Devices and methods for supporting sleep transitions

Abstract

Apparatus and method for supporting a user in cycling between different sleep states. The apparatus comprises a flexible cover 200 for covering at least part of a user and comprising at least two flui

Description

Technical field The invention relates to an apparatus and method for supporting a user in their transition from one sleep state to another. In particular, the present disclosure relates to an apparatus and method for controlling the flow of fluid within one or more fluid channels within a bed cover to encourage a user to continue their transition towards a desired sleep state. Background While sleeping, a person can be in a number of different sleep states. These sleep states fall broadly into two categories: non-rapid eye movement (NREM); and rapid eye movement (REM). NREM can be divided into three sleep states, known as stages: • Stage 1 • Stage 2 • Stage 3 Stage 1 is the lightest stage of sleep, where the person is just drifting off to sleep. During this stage, the body temperature drops slightly, and muscle activity slows down. In stage 2, the person is in a slightly deeper sleep than in stage 1. Brain waves slow down even further, and the body continues to relax. Body temperature drops further, and heart rate and breathing rate also slow down. Stage 3 is the deepest stage of NREM sleep, also known as slow-wave sleep or deep sleep. During this stage, the brain produces slow delta waves, and it becomes more difficult to wake the person up. Body temperature drops even further, and blood pressure and heart rate decrease significantly. This is the stage where the body undergoes most of its restorative processes, including the release of growth hormone and the repair and regeneration of tissues. REM sleep, on the other hand, is a stage of sleep where the brain becomes more active, and dreams occur. During this stage, body temperature regulation becomes less effective, and the body may actually become slightly warmer. Breathing and heart rate become more irregular, and muscle activity is temporarily paralyzed. This stage is important for cognitive functioning and emotional regulation. Known systems for managing sleep may include the use of wearable devices to determine physiological parameters of a sleeping person. However, such systems are intrusive and can interrupt sleep. In some known systems, a sleep environment may be created within a volume surrounding the sleeping person, which is known as ‘tenting’. In these systems, the environment provided by the volume may be controlled to force a sleeping person into a particular sleep state. However, these systems lose the feeling of comfort a person gets from being in bed. In addition, forcing a sleeping person into new sleep states can be detrimental to sleep. In other known systems, the temperature of a user whilst they sleep may be controlled by controlling the temperature of a mat that is placed on a mattress, with the user sleeping on top of the mat. The temperature of the mat may be controlled based on, for example, a sleep history of the user, the local weather, temperature preferences and determined sleep states. Whilst this may allow for some thermoregulation of the user, such systems tend to be inefficient, as there is a limited contact surface area through which temperature control can be affected. Such systems can also feel uncomfortable to the user, with heating or cooling being localised to a specific area, resulting in an unpleasant ‘chill’ sensation. Summary Methods and apparatus disclosed herein are directed to solving one or more problems in the prior art, including those disclosed herein. In particular, methods and apparatus disclosed may encourage or facilitate the body of a sleeping person to cycle through sleep stages when they are ready to do so. According to the invention in a first aspect, there is provided an apparatus for supporting a user in transitioning from one sleep state to another. The apparatus comprises a flexible cover for covering at least part of a user when the user is lying on a surface, such as a bed. The cover comprises at least two fluid channels; a first fluid driver for driving a fluid into the cover through a first fluid channel; a second fluid driver for driving a fluid out of the cover through a second fluid channel; and one or more temperature and / or humidity sensors positioned within at least one of the fluid channels for sensing a temperature and / or humidity of the fluid in the corresponding fluid channel. The cover further comprises a computer processor configured to: obtain temperature and I or humidity data from the one or more sensors; obtain control instructions for at least one of the fluid drivers; and control at least one of the fluid drivers based on the obtained control instructions, wherein the control instructions correspond with sleep state data determined for the user based on the obtained sensor data. In an example, the first fluid driver is configured to drive a first fluid into the cover through the first fluid channel; and the second fluid driver is configured to drive a second fluid out of the cover through the second fluid channel. The first and second fluids may be the same fluid or different respective fluids. In an example, the sleep state data identifies whether a user is in transition from one sleep state to another. In an example, the computer processor is configured to determine, based on the obtained temperature and / or humidity data, the sleep state data indicative of the sleep state of the user. In an example, the computer processor is configured to determine the sleep state data based on a rate of change of the heat energy generated by the user. The rate of change of the heat energy generated by the user may be determined based on time-series data obtained from the one or more temperature and I or humidity sensors. In an example, if the rate of change of the heat generated by the user is detected as being above a threshold, the computer processor is configured to control the rate at which fluid is driven through at least one of the fluid channels. In an example, the computer processor is configured to determine a rate at which fluid is to be driven through at least one of the fluid channels based on the sleep state data, and to control at least one of the fluid drivers to drive the fluid through the fluid channels at the determined rate. In an example, at least one fluid channel extends linearly across at least part of the cover. In an example, each fluid channel comprises a plurality of apertures for allowing the or each fluid to permeate into and out of the fluid channel. In an example, each fluid channel comprises a respective fluid driver at one end thereof and the size of the apertures in each channel increases with distance from the corresponding fluid driver. The apertures may be formed in a base portion of the corresponding fluid channel. In an example, the first fluid driver may be arranged to draw air into the first fluid channel, and the plurality of apertures ofthe first fluid channel allow airto permeate out of the coverthrough a lower surface ofthe cover, towards the user. In an example, the second fluid driver is arranged to drive air out ofthe second fluid channel, and the plurality of apertures of the second fluid channel allow air proximate to the user to enter the second fluid channel from beneath the bed cover. In an example, each fluid channel includes a fluid driver at a first end, and a second end of the fluid channel is closed such that fluid cannot enter or leave the fluid channel at the closed end. The first fluid driver may be arranged to drive the fluid into the first fluid channel through the first end, and the second fluid driver may be arranged to drive the fluid out ofthe first end ofthe second fluid channel. The one or more temperature sensors and / or the one or more humidity sensors may be located proximate to one or more ofthe plurality of apertures. The fluid in at least one ofthe fluid channels may comprise ambient air. In an example, the apparatus comprises a plurality of fluid channels and a plurality of fluid drivers, wherein each fluid channel includes a fluid driver at one end thereof. In an example, each fluid driver comprises a fan or impeller. In an example, at least one ofthe fluid channels comprises a first fluid driver at a first end thereof and a second fluid driver at a second end thereof. In an example, the apparatus further comprises one or more motion sensors configured to detect movement ofthe cover as a result of movement ofthe user, and the obtained control instructions correspond with sleep state determined for the user based on motion detected by the motion sensors. Alternatively, or in addition, the computer processor is configured to obtain motion data from the one or more motion sensors, and to determine the sleep state data based on the obtained motion data. In an example, the sleep state data is determined based on duty cycle data obtained from the one or more fluid drivers. In an example, the computer processor is further configured to receive duty cycle data from the one or more fluid drivers and to determine the sleep state data based on the received duty cycle data. In an example, the first fluid driver is connected to a source of cooled air. In an example, the bed cover comprises a duvet. In an example, fluid enters the one or more fluid channels via a permeable outer layer of the duvet. In an example, the bed cover comprises a sleeping bag. According to the invention in a second aspect, there is provided a method of supporting a user’s transition from one sleep state to another by controlling the flow of fluid within a flexible bed cover, the flexible bed cover comprising at least two fluid channels, and at least two fluid drivers, a first of the fluid drivers being arranged to drive fluid into the cover through a first fluid channel, a second of the fluid drivers being arranged to drive fluid out of the cover through a second fluid channel; wherein one or more temperature and / or humidity sensors are positioned within at least one of the fluid channels, the method comprising: obtaining sensor data from the temperature and I or humidity sensors; obtaining, based on the obtained sensor data, control instructions