Patent Publication Number: US-2020281526-A1

Title: Hat and monitoring system

Description:
The present invention relates to a hat for a neonate, and a monitoring system for a neonate, in particular the physiological condition of a neonate including but not limited to heart rate; breathing rate; and Oxygen Saturation SpO2). 
     Newborn babies and those up to 28 days of life (neonates) in the UK are generally given a bonnet or hat immediately following birth, to help them maintain an appropriate body temperature. 
     A number of commercially produced hats for neonates are available as part of continuous positive airway pressure (CPAP) systems. Makers include Carefusion, Fisher and Paykel, and Intersurgical. Such hats are available in a range of sizes. 
     One difficulty with a number of existing hats is in conveniently obtaining access to the neonate&#39;s head, for instance to perform a cranial ultrasound procedure. A further problem arises with the interaction of the hat and a CPAP mask and associated tube(s). It is necessary for the CPAP mask to be supported in the correct position on the neonate&#39;s head, for instance by a connection to a hat. Injuries can be inflicted on neonates (e.g. on the nasal septum) by an inappropriately fitted CPAP mask, so it is important to ensure that such systems are fitted appropriately. 
     In the UK, around 10% of newborn babies need some form of resuscitation at birth: 85,000 per year in the UK, 400,000 in the USA and at least 13,500,000 worldwide. Accurate monitoring of heart rate is vital to guide such interventions: both to identify when intervention is required, and to monitor how the newborn (neonate) is responding to the resuscitation. The stethoscope is the current standard of care for monitoring the neonate heart rate in the key moments following birth. However, the stethoscope&#39;s use is subject to delays and errors, which can ultimately have a severe impact on the future wellbeing of the child. 
     US2010/0249557 discloses a hat for a neonate that includes a pulse oximeter, for monitoring the heart rate of a neonate. U.S. Pat. No. 8,768,424 describes a photoplethysmography device for measuring heart rate. 
     According to a first aspect of the invention, there is provided a hat for a neonate comprising: a central portion; a first side portion and second side portion attached to opposite sides of the central portion; a first fastener; a top flap and a second fastener; 
     wherein the hat has an unfolded configuration in which the first and second portions extend away from each other from the central portion in opposite directions; and a worn configuration in which the hat wraps a neonate&#39;s head with the central portion in contact with the back of the neonate&#39;s head, the first portion wrapped around a first side of the neonate&#39;s head and the second portion wrapped around a second side of the neonate&#39;s head; 
     the first and second portions being configured to be fastened together in the worn configuration by the first fastener so that the first portion, central portion and second portion together define a hat rim encircling the neonate&#39;s head; and 
     the top flap is configured to cover the top of the neonate&#39;s head in the worn configuration, with the top flap being configured to be fastened to at least one of the first, central and second portions by the second fastener. 
     The term neonate may refer to an infant that is less than four weeks old. 
     The unfolded configuration of the hat makes it easy to put on a neonate, for example by placing the neonate&#39;s head on the central portion (with the hat in an unfolded configuration) and wrapping the hat around the head. 
     In some embodiments the central portion can be pulled backwards to reveal the fontanelle to allow access for scanning and other medical procedures. 
     The hat may be substantially T-shaped when in an unfolded configuration, with the top flap being connected to the central portion. 
     The first and second portions may be configured to overlap on the neonate&#39;s forehead when fastened together by the first fastener. 
     The first fastener and/or the second fastener may comprise a hook and loop fastener. Hook and loop fasteners are quick and easy to fasten and unfasten, and provide reliable and secure attachment (especially, but not exclusively, in the context of a single use item). 
     In some embodiments the loop portion of the first fastener and/or second fastener may be provided by a fabric from which the hat is made, rather than by a patch of loop material attached to the fabric. This may give more flexibility in where the fastener can be attached. 
     The first fastener may be configured to provide a plurality of fastening positions so as to allow a range of adjustment of the length of the hat rim, so as to accommodate a range of neonate head sizes. 
     The range of adjustment may be at least 1 cm, or at least 0.5 cm, or 2 cm. 
     The hat may further comprise a strap for supporting a continuous tube (e.g. a continuous airway pressure or CPAP tube) adjacent to the neonate&#39;s forehead when the first, central and second portions encircle the neonate&#39;s head. 
     The strap may comprise an elastic fabric material. The strap may comprise a strap fastener, for fastening the strap to at least one of the first and second portions. 
     The strap may be fixed at one end to one of the first or second portion, and the other end of the strap may be securable to the other of the first or second portions using the strap fastener. The detachable strap may be securable to either the first or second portions via hook and loop attachments. 
     The strap may comprise a friction enhancing lining on an inner surface thereof. The friction enhancing lining may comprise silicone rubber. 
     The hat may comprise a first plurality of eyelets in the first portion adjacent to the hat rim, and a second plurality of eyelets in the second portion adjacent to the hat rim. The first and second plurality of eyelets may be for securing a CPAP mask to the neonate&#39;s face using CPAP cords that thread into the eyelets. The plurality of eyelets in each of the first and second portion may provide a range of CPAP mask securing locations or endotracheal tube securing locations, or securing locations for other fittings. 
     The eyelets may be strengthened by stitching a hem around each eyelet. This may provide a firm fixation point for the securing tethers of either a CPAP mask or endotracheal tube. 
     The hat may comprise at least one external loop through which a tube (such as a CPAP tube, or an intubation tube) may be supported adjacent to the exterior of the hat. 
     The at least one external loop may comprise a first and second external loop, arranged to be positioned on either side of the neonate&#39;s forehead when the hat is worn. 
     The hat may comprise a first dart between the first and central portion and a second dart between the second and central portion. A third dart may be provided in the central portion, the third dart arranged to improve the conformation of the central portion with the back of the neonate&#39;s head. 
