the preservation liquid 110 and the body tissue 10 preserved therein. In so doing, the apparatus 1 is configured to influence a temperature at which the body tissue 10 is preserved based on a temperature of the material in the thermal energy store 210 (e.g. to influence a temperature of the preservation liquid 110 in the container unit 100). In other words, the apparatus 1 may be configured to passively manage a temperature of the preservation liquid 110 in the container unit 100. In particular, the apparatus 1 may be configured to permit thermal transfer between the thermal energy store 210 and the preservation liquid 110 in the container unit 100. Additionally, or alternatively, for the preservation of body tissue 10 within the container unit 100, the apparatus 1 may be configured to circulate fluid to that body tissue 10, e.g. to the native vasculature of the body tissue 10. While this may comprise circulation of a liquid perfusate through the body tissue 10, in the example of Fig. 2, the apparatus 1 is a body tissue 10 persufflation apparatus configured to supply gaseous oxygen perfusate to the body tissue 10. For this, the apparatus 1 comprises the persufflation gas store 240. This may comprise a gas cannister which stores persufflation gas (and / or it may comprise means for onboard generation of persufflation gas). One or more fluid conduits are provided for connecting the gas store 240 to the body tissue 10. The gas delivery line 241 is connected to the gas store 240. The base unit 200 houses the gas store 240 and the gas delivery line 241. The gas delivery line 241 (of the base station) may couple to one or more conduits for connection to the body tissue 10. As mentioned above, the container unit 100 and any conduits of the container unit 100 may themselves be single-use (e.g. consumable) products. The base unit 200 may be multi-use. The apparatus 1 may comprise a plurality of couplings for connecting gas flow line(s) of the base unit 200 to the components in the container unit 100. As shown in Fig. 2, the inlet connection 141 couples the gas delivery line 241 to the tubing 142. The tubing 142 may comprise one or more different fluid conduits for coupling the gas delivery line 241 to the body tissue 10, e.g. to different portions of the native vasculature of the body tissue 10 (e.g. to different veins and / or arteries). In Fig. 2, the tubing 142 is shown by two dashed lines, but this is just to show the flow path through the body tissue 10. It is to be appreciated however that one or more pieces of tubing 142 may be coupled to the body tissue 10 to deliver input gas and one or more pieces of tubing 142 may be coupled to the body tissue 10 to receive gas which has passed through the body tissue 10 from the input tubing. The output tubing portion(s) may couple to the base unit 200 for delivering gas thereto. As shown in Fig. 2, the outlet connection 143 couples the tubing 142 to the gas receiving line 243 of the base unit 200. In other words, a gas flow path is defined through the apparatus 1 for delivering persufflation gas to the body tissue 10. The apparatus 1 may deliver persufflation gas from the gas store 240 (in the base unit 200) to the body tissue 10 (in the container unit 100) via this flow path. The apparatus 1 may also define a flow path for receiving this gas which has been delivered to the body tissue 10, and for returning this gas to the base unit 200. The base unit 200 may comprise a storage component (e.g. gas canister) for receiving the discarded gas, and / or the apparatus 1 may comprise an outlet for venting gas. In Fig. 2, the gas outlet 244 is shown. The gas outlet 244 is configured to vent persufflation gas which has passed through the body tissue 10 (e.g. which has been received from the tubing 142 via the gas receiving line 243). As will be described in more detail below, the apparatus may also include one or more other gas flow paths for delivering gas through the apparatus. The apparatus may include a gas flow path arranged to deliver gas into preservation liquid in the container unit. For example, this gas flow path may be coupled to the container unit, e.g. to a lower region thereof (such as in a floor of the container unit), to deliver gas to that region of the container unit. This may cause that gas to bubble up through the preservation liquid therein. This gas flow path may be for persufflation gas (e.g. the same gas to be delivered to the body tissue), or it may be for another gas (e.g. a gas suitable for contacting the body tissue). Such an additional gas flow path may facilitate agitation of the preservation liquid in the container unit (e.g. to inhibit thermal stratification occurring therein). This gas flow path may be different, e.g. independent, to the gas flow path mentioned above for delivering gas to the body tissue, or the two may be connected (e.g. they may be two different branches for gas to flow from the same gas source). As will be described in more detail below in