Patent Description:
The dose of many medicaments is dependent on the weight of the patient. However, it is currently difficult to measure a patient's weight quickly and accurately where they are unable to stand. The efficacy of drugs is reduced if the wrong dose is administered, and the risk of side-effects is increased.

Upon admission to hospital many patients are unable to support their own weight due to unconsciousness or due to suspected injury, in particular suspected back, neck or leg injuries. Moreover, where patients are admitted with chest pain or breathlessness, hospital procedure is for such patients to remain in a lying or sitting position. It is not possible for such patients to be weighed on conventional weighing scales as these require the patient to stand. Although weighing devices such as hoists are available in hospitals, these involve placing the patient in the hoist and lifting the patient off the bed/trolley in order for a weight to be taken. This is time consuming, requires suspending the patient, with consequent safety issues e.g. hoists can topple if not used appropriately. Alternatively, floor scales can be used which weigh both patient and trolley. Floor scales tend to be extremely heavy, thus non-portable, and need to be large enough to accommodate a trolley. Both the aforementioned methods require considerable space, which is often at a premium in hospital emergency areas.

Upon admissions into hospital, children's weight is typically estimated using generalized calculations dependent on the child's age. Weight is currently commonly estimated using the equation: <MAT>.

However, the weight of children of the same age can greatly differ. This is an inaccurate method of calculating weight, and this can prove dangerous where such calculations are used to calculate doses of medicaments including opiates.

In addition, where there is limited or no access to scales or where drugs must be administered quickly, adult weights are also frequently estimated. Research has shown that these estimates are often inaccurate, particularly where medical staff are estimating the weight of a patient, rather than the patient providing an estimate of their own weight.

It is also difficult to measure a patient's weight when they refuse to keep still for periods during the weighing process, for instance where the patient is a child, or where the patient is confused, drunk and/or uncooperative.

Some medicaments must be administered within a maximum time from an event. For instance, the drug for stroke must be given within <NUM>½ hours from the onset of symptoms, with the hospital standard in the UK as <NUM> hour from patient admission. Accordingly, time is of the essence during the admissions procedure. However, weighing procedures for patients who are unable to support their own weight can be lengthy. The use of a hoist is commonly associated with a weighing procedure of up to <NUM> minutes or longer. Providing a faster procedure for weighing suspected stroke victims would provide significant advantages. Furthermore, patients being admitted with a serious condition such as stroke are vulnerable and often fearful of what may happen next. To place such patients in a hoist can greatly add to their distress.

The patient transfer device PatSlide® is commonly used to transfer patients from one surface to another in hospitals, for instance from trolleys to beds. Other similar devices exist. This patient transfer device consists of a flexible sheet of plastic with good slip properties on its surface, enabling patients to be transferred smoothly and easily with minimal risk of back strain to hospital staff. The use of these devices in hospitals is a well-accepted and common procedure.

<CIT> discloses an apparatus, system, and method for weighing an individual on a backboard. The backboard is configured to support a supine individual during transportation. An upper surface of the backboard is configured to receive the supine individual. A scale is embedded within the backboard beneath the upper surface. The embedded scale is configured to determine a weight of the supine individual in response to the upper surface receiving the supine individual.

<CIT> discloses a load detection sensor unit for a bedding comprises a plurality of load detection devices and a signal processing circuit which is connectable to an external electrical unit. The signal processing circuit includes a plurality of analog switches connected to the load detection devices, a single output line connected to the analog switches, and a load resistor connected to the single output lines. The analog switches are turned on sequentially so that output signals of the load detection devices are serialized and transmitted to the external electrical unit through the single output line. The load detection devices and the signal processing circuit are formed integrally on an elastic film and connected through elastic conductors.

The weighing apparatus of the present invention provides a quick, accurate weight measurement for patients who cannot support their own weight and this may take place during the procedure of transferring the patient from one surface to another, for instance from a hospital trolley to a bed. The weighing apparatus of the present invention is thus particularly suitable for use in a hospital admissions ward where medicaments must be prescribed quickly, and such prescription is dependent on the weight of the patient. In hospital admissions wards, diagnosis has not yet occurred and a significant number of patients cannot support their own weight on conventional weighing apparatus.