     The first and second dart may extend substantially toward the rim from a top edge of the hat, the top edge being on the opposite side of the hat to the hat rim. 
     The second fastener may comprise a plurality of fastening locations spaced around the perimeter of the top flap. 
     The first, second, and central portions, and the top flap, may be substantially formed from a fabric material. 
     The fabric material may be stretchable substantially in one direction only. The direction may be along the circumference. This enables the hat to provide a comfortable fit, while accommodating a range of head sizes and shapes. 
     The fabric may have at least an inner ply and an outer ply. The inner ply may be larger in extent than the outer ply (or the outer ply may be larger than the inner ply). The outer ply may be provided in regions of the inner ply. 
     According to an aspect of the invention, there is provided a hat for a neonate comprising an inner fabric ply and an outer fabric ply, a first hole through the inner fabric ply at a first location and a second hole through the outer fabric ply at a second location, wherein, when the hat is worn by a neonate, the first location is adjacent to the forehead and the second location is adjacent to the rear of the head, the first and second hole allowing an optical physiological sensor lead to be threaded through a space between the inner and outer plies between the first and second holes. The inner ply may be larger in extent than the outer ply (or the outer ply may be larger than the inner ply). The outer ply may be provided in regions of the inner ply. 
     The inner ply may comprise a material that is stretchy in a single direction. The outer ply may comprise a hook accepting material (for a hook and loop fastener). 
     The optical physiological sensor may comprise at least one of: an optical heart-rate sensor, a pulse oximeter, and optical breathing sensor, an optical blood flow sensor, or any other optical physiological sensor. 
     The hat of the first aspect may further comprise an inner hole through the inner fabric ply at a first location and an outer hole through the outer fabric ply at a second location. The first location may be in one of the first portion and second portion. The second location may be in the central portion or the other of the first and second portion. The inner and outer hole may allow an optical physiological sensor lead to be threaded through a space between the inner and outer plies between the inner and outer holes. 
     The inner hole may be a first inner hole, and the hat may further comprise a second inner hole through the inner fabric ply, spaced apart from the first inner hole by 0.5 cm to 3 cm. 
     The inner holes may be through the inner fabric ply and not the outer fabric ply. 
     The outer hole may be a first outer hole, and the hat may further comprise a second and third outer hole disposed between the inner hole and the first outer hole. 
     The outer holes may be through the outer fabric ply and not the inner fabric ply. 
     The second and third outer holes may be spaced apart from each other by between 0.5 cm and 3 cm. 
     The second and third outer holes may be arranged to allow an optical physiological sensor lead to be threaded between the second and third outer holes, so as to enable the optical physiological sensor lead to be cut between the second and third outer holes while the hat is worn. The physiological sensor may then be conveniently removed from the hat. 
     According to a second aspect, there is provided an optical physiological sensor comprising: a flexible circuit board, a light emitter and a light detector; 
     the flexible circuit board having:
         a sensor portion to which the light emitter and light detector are connected;   a module portion including contacts for electrically connecting the light emitter and light detector to a readout module; and   an elongate lead portion between the sensor portion and module portion.       

     The elongate lead portion may be flexible. 
     The light emitter may comprise a plurality of light emitting elements. 
     The sensor portion may comprise a package that includes both the light emitter and light detector. 
     The light emitter may comprise a light emitting element with a first output wavelength, and a light emitting element with a second, different output wavelength. 
     The light emitter may further comprise a light emitting element with a third output wavelength, different from the first and second output wavelengths. The light emitter may further comprise a light emitting element with a fourth output wavelength, different from the first, second and third output wavelengths. 
     The flexible circuit board may include a tang extending away from the sensor portion in a different direction to the lead. The tang may extend in a direction at 180 degrees to the lead, or at another angle. 
     The light detector may be a single photodetector or an array of detectors in the form of a multi-pixel camera. The light detector may be operable to detect wavelengths within and/or outside the visible spectrum. 
     The tang may be an elongate member. The tang may extend away from the sensor portion at an angle of between 135 and 155 degrees from the lead, or between 170 and 190 degrees from the lead (e.g. at substantially 180 degrees from the lead). 
     The tang may comprise at least one lateral projection or recess configured to assist in preventing withdrawal of the tang through a hole (e.g. the second inner hole). The tang may comprise a barbed or hammerhead shaped structure, with a sloped edge to enable the tang to be inserted through a hole (e.g. the second inner hole), and a lateral edge (substantially perpendicular to a direction of insertion) for inhibiting withdrawal of the tang from the hole in which it is inserted. The tang may comprise a substantially circular or spherical ‘blob’ for assisting in retaining the tang in the hole. The applicant has found that a curved feature (e.g. a curved projection) may make removal of the tang easier, at the same time as providing an acceptable degree of retention within the hole (e.g. second inner hole) 
     The width of the lead may be less than 1 cm. The thickness of the lead may be less than 0.5 mm. 
     The module portion may comprise a substantially rigid planar element for supporting the contacts. 
     The module portion may comprise a ferromagnetic element. 
     The hat of the previous aspects may further comprise the optical physiological sensor of the second aspect. 
     At least part of the elongate lead portion of the optical physiological sensor may be disposed between an inner and an outer ply of the hat. 
     The sensor portion may be supported by the hat at an inner surface of the hat near the rim of the first portion or the second portion, such that the sensor portion is positioned on a neonate&#39;s forehead when the hat is worn. 
     The sensor portion may be supported between the first inner hole and the second inner hole, the first inner hole receiving the elongate lead portion, and the second inner hole receiving the tang. 
     The elongate lead portion may be threaded between the second and third outer holes, so as to enable the lead to be cut between the second and third outer holes while the hat is worn. The sensor portion may then be conveniently removed from the hat. 