relation to Fig. 3, the container unit may be arranged to direct some of the gas that would be delivered from the gas flow path to the body tissue to a separate conduit for delivery into the bottom of the container unit. As such, apparatuses of the present disclosure may be configured to preserve body tissue 10 in a preservation liquid 110 within the container unit 100, and / or to circulate persufflation gas to this body tissue 10 preserved in the container unit 100. Additional sensor data for controlling operation of the apparatus As described above in relation to Fig. 1, the apparatus may include at least one sensor in the thermal energy store 210. For Fig. 1, this was the first sensor 251, but for Fig. 2, there are three sensors in the thermal energy store: first sensor 251, second sensor 252 and third sensor 253. The apparatus 1 may also include an ambient sensor 256. The ambient sensor 256 may be coupled to an external region of the apparatus 1 or it may be located proximal to an external region of the apparatus 1. The one or more sensors within the thermal energy store 210 (first to third sensors 251,252, 253) may each comprise a temperature sensor. Each sensor may be located at a different height within the thermal energy store 210. As shown in Fig. 2, the first sensor 251 is the lowest sensor, the third sensor 253 is the highest sensor, and the second sensor 252 is located between the first sensor 251 and the third sensor 253. The sensors may be distributed across a substantial portion of the overall height of the thermal energy store 210, e.g. with the first sensor 251 located towards the bottom of the thermal energy store 210 and the first sensor 251 located towards the top of the thermal energy store 210. Each sensor may be located in or adjacent to a wall of the thermal energy store 210 which houses material, such as ice. For example, with the thermal energy store 210 full of material, the sensors may be at least partially in contact with that material, or located adjacent to that material (e.g. coupled to it via another component). The functionality and operation of each of these sensors may be the same as that already described in relation to Fig. 1. By having a plurality of sensors (which are at different heights) in the thermal energy store 210, the controller 250 may be configured to obtain an indication of temperatures at different heights within the thermal energy store 210. The first sensor 251 may provide an indication of a temperature in a lower region of the thermal energy store 210, with the second and third sensors 252, 253 providing indications of temperatures in higher regions of the thermal energy store 210. In other words, the apparatus 1 is configured to obtain an indication of the temperature of the material in the thermal energy store 210 at different heights within the thermal energy store 210. As with the example of Fig. 1, the controller 250 may be configured to determine when the material (e.g. ice) adjacent to each sensor 251,252, 253 changes phase (e.g. melts). That is, based on a value for the temperature from said sensor and / or a rate of change of temperature from that sensor, the controller 250 may determine that melting has occurred. The controller 250 may be configured to monitor temperature values from sensors at different heights within the thermal energy store 210 to determine how high within the thermal energy store 210 the melted ice has reached. By having numerous sensors in the thermal energy store 210 at different heights, the controller 250 may be configured to track the progress of the ice melt through the thermal energy store 210, e.g. to identify the rising water levels within the thermal energy store 210 (and thus further ice being melted). The controller 250 may be configured to determine a proportion of the ice which has melted within the thermal energy store 210 based on the height that the meltwater has reached within the thermal energy store 210. For example, the controller 250 may be configured to determine a percentage amount of ice remaining, e.g. based on stored data indicative of the expected final height for the meltwater within the thermal energy store 210. The controller 250 may be configured to predict when all the ice will have melted based on the rate of progression of ice melt within the thermal energy store 210. For example, the controller 250 may be configured to determine a proportion of the amount of melted ice within the thermal energy store 210. Based on this proportion and the amount of time taken since the ice was initially put within the thermal energy store 210, the controller 250 may be configured to predict when all of the ice will melt. As with the apparatus 1 of Fig. 1, the controller 250 may output an alert containing a predicted melt completion time and / or display this on a display of the apparatus 1 to enable a user of the apparatus 1 to refresh the material accordingly. The controller 250 may be configured to predict the melt completion