According to an aspect of the present invention, there is provided an apparatus to weigh a patient comprising a patient transfer board configured to support a patient in a supine position, wherein an upper surface of the patient transfer board is configured to receive the supine patient, the upper surface having a width and a length;.

According to one embodiment, more than <NUM>% of the transducers are provided <NUM> or less from an outer boundary of the patient transfer board.

Generally, each transducer is no more than <NUM> from another of the transducers.

According to one embodiment, at least one transducer is provided beneath every unit area of the area of the patient transfer board configured to receive the supine patient, wherein said unit area corresponds to <NUM>,<NUM><NUM>,
wherein more than <NUM>% of the transducers are provided <NUM> or less from an outer boundary of the patient transfer board.

According to a further aspect of the present invention, there is provided a method of weighing a patient including the steps of:.

According to one embodiment, there is provided a method of transferring a patient from a first surface to a second surface using the apparatus provided herein comprising:.

According to a further embodiment there is provided a kit of parts comprising any one of the weighing apparatuses as described herein and instructions for use. Where appropriate, teaching relating to any aspect or embodiment may relate to any other embodiment.

All numerical values provided incorporate <NUM>% less than and <NUM>% more than the numerical value provided.

According to a first aspect of the present invention, there is provided an apparatus to weigh a patient comprising a patient transfer board configured to support a patient in a supine position, wherein an upper surface of the patient transfer board is configured to receive the supine patient,.

Typically, more than <NUM>% of the transducers are provided <NUM> or less from an outer boundary of the patient transfer board. Suitably, around <NUM>% of the transducers are provided <NUM> or less from an outer boundary of the patient transfer board.

According to one embodiment, more than <NUM>% (generally around <NUM>%) of the transducers are provided <NUM> or less from an outer boundary of the patient transfer board.

The plurality of transducers includes at least <NUM> transducers, and typically each transducer is no more than a distance of <NUM> from another of the transducers, generally no more than a distance of <NUM> from another of the transducers.

The transducers are provided at three or more positions across the width of the patient transfer board.

Suitably more than <NUM>% of the transducers are provided <NUM> or less from an outer boundary of the patient transfer board.

According to an aspect of the present invention, at least one transducer is provided beneath every unit area of the area of the patient transfer board configured to receive the supine patient, wherein said unit area corresponds to <NUM>,<NUM><NUM>,
wherein more than <NUM>% of the transducers are provided <NUM> or less from an outer boundary of the patient transfer board.

The apparatus of the present invention is configured to provide the dual functions of patient transfer device and weighing device. To achieve this dual functionality, the apparatus must combine accuracy in weighing with a relatively low weight and a relatively low maximum thickness. In addition, the lateral edge height of the apparatus is generally relatively low to allow easy movement of a patient onto and from the apparatus.

The apparatus of the present invention allows a weight measurement to be provided quickly and accurately for patients who are unable to support their own weight, for instance because of suspected back, neck or leg injuries, breathlessness dizziness or unconsciousness. This is particularly advantageous in the admissions department of hospitals, allowing medicine to be prescribed at the correct dose quickly and accurately. The dose of many medicines is dependent on the weight of the patient to be treated. If the incorrect dose is determined due to inaccuracies in the weighing method, the efficacy of the medicine may be adversely affected and the risk of adverse side effects will generally increase. Drugs such as gentamicin may cause significant harm if a patient is overdosed.

These arrangements promote accurate weighing on soft or non-horizontal surfaces, and this is particularly advantageous in a hospital setting where patients may be weighed during transfer between beds or trolleys. These arrangements also allow weighing of patients who will not lie still for any significant length of time and this is of particular use in the weighing of children and patients who are confused due to, for example a medical condition or through intoxication through drugs or alcohol.

The upper surface of the patient transfer board should generally be freely supported on the plurality of transducers to enable accurate measurement of forces applied to the upper surface.

Where the patient transfer board includes at least one transducer every unit area (generally every <NUM>,<NUM><NUM> portion, suitably every <NUM>,<NUM><NUM> portion) of its surface, the accurate measurement of a patient's weight is not dependent on the patient's position on the patient transfer board. This allows the weighing of patients who are not provided centrally on the patient transfer board, for instance on an edge of the patient transfer board. This is more likely where a patient is weighed during transfer from one surface to another.