     The sensor portion may comprise an transparent element, arranged to be between the light emitter and light detector, and the skin, in use (i.e. covering the light emitter and light detector). The transparent element may be less than 1 mm thick. The transparent element may comprise silicone. The transparent element may be transparent at the wavelengths emitted by the light emitter. The thickness of the transparent element may be less than 1 mm, or less than 0.5 mm. 
     The transparent element may comprise a region that is adhesive or tacky to skin. 
     The light emitters and detectors may be separated from each other by a baffle to avoid light shunting. 
     The sensor portion may further comprise at least one electrode for making an electrical connection to the skin of a neonate. The at least one electrode may be a wet electrode, or may be configured for coupling to skin via a hydrogel or by capacitive coupling. The at least one electrode may be suitable for performing an ECG measurement. 
     The sensor portion may comprise an array of sensors, the array of sensors comprising at least one optical sensor and at least one electrode. 
     According to a third aspect, there is provided a readout module for an optical physiological sensor, wherein the readout module comprises: 
     an electrical power store for powering the readout module; 
     an electronic circuit for providing a drive signal to a light emitter of the physiological sensor and for receiving the signal from a light detector of the physiological sensor; 
     a processor for processing the signal from the light detector to produce data; and 
     a wireless transmitter, configured to wirelessly transmit the data from the readout module to a base station. 
     The readout module may be further configured to obtain an ECG measurement from the at least one electrode of the sensor module. The processor may be configured to process a signal derived from the at least one electrode to produce ECG data, and the wirelessly transmitted data may comprise ECG data. 
     The readout module may further comprise: a housing containing the electrical power store, the electronic circuit and the wireless transmitter, and a cradle configured to receive the housing and a module portion of an optical physiological sensor (e.g. according to a previous aspect). 
     The readout module may further comprise a permanent magnet for attaching a module portion of an optical physiological sensor to the readout module by attracting a ferromagnetic element of the module portion. 
     The readout module may further comprise a connector for engaging a plurality of electrical contacts of a module portion of an optical physiological sensor. 
     The connector may comprise a plurality of pogo pins. 
     The readout module may comprise a status indicator configured to display an indication of the status of the readout module. The status indicator may be a light emitting element. The light emitting status indicator may be configured to emit at least two different colours. The status indicator may be configured to indicate an amount of charge in the electrical power store. The status indicator may be configured to indicate a fault status. 
     The readout module may be waterproof according to the IPX-7 standard. 
     The processor may encrypt the signal from the light detector to produce encrypted raw sensor data for transmission. Alternatively the processor may be configured to process the raw data locally (e.g. in real time, or with a delay of less than 1 second) to determine at least one of: heart rate, breathing, SpO2 and other relevant physiological signals. This may allow a reduced bandwidth of data to be transmitted thereby saving power in the module. 
     According to a fourth aspect, there is provided a monitoring system for a neonate, comprising a readout module according to the third aspect, and the optical physiological sensor of any previous aspect. 
     The system may include the hat of any previous aspect. 
     According to a fifth aspect, there is provided a receiving station comprising a display and a docking portion for receiving a readout module of an optical physiological sensor, wherein: 
     the receiving station is configured to wirelessly receive data from a readout module of an optical physiological sensor, and to display an indication of a physiological parameter (e.g. heart rate, breathing rate, SpO2, blood flow etc) of the neonate on the display; 
     the docking portion comprises charging contacts by which the receiving station is operable to charge the readout module. 
     The receiving station may further comprise a ferromagnetic element in the docking portion, to enable a readout module to be fixed in place in the docking portion using a permanent magnet of the readout module. 
     The docking portion may be a first docking portion, and the receiving station may comprise a second docking station for receiving and charging a second readout module. 
     The receiving station may further comprise an indicator operable to provide a visual indication every 6 seconds. 
     The indicator may comprise a light source (e.g. an LED) configured to flash or change state every 6 seconds. For example, the indicator could stay on for 6 seconds, then go off for 6 seconds, or briefly illuminate every 6 seconds. 
     The indicator may be used to improve the accuracy of a stethoscope reading of heart rate. At present, the clinician taking a stethoscope heart rate must count a 6 second interval at the same time as counting the heart beats (which can be cognitively challenging). The accuracy of a clinician&#39;s stethoscope reading may be improved with the use of the timing indicator. 
     The receiving station may further comprise non-volatile data storage. The receiving station may be configured to store data from the readout module of the optical physiological sensor and/or a time history of the physiological parameter. 
     The receiving station may be configured to process the data from the readout module of the optical physiological sensor to determine at least one of: heart rate, breathing rate, SpO2, and blood flow. 
     The receiving station may be configured to use the display to indicate at least one of: heart rate, breathing rate, SpO2, and blood flow. 
     According to a sixth aspect, there is provided a monitoring system for a neonate comprising the receiving station of the fifth aspect, and a readout module according the third aspect. The monitoring system may include the hat of any previous aspect. 
     Any of the features of any aspect may be combined with any other aspect, including the optional features. 