time based also on other input data. For example, the controller 250 may be configured to obtain an indication of an ambient temperature, e.g. for the environment in which the apparatus 1 is located (e.g. from the ambient sensor 256). The controller 250 may be configured to factor ambient temperature into its melt time predictions (e.g. with increased ambient temperature increasing the expected melt rate, and vice-versa). As will be appreciated, the present disclosure may also apply to use of other materials to ice, e.g. other phase change materials. The monitoring of the contents of the thermal energy store 210 may still be applicable when other materials are stored in the thermal energy store 210. Again, the controller 250 may be configured to determine a thermal energy storage capacity for the thermal energy store 210 based on detecting that a phase change event has occurred for the material within the thermal energy store 210. Container unit of Fig. 3 An example container unit 100 will now be described with reference to Fig. 3. The container unit 100 of Fig. 3 may be used as part of the apparatus 1 of Figs. 1 and 2. Fig. 3 shows a container unit 100. As with the example of Fig. 2, the container unit 100 of Fig. 3 may be arranged to receive a preservation liquid 110, and to preserve a biological product such as body tissue 10 within that preservation liquid 110. The container unit 100 may also include an agitator. In the example of Fig. 3, the agitator includes agitator port 150 and an agitator conduit 155. As with Fig. 2, the container unit 100 includes one or more components for delivering fluid (e.g. persufflation gas) to the body tissue 10. For this, the container unit 100 includes an inlet connection 141, an inlet tubing connector 144, tubing 142, an outlet tubing connector 145 and an outlet connection 143. The container unit 100 may also include a humidifier 160. The humidifier 160 may include a humidifier inlet 162 and a humidifier outlet 164. An agitator connection 146 is also included. The container unit 100 may also include an obstruction member 120. The instruction member may comprise one or more flanges 122. Agitation of preservation liquid One or more walls of the container unit 100 define an internal volume in which preservation liquid 110 is to be stored. The body tissue 10 is preserved in preservation liquid 110 in the internal volume of the container unit 100. As described above in relation to Fig. 2, the apparatus 1 may be configured to influence a temperature of the preservation liquid 110 in the container unit 100 through thermal coupling of that container unit 100 to the thermal energy store 210 (e.g. via the container unit receiving portion 227 and along the thermal transfer path). For this, one or more outer surfaces of the container unit 100 may be located in proximity of the container unit receiving portion 227 of the base unit 200, and heat may be transferred therebetween radiatively. The present inventors have identified that the biological product preserved in the preservation liquid 110 may experience beneficial preservation by providing agitation of the preservation liquid 110 in the container unit 100. This approach may inhibit thermal stratification occurring within the preservation liquid 110 in the container unit 100, and so the biological product may experience a more uniform surrounding temperature. In turn, this may facilitate better temperature management of the body tissue 10, as the temperature in closest proximity to the thermal transfer path in the base unit 200 (i.e. the liquid adjacent to the walls of the container unit 100) will be at a temperature which is more representative of the temperature felt by the biological product. For the container unit 100 of Fig. 3, agitation of the preservation liquid 110 may be provided through delivery of a gas to the preservation liquid 110. In particular, a gas may be bubbled through the preservation liquid 110 from a lower portion thereof. This gas bubbling may act to distribute heat more uniformly within the preservation liquid 110. For this, the container unit 100 comprises the agitator port 150 and the agitator conduit 155. The agitator port 150 comprises an inlet to the internal volume of the container unit 100. The agitator port 150 may be located in a floor (bottom wall) of the container unit 100. For example, the agitator port 150 may provide an opening into a lower region of the internal volume of the container unit 100. The agitator port 150 is coupled to a supply of gas by the agitator conduit 155. The agitator conduit 155 comprises a channel through which gas may flow to the agitator port 150. The agitator conduit 155 may be located on an external surface of the container unit 100 (e.g. opposite to the internal volume), as shown in Fig. 3. Alternatively, the agitator conduit 155 may be located inside the internal volume of the container unit 100. For example, the agitator conduit 155 may extend from the inlet tubing connector 