Generally, the unit areas provided above are substantially square, or substantially circular. Alternatively, the unit areas may be rectangular or oval, generally the width of the rectangular/oval unit areas is no less than half of the length of the rectangular/oval unit areas.

The provision of transducers spaced within a maximum distance from one another ( within <NUM> from one another, suitably within <NUM> from one another) allows the possibility of a less rigid material to be used (having a lower flexural modulus) for the upper surface of the patient transfer board. This promotes patient comfort, and also provides ease of transfer between surfaces, including surfaces at different heights.

Including a plurality of transducers and providing the transducers in the claimed arrangements ensures optimal weighing accuracy.

The patient transfer board of the present invention includes at least <NUM> transducers, and this is promotes accurate weighing in particular where the patient weighs more than <NUM>.

According to one embodiment, the patient transfer board of the present invention includes <NUM> or more transducers; generally, <NUM> to <NUM> transducers, suitably <NUM> transducers.

According to a further embodiment, the patient transfer board includes <NUM> to <NUM> transducers; suitably <NUM> to <NUM> transducers; more suitably <NUM> or <NUM> transducers.

According to one embodiment, each transducer is no more than a distance corresponding to <NUM>% of the width of the upper surface, generally no more than <NUM>% of the width of the upper surface of the patient transfer board.

Generally, each transducer is no more than a distance corresponding to <NUM>% (typically no more than <NUM>%, suitably no more than <NUM>%) of the average width of the upper surface of the patient transfer board configured to receive the supine patient from another transducer.

Alternatively, each transducer is no more than a distance corresponding to <NUM>% (typically no more than <NUM>%, suitably no more than <NUM>%) of the maximum width of the upper surface of the patient transfer board configured to receive the supine patient from another transducer.

Typically, the patient transfer board is generally rectangular or oval in shape, and the width of the patient transfer board does not significantly alter along its length.

According to one embodiment, the area of the patient transfer board configured to receive the supine patient comprises at least one transducer every unit area, said unit area corresponding to <NUM>% of the width of the upper surface of the patient transfer board squared, generally to <NUM>% of the width of the upper surface squared, typically <NUM>% of the width of the upper surface squared.

Generally, the unit area corresponds to <NUM>% (typically no more than <NUM>%, suitably no more than <NUM>%) of the average width of the upper surface of the patient transfer board squared.

Alternatively, the unit area corresponds to <NUM>% (typically no more than <NUM>%, suitably no more than <NUM>%) of the maximum width of the upper surface of the patient transfer board squared.

The apparatus includes a patient transfer board, including transducers configured to determine the weight of a patient through forces applied to the upper surface of the patient transfer board. The apparatus generally also includes a surround, extending around each lateral outside boundary, or side of the patient transfer board, generally also extending around each longitudinal outside boundary or end of the patient transfer board. The transducers are not configured to measure forces applied to the surround. The surround is generally sloped from the outer boundary of the patient transfer board towards the horizontal, to provide a lower edge height or thickness compared to the outer boundary of the patient transfer board.

According to one embodiment, the lateral outside boundary of the apparatus has a thickness of <NUM> or less, typically <NUM> or less, generally around <NUM> or less.

The patient transfer board generally includes an end towards which the patient places their head during the weighing procedure. The patient transfer board may include an end or portion towards one end configured to receive the patient's head during the weighing procedure. This is advantageous as the half of the patient including the head is heaviest.

According to one embodiment, <NUM>% or more of the transducers are provided within the half of the length of the patient transfer board extending from the end configured to receive the patient's head during use; generally, <NUM>% or more; typically, <NUM> to <NUM>% of the transducers are provided within <NUM>% of the length of the patient transfer board extending from the end configured to receive the patient's head during use.

Alternatively, the transducers may be relatively evenly distributed along the length of the patient transfer board.

According to one embodiment, <NUM>% or more (generally more than <NUM>%) of the transducers are provided towards the outer boundary of the patient transfer board, generally within the outer <NUM>% of the width of the patient transfer board, and/or towards the outer <NUM>% of the length of the patient transfer board; typically, more than <NUM>% of the transducers; suitably more than <NUM>% of the transducers. For instance, where the patient transfer board is <NUM> wide, <NUM>% or more of the transducers are generally provided within <NUM> from a first side, or within <NUM> of the second side.