that correspond with sleep state data determined for the user based on the obtained sensor data, the sleep state data being indicative of a sleep state of the user; and controlling the flow of fluid through at least one of the fluid channels within the bed cover based on the obtained control instructions. In an example, the sensor data provides an indication of the heat energy generated by the user of the flexible bed cover. The sensor data may be used to determine a rate at which the user is dissipating heat energy into their local sleep environment. The local sleep environment may be defined by the cavity formed by the bed cover, within which the user is located. In an example, the method further comprises determining sleep state data based on the obtained sensor data. The sleep state data may identify whether the user is in a transition from one sleep state to another. The sleep state data may be determined based on a comparison of the temperature and I or humidity data with one or more threshold values. In an example, the method further comprises obtaining sensor data from one or more motion sensors for detecting motion of the user and determining the sleep state data based on the obtained motion data. The sleep state data may be further determined based on a comparison of the motion data with one or more threshold values. In an example, the method further comprises obtaining vibration data from a vibration sensor and determine the sleep state data based on the obtained vibration data. The sleep state data may be further determined based on a comparison of the vibration data with one or more threshold values. The vibration data may be indicative of the user’s heartbeat. In an example, controlling the flow of fluid through the one or more fluid channels comprises controlling operation of the one or more fluid drivers based on the obtained sleep state data. Controlling the flow of fluid through the one or more fluid channels may comprise one or more of (i) controlling rate at which fluid is driven through the fluid channels, (ii) controlling the duration for which fluid is driven through the fluid channels, and (iii) controlling the number of fluid drivers that are actively driving fluid through the fluid channels. In an example, the method further comprises receiving data associated with the operation of the one or more fluid drivers and determining the sleep state data based on the data received from the one or more fluid drivers. In an example, the method further comprises determining whether the rate at which the user is generating heat energy for a given operational status of the one or more fluid drivers exceeds a threshold value, and responsive to a positive determination, modifying operation of the fluid drivers further. Modifying the operation of the fluid drivers may comprise one or more of adjusting a work, rate or duty cycle of the fluid drivers to encourage expulsion of the fluid within the fluid channels. According to the invention in a third aspect, there are provided computer program products including computer program code configured, when executed on a computer processor, to control a data processor to undertake the steps of any method described herein. Brief description of the drawings Embodiments of the disclosed methods and apparatus will be described in detail below, with reference to the accompanying drawings, in which: Figure 1 is an example of a conventional bed cover; Figure 2A shows a first example of a bed cover in accordance with the present disclosure; Figure 2B shows a second example of a bed cover in accordance with the present disclosure; Figure 3A shows a perspective view of a further example of a bed cover in accordance with the present disclosure; Figure 3B shows an exploded view of the bed cover shown in Figure 3A; Figure 3C shows an example of a push and a pull channel in accordance with the present disclosure; Figure 4 shows an example of an apparatus for controlling the flow of fluid through a fluid channel of the present disclosure; Figure 5 is a cross-sectional view of a fluid channel of the present disclosure; Figure 6 is an example of a method for controlling a fluid driving apparatus based on a determined sleep state of a user; and Figure 7 is an example of a method for controlling a fluid driving apparatus based on sensor data and data relating to an operation of a fluid driving apparatus. Detailed Description Generally, disclosed herein are methods and apparatus for supporting a user’s transition from one sleep state to another. Figure 1 shows perspective and exploded views of a conventional bed cover 100. The cover 100 may include, for example, a duvet, quilt, comforter, sleeping bag, or the like. The cover 100 is flexible such that a user can draw the cover 100 across at least part of their body whilst sleeping or resting on a given surface, such as a mattress. It will be appreciated that whilst the term ‘bed cover’ is used throughout this description, users need not be restricted to using a cover 100 in combination with a bed. For example, in some embodiments, the flexible bed cover may wrap around the user’s body, such as where the cover comprises a sleeping bag. In the example shown, the bed cover 100 includes an insert cover 101 in which an insert 102 is contained. In the exploded view, the insert cover 101 is shown with an upper layer 101a and lower layer 101b, but it will be appreciated that in some examples, the insert cover 101 may form a single piece with an opening to receive the insert 102. The insert 102 includes an insulting material for retaining heat, such as down feathers, synthetic fibres, wool, cotton, ora combination thereof. The amount of insulating material used may correspond to a desired heat retention level. For example, a winter duvet will usually include more insulating material, or a higher density of insulating material, than a summer duvet. The insert 102 may also include stitching or baffles (not shown) that create pockets or compartments that help hold the insulating material in place. A baffle-box construction may be used to improve loft and heat retention of the bed cover 100. The insulating material is designed to trap air or impede its exit from beneath the cover. The insert cover 101 encapsulates the insert 102 and acts as a protective layer. The insert cover 101 is usually thinner than the insert 102 itself, and may be made from materials such as cotton, linen, silk, microfibres, synthetic fibres, etc. The insert 102 may be secured within the insert cover 101 by means of an attachment portion 103. For example, the insert cover 101 may include an opening for receiving the insert 102, with the opening being sealable way of the attachment portion. The attachment portion 103 may include, for example, one or more: zips, poppers, ties, buttons, or a combination thereof. In this way, the insert cover 101 may form a removable layer that can be removed and replaced, e.g., for washing and / or changing an aesthetic. The location of the attachment portion 103 shown in Figure 1 is typical of a duvet. It will be appreciated that, whilst the attachment portion 103 is shown in Figure 1 as being at an edge of the insert cover 101, any number of attachment portions 103 may be arranged at any suitable location of the insert cover 101, so long as the insert 102 is covered and distributed across a large enough area to form a bed cover 100. Alternatively, there may be no attachment means, for example, where the bed cover 100 forms a single piece (e.g., a comforter or a sleeping bag), with the insert 102 being secured within its covering via e.g., stitching or glue along an outer perimeter edge. Figure 2A shows an example of a bed cover 200 in accordance with the present disclosure. In Figure 2A, the bed cover 200 is shown as comprising a lower layer 201, an insulating layer 202 and at least two fluid channels 203a, 203b fortransporting a fluid into and out of the bed cover 200. At the end of each fluid channel, a respective fluid driver 204a, 204b is provided for driving fluid through the corresponding fluid channel. The insulating layer 202 may comprise an insulating material, such as any of those described previously in relation to Figure 1. It will be appreciated that in some examples, the insulating layer 202 may not form a layer that is separate from the fluid channels 203a, 203b, for example, the fluid channels 203a, 203b, may form walled cavities that extend through the insulating material or are positioned between sections of insulating material. In use, the cover 200 may define a cavity in which the user sleeps or rests, with the air within the cavity region being warmed by heat energy radiated by the user. This cavity may define a local sleep environment of the user. The lower layer 201 has a higher permeability than the insulating layer 202 such that the air warmed by the user can be drawn up through the lower layer 201, into at least one of the fluid channels 203a, 203b. Similarly, the higher permeability of the lower layer 201 may also allow air that has been drawn into one of the fluid channels 203a, 203b, to be expelled out of the lower layer 201 of the bed cover 200, towards an underlying user. As will be appreciated, at least a portion of the fluid channel will have a higher permeability than the insulating layer 202, to ensure that fluid can enter the fluid channel. In some examples, such as that shown in Figure 2A, the insulating layer 202 may be arranged above the fluid channels 203a, 203b. In such examples, the lower permeability of the insulating layer 202 ensures that fluid within the fluid channels 203a, 203b cannot escape via the insulating layer 202. The arrangement of layers in this way means the heat- and moistureretaining layer is lifted away from the body of the user, thereby increasing the volume of air within the user’s local sleep environment. Each fluid channel is arranged to receive a fluid and to provide a channel through which the fluid can be driven. In preferred examples, the fluid corresponds to air. One of the fluid channels may provide a path through which ambient air in the vicinity of the user is collected and drawn out of the bed cover 200 (a push channel). The other channel may provide a path through which cooler air is driven into the bed cover 200 (a pull channel) and