144 towards a lower region of the internal volume. The agitator conduit 155 and port 150 are arranged to deliver gas to a lower region of the internal volume of the container unit 100. That is, the two are configured to supply a gas into the preservation liquid 110 in the container unit 100. The supplied gas delivered to the lower region of the preservation liquid 110 will bubble up through the preservation liquid 110, thereby inhibiting thermal stratification of that preservation liquid 110. The container unit 100 may be for a body tissue persufflation apparatus. In which case, the apparatus 1 (and thus container unit 100) are configured to circulate gaseous oxygen perfusate to the body tissue 10 in the container unit 100. The agitator conduit 155 may couple the agitator port 150 to the supply of gaseous oxygen perfusate for the persufflation apparatus. For example, one or more conduits of the container unit 100 may be coupled to the gas store 240 (via the gas supply line) in the base unit 200. The agitator conduit 155 may be coupled to one of these said conduits for coupling to the supply of gas. In Fig. 3, this is shown via agitator connection 146. The agitator connection 146 is located downstream of the inlet connection 141 of the container unit 100 (which is for connecting to the base unit 200 to receive persufflation gas therefrom). In other words, the container unit 100 provides a gas channel (from the agitator connection 146, through the agitator conduit 155, and into the agitator port 150) arranged to provide persufflation gas to preservation liquid 110 in the container unit 100. This arrangement may enable at least some persufflation gas to be delivered to the preservation liquid 110 to distribute heat therein. This gas channel may be small relative to the other channels for carrying persufflation gas, thereby to limit the amount of gas which flows in through the agitator port 150, as the thermal stratification inhibition may occur with a relatively small amount of gas provided. Additionally, or alternatively, the agitator connection 146 may comprise a valve for limiting the amount of persufflation gas which is delivered through the agitator port 150. Persufflation gas delivery As with the container unit 100 of Fig. 2, the container unit 100 of Fig. 3 is configured to circulate gaseous oxygen perfusate to the body tissue 10 preserved in the container unit 100. For this, the container unit 100 is configured to couple to a source of persufflation gas in the base unit 200, thereby to receive persufflation gas. The container unit 100 may also be configured to couple to the base unit 200 to provide discarded persufflation gas thereto. The inlet connection 141 of the container unit 100 is configured to couple to a source of persufflation gas in the base unit 200. For instance, the inlet connection 141 may be configured to couple to the gas supply line shown in Fig. 2. The inlet connection 141 is located external to the internal volume of the container unit 100. The humidifier 160 is coupled to the inlet connection 141. The humidifier 160 is located on an external wall of the container unit 100. Providing the humidifier 160 on the external wall may simplify manufacturing of the container unit 100, e.g. by enabling simpler moulding to be performed. The humidifier 160 comprises the humidifier inlet 162 and the humidifier outlet 164. The humidifier inlet 162 is coupled to the inlet connection 141. For example, a conduit may extend from the inlet connection 141 through to the humidifier inlet 162. The agitator connection 146 may be provided in said conduit. The humidifier 160 may be at least partially filled with a liquid, such as the preservation liquid 110 of the internal volume of the container unit 100 (the two volumes of preservation liquid 110 may be separate or connected in some way). The humidifier inlet 162 may be located in a lower region of the humidifier 160. The humidifier outlet 164 may be located in a higher region of the humidifier 160. A conduit may extend from the humidifier outlet 164 into the internal volume of the container unit 100. As shown in Fig. 3, a conduit which is coupled to the humidifier outlet 164 may be coupled to the inlet tubing connector 144. At which point, the conduit is coupled to tubing 142 which is to be connected to the body tissue 10, e.g. to the native vasculature thereof. Similarly, tubing 142 may extend from the body tissue 10, e.g. from the native vasculature thereof, to the outlet tubing connector 145, where that tubing 142 is connected to a separate conduit. That separate conduit may extend through to the outlet connection 143. The outlet connection 143 may be coupled to a component of the base unit 200 for discarding gas, e.g. to the gas receiving line 243 shown in the base unit 200 of Fig. 2. The inlet connection 141 is configured to receive gaseous oxygen perfusate from the base unit 200 (e.g. from the gas store 240). The container unit 100 is configured to provide