Typically, more than <NUM>% of the transducers are provided within the <NUM>% of the width closest to each side of the upper surface of the patient transfer board; generally, within the <NUM>% of the width closest to each side of the upper surface of the patient transfer board. Generally, <NUM>% or more of the transducers are provided within the <NUM>% of the width closest to each side of the upper surface of the patient transfer board, suitably <NUM>% or more of the transducers.

Typically, <NUM>% or more of the transducers are provided within the outer <NUM>% of the length of the patient transfer board; generally, <NUM>% or more; suitably <NUM>% or more within the outer <NUM>% of the length of the patient transfer board. According to one embodiment, around <NUM>% of the transducers are provided within the outer <NUM>% of the length of the patient transfer board.

According to one embodiment, the apparatus is configured to weigh an adult human and at least one transducer is provided within <NUM> of an outer boundary, circumference or side of the patient transfer board. Typically, each lateral outside boundary, or side of the patient transfer board is within <NUM> of at least one transducer. Suitably each longitudinal outside boundary or end of the patient transfer board is within <NUM> of at least one transducer.

Generally, <NUM>% or more of the transducers are provided within <NUM> of the outer boundary of the upper surface of the patient transfer board, typically <NUM>% or more of the transducers, suitably <NUM>% or more of the transducers.

According to one embodiment, more than <NUM>% of the transducers are provided from <NUM> or less (generally from <NUM> or less) from a lateral outside boundary or side of the patient transfer board, typically <NUM>% or more of the transducers, suitably <NUM>% or more of the transducers, typically <NUM>% or more of the transducers, suitably around <NUM>% of the transducers.

Typically, <NUM>% or more of the transducers are provided within the outer <NUM> to <NUM>% of the length of the patient transfer board.

Suitably more than <NUM>% of the transducers are provided from <NUM> or less, generally from <NUM> or less of a longitudinal outside boundary or end of the patient transfer board; generally, <NUM>% or more; typically, around <NUM>% of the transducers.

According to one embodiment, each transducer is no more than around <NUM> from another transducer.

According to one embodiment, the apparatus includes a patient transfer board, where at least one transducer is provided beneath each <NUM>,<NUM><NUM> portion of the upper surface of the patient transfer board configured to receive the supine patient, generally at least one transducer beneath each <NUM>,<NUM><NUM> portion of the patient transfer board configured to receive the supine patient, typically at least one transducer beneath each <NUM>,<NUM><NUM> portion of the patient transfer board configured to receive the supine patient.

According to one embodiment, the transducers are provided at at least four positions, typically <NUM> or <NUM> positions across the width of the patient transfer board.

According to one embodiment, the transducers are provided at seven or more positions along the length of the patient transfer board, generally at least eight positions, typically eight to ten positions along the length of the patient transfer board, suitably ten or eleven positions.

The provision of a plurality of transducers, positioned relatively close to each other (<NUM> or less from each other, suitably less than <NUM> from each other) allows the upper surface to be formed from a material having lower associated rigidity, this promotes patient comfort and some degree of flex facilitates ease of patient transfer across the upper surface and ease of sliding. Due to the transducer arrangement of the present invention, the upper surface does not touch the lower surface of the patient transfer board even where a more flexible material is used.

According to one embodiment, the upper surface of the patient transfer board has an associated flexural modulus of at least 8GPa. Suitably the upper surface of the patient transfer board has an associated flexural modulus of less than 25GPa. Suitably the lower surface of the patient transfer board has a higher associated rigidity than the upper surface.

The inventors overcame numerous problems in providing a patient transfer and weighing device having an associated weight low enough to allow it to be handled by one medical practitioner whilst also maintaining the accuracy of the weighing procedure. As the weight is related to the thickness of the apparatus, this must also be a consideration.