down towards an underlying user. In this way, the two channels may provide respective paths for circulating air into and out of the bed cover, and in turn, the user’s local sleep environment. In Figure 2A, the fluid channels 203a, 203b are shown as being separate from one another, but it will be appreciated that in some examples, the fluid channels 203a, 203b may be formed within a single layer. An example of this is shown in Figure 3A, which shows the fluid channels 203a, 203b as being formed within a cooling layer that is arranged beneath the insulating layer 202. In Figure 2A, the fluid channels 203a, 203b are shown as having a circular cross-section, but it will be appreciated that other conduit shapes may be used provided that the fluid channel is able to act as a conduit fortransporting fluid. In preferred examples, the channels 203a, 203b are made from a material that is breathable, resilient, and conformable. That is, the channel permits passage of fluid, such as air into the channel, whilst also having a shape that is sufficiently rigid to maintain the channel’s shape and the required flexibility to allow the cover to conform to the user’s body shape when in use. An example of a material with these properties is a 3D spacer mesh material. It has been found that this type of material is able to support the weight of (or force exerted by) the insulating material, whilst still providing the desired flexibility and resistance to mechanical forces that would otherwise block the fluid channel. In some examples, the 3D spacer mesh material may be covered with a nylon sleeve. The nylon sleeve may comprise a plurality of apertures for allowing the fluid to permeate into the fluid channel. The diameter (or more generally, area) of the apertures may vary with distance from the end of the corresponding fluid channel at which the fluid driver is located, as will be described further in relation to Figure 3C. Returning to Figure 2A, a first fluid driver 204a is shown as driving a fluid into the cover 200 through a first fluid channel 203a. As described above, the fluid may comprise air, and the air may be driven into the fluid channel 203a and down towards the user, via the lower layer 201. This downward path corresponds to the path of least resistance by virtue of the relative difference in permeabilities between the insulating layer 202 and lower layer 201. Fluid channel 203a may be considered a ‘pull channel’ in that it provides a path for directing the air that has been pulled into the cover 200 by the first fluid driver 204a, down towards the user. In Figure 2A, a second fluid driver 204b is shown as driving fluid out of a second fluid channel 203b. As mentioned above, the second fluid channel 203b may be arranged to receive fluid, such as warm ambient air from beneath the bed cover 200. The relative difference in permeability between the lower layer 202 and insulating layer 201 means that the path of least resistance will be upwards, from the lower layer 201, into the fluid channel 203b. The second fluid channel 203b may be considered a ‘push’ channel in that it provides a path through which air can be pushed out of the bed cover 200 by the corresponding fluid driver 204, away from the user. In this way, the combined operation of the first and second fluid drivers 204a, 204b creates a circulating current of fluid through the bed cover. Each fluid driver (or more generally ‘fluid driving apparatus’) may comprise a fan or impeller that is configured to generate a directional flow of fluid through the corresponding fluid channel. Each fluid driver may be connected to a control unit (not shown) that is configured to control at least one of the rate, duration and direction in which fluid is driven through the corresponding channel. Controlling operation of the fluid drivers will be described further in relation to Figure 4. Generally, each fluid driver may comprise or be connectable to a power source, with operation of the fluid driver being controllable by controlling or varying the supply of power to the fluid driver. Preferably, the air drawn into the pull channel 204a is cooler than air expelled from the push channel 204b by virtue of having been sourced from somewhere other than the immediate vicinity of the user. For example, the first channel 204a may be connected to a source of cool air (not shown), such as that produced by an air conditioner. Alternatively, the air may be sourced from the air outside of the cover 200, which may be cooler than the warm air trapped beneath the cover 200. In some examples, the air pulled into the cover 200 may not necessarily be at a lower temperature than the air expelled from the cover 200 but the combined operation of the push and pull channels (or rather, their corresponding fluid drivers) may nevertheless promote cooling of the user by generating an airflow over the user’s body. By measuring the temperature and / or moisture of the air circulating into and out of the cover 200, an amount of heat energy generated by the user over a given time period, can be estimated. This heat energy may correspond to heat energy that the user has dissipated as a result of lowering their core body temperature as they transition to deeper sleep states. The amount of and / or rate at which the user is determined as dissipating heat energy into their local sleep environment may be correlated to a likely sleep state transition of the user. Returning to Figure 2A, the first fluid driver 204a is shown as drawing air into the first fluid channel 203a (pull channel) at a first end of the fluid channel 203a. The opposite end of the fluid channel 203a may be closed such that air cannot escape and is instead directed downwards via the lower layer 201. Similarly, the second fluid channel 203b (push channel) may also be closed at one end, such that fluid collected by the second fluid channel 203b is driven out of the other end of the fluid channel 203b, corresponding to the end at which the second fluid driver 204b is located. In some examples, the first and second fluid drivers 204a, 204b may be located at the same ends of the corresponding fluid channels 203a, 203b, with the first and second fluid drivers 204a, 204b causing fluid to flow in opposite directions (as shown). In such examples, the push and pull channels may be blocked at the same respective ends. It may be desirable to have the fluid drivers to be located towards a lower edge of the bed cover, such that any noise generated by the fluid drivers is not within the vicinity of the user’s face, and so that warmed fluid is not expelled from the bed cover, back towards the user’s face. In alternative examples, the first and second fluid drivers 204a, 204b may be provided at different respective ends of the corresponding fluid channel (i.e., in an alternating pattern). In Figure 2A, the push and pull channels 203a, 203b (and corresponding fluid drivers 204a, 204b) are shown as running parallel to one another, extending linearly across at least part of the bed cover200. In some examples, the push and pull channels may extend across an entire length (and / or width) of the bed cover 200. It will be appreciated that, whilst only one push and pull channel is shown in Figure 2A, in some examples, the cover 200 may comprise a plurality of push and / or pull channels. In some examples, the cover 200 may comprise a plurality of push and pull channels distributed uniformly throughout the cover 200, i.e., across its surface. This may be desirable as it will ensure uniform airflow across the user’s body. In some examples, at least some of the push and pull channels may be arranged in an alternating pattern of push-pull (or vice versa). Alternatively, at least some of the neighbouring fluid channels 203a, 203b may be of the same type, thereby forming groups in which fluid is either driven into or out of a corresponding region of the cover 200. In yet further examples, the direction in which fluid is driven by a given fluid driver may be controllable such that whether the corresponding fluid channel is a ‘push’ or ‘pull’ channel can be selectively controlled, for example, by controlling the direction in which fluid is driven by the fluid driver. In some examples, at least one of the fluid channels 203a, 203b may be arranged to receive a liquid or gel coolant (i.e., not just air), and the corresponding fluid driver may be configured to control the rate at which the coolant is driven into or out of the corresponding fluid channel. In such examples, there may be provided an additional reservoir of coolant that is connected to the fluid channel and the fluid driver may be a motor or pump that directs coolant into and or out of the fluid channel. The rate at which coolant is driven into and I or out of the fluid channels may be dependent on a determined sleep state of the user, as will be described further in relation to Figures 4 - 7. Figure 2B shows a further example of a bed cover 200 in accordance with the present disclosure. The bed cover 200 shown in Figure 2B differs from that shown in Figure 2A in that the fluid drivers 204a, 204b are configured to drive fluid out of their respective fluid channels 203a, 203b. That is, each fluid channel 203a, 203b is a push channel. As described above, the push channels may receive warm ambient air from beneath the bed cover, and the corresponding fluid driver may expel the ambient air out of one end of the fluid channel. In these examples, there is no circulation of cooler air into the bed cover 200, but the removal of the warm air by the push channels may nonetheless support the user in lowering their body temperature by preventing a build-up of warm air within the user’s local sleep environment. In Figure 2B, operation of the fluid drivers 203a, 203b may be controlled based on a determined sleep state of the user, such as whether they are determined as transitioning to a deeper sleep state. Alternatively, operation of the fluid drivers may be controlled independently of a determined sleep state, e.g., based on a predetermined schedule. The predetermined schedule may correspond to the fluid drivers periodically being switched on or off, for example. In Figure 2B, two push channels 203a, 203b and two corresponding fluid drivers 204a, 204b are shown, however, in some examples, there may be fewer (e.g. one) or more than this. In one example, there may be one fluid driver, that pushes air out of one or more fluid channels. For example, the fluid channels may form a connected network of channels, with the one or more fluid drivers pushing fluid out of this network. Figures 3A and 3B show an example of a bed cover 300 in accordance with the present disclosure. Figure 3A shows a perspective view of the bed cover 300; Figure 3B shows an exploded view of the bed cover 300. In Figures 3A and 3B, the bed cover 300 is shown as comprising a plurality of layers 301 -307, with at least one layer corresponding to an insulating layer 303. The insulating layer 303 may correspond to the insert I insulation layers described previously in relation to Figures 1, 2A and 2B, bar some structural modifications as will be described below. In Figure 3B, the insulating layer 303 is shown as being sandwiched between one or more upper and lower layers, which together form the bed cover 300. The upper-most layer 301 and lower-most layer 307 (or more generally, an outer-most layer) may be used to protect the contents of the bed cover 300, as well as facilitate the securing of the other layers togetherto form a single item. Additionally, or alternatively, the upper-most and lower-most layers may serve an aesthetic and / or comfort function. In some examples, the upper-most layer 301 and lower-most layer 307 are removable, e.g., via one or more attachment portions, as described in relation to Figure 1. In some examples, the one or more layers above the insulating layer 303, such as layers 301 and 302, may comprise further insulating layers, i.e., have a lower air permeability (more insulating) than the one or more layers beneath the insulating layer 303. Different heat insulating layers may be used depending on, for example, a desired tog rating for the bed cover. In some examples, the one or more insulating layers 301, 302, 303 may be formed of a relatively rigid material to prevent constrictions in the fluid channels by spreading the load of weighty objects over a larger area of the cover. Additionally, or alternatively, this resistance to constriction may be achieved by the rigidity of the material used for the fluid channels. Beneath the insulating layer 303, a cooling layer 304 is formed. The cooling layer 304 comprises a plurality of fluid channels 307 described previously, at least one fluid channel may correspond to a push channel or a pull channel; or there may be at least two channels, with one comprising a push channel and the other comprising a pull channel. In Figures 3A and 3B, the channels 307 extend from side-to-side and are spaced apart at regular intervals. Additionally, or alternatively, the channels 307 may extend from front-to-back. In examples where the bed cover 300 may need to wrap around the user’s body, for example, in the case of a sleeping bag, the channels 307 may be provided at a portion that is expected to be outward facing during use. Generally, a larger number of channels 307, distributed uniformly across the cover 300 will provide better fluid circulation into and I or out of the coverthan a smaller number of sparsely distributed channels 307. It will be appreciated that, in Figure 3B, the cooling layer 304 is shown as a separate layer to the insulation layer 303, but in some examples, the insulation layer 303 and the cooling layer 304 may form a single layer, e.g., walled cavities within the insulation layer 303 may form the fluid channels 307. In such examples, each fluid channel 307 may form a separate unit that is secured within a corresponding cavity within the insulating layer 303, without the fluid channels 307 being attached to a separate layer that spans the length and width of the bed cover 300. In other examples, the cooling layer 304 may be a separate layer, formed of a material that is different from the insulating layer 303, with the fluid channels in the cooling layer 304 being slotted into corresponding cavities formed in the insulating layer 303. In Figures 3A and 3B, a plurality of fluid drivers 308 are shown, one for each corresponding fluid channel 307. The fluid drivers 308 may correspond to the fluid drivers described previously. In Figures 3A and 3B, each fluid channel 307 is shown as having a fluid driver at 308, or proximal, to a respective end of the fluid channel 307. In some examples, at least some of the fluid channels 307 may have a fluid driver 308 at (or proximal to) both ends. As described previously, at least some of the fluid drivers 308 are configured to remove heat energy that has built up in the user’s local sleeping environment (and that has been absorbed by the corresponding fluid channels 307 of the cover 300). In some examples, at least some of the fluid drivers 308 are configured to replenish fluid into the user’s local sleeping environment (e.g. by pushing cooler air in). The temperature and / or moisture of the fluid in the channel(s) 307 may be indicative of the amount of heat energy that has been shed by the user over a given time period. Returning to Figure 3B, a further layer 305 is shown beneath the cooling layer 305. This further layer 305 comprises a plurality of apertures 309 for allowing fluid, such as air, to circulate into and I or out of the cover 300 via the fluid channels 307. The apertures 309 may be arranged such that each fluid channel 307 has, along the length of its underside, a series of inlets (or outlets, depending on the direction flow) through which air can be exchanged across the surface of the fluid channel 307. It will be appreciated that layers 306 and 307 beneath this further layer 305 will be formed of material(s) with relatively high permeability so that heat and moisture generated by the user can pass through them and enter at least some of the fluid channels 307 (push channels) via the apertures 309. Similarly, the relatively high permeability of layers 306 and 307 allows fluid driven into at least some of the fluid channels (pull channels) to travel downwards, via the apertures 309, through the one or more lower layers 306, 307 and out of an underside of the bed cover 300. In some examples, the size of a given aperture 309 may depend on its distance from a nearest fluid driver 308. An example of this is shown in Figure 3C, which shows a top-down view of two fluid channels, 307a, 307b, each having respective fluid drivers 308a, 308b at respective ends thereof. Each fluid channel 307a, 307b is shown as having apertures 309 (dashed) formed within a respective base portion, with the size of each aperture increasing with distance from the nearest fluid driver 308. For example, in Figure 3C, the largest aperture is located at a far (distal) end of the fluid channel. It has been found that this arrangement of apertures promotes a uniform flow rate of the fluid throughout the length of the fluid channel. Generally, the pressure of the fluid within the fluid channel will be higher closerto the corresponding fluid driver, and so the provision of larger apertures away from the fluid driver ensures that there is sufficient pressure for the fluid to permeate into or out of the fluid channel at the far ends of the fluid channel. In examples where the fluid is air, it has been found that this arrangement of apertures can reduce the work required by the fans or impellers to achieve effective air circulation. It will be appreciated that Figure 3C is an illustrative example and that in other examples, the shape of the apertures and the distances between them may vary. In Figure 3C, the apertures 309 shown for the first fluid channel 307a (pull channel) are shown as shaded, to indicate that the fluid contained therein will flow downwards. For the non-shaded apertures 309 for the second fluid channel 307b (push channel), fluid is received from the one or more layers beneath the fluid channel 307b. Returning to Figure 3B, the further layer 305 is shown as being formed above a sensing layer 306 at which one or more sensors 310 are disposed. The sensors 310 may be configured to obtain data from which a user’s sleep state can be determined. For example, stage 3 of NREM sleep is usually associated with a drop in body temperature and I or reduction in muscle activity, so a transition towards this sleep state may be identifiable by detecting changes in the heat generated by the user and I or their movement. For example, it may be that, as a user lowers their body temperature, e.g., via sweating, a detectable build-up of heat and moisture within at least some of the fluid channels 307 occurs. The one or more sensors 310 may include temperature sensors and I or humidity sensors. The sensors 310 may be positioned at regular intervals along the length of one or more fluid channels 307 so that the temperature and moisture of the air contained therein can be detected at multiple locations. The purpose of the temperature and humidity sensors is to detect the temperature and humidity of the air within the fluid channel 307, not the body temperature or moisture of the user’s skin or the bed cover as a whole. A larger number of sensors 310 distributed throughout one or more fluid channels 307 allows for the collection of more data, which in turn, allows for a more accurate estimation of the user’s sleep state. In some examples, at least one of the sensors may comprise a seismic or vibrational sensor, from which information relating to the user’s heartbeat and I or other types of movement indicative of a user’s sleep state. As mentioned previously, at least two of the fluid channels may correspond to respective push and pull channels. The one or more sensors in each channel may therefore provide an indication of the temperature and I or humidity of the fluid that is either being driven into or out of that channel. By monitoring the difference between the temperature and I or humidity of the fluid being driven out of the push channel, and the temperature and / or humidity of the fluid being driven into the pull channel, over a given time period, an amount of heat energy (e.g., in joules) that has been removed from the cover can be determined. This may provide an indication of the heat energy that a user has shed within that time period, which in turn may provide an indication of whether they are ready to transition, or are in the