    
    
     
       Embodiments of the invention will be described, purely by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a view of a system according to an embodiment; 
         FIG. 2  is a view of a neonate wearing a hat according to an embodiment; 
         FIG. 3  is an exploded diagram of a readout module according to an embodiment; 
         FIG. 4  is a view of a hat according to an embodiment in an unfolded configuration from the exterior side of the hat; 
         FIG. 5  is a view of the hat of  FIG. 4  in an unfolded configuration from the interior side of the hat; 
         FIG. 6  is a view of the hat of  FIG. 4  with a neonate positioned on the central portion of the hat, ready for the hat to be wrapped around the neonate&#39;s head; 
         FIG. 7  is a view of the hat of  FIG. 4  in a worn configuration on the head of a neonate, also showing an optical physiological sensor and associated readout module; 
         FIG. 8  is a diagram of the inner side of a hat according to an embodiment; 
         FIG. 9  is a diagram of the outer side of the hat of  FIG. 8 ; 
         FIG. 10  is a diagram of the inner side of a hat according to a further embodiment; 
         FIG. 11  is a diagram of the outer side of a hat according to the further embodiment 
         FIG. 12  is a diagram of the inner side of a hat according to an embodiment; 
         FIG. 13  is a diagram of the outer side of a hat according to an embodiment; 
         FIG. 14  is a view of a hat according to an embodiment being worn by a neonate, and further including a CPAP mask and associated tubes; 
         FIG. 15  is an exploded diagram of a module portion of a pulse oximeter according to an embodiment; 
         FIG. 16  is an exploded diagram of a sensor portion of an optical physiological sensor according to an embodiment; 
         FIG. 17  is a view of the module portion of the optical physiological sensor of  FIG. 14 , with the module portion partly inserted into a cradle of a readout module; 
         FIG. 18  is a view of the cradle of  FIG. 16  with the module portion fully engaged with the cradle, and with a readout module housing engaged with the cradle; 
         FIG. 19  is view of a receiving station according to an embodiment, with a first and second readout module inserted in a first and second docking portion of the receiving station; 
         FIG. 20  is a view of the receiving station of  FIG. 19  hanging from an edge of a resuscitaire. 
     
    
    
     Referring to  FIG. 1  a system  100  for neonatal physiological monitoring is shown, comprising: a hat  200 , optical physiological sensor  300 , readout module  400  and base station  500 . 
     The hat  200  is worn by a neonate  120 , with the neonate lying on a resuscitaire  110 . The optical physiological sensor  300  is supported by the hat  200  adjacent to the skin of the neonate  120 , so as to monitor the physiological signals of the neonate  120 . The optical physiological sensor  300  includes a lead, connecting a light emitter(s) and light detector(s) of the optical physiological sensor  300  to a readout module  400 . The readout module  400  provides drive signals to the light emitter(s), and receives signals from the light detector(s). The readout module  400  comprises a wireless transmitter, configured to transmit data (either raw physiological or processed physiological data) derived from the light detector(s) signals (e.g. heart rate, breathing rate, SpO2, blood flow, etc) to the base station  500 . The base station  500  is configured to receive the data from the readout module  300 , and to display physiological signals of the neonate. 
     As shown in  FIG. 2  the hat  200  supports a sensor portion  302  of the optical physiological sensor  300  adjacent to the skin of the neonate  120 , so as to enable a physiological signal measurement. The sensor portion  302  is preferably supported adjacent to the forehead of the neonate  120 , which is a good location to perform measurements. 
     A pressure indicator may be woven into the fabric that indicates if the hat is too tight. The pressure indicator may comprise a region of zig zag stitching, the length of which indicates an amount of extension (strain) of the fabric. The pressure indicator may indicate that the hat is too tight when the pressure indicator exceeds a predetermined length (e.g. 1 cm). This may ensure that the hat does not cause any facial congestion or oedema or worsen any existing facial oedema. 
     The elongate lead may be formed into a curved region, arranged to conform more easily with the curvature of the head. This may ensure that the elongate lead follows the contours of the baby&#39;s head, reducing the likelihood of pressure damage. The optical physiological sensor  300  (examples of which will be described in more detail later) includes an elongate lead  301  connecting a module portion of the sensor  300  (for connection to the readout module  400 ) to the sensor portion  302 . The hat  200  may be configured to support the lead  301  against the opposite side of the neonate&#39;s head to the readout module  400 , so that the lead  301  passes under the neonate&#39;s head on its way to the readout module  400 . This configuration helps to limit any movement of the sensor portion  302  relative to the neonate&#39;s head, resulting in improved reliability and accuracy of performing the optical physiological measurement (e.g. a photoplethysmogram measurement). 
       FIG. 3  is an exploded diagram of a readout module  400  according to an embodiment. In this example, the readout module  400  comprises: an upper housing  402   a , a lower housing  402   b , a seal element  403 , fasteners  404 , electrical power store/battery  405 , readout circuit board  406 , readout circuit (including processor, power management, LED drive, detection circuit and wireless transmitter)  407  (on the reverse side of the readout circuit board  406 ), connectors  408 , permanent magnets  409  and an optional semi-permeable membrane  410 . 
     The upper housing  402   a  and lower housing  402   b  engage with each other (e.g. by a snap fit), and together define a housing of the readout module  400 . The seal element  403  ensures that the housing is waterproof, for example to IPX7 standard. The optional semi-permeable membrane  410  may comprise a gas permeable hydrophobic membrane such as Gore-Tex®, so as to allow any undesirable chemical gases or vapours within the housing  402  to escape while maintaining a waterproof housing. 
     The readout circuit board  406  is secured to the lower housing  402   b  by two screw type fasteners  404 . On one side of the readout circuit board  406  is an electrical power store  405 , which may be re-chargeable. The power store  405  may comprise a re-chargeable battery (e.g. lithium-ion), or a supercapacitor. On the reverse side of the readout circuit board  406  is disposed an electrical circuit  407 . The electrical circuit  407  is configured to provide output signals for driving a light emitter  310  of an optical physiological sensor  300 , and to readout signals from a light detector  311  of the optical physiological sensor  300 . In noise challenged environments the light emitter  310  can be driven in a modulated fashion and the detector  311  operated in a heterodyne lock in mode. There may be a plurality of light detectors  311  and light emitters  310 . 
     The readout circuit  407  may be configured in accordance with the teaching of U.S. Pat. No. 8,768,424. In some embodiments, the readout circuit  407  may comprise a processor, configured to process signals from the light detector  311  to determine at least one of: heart rate and a level of blood oxygen saturation, breathing rate and blood flow. Alternatively, the readout circuit  407  may transmit data in a more raw form to the receiving station  500 , and the receiving station may process the data to determine at least one of heart rate, a level of blood oxygen saturation, breathing rate, blood flow and ECG measurement. 