humidification of this gas prior to delivery to the body tissue 10 in the container unit 100. For this, the gas is delivered from the inlet connection 141 into the preservation liquid in the humidifier 160 (via the humidifier inlet 162). The humidifier 160 is arranged for received persufflation gas to be bubbled through the preservation liquid. For example, the humidifier inlet 162 may be located in a lower portion of the humidifier 160. The humidifier outlet 164 is configured to receive humidified persufflation gas which has been bubbled through the preservation liquid in the humidifier 160. For example, the humidifier outlet 164 may be located in an upper portion of the humidifier 160. The container unit 100 is arranged to deliver humidified persufflation gas from the gas humidifier 160 to the body tissue 10 preserved in the container unit 100. For this, one or more tubes may be configured to couple the humidifier outlet 164 to the body tissue 10, e.g. to the native vasculature of the body tissue 10. The inlet tubing connector 144 may be included to couple a conduit extending from the humidifier outlet 164 to tubing 142 which is to be coupled to the body tissue 10 (e.g. at least partially inserted into the native vasculature thereof). For example, this may be included where a different type of tubing 142 is used for contacting the body tissue 10. Similarly, tubing 142 may be provided which couples the body tissue 10 to the outlet connection 143 (e.g. via the outlet tubing connector 145). The outlet connection 143 is configured to couple to the base unit 200 (e.g. to the gas receiving line 243 in the base unit 200 shown in Fig. 2) for discarding gas thereto. In other words, the container unit 100 is arranged to provide two different gas flow paths. For both gas flow paths, gas is received from the base unit 200 through the inlet connection 141, and this may ultimately be returned to the base unit 200 via the outlet connection 143. For the first gas flow path, the gas is humidified in the humidifier 160 on the outside of the container unit 100 before being delivered to the body tissue 10. For the second gas flow path, the gas may be directed through the agitator conduit 155 and into the preservation liquid 110 through the agitator port 150. At least one conduit may be coupled to the outlet connection 143 which is for receiving gas in the container unit 100 (e.g. agitator gas) which has not travelled through the body tissue 10, e.g. to retain pressure levels within the internal volume of the container unit 100. Obstruction member The obstruction member 120 is included in the internal volume of the container unit 100. The obstruction member 120 may be a separate component to the container unit 100, e.g. it may be a component which is insertable into the internal volume of the container unit 100. The obstruction member 120 comprises one or more flanges 122. The flange(s) 122 extend radially around a perimeter of the obstruction member 120. The flange(s) 122 may be located at a lower region of the obstruction member 120. The obstruction member 120 comprises one or more walls which extend upwards from the flange(s) 122. The walls may extend towards a ceiling of the obstruction member 120 (at an upper region of the member). The wall(s) include one or more apertures. The obstruction member 120 is sized to fit within the internal volume of the container unit 100 and to surround the body tissue 10. The flange(s) 122 are arranged to contact the internal wall(s) of the container unit 100. The flange(s) 122 may be arranged to abut the internal wall(s) of the container unit 100 to hold the obstruction member 120 in a fixed position within the internal volume of the container unit 100. The apertures in the obstruction member 120 are configured to permit movement of liquid therethrough. In particular, the obstruction member 120 is arranged to permit movement of preservation liquid 110 through the apertures, e.g. as it sloshes about within the internal volume of the container unit 100. The obstruction member 120 is configured to surround the body tissue 10 within the internal volume of the container unit 100. The obstruction member 120 is configured to permit movement of preservation liquid 110 through the apertures, but to inhibit movement of the body tissue 10 therethrough. In other words, the obstruction member 120 is arranged to provide a constraining volume to limit the amount by which body tissue 10 may move within the container unit 100. The obstruction member 120 may be flexible and resilient. For example, the obstruction member 120 may be arranged to be securely inserted into the internal volume of the container unit 100 and to define an internal volume therewithin for limiting lateral movement of the body tissue 10 within the container unit 100. Advantageously, this arrangement may enable provide additional protection for the body tissue 10 within the container unit 100. In particular, any lateral movement of the body tissue 10, e.g. due