process of transitioning to a deeper sleep state. In additional or alternative examples, the sensors 310 may include one or more motion sensors for detecting movement of the bed cover 300. Movement of the bed cover 300 tends to be indicative of movement of the underlying user. The motion sensors may include, for example, accelerometers, gyroscopes, cyclometers, optical sensors, etc. The motion sensors may also be arranged within the bed cover 300 in the same manner as the temperature and / or humidity sensors. However, unlike the temperature and I or humidity sensors, the motion sensors need not necessarily be located within the fluid channels 307 and so may be arranged differently (e.g., located outside of the apertures 309, at a separate portion of the sensing layer 306, or at a different location within the bed cover 300). In some examples, the motion sensors may be external to the bed cover 300, for example, a user’s smartwatch or mobile phone may be used to detect motion of the user. The combination of temperature, humidity and motion sensors allows for richer data to be gathered, improving the accuracy with which a user’s sleep state can be determined. In some examples, the one or more sensors 310 are provided with protective mechanical shielding. In the example of Figure 3B, the sensors 310 are arranged proximal to the apertures 309 such that the superposition of the insulating layer 303, cooling layer 304, further layer 305 and sensing layer 306 results in the sensors 310 being located at least partially within a corresponding fluid channel 307. It will be appreciated that this specific arrangement of layers is an illustrative example, and that in other examples, the sensors 310 may be affixed to the walls or base of the fluid channel 307 or provided at the layer directly beneath the fluid channel 307 without a separate further layer 305 providing just the apertures 309. Figure 3B further shows a bottom-most layer 307 that is intended to be directly above the user during in use of the bed cover 300. In one example, the bottom-most layer 307 may include an inner section (e.g., having a high permeability), and an outer-section, with the outer-section providing a portion that the user can grab when drawing the cover across themselves. It will be appreciated that the bed cover 300 shown in Figures 3A and 3B is an illustrative example and that the bed cover 300 of the present disclosure need not be restricted to this precise number of layers. Figure 4 shows schematically an example apparatus for supporting a user’s transition between sleep states. In Figure 4, the fluid channels and fluid drivers correspond to those shown in Figure 3C, but with each fluid channel having a plurality of sensors 310 positioned along its length. As described previously, the sensors 310 may include at least one of: temperature sensors 401, humidity sensors 402 and motion sensors 403. The sensors 410 may protrude (radially) inwards, i.e., point towards the centre of the fluid channel when viewed along the length of the ventilation channel, as shown in Figure 5. It will be appreciated that, whilst the push and pull channels in Figure 4 are shown as each comprising the same number of sensors, arranged in the same manner, this is merely an illustrative example. In other examples, the push and pull channels may each have a different number and / or layout of sensors. In Figure 4, a control unit 404 is shown as receiving inputs from the sensors 310 and the fluid drivers 308a, 308b. The control unit 404 may be configured to generate outputs that are input to the fluid drivers 308a, 308b to control their operation, as will be described further below. As discussed previously, as the user transitions to a deeper sleep state, they will lower their core body temperature by shedding heat (e.g., via sweating). The rate at which the user is detected as having shed heat energy may be indicative of whether a user is ready to transition to, or is in the process of transitioning to, a deeper sleep state. Stage 3 of NREM sleep, for example, is associated with restorative processes, such as growth and repair. It is also within this stage of sleep that brain’s glymphatic system ‘cleans the brain’ using blood and cerebrospinal fluid (CSF). It may therefore be desirable to ensure that a user is able to successfully transition to this sleep state, so that the user can benefit from these restorative processes properly. A lack of NREM stage 3 sleep has been linked to a weakening of the immune system and a heightened risk of dementia or chronic illnesses such as cancer, for example. Accordingly, the sensor data generated by the one or more sensors may be used to determine a temperature and I or humidity of the fluid within the corresponding fluid channel. By measuring the difference in temperature and / or humidity of the fluid (or fluids) circulating into and out of the cover, an amount of heat energy attributable to the shedding of heat by the user can be determined. The rate at which the user is detected as generating heat energy (e.g., x Joules per minute) may be compared with a threshold value, to determine whether the user is ready to (or in the process of transitioning to) a deeper sleep state. In some examples, the control unit 404 may be configured to process the sensor data and determine a corresponding sleep state of the user. For example, the control unit 404 may correspond to one or more processors located within the bed cover 300, e.g., attached to the sensing layer 306. In other examples, the control unit 404 may be configured to receive the sensor data and provide this to a remote device 407, i.e., separate from the bed cover 300, which then performs the necessary processing for determining a user’s sleep state. An example of this is shown in Figure 4, which shows the control unit 404 as having a network interface 405 that allows data to be transmitted to a remote device 407 for further processing. The data may be transmitted to the remote device 404 via a wireless network such as Wi-Fi, Bluetooth, cellular network, etc. The remote device 407 may provide the results of the analysis to the control unit 404 or may simply provide instructions which the control unit 404 issues to the fluid drivers. The remote device 407 could include, for example, a user’s phone or smart-watch, or a more computationally powerful device, such as a server. As mentioned above, the sleep state of the user may be determined based on the rate at which the user is detected as shedding heat energy and / or their muscle activity. The determined sleep state may correspond to the user being in one of a waking state, a given stage of NREM sleep, in REM sleep, or transitioning or likely to transition between one of these states. In some examples, the sleep state may correspond to being in a sub-stage of one of these sleep states. Different sleep states may be associated with different thresholds of temperature, humidity and I or motion, or different rates of change in one or more these values, which can be mapped to corresponding sleep states. Hence by monitoring changes in one or more of these values over time, and comparing these with one or more threshold values, a corresponding sleep state can be determined for the user. In preferred examples, determining the sleep state of the user comprises determining whether the user is ready to, or in the process of, transitioning to a deeper sleep state, such as stage 3 NREM sleep. Additionally, or alternatively, determining the sleep state of the user may correspond to determining whether a physiological process is occurring within the user’s body, based on a rate at which the user is shedding heat, which may not be restricted to a specific sleep state (but the extent of which may vary depending on which stage of sleep the user is experiencing). That is, the determined sleep state may not necessarily correspond to a specific stage within NREM or REM sleep, for example, but may nonetheless correspond to an identifiable sleep state. The threshold values used to determine a sleep state for the user may be determined empirically or theoretically. For example, the relationship between heat energy generation and sleep states may be known (see e.g., Siegel, J. M. (2001). Body temperature and sleep: A thermostatic model of sleep regulation. Nature, 413(6851), 157-161). In one example, it may be that test data is collected from multiple bed cover users, and is supplemented with additional physiological data, such as heart rate, blood pressure, skin surface temperature, eye movement, polysomnographic data, etc. In this way, a model can be built that correlates heat energy circulated out of the cover 300 and / or movement of the cover 300 or the user, with corresponding sleep states. This model may be used to map time-series temperature, moisture and / or motion data to corresponding sleep state data. In Figure 4, the control unit 404 is shown as being located within the bed cover 300, but it will be appreciated that the control unit 404 may be external to the bed cover 300. For example, the sensors 310 and I or fluid drivers 308 may each be operable to transmit data to an external control unit 404 and respond to instructions received therefrom. In other examples, it may be that there are separate control units 404 for the sensors 310 and fluid drivers 308, with each of these control units 404 being connected to an intermediate device, such as remote device 407. As mentioned previously, the control unit 404 may be configured to receive data from and transmit data to the fluid drivers 308a, 308b. The data received from the fluid drivers 308a, 308b may include duty cycle data, such as a percentage of time the fans or impellers have been running within a given time period. Additionally, or alternatively, the data may indicate a speed at which the fans or impellers are being driven and / or a number of fans or impellers that are currently active or inactive within the bed cover 300. In some examples, the control unit 404 may not receive this data directly from the fluid drivers 308; instead, this data may be inferred from the most recent instruction(s) sent to the fluid drivers 308 from the control unit 404. The control unit 404 is configured to control the fluid drivers based on a determined sleep state of the user. This