     Modulation of the light emitters may be necessary to avoid noise (both optical and electrical) but also to separate the different wavelengths deployed. To strengthen the selectivity a bandpass filter can be deployed before the ADC and subsequent digital lock in. Alternatively an analogue demodulator such as a Gilbert cell and low pass filter can be deployed in the analogue detection path. 
     In another electronic design implementation, the wavelengths can be transmitted in a time division multiplexing format (effectively DC version) and ambient background can be removed by the transmission of a null signal. 
     The readout module  400  may comprise a pair of permanent magnets  409 , which are used to maintain engagement between the readout module  400  and the receiving station  100  (e.g. during charging), and between the connectors  408  of the readout module  400  and contacts of a module portion  305  of the optical physiological sensor  300 . 
     The connectors  408  may comprise at least one pogo-pin type connector. Pogo pin connectors comprise a telescopic sprung contact, for making reliable contact without the need for a plug type connector. The pogo-pins may be arranged in a rectangular or circular array. 
     The readout module  400  may be configured to obtain an ECG measurement from at least one electrode in contact with the skin of the neonate. 
       FIGS. 4 to 14  each show various views of hats according to embodiments of the invention. Although there are differences between the embodiment shown in  FIGS. 4, 5 and 6 , the embodiment shown in  FIGS. 8 and 9 , the embodiment shown in  FIGS. 10 and 11 , and the embodiment shown in  FIGS. 12 and 13 , a large number of features are common to each. The description below relates to each of the example embodiments unless otherwise noted. 
     The hat  200  is configured to wrap around a neonate&#39;s head, with the central portion  201  in contact with the back of the neonate&#39;s head. The first portion  202  is arranged to wrap around a first side and the forehead of the neonate&#39;s head, and is configured to carry a sensor portion  302  of an optical physiological sensor  300 . 
     As can most clearly be seen in  FIG. 6 , the hat  200  is arranged to bring the sensor portion  302  into contact with the forehead of a neonate  120  when the hat  200  is worn. The second portion  203  is arranged to wrap around the second side and the forehead of the neonate&#39;s head, overlapping with the first portion  202 , so as to encircle the neonate&#39;s head with the first, central and second portions  201 ,  202 ,  203  (as shown in  FIGS. 7 and 10 ). 
     The hat  200  comprises a first fastener  208  arranged to fasten the first and second portions  202 ,  203  together in the worn position. The first fastener  208  may be any suitable fastener (e.g. button, popper, etc), but preferably comprises a hook and loop type fastener. For instance, the first fastener  208  may comprise a hook portion  208   a  on an outer side of the first portion  202 , and a loop portion  208   b  on an inner side of the second portion  203  (as shown in  FIGS. 8 and 9 ). 
     In each example fastener described herein, the location of the hooks and loops can be reversed. For example, for the first fastener  208 , a hook portion may be located on the first or second portion, and the corresponding loop portion may be located on the other of the first or second portion. In some embodiments a loop portion of a fastener may be provided by a fabric from which the hat is made, without the need for a patch of a specific loop material. For example, the first fastener  208  may comprise a hook portion  208   a  on an outer side of the second portion  203 , and a corresponding loop portion  208   b  on an inner side of the first portion  202  (as shown in  FIGS. 12 and 13 ). 
     The top flap  204  in each example embodiment is attached to the central portion  201  of the hat (although in other embodiments, could conceivably be attached to the first or second portion  202 ,  203 ), and is operable to cover the top of a neonate&#39;s head when the hat  200  is worn. The top flap  204  includes a second fastener  211 , which conveniently comprises at least one hook portion.  FIGS. 4 and 5  show an embodiment with a single central hook portion;  FIGS. 8 and 9  show an embodiment with three hook portions, spaced apart along the inner edge of the top flap  204 , and  FIGS. 10 and 11  show an embodiment with three loop portions, spaced apart along the inner edge of the top flap  204 .  FIGS. 12 and 13  show an embodiment in which the second fastener  211  comprises two loop portions, on either side of the top flap  204 . The loop portions of the second fastener  211  may be provided on protruding “ears” that extend outward from the top flap  204 . 
     The second fastener  211  may further comprise complementary hook/loop portions, positioned on at least one of the first and second portions  202 ,  203 , so as to secure the top flap  204  over the top of the head of the neonate  120 , as shown in  FIGS. 9 and 11  and  FIGS. 12 and 13 . 
     A hat  200  according to an embodiment may be advantageous over prior art neonatal hats, independent of it including any physiological sensor. An unfolded hat arrangement that is subsequently wrapped around a neonate&#39;s head is easier to put on. As illustrated in  FIG. 6 , the neonate can simply be placed on the unfolded hat, then the hat wrapped around the neonate&#39;s head to provide an accurate and proper fit. The first fastener  208  may accommodate straightforward and simple adjustment of the size of the head, as it is being put on, in contrast to hats that do not unfold, where an incorrect judgement about the appropriate size hat can be remedied only by trying a different sized hat. In addition, the top flap  204  provides fast and easy access to the top of the neonate&#39;s head, enabling cranial ultrasound procedures to be performed without the need to disturb the hat  200 . 
     The hat  200  shown in  FIGS. 4 and 5  includes an optical physiological sensor  300  (and the hats shown in  FIGS. 8 to 13  are likewise for use with an optical physiological sensor). The physiological sensor  300  comprises a lead portion  301 , sensor portion  302 , and module portion  305  (the module portion shown in  FIG. 10 , but hidden by the readout module  400  in  FIGS. 4 and 5 ). The sensor portion  302  of the physiological sensor  300  is held in position by the lead portion  301  being routed through the hat  200 . In these example embodiments, the sensor portion  302  is further held in place using a tang  303  of the sensor  300  that is received in a hole in the hat  200 , but this is not essential (e.g. alternative further support means may be provided for the sensor portion  302 ). 