to motion of the apparatus 1 as a whole (e.g. in transit), may be limited within the container unit 100. In turn, this may reduce the likelihood of impact-induced damage to the body tissue 10, as well as the likelihood of the movement of the body tissue 10 dislodging any tubing 142 coupled to the body tissue 10. Alternatives and variations It will be appreciated that the examples described above should not be considered limiting. Instead, the examples are just intended to demonstrate aspects of the technology. In the examples described above for Figs. 1 and 2, the thermal coupling between the thermal energy store 210 and the container unit 100 may be passive, e.g. with no components which actively control this flow of thermal energy. However, the apparatus may include one or more active components for managing this flow of thermal energy. For example, the apparatus may comprise a thermoelectric modulation device, such as a Peltier device. The thermoelectric modulation device may be configured to selectively direct thermal energy in either direction between the thermal energy store 210 and the container unit 100 (along the thermal transfer path). For example, the controller may be configured to control operation of the thermoelectric modulation device based on data obtained from one or more temperature sensors of the apparatus, e.g. to retain a temperature of the container unit 100 within a selected temperature range. Similarly, in the examples described herein, the controller 250 may be configured to determine, based on sensor data from the thermal energy store 210, additional or alternative properties to inferring a phase change event has occurred. For example, the controller 250 may be configured to infer one or more thermal properties of the container unit 100 based on the thermal energy store data - e.g. where a quicker melt rate was identified, the controller 250 may determine that the temperature of the container unit 100 was elevated (and vice-versa). Advantageously, this may enable measurements taken from a sterile and / or reusable portion of the apparatus 1 to be used for detecting one or more properties of the biological product and / or its preservation. For example, in the examples described herein, the biological product to be preserved by the biological product preservation apparatuses is in the form of body tissue 10, such as a replacement organ. However, it will be appreciated that other forms of biological product may be preserved in apparatuses of the present disclosure. For example, the biological product could be different body tissue to a replacement organ, e.g. it may comprise artificial tissue. Alternatively, the biological product may comprise any of: drugs, vaccines, blood (or other body fluids). The biological product may comprise any product which may be used in a clinical scenario, e.g. for medical reasons such as facilitating treatment of a patient. As will be appreciated in the context of the present disclosure, preservation apparatuses disclosed herein may beneficially provide tightly controlled thermal management of a product preserved within the container unit 100, and this thermal management may beneficially be employed to any suitable biological product. Likewise, while examples include delivery of persufflation gas to body tissue, this need not be considered limiting. No such fluid circulation may included and / or an alternative circulation such as liquid perfusate may be utilised. As another example, a particular thermal transfer path is shown in the figures for coupling the thermal energy store 210 to the container unit 100. For this, there may be both radiative and conductive thermal transfer, but it is to be appreciated that this need not be the case. For example, there may be no air gap 230 between the container unit receiving portion 227 and the container unit 100. Likewise, it should be appreciated that the particular structural arrangement which couples the thermal energy store 210 to the container unit 100 need not be considered limiting. For example, the container unit 100 could be placed in the thermal energy store 210 itself, e.g. the container unit 100 may be placed in an ice storage vessel to thermally couple the container unit 100 to the thermal energy store 210. Similarly, in examples described herein the material within the thermal energy store 210 has been described as ice. Likewise, the selected temperature range has generally been described as a relatively cool temperature range. However, neither should be considered limiting. Any suitable material may be used within the thermal energy store 210. For instance, the material may be selected to be a material which undergoes a phase change at a temperature relatively close to the selected temperature range for the container unit 100. For example, a phase change material may be utilised. As will be appreciated, any particular phase change may be utilised. Ice may be beneficial due to its relative abundance, but other