may involve controlling the duration and I or rate at which fluid is driven through the fluid channels 307, for example by controlling the duration for which the fluid drivers are active (or scheduled to be active) and I or the speed at which the fluid drivers drive fluid into or out of the corresponding fluid channel. The control unit 404 may be configured to control the fluid drivers on an individual or group basis. For example, the control unit 404 may selectively switch different fluid drivers on or off and I or vary the speed, depending on the rate at which the user is determined as generating heat energy. In some examples, the control unit 404 may comprise or have access to information relating to the layout of sensors and I or fluid drivers, such that it can be determined whether data received from therefrom corresponds to a push or pull channel. Additionally, or alternatively, this data may be provided to the control unit 404 by the sensors and / or fluid drivers 308a, 308b. The control unit 404 may be configured to use this information to selectively control the rate at which fluid is driven through the one or more push or pull channels. In some examples, the direction in which fluid is driven by the fluid drivers 308a, 308b may be controllable, such that the fluid driver can either push fluid into or out of the fluid channel. For example, the direction in which a rotary component, such as a propeller or blades, of the fluid driver rotates may determine whether fluid is pushed into or out of the corresponding fluid channel. The control unit 404 may be operable to control this direction of rotation (e.g., clockwise or anticlockwise) based on the determined sleep state for the user. In some examples, the user’s sleep state may be determined based on a combination of the obtained sensor data and data associated with the fluid drivers 308. For example, if despite having adjusted operation of the fluid drivers based on a previously determined sleep state, it is determined that the amount of heat energy generated by the user over a given time period is still above a threshold value, this may indicate that the user is unlikely to remain transitioning to, or within, a desired sleep state. In response to this, the control unit 404 may be configured to increase the speed of at least some of the fluid drivers (e.g. fans or impellers) further, to increase the rate at which fluid is driven into and I or out of the bed cover 300. This may correspond to increasing the rate at which air is circulated through the cover 300 and passed over the user’s body. Additionally, or alternatively, the control unit 404 may be configured to extend the period for which the fluid drivers are on and I or to increase the number of fluid drivers that are active within the bed cover 300. Conversely, if it is determined that the user is likely to continue transitioning to a deeper sleep state, then the control unit 404 may schedule a switching off of one or more of the fluid drivers 308, and I or reduce a work rate of one or more of the fluid drivers 308 (i.e., decrease the speed, number of fluid drivers 308 that are active and / or the duration for which one or more fluid drivers are active). Figure 6 shows an example of a method 600 for supporting a user as they transition between different sleep states. The method 600 enables the bed cover 200, 300 described previously in relation to Figures 2A - 5 to regulate circulation of the fluid into and out of the bed cover 200, 300. At step 601, sensor data is received from the one or more sensors 310. As described previously, these sensors 310 may include one or more temperature sensors 401, humidity sensors 402, seismic sensors and / or motion sensors 403. Hence, step 601 may involve receiving one or more of temperature, humidity and I or motion data. The sensors 310 may be arranged as described previously. Generally, the sensor data provides an indication of heat energy generated by the user (e.g., via sweating) and / or their movement and / or heartbeat. This data may be collected as time-series data, such that an amount of heat energy generated by the user per unit time can be determined. At step 602, sleep state data indicative of a sleep state of the user is obtained. The sleep state data is determined based on the received sensor data. This sleep state data may be determined in any of the manners described previously. For example, based on detected changes in the temperature and I or humidity of the fluid in the fluid channels 307 and / or changes in detected motion of the bed cover 300 or the user, and / or changes in vibration that correspond with changes to the user’s heartbeat. As before, the sleep state data may identify whether the user is in the process of transitioning, or ready to transition, from one sleep state to another. In some examples, determining the sleep state of the user may involve determining an amount, or a rate at which the user is generating heat energy. If the amount, or rate, is determined as exceeding a threshold value, this may be indicative of the user transitioning to a deeper sleep state by virtue of lowering their core body temperature. Different sleep states and sleep state transitions may be associated with different thresholds in the amount or rate of heat energy generation. At step 603, the flow of fluid through the one or more fluid channels 307 is controlled based on the obtained sleep state data. This may involve for example, switching one or more fluid drivers 308 on or off, extending or decreasing the time for which the fluid drivers 308 are scheduled to be switched on and I or increasing or decreasing the speed of the fluid drivers 308. More generally, this may involve regulating the flow of fluid through the fluid channels 307 via operation of the one or more fluid drivers 308. Different determined sleep states may be associated with different fluid driving rates, for example. In some examples, step 603 may comprise controlling the rate at which fluid (or fluids, where respective push and pull channels receive different fluids, or fluids having different properties) is (or are) circulated through the bed cover 200, 300. The arrangement of fluid channels and fluid drivers is such that fluid is circulated into and out of the user’s local sleep environment. In some examples (a first mode of operation), responsive to the user being detected as transitioning to a deeper sleep state, the fluid drivers may be controlled to stop or slow the rate at which fluid circulates through the bed cover 200, to allow the user to naturally maintain a core body temperature that is optimal for that sleep state. This may correspond to the situation where the user is identified as having shed sufficient heat energy to begin transitioning to a deeper sleep state, such as stage 3 of NREM sleep. In such examples, the fluid driving rate of at least some of the fluid drivers is reduced, to ensure that the air flow generated across the user’s body does not interfere with the user’s ability to transition to the deeper sleep state. In such a situation, it may be desirable to allow the user to naturally thermoregulate their core body temperature. In these examples, it may be that the fluid drivers run most of the time to prevent a build-up of heat and moisture within the vicinity of the user. The fluid driving rate may be increased once the user is determined as no longer transitioning to a deeper sleep state. In some examples, if it is determined that the user is transitioning to a deeper sleep state, but the heat energy being released per unit time is staying above a threshold amount, the work rate of the fluid drivers may be increased, to prevent the build-up of heat and sweat from preventing the user from remaining in, or continuing to transition to, the desired sleep state. In some examples (a second mode of operation), responsive to the user being detected as transitioning to, or being ready to transition to, a deeper sleep state, the rate at which fluid is driven through the fluid channels may be increased. For example, the work rate of the fluid drivers may be increased, in anticipation of the user dissipating more heat energy as they lower their core body temperature. Alternatively, or in addition, the number of active fluid drivers may be increased, and I or the duration for which they are scheduled to be active. In such examples, once it is determined that the user has completed or is likely to complete the transition, the fluid driving rate of the one or more fluid drivers is reduced. In some examples, different sleep states may be associated with different fluid driving rates, e.g. the speed, duration and / or number of active fans may be increased in proportion to the amount of heat energy that the user is detected as, or predicted, to generate as they transition to a deeper sleep state. The amount of heat energy generated by the user will correlate with their sleep states and the transitions therebetween. Whether or not the fluid driving rate is increased or decreased may depend on the specific sleep state transition that is determined for the user. In some examples, the user may be able to select which of the first or second modes of operation is used to control the fluid driving rate of the one or more fluid drivers. The method 600 shown in Figure 6 may correspond to the method executed by the control unit 306 described previously, for example. The obtained sleep state data may be used by the control unit 306 to make a control decision with respect to control of the fluid drivers 308. Alternatively, the obtained sleep state data may comprise instructions which themselves have been generated based on sleep state analysis performed at a separate device, such as a connected remote device 407. In some examples, the processing may be distributed between the control unit 40 and the remote device 407. In some examples, the method 600 may further comprise receiving data associated with one or more fluid drivers 308. This data may provide an indication of the operation status of the fluid drivers 308, such as duty cycle data, work rate data, speed data, etc. The obtained sleep state data may be determined based on both the received sensor data and the data associated with the one or more fluid drivers 308. For example, if the fluid driving