     The hat  200  may comprise an inner and outer fabric ply. In some embodiments a first outer hole  210  may be provided through the outer ply (and not the inner ply) in the central portion  201 , and a first inner hole  212  may be provided through the inner ply (and not the outer ply) in the first portion  202 . The first inner and first outer hole are thereby configured to allow the lead  301  of an optical physiological sensor  300  to be supported/concealed between the inner and outer ply, from a suitable location for the sensor portion  302  of the sensor  300 , to a location that is suitable for the lead  301  to exit the hat (e.g. in the central portion  201 , the first portion  202 , or the second portion  203 ). 
     A second inner hole  213  may be provided spaced apart from the first inner hole  212  (as shown in  FIGS. 5 and 9 ), by a distance sufficient to accommodate the sensor portion  302  of the sensor  300 . The distance between the first inner hole  212  and second inner hole  213  is preferably between 0.5 cm and 3 cm. The second inner hole  213  is arranged to receive a tang  303  of the sensor  300 , so as to support the sensor portion  302  in the proper position within the hat  200 . In other embodiments, alternative means may be used to secure the sensor portion  302  in position (e.g. a hook and loop fastener, or magnetic elements). 
     As shown in  FIGS. 8 to 11 , further outer holes may be provided to enable at least part of the sensor  300  to be removed from the hat  200  without disturbing the neonate  120 . A second outer hole  216  and third outer hole  217  may be provided, between the first inner hole  212  and the first outer hole  210 , where the lead  301  respectively enters and exits the gap between the inner and outer ply of the hat  200 . The lead  301  may thereby be routed to the exterior of the hat  200  between the second and third outer holes  216 ,  217  on its way to the first outer hole  210 . In addition to providing further support for the lead portion  301 , this arrangement allows the lead  301  to be conveniently cut while the hat is being worn. Once the lead  301  is cut, the part of the lead  301  that is attached to the module portion  305  can easily be withdrawn from the hat  200  by gently pulling it. This then allows the sensor portion  302  to be removed thereby limiting the time that the sensor is in contact with the skin. 
     The second and third outer holes  216 ,  217  are preferably positioned on an exterior part of the first portion  202  that is not overlapped by the second portion  201  when the hat  200  is worn. The second and third outer holes  216 ,  217  are preferably closer to the first inner hole  212  than the first outer hole  210 , so as to reduce the length of lead  301  remaining in the hat  200  if the lead  301  is cut between the second and third outer holes  216 ,  217 . The lead  301   a  between the second and third outer holes  216 ,  217  can be seen in  FIG. 10 . 
     In more general terms, the hat  200  may be provided with a first sensor hole and second sensor hole for retaining the sensor within the hat  200 . In the examples of  FIGS. 8 to 11 , the first and second sensor hole are the first and second inner hole  212 ,  213 , which are configured to receive the lead  301  and tang  303  of the sensor. In the example of  FIGS. 12 and 13 , the first and second sensor holes  222 ,  223  are through holes in the single-play material  231 , but not through the hook accepting second-ply  232 . The distance between the first and second sensor hole  222 ,  223  may be between 0.5 cm and 3 cm. A first outer hole  210  may be provided in the hook accepting outer ply  232  to allow a sensor lead to exit the space between the inner ply (e.g. SPL) and the outer ply. Each of the first sensor hole  222 , second sensor hole  223 , and first outer hole  210  may be arranged on a substantially straight line on the fabric hat material (before darts  207  are sewn). 
     In  FIGS. 8 and 9 , dotted lines indicate stitching, dot-dash lines indicate overlocking and the solid line represents the outline. Single layer holes (through either the inner or outer ply only) are indicated by a concentric rectangles with a dotted outer rectangle, and double layer holes (through both inner and outer ply) are indicated by a solid line concentric rectangles. The rim  214  of the hat is indicated in  FIGS. 8 to 11 . 
       FIGS. 12 and 13  show an embodiment in which a single ply material is used to form the hat (such as a spun-bond-laminate, or SBL material). The outline of the single-ply material  231  is shown in  FIGS. 12 and 13 . A further layer  232  (e.g. a second ply) of hook accepting material may be attached to the single-ply material  231 , in areas at which a loop fastener is intended to be attachable. In the embodiment of  FIGS. 12 and 13 , the completed hat  200  comprises a substantially continuous region of hook accepting material along the rim of the hat, for removably adhering to hook portions of the first and second fasteners  208 ,  211  and of the CPAP loop elements  209 . The region of hook accepting material  232  along the rim of the hat provides a wide range of hook accepting area, improving the adjustability of the hat. The hook accepting material  232  may comprise multiple layers laminated together, for example a cotton/foam/velour layer structure, in which the velour is hook accepting. 
     The hat  200  may comprise at least one dart  207 , to improve the fit of the hat on the head of a neonate particularly around the curvature of the occiput  120 . There is preferably a dart  207  between the central portion  201  and the first portion  202 , and between the central portion  201  and the second portion  203 . The darts  207  preferably extends from the top edge of the hat (opposite the rim  214 ), to around halfway between the top edge and the rim  214 . The darts  207  may be non-parallel, for example being angled so that the gap between them is smaller nearer to the rim  214 . In  FIGS. 8 and 9  the darts  207  are shown in a closed configuration, and in  FIGS. 10 and 11  the darts  207  are shown before their edges have been drawn together. A dart  207  may be provided in the central portion  201 , as shown in the embodiment of  FIGS. 12 and 13 . Drawing the darts  207  closed may comprise sewing together points  227  of the hat  200 , which may be inward from the edge of the fabric  231 . 
     The hat  200  is provided with a number of features for securing/supporting CPAP apparatus or an intubation tube. The hat may include at least one of a strap  206 , loop elements  209 , and eyelets  205 , for this purpose. 