According to one embodiment, the present invention provides a patient transfer and weighing apparatus configured for use with an adult human having an associated accuracy of +/- <NUM> (generally +/- <NUM>) for weights from <NUM> to <NUM>, a weight of less than <NUM>, generally less than <NUM>, suitably less than <NUM>, typically less than about <NUM>) and a maximum thickness of less than <NUM>, suitably less than <NUM> (generally around <NUM>). Typically, the apparatus includes at least <NUM> transducers, typically at least <NUM> transducers, generally <NUM> to <NUM> transducers.

Generally, the apparatus of the present invention has a density of less than <NUM>/m<NUM>, generally less than <NUM>/m<NUM>, suitably less than <NUM>/m<NUM>, more suitably around <NUM>/m<NUM>.

By ensuring that the apparatus of the present invention has a relatively low density, the inventors have ensured that one medical practitioner can safely handle the apparatus quickly, easily and without undue effort. This is important in an emergency setting.

Where the apparatus is configured to weigh an adult human, it suitably weighs less than <NUM>, generally less than <NUM>; typically, around <NUM>. According to one embodiment, the apparatus weights less than <NUM>, suitably from <NUM> to <NUM>.

Where the apparatus is configured to weigh a human child, it suitably weighs less than <NUM>, generally less than <NUM>. However, generally a child will be weighed on the same apparatus as an adult.

The apparatus of the present invention is suitably configured to measure weights of <NUM> to <NUM> at an accuracy of +/- <NUM>; typically, +/- <NUM>; suitably +/- <NUM>.

According to one embodiment, the apparatus of the present invention is configured to weigh an adult human and a child human. The apparatus of the present invention is generally suitable to weigh children from <NUM> months.

This is generally achieved by ensuring that the apparatus is sensitive enough to obtain an accurate reading when the weight of the patient is spread over only some of the transducers.

Generally, an accurate measurement is achievable where the weight of the patient is spread over <NUM>% or more, typically <NUM>% or more, suitably <NUM>% or more of the transducers. This is advantageous in the weighing of children, as well as in the weighing of patients who are unable or unwilling to stay still during the weighing procedure, or for the weighing of patients who are not positioned centrally on the patient transfer board.

The maximum thickness of the apparatus does not generally exceed <NUM> and is generally <NUM> to <NUM>. However, the thickness of the apparatus at its lateral outside boundary is generally less than half of the maximum thickness. Generally, the thickness of the apparatus at its lateral outside boundary is <NUM> to <NUM>, typically <NUM> to <NUM>. According to one embodiment, the thickness of the apparatus at its lateral outside boundary is <NUM> to <NUM>, generally <NUM> to <NUM>, suitably around <NUM>.

The lateral outside boundary of the apparatus of the present invention generally has a thickness of <NUM> or less, preferably <NUM> or less. This is generally achieved through the provision of a surround extending around each lateral outside boundary, or side of the patient transfer board, generally also extending around each longitudinal outside boundary or end of the patient transfer board. There are generally no transducers provided beneath the upper surface of the surround and the transducers are not generally configured to measure forces applied to the surround. The surround is generally sloped from the outer boundary of the patient transfer board towards the horizontal, to provide a lower height edge compared to the outer boundary of the patient transfer board. This facilitates ease of patient transfer onto and off of the apparatus, in particular ease of sliding.

As noted above, the apparatus of the present invention is generally configured for use in the transfer of patients from one surface to another, as well as for weighing. To facilitate ease of transfer, the coefficient of friction of the upper layer of the apparatus is generally <NUM> or less.

Alternatively, the coefficient of friction of the upper surface of the apparatus may be higher than provided above, and ease of transfer across the apparatus may be facilitated through the use of a slide sheet, comprising a low friction surface. The slide sheet may be removable or comprise part of the apparatus.

The lower surface of the apparatus may include non-slip or non-skid areas having a high friction coefficient to reduce the risk of the apparatus slipping during the transfer/weighing procedure.

The apparatus of the present invention is generally X-ray translucent and static insulative. The apparatus is generally completely enclosed with no gaps to promote ease of cleaning and infection control.

The apparatus of the present invention generally provides a measurement of the summed weight of the patient within <NUM> seconds of the patient being placed or slid onto the patient transfer board.