rate has been increased but the amount of heat energy generated by the user per unit time is staying above a threshold level, this may indicate that the user is transitioning to a yet deeper sleep state. Alternatively, or in addition, if is determined that the user is transitioning to a deeper sleep state but the amount of heat energy being generated by the user is staying above a threshold level, then this may indicate that the user is at risk of transitioning out of that sleep state. In such an instance, the fluid driving rate of the fluid drivers may be increase further, to prevent a build-up of heat and I or moisture within the user’s sleep environment from interfering with the user’s transition to that sleep state. In some examples, the method 600 may further comprise determining the sleep state data, i.e., rather than simply obtaining it or instructions that have been generated based on the determined sleep state data. For example, the method 600 may comprise determining whether the user is transitioning between sleep states based on a comparison of the sensor data and fluid driver data with one or more threshold values. Figure 7 shows an example of a method 700 for controlling the fluid driving rate of fluid drivers based on determined sleep state data. At step 701, sensor data is obtained for a first time period. This sensor data corresponds to the sensor data described previously, i.e. measured values of one or more of: temperature, humidity, motion, and vibration. In some examples, the data may be time-series data. At step 702, a rate of change in the measured sensor values is determined. For example, a rate of change in the detected temperature, humidity, motion and / or vibration. At step 703, the rate of change of the measured sensor values is compared with one or more threshold values. As described above, this may involve comparing the measured temperature, humidity and / or motion values against one or more threshold values. If the rate of change of temperature and / or humidity exceeds a threshold value, this may indicate that the user is transitioning to, or is ready to transition to, a deeper sleep state. Likewise, if the detected motion drops below a threshold value, this may also indicate that the user is transitioning to, or is ready to transition to, a deeper sleep state (e.g., stage 3 NREM sleep). Alternatively, or in addition, a drop in heartrate detected by the seismic sensor may further indicate that the user is transitioning to a deeper sleep state. It will be appreciated that different sensor measurements may be associated with different respective threshold values, or that sensor measurements may be combined to form a single parameter, indicative of the user’s sleep state, which is then compared against a corresponding threshold value. In some examples, the temperature and I or moisture data may be used to determine an amount of heat energy being generated by the user per unit time. From this, a drop in the user’s core body temperature can be inferred. If the comparison of the received sensor data with one or more threshold values indicates that the user is not transitioning to, or not ready to transition to, a deeper sleep state, the process 700 may end or return to step 701. At step 704, operation of the one or more fluid drivers 308 is controlled. Although not shown as a separate step, step 703 may be equivalent to determining sleep state data for the user and hence operation of the fluid driver(s) 308 is controlled based on the determined sleep state data (as described previously, i.e. in accordance with the first and I or second modes of operation). At step 705, sensor readings over a subsequent time period are obtained for a given operation status of the fluid drivers 308. For example, step 705 may involve obtaining sensor data from the one or more sensors 310 and obtaining fluid driver data from the one or more fluid drivers 308. At step 706 a rate of change is determined for the sensor measurements obtained over the second time period. At step 707, the determined rate of change in the sensor values is compared with one or more threshold values. This may involve, for example, determining further sleep state data for the user based on the received sensor data and data associated with fluid drivers 308, such as work rate and duty cycle data. The determined sleep state may include whether the user is at risk of transitioning away from a deeper sleep state. If, at step 707 it is determined that a user is not at risk of transitioning away from the deeper sleep state, the method proceeds to step 708. At step 708 the fluid driving rate of the one more fluid drivers may be reduced. Step 708 may comprise at least one of: switching one or more of the fluid drivers 308 off, reducing a time for which the fluid drivers 308 are scheduled to be switched on, and reducing the speed at which they drive fluid through the fluid channels 307. Alternatively, the fluid driving rate may be maintained at the rate determined for that sleep state transition. Conversely, if at step 707, it is determined that the user is unlikely to successfully transition to the deeper sleep state, then the method proceeds to step 709. In such an instance, this may indicate that the user is at risk of over-heating and moving out of the desired sleep state transition. For example, if at step 704 if the fluid driving rate of the fans was increased (in accordance with the second mode of operation), but the temperature and I or humidity within the fluid channels has remained above a threshold level, this may indicate that a build-up of heat in the user’s local sleep environment is likely to impede the user’s ability to transition to a desired sleep state. At step 709, operation of the one or more fluid drivers 308 is modified further. This may involve one or more of: increasing the duration, speed and I or number of fluid drivers 308 that are active. Generally, this may correspond to increasing the fluid driving rate of the one or more fluid drivers 308, to encourage expulsion of fluid within the fluid channels 307 that has been heated by the user. In some examples, modifying the operation of the fluid drivers 308 may comprise adjusting the work rate or duty cycle of the fluid drivers 308. Although not shown as a further step, the fluid driving rate of the one or more fluid drivers may be reduced once it is determined that the user is no longer at risk of transitioning away from a desired sleep state and I or once the user is identified as having successfully transitioned to the desired sleep state. A computer program may be configured to provide any of the above-described methods. The computer program may be provided on a computer readable medium. The computer program may be a computer program product. The product may comprise a non-transitory computer usable storage medium. The computer program product may have computer-readable program code embodied in the medium configured to perform the method. The computer program product may be configured to cause at least one processor to perform some or all of the method. Various methods and apparatus are described herein with reference to block diagrams or flowchart illustrations of computer-implemented methods, apparatus (systems and / or devices) and / or computer program products. It is understood that a block of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, can be implemented by computer program instructions that are performed by one or more computer circuits. These computer program instructions may be provided to a processor circuit of a general purpose computer circuit, special purpose computer circuit, and / or other programmable data processing circuit to produce a machine, such that the instructions, which execute via the processor of the computer and / or other programmable data processing apparatus, transform and control transistors, values stored in memory locations, and other hardware components within such circuitry to implement the functions / acts specified in the block diagrams and / or flowchart block or blocks, and thereby create means (functionality) and / or structure for implementing the functions / acts specified in the block diagrams and / or flowchart block(s). Computer program instructions may also be stored in a computer-readable medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instructions which implement the functions / acts specified in the block diagrams and / or flowchart block or blocks. A tangible, non-transitory computer-readable medium may include an electronic, magnetic, optical, electromagnetic, or semiconductor data storage system, apparatus, or device. More specific examples of the computer-readable medium would include the following: a portable computer diskette, a random-access memory (RAM) circuit, a read-only memory (ROM) circuit, an erasable programmable read-only memory (EPROM or Flash memory) circuit, a portable compact disc read-only memory (CD-ROM), and a portable digital video disc readonly memory (DVD / Blu-ray). The computer program instructions may also be loaded onto a computer and / or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer and / or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions / acts specified in the block diagrams and / or flowchart block or blocks. Accordingly, the invention may be embodied in hardware and / or in software (including firmware, resident software, micro-code, etc.) that runs on a processor, which may collectively be referred to as “circuitry,” “a module” or variants thereof. It should also be noted that in some alternate implementations, the functions / acts noted in the blocks may occur out of the order noted in the flowcharts. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality / acts involved. Moreover, the functionality of a given block of the flowcharts and / or block diagrams may be separated into multiple blocks and / or the functionality of two or more blocks of the flowcharts and / or block diagrams may be at least partially integrated. Finally, other blocks may be added / inserted between the blocks that are illustrated. It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed systems and methods. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed systems and methods. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