     A plurality of eyelets  205  are provided in each of the first and second portion  202 ,  203 , on either side of the central portion  201  of the hat  200 . Three eyelets  205  may be provided on each of the first and second portion  202 ,  203 , which enables lacing for a CPAP mask (or similar) to be secured at different locations to the hat  200 , providing for an improved fit over a broader range of head shapes and sizes. 
     A strap  206  may be attached to the first portion  202  (as shown in  FIGS. 10 and 11 ) or the second portion  203  (as shown in  FIGS. 8 and 9 ) at one end (by sewing). A strap fastener  215  may be provided for securing the other end of the strap  206  to the first portion  202  or the second portion  203 . The strap fastener  215  may comprise a hook and loop fastener. The strap fastener  215  may comprise a hook portion  215   a  at the end of the strap  206 , and a corresponding loop portion on the exterior of the second portion  203 , as shown in  FIG. 9 . Alternatively, the strap fastener  215  may comprise a loop fastener  215   a  on the strap  206 , and a hook fastener  215  on the first or second portion  203  (as in the embodiment of  FIGS. 10 and 11 ). In the embodiment of  FIGS. 12 and 13  the CPAP strap  206  may be a separate part that comprises hook fasteners at each end, which is attachable to the hook accepting fabric portion  231 . 
     The loop element  209  may comprise a loop (or hook) region of hook and loop fastener material, so that a strip of hook material may be adhered to the loop element to secure a tube adjacent to the loop element (such a hook region  219  being shown in  FIG. 12 ). A loop element or region  209  is disposed on the exterior side, or at the edge of each the first and second portions  202 ,  203 . The loop region  209  may comprise part of a larger continuous region of hook accepting material (e.g. as described above with reference to  FIGS. 12 and 13 ). The strap  206  and/or the strips of material for adhering to the loop element  209  may comprise an elastic fabric material. The strap  206  and/or loops  209  may comprise a friction enhancing inner surface region, which may comprise a material such as silicone rubber. 
     All material that is to be sewed to the main hat material  200  is preferably of a form that is compatible. 
       FIG. 14  illustrates the strap  206 , loop elements  209  and eyelets  205  in use, with a CPAP mask  220  supported in the correct position on a neonate by the hat  200 . The CPAP exhaust tube  220  is supported under the strap  206 , and the two supply tubes are supported by adhering a hook fastener strip to each loop element  209 . The strap/lacing of the mask is threaded through an appropriate pair of eyelets  205  at each of the first and second portion  202 ,  203 . 
     The sensor  300  is shown in  FIGS. 7 and 15 to 17 , and comprises a flexible circuit board that includes the sensor portion  302 , lead portion  301  and module portion  305 . Using a single flexible circuit board to define all of these parts of the sensor  300  eliminates connections between a sensor portion and lead, and between a lead and a subsequent connector, which are potential points of failure. Furthermore, this approach results in a very low profile arrangement: the thickness of the flexible circuit board may be less than 0.5 mm. 
       FIG. 15  shows the construction of the module portion  305  of the sensor  300  in more detail. The module portion  305  is arranged to engage with the readout module  400  and to provide an electrical connection between the sensor  300  and readout module  400 . 
     The module portion  305  comprises: contacts  301 , conducting tracks (not shown); a ferromagnetic element  307  and a rigidiser  306 . The contacts  301  are exposed conducting regions that are connected to conducting tracks of the lead  301 , that are in turn connected to the light emitter  310  and light detector  311  at the sensor portion  302 . The ferromagnetic element  307  is a substantially planar sheet of a magnetic material such as steel. The rigidiser  306  is a substantially planar element (e.g. a plate) that is stiffer than the flexible circuit board, and which supports the contacts  301  from behind. The rigidiser  306  may fit in a recess or through hole in the ferromagnetic element  307 . 
       FIG. 16  shows the sensor portion  302 , which comprises the light emitter  310 , light detector  311 , compressible element  308  and transparent element  309 . The light emitter  310  may comprise a plurality of light emitting elements (such as light emitting diodes or LEDs). There may be more than one colour LED (e.g. infra-red, green, red etc). The light detector  311  may comprise a photodiode (or an array of photodiodes, or a multi-pixel camera chip not necessarily operating in the visible region). Where the light detector  311  comprises a plurality of light detecting elements, at least some of the light detecting elements may be configured with a different spectral response to the others (e.g. using a spectral filter), so that additional information may be obtained at the same time from more than one colour light emitter. Alternatively independent component analysis can be implemented on multi-detectors to separate out orthogonal components. 
     In the example shown, the light emitter  310  comprises a plurality of discrete LEDs, arranged around a central light detector  311 . In other embodiments the light detector  311  and light emitter  310  may be disposed in a single package. In some embodiments the light emitter  310  and detector  311  may be separated by a baffle, which prevents light from the emitter  310  being directly detected by the detector  311 . Or the LED&#39;s may be positioned at a lower level than the photodetector (relative to the transparent element  309 ) so that no direct light shunting occurs. 
     The compressible element  308  is formed of an elastic material, such as a closed cell foam, so that the optically transparent element  309  can conform to the skin of the neonate  120 , minimising the potential for a pressure injury. The transparent element  309  may also be relatively soft (e.g. compared to glass or polycarbonate), for instance being formed from optically clear silicone. The addition of an adhesive or tacky layer to the outer side of the transparent element  309  may help the sensor portion  302  to remain in contact with the skin and reduce slippage across the skin. Cross-polarisers can be placed between layers  308  and  309  to reduce internal reflection shunting. 