materials could also be used. Similarly, as described above, the controller 250 may be configured to control operation of the apparatus 1 based on data from one or more sensors of the apparatus 1. It will be appreciated that the particular types of sensor shown and their arrangement should not be considered limiting. For example, the sensors may be temperature sensors, but they could also sense other properties which are indicative of temperature. For example, for the thermal energy store 210, an indication of the proportion of melted ice may be determined using another type of sensor, e.g. an impedance sensor, a capacitance sensor or other sensor which is able to determine a difference between water and ice based on their respective properties (e.g. electrical properties). Likewise, while three sensors are shown in Fig. 2, there may be more or fewer sensors, and their respective locations may be different. For example, as will be appreciated, the controller 250 may be configured to determine an amount of melted water based on data obtained from any particular sensor location within the thermal energy store 210. It will be appreciated from the discussion above that the examples shown in the figures are merely exemplary, and include features which may be generalised, removed or replaced as described herein and as set out in the claims. With reference to the drawings in general, it will be appreciated that schematic functional block diagrams are used to indicate functionality of systems and apparatus described herein. In addition, the processing functionality may also be provided by devices which are supported by an electronic device. It will be appreciated however that the functionality need not be divided in this way, and should not be taken to imply any particular structure of hardware other than that described and claimed below. The function of one or more of the elements shown in the drawings may be further subdivided, and / or distributed throughout apparatus of the disclosure. In some examples, the function of one or more elements shown in the drawings may be integrated into a single functional unit. As will be appreciated by the skilled reader in the context of the present disclosure, each of the examples described herein may be implemented in a variety of different ways. Any feature of any aspects of the disclosure may be combined with any of the other aspects of the disclosure. For example, method aspects may be combined with apparatus aspects, and features described with reference to the operation of particular elements of apparatus may be provided in methods which do not use those particular types of apparatus. In addition, each of the features of each of the examples is intended to be separable from the features which it is described in combination with, unless it is expressly stated that some other feature is essential to its operation. Each of these separable features may of course be combined with any of the other features of the examples in which it is described, or with any of the other features or combination of features of any of the other examples described herein. Furthermore, equivalents and modifications not described above may also be employed without departing from the invention. Certain features of the methods described herein may be implemented in hardware, and one or more functions of the apparatus may be implemented in method steps. It will also be appreciated in the context of the present disclosure that the methods described herein need not be performed in the order in which they are described, nor necessarily in the order in which they are depicted in the drawings. Accordingly, aspects of the disclosure which are described with reference to products or apparatus are also intended to be implemented as methods and vice versa. The methods described herein may be implemented in computer programs, or in hardware or in any combination thereof. Computer programs include software, middleware, firmware, and any combination thereof. Such programs may be provided as signals or network messages and may be recorded on computer readable media such as tangible computer readable media which may store the computer programs in non-transitory form. Hardware includes computers, handheld devices, programmable processors, general purpose processors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), and arrays of logic gates. Any controller described herein may be provided by any control apparatus such as a general-purpose processor configured with a computer program product to program the processor to operate according to any one of the methods described herein. The functionality of the controller may be provided by an application specific integrated circuit, ASIC, or by a field programmable gate array, FPGA, or by a configuration of logic gates, or by any other control apparatus. 5 Other examples and variations of the disclosure will be apparent to the skilled addressee in the context of the present disclosure.