1. An apparatus for supporting a user in transitioning from one sleep state to another, the apparatus comprising:a flexible cover for covering at least part of a user when the user lying on a surface, the cover comprising:at least two fluid channels;a first fluid driver for driving a fluid into the cover through a first fluid channel;a second fluid driver for driving a fluid out of the cover through a second fluid channel;one or more temperature and I or humidity sensors positioned within at least one of the fluid channels for sensing a temperature and I or humidity of the fluid in the corresponding fluid channel;the apparatus further comprising a computer processor configured to:obtain temperature and / or humidity data from the one or more sensors;obtain control instructions for at least one of the fluid drivers; andcontrol at least one of the fluid drivers based on the obtained control instructions, wherein the control instructions correspond with sleep state data determined for the user based on the obtained sensor data.

2. The apparatus according to any preceding claim, wherein the sleep state data identifies whether a user is in transition from one sleep state to another.

3. The apparatus according to any preceding claim, wherein the computer processor is configured to determine, based on the obtained temperature and / or humidity data, the sleep state data indicative of the sleep state of the user.

4. The apparatus according to any preceding claim, wherein, if the sleep state data identifies a transition from one sleep state to another, the computer processor is configured to control at least one of the first and second fluid drivers to drive the fluid through the corresponding respective fluid channel.

5. The apparatus according to claim 3 or 4, wherein the computer processor is configured to determine the sleep state data based on a rate of change of the heat generated by the user.

6. The apparatus according to claim 5, wherein, if the rate of change of the heat generated by the user is determined as being above a threshold, the computer processor is configured to control at least one of the fluid drivers to drive the fluid through the fluid channels.

7. The apparatus according to any preceding claim, wherein the computer processor is configured to determine a rate at which fluid is to be driven through at least one of the fluid channels based on the sleep state data,and to control at least one of the fluid drivers to drive the fluid through the fluid channels at the determined rate.

8. The apparatus according to any preceding claim, wherein each fluid channel extends linearly across at least part of the cover.

9. The apparatus according to any preceding claim, wherein each fluid channel comprises a plurality of apertures for allowing air to permeate into and out of the fluid channel.

10. The apparatus according to claim 9, wherein the first fluid driver is arranged to draw air into the first fluid channel, and wherein the plurality of apertures of the first fluid channel allow air to permeate out of the cover through a lower surface of the cover, towards the user.

11. The apparatus according to claim 9 or claim 10, wherein the second fluid driver is arranged to drive air out of the second fluid channel, the plurality of apertures of the second fluid channel allowing air proximate to the user to enter the second fluid channel from beneath the cover, away from the user.

12. The apparatus according to any of claims 9 to 11, wherein each channel comprises a respective fluid driver at one end thereof, and wherein the size of the apertures in each channel increases with distance from the corresponding fluid driver.

13. The apparatus according to any of claims 9 to 12, wherein the one or more temperature sensors and / or the one or more humidity sensors are located proximate to one or more of the plurality of apertures.

14. The apparatus according to any preceding claim, wherein each fluid channel comprises a fluid driver at a first end; anda second end of the fluid channel is closed such that fluid cannot enter or leave the fluid channel at the closed end.

15. The apparatus according to claim 14, wherein the first fluid driver is arranged to drive the fluid into the first fluid channel through the first end, and wherein the second fluid driver is arranged to drive the fluid out of the first end of the second fluid channel.

16. The apparatus according to any preceding claim, further comprising one or more motion sensors configured to detect movement of the cover as a result of movement of the user,wherein the computer processor is further configured to obtain motion data from the one or more motion sensors, and to determine the sleep state data based on the obtained motion data.

17. The apparatus according to any preceding claim, wherein the computer processor is further configured to receive duty cycle data from at least one of the fluid drivers, and to determine the sleep state data based on the received duty cycle data.

18. The apparatus according to any preceding claim, wherein the fluid comprises ambient air and I or cool air received from a source of cool air.

19. The apparatus according to any preceding claim, wherein at least one of the fluid drivers includes an impeller.

20. The apparatus according to any preceding claim, wherein the cover includes a duvet.

21. A method of supporting a user’s transition from one sleep state to another by controlling the flow of fluid within a flexible bed cover, the flexible bed cover comprising at least two fluid channels, and at least two fluid drivers, a first of the fluid drivers being arranged to drive fluid into the cover through a first fluid channel, a second of the fluid drivers being arranged to drive fluid out of the cover through a second fluid channel;wherein one or more temperature and I or humidity sensors are positioned within at least one of the fluid channels, the method comprising:obtaining sensor data from the temperature and I or humidity sensors;obtaining, based on the obtained sensor data, control instructions that correspond with sleep state data determined for the user based on the obtained sensor data, the sleep state data being indicative of a sleep state of the user; andcontrolling the flow of fluid through at least one of the fluid channels within the bed cover based on the obtained control instructions.

22. A computer program product including computer program code configured, when executed on a computer processor, to control a data processor to undertake the steps of the method of claim 21.533

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