     In some embodiments, the sensor portion  302  may comprise at least one electrode for making electrical contact with the skin of the neonate, for example to perform an ECG measurement. The lead  301  may comprise at least one branch for connecting further electrodes at different positions on the neonate (for example, not on the head). The electrodes may be of any suitable type, including (but not limited to) wet electrodes, electrodes configured for capacitive coupling to the skin, and electrodes configured for connection to skin via a coupling gel (e.g. a hydrogel). The tang  303  extends away from the sensor portion  302 , in a different direction to the lead  301 . In the example embodiment, the tang is at an angle of approximately 145 degrees to the lead  301 , which results in the tang  303  being approximately parallel with the rim  314  of the hat  200  when the sensor portion  302  is between the first and second inner hole  212 ,  213 . In some embodiments the tang  303  may extend away from the sensor portion at around 180 degrees from the lead  301 . 
       FIGS. 17 and 18  illustrate how the module portion  305  of the sensor is connected to the readout module  400 . A cradle  401  is provided, which assists in engaging and maintaining engagement between the module portion  305  and the readout module  400 . The cradle  401  is configured to receive part of the housing base  402   b , and has a wall that guides the housing into the proper location in the cradle  401 . The cradle  401  further includes a slot in the base thereof, through which the module portion  305  of the sensor  300  can be inserted. The module portion  305  may subsequently be located within a slot of the cradle  401 , with the lead portion  301  exiting the cradle  401  through the slot  401 . The cradle  401  may be configured to require the cradle  401  to be initially moved relative to the module portion  305  in the direction of the lead  301  to disengage the module portion  305  from the slot. This helps to prevent the module portion  305  being disturbed in use, and helps maintain a secure connection between the readout module  400  and sensor  300 . 
     As shown in  FIG. 18 , when the readout module  400  is received within the cradle  401 , the magnets of the readout module  400  may align with the ferromagnetic element  307  of the module portion  305 , which urges the connector  408  into electrical contact with the contacts  304 . 
       FIG. 19  shows a receiver station  500 , comprising a display  501  and a pair of docking portions  501 . 
     The display  501  is for indicating the heart rate and other physiological variables of the neonate  120 , based on data transmitted to the receiver station  500  wirelessly by the readout module  400 . The receiver station  500  may be configured to show a time history of the pulse rate or blood oxygen saturation as a graph, the instantaneous pulse rate (e.g. as number indicating beats per minute), the breathing rate, an indication of battery status (e.g. for a charging module  400 , or the transmitting module  400 ), the time, or any other information that may be appropriate. 
     Each docking portion is configured to receive a readout module  400 . The receiver station  500  may be configured to charge each readout module  400  via each docking portion  502 . 
     The receiver station ( 500 ) may contain adequate storage to collect all data from a recording session in a non-volatile format. This is useful for training purposes, medico-legal reasons and clinical records for example. Data can be accessed by removing the internal storage card, by wired or wireless connections. 
     The receiver station  500  may further comprise a hanger  504 , by which the receiver station  500  can be secured to a sidewall of a resuscitaire, as shown in  FIG. 20 . 
     The embodiments described above address a number of potential applications. In one use case, a clinician may identify a need for heart rate monitoring of a neonate, following an assessment of the neonate on delivery. 
     A prepared hat  200  may be positioned on a resuscitaire  110  in the unfolded configuration. The prepared hat  200  includes a sensor  300 , as described above. The sensor  300  may be already connected to a readout module  400 , which may already be in communication with the receiving station  500 . 
     The neonate may be placed with their head on the central portion  201  of the hat  200 , and the hat  200  wrapped around the head, so that the sensor portion  302  contacts the head (e.g. forehead) of the neonate  120 . If a readout module  400  is not already engaged with the module portion  305 , a readout module  400  may be taken from the docking portion  502  and engaged with the readout module  400  (e.g. by placing it in cradle  401 ). 
     The readout module  400  may subsequently transmit data derived from the output of the sensor  300  to the receiver station  500 . As already discussed, the processing of the data from the sensor  300  to determine heart rate (and/or blood oxygen saturation, breathing rate etc) may take place at the readout module  400  and/or the receiver station  500 . The receiver station subsequently displays the heart rate and/or blood oxygen saturation (e.g. an instantaneous indication and/or a time history in the form of a graph). 
     The hat  200  may be kept on the head of the neonate  120  while any treatment to remedy poor respiratory function and/or heart rate etc is given. An accurate time history of the heart rate etc made available at the resuscitaire will assist the treating clinician in determining whether their actions are having the desired effect. If it is determined that the neonate  120  needs to be transferred to a neonatal intensive care unit (NICU), the physiological signals of the neonate can continue to be monitored during transit of the resuscitaire to the NICU. 
     Once the neonate is stabilised, or has arrived at the NICU, the hat  200  may be removed, or the sensor removed from the hat  200 . Removing the sensor can be achieved by cutting the lead  301  between the second and third outer hole, and then pulling the lead from the hat  200 . In some embodiments (such as that of  FIGS. 12 and 13 ), removing the sensor may comprise cutting the lead  301  outside the hat (e.g. not between second and third outer holes). The sensor element can subsequently be removed by briefly lifting the first portion  202  and detaching the sensor portion  302  from the interior. Each hat  200  and sensor  300  may be a single-use disposable item. 
     In another use-case, the hat may be applied as a matter of routine to each newborn, so that the physiological signals can be assessed to ensure that they are healthy before they leave the delivery suite. 
     A further use-case is for babies older than 4 weeks (e.g. for babies up to 6 months or even 1 year old), for instance to monitor for the onset of SIDS (sudden infant death syndrome). Although a hat for a neonate has been described, the same principles are also applicable to a hat for an older baby. 
     One issue present in the delivery room is the availability of ECG equipment for newborn monitoring. A device that is being used to monitor the fetal ECG could be transferred to continue to monitor the newborn ECG, simply by swapping the data receiving device from the electrodes used to monitor the mother and/or fetus to the electrodes on the sensor portion that are connected to the newborn baby (e.g. in the hat). Using the same interface to the cardiotocogram printout mechanism could allow for data recording. 
     A number of examples have been described, which are not intended to limit the scope of the invention, which is limited only by the appended claims.