Claims

1. A biological product preservation apparatus comprising:a container unit for preserving a biological product;a thermal energy store, wherein the thermal energy store is thermally coupled to the container unit for managing a temperature of a said biological product in the container unit;one or more sensors configured to obtain an indication of a temperature of the thermal energy store; anda controller configured to control operation of the apparatus based on the obtained indication of temperature of the thermal energy store.

2. The apparatus of claim 1, wherein the thermal energy store is arranged to store a material which acts as a store of thermal energy for managing the temperature of the biological product in the container unit.

3. The apparatus of claim 2, wherein the apparatus is configured to permit replacement of said material in the thermal energy store, optionally wherein the thermal energy store is removable.

4. The apparatus of any preceding claim, wherein the thermal energy store is arranged to store a phase change material, optionally wherein the thermal energy store is arranged to store ice.

5. The apparatus of any preceding claim, wherein controlling operation of the apparatus based on the obtained temperature data comprises determining an indication of a status of: (i) the biological product in the container unit, and / or (ii) the thermal energy store.

6. The apparatus of claim 5, wherein the controller is configured to output a status signal comprising an indication of the determined status.

7. The apparatus of claim 5 or 6, wherein determining an indication of the status of the thermal energy store comprises determining a status of material in the thermal energy store.

8. The apparatus of claim 7, wherein determining the indication of the status comprises determining an indication of a phase of the material in the thermal energy store.

9. The apparatus of claim 7 or 8, wherein determining the indication of the statuscomprises determining a proportion of the material in the thermal energy which has changed phase.

10. The apparatus of any preceding claim, wherein the controller is configured to predict a time at which material in the thermal energy store should be refreshed based on the obtained indication of temperature of the thermal energy store.

11. The apparatus of claim 10, wherein the controller is configured to output a prediction signal indicating the predicted time at which the material in the thermal energy store should be refreshed.

12. The apparatus of claim 10 or 11, wherein the predicted time at which the material in the energy store should be refreshed comprises a time at which a threshold amount of the material in the thermal energy store has changed phase, optionally wherein the threshold amount comprises all of the material in the thermal energy store.

13. The apparatus of claim 12, wherein the material in the thermal energy store is waterbased, and wherein the predicted time at which the material in the energy store should be refreshed comprises a time at which all of the ice in the thermal energy store has melted.

14. The apparatus of any preceding claim, wherein the one or more sensors are configured to obtain an indication of temperature at different heights within the thermal energy store.

15. The apparatus of claim 14, wherein the controller is configured to determine a proportion of the material within the thermal energy store which has changed phase based on temperature data associated with different heights within the thermal energy store.

16. The apparatus of any preceding claim, wherein the controller is configured to control operation of the apparatus based on a rate of change of temperature in the thermal energy store.

17. The apparatus of claim 16, wherein the controller is configured to determine a phase change event has occurred in the thermal energy store based on the rate of change of temperature.

18. The apparatus of any preceding claim, wherein the controller is configured to outputa signal in response to determining that a threshold amount of the material in the thermal energy store has changed phase.

19. The apparatus of any preceding claim, wherein the biological product comprises body tissue.

20. The apparatus of any preceding claim, wherein the container unit is configured to preserve the biological product in preservation liquid.

21. The apparatus of claim 20, as dependent upon claim 19, wherein the apparatus comprises a fluid delivery system configured to circulate fluid to the body tissue in the container unit.

22. The apparatus of claim 21, wherein the apparatus is a persufflation apparatus and the fluid delivery system comprises a gas supply system configured to supply persufflation gas to the body tissue in the container unit.

23. A base unit for a biological product preservation apparatus, the base unit comprising: a container unit receiving portion arranged to receive a container unit for preserving a biological product;a thermal energy store, wherein the thermal energy store is thermally coupled to the container unit receiving portion for managing a temperature of a said biological product in a said container unit;one or more sensors configured to obtain an indication of a temperature of the thermal energy store; anda controller configured to control operation of the apparatus based on the obtained indication of temperature of the thermal energy store.

24. A method of preserving a biological product, the method comprising:preserving a biological product in a container unit of a biological product preservation apparatus, wherein the container unit is thermally coupled to a thermal energy store for managing a temperature of the biological product in the container unit;obtaining an indication of a temperature of the thermal energy store; andcontrolling operation of the apparatus based on the obtained indication of temperature of the thermal energy store.

25. A computer program product comprising computer program instructions configured toprogram a biological product preservation apparatus to implement the method of claim 24.s

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