Where the apparatus is configured for weighing a human adult, the apparatus generally has an associated length of <NUM> to <NUM>, and an associated width of <NUM> to <NUM>, generally around <NUM>. The apparatus generally includes the patient transfer board and a surround at both sides of the patient transfer board. The surround generally extends less than <NUM> from the sides of the patient transfer board, typically around <NUM> from both of the sides of the patient transfer board.

The patient transfer board is generally elongated and flat. Generally, the patient transfer board provides a flat surface for the patient to be slid onto. The upper surface of the patient transfer board may flex, but is not generally concave when the patient is removed. This assists in the transfer of the patient off the apparatus.

The apparatus of the present invention is generally for use in a hospital.

The apparatus generally includes handles to promote ease of handling.

There are not suitably any sharp edges or protrusions on the apparatus of the present invention.

According to one embodiment, the apparatus of the present invention may be provided in more than one piece to allow for easy transport. In such embodiments, the pieces may be connected together prior to use. Alternatively, the apparatus may be folded to allow it to be transported more easily. Such embodiments would allow the apparatus to be used, for instance with patients in community settings, including those that are bed bound and/or obese.

The patient transfer board may be formed from any suitable material. Particular mention may be made of carbon fibre, fiberglass, honeycomb aluminium, metallic alloys and plastics material. The outer surfaces of the patient transfer board, and surround are generally covered with a vinyl or plastic layer.

The skilled man will be well aware of many different transducers which may be used. Mention may be made of torsion, tension and compression load cells. Generally, the transducers are electronic. The transducers may be strain gauges. Alternatively, or additionally the transducers may be pneumatic or hydraulic.

Generally, the apparatus includes a single type of transducer. Alternatively, one or more different types of transducer may be used.

The summing means receives signals from each of the transducers and produces a signal corresponding to the sum of the weight sensed by all of the transducers. Generally, the transducers communicate with the summing means electronically, generally through wired connection.

Typically, the summed weight is displayed by a digital display provided on the apparatus, and in communication with the summing means. Generally, the weight of the patient is summed and displayed within <NUM> seconds of the patient being placed or transferred onto the apparatus, typically less than <NUM> seconds, suitably less than <NUM> seconds.

The summed weight is displayed by a digital display on the apparatus or can be displayed remotely on other devices, suitably through wireless connections such as Bluetooth ®.

The apparatus may be powered by battery, and the apparatus may include an indication of the extent to which the apparatus is charged, and optionally an alert to notify the user that the battery power is low.

Although generally configured to transfer/weigh humans, according to one embodiment, the apparatus of the present invention may be used for other subjects, in particular animals such as dogs and cats.

In order to ensure an accurate measurement, the patient should be supported entirely by the apparatus during the weighing procedure. Where the patient is transferred onto the apparatus through the help of others (for instance, medical practitioners), all physical support should be withdrawn during the weighing procedure. The patient may place their hands across their chests during the weighing procedure.

Typically, the patient is provided on the upper surface of patient transfer board for at least <NUM> secs, generally at least <NUM> seconds. According to best medical practice, there is a pause between transferring patients onto a patient transfer device and transferring them off. This is to ensure that the patient doesn't have too much momentum upon transfer to the second surface, especially where the second surface is lower than the first. The weight of the patient could be measured during this pause.

Prior to transfer procedure, the first and second surfaces should be aligned as much as possible, and where either of the surfaces are easily movable, any brakes should be applied. Generally, the patient is tilted slightly to one side to allow the first side of the patient transfer board to be placed partially under the patient.

The apparatus of the present invention spans the first and second surfaces, providing a smooth bridge, spanning any gaps or differences in height between the two surfaces.

The apparatus of the present invention provides the dual functionality of patient transfer, and patient weighing. This allows the patient's weight to be measured quickly and easily during the normal procedures which the patient would undergo during admission into hospital. Medicines can be prescribed accurately in accordance with the patient's weight. In addition, the patient's weight can be monitored over prolonged timescales and this can screen for malnutrition.

According to a further aspect of the present invention there is provided a kit of parts comprising the apparatus as described herein, and instructions for use.

The apparatus is generally calibrated prior to being packaged in the kit of parts, and is used within <NUM> years of calibration.

Alternatively, or additionally, the instructions may include instructions for calibrating the apparatus prior to use.

The kit of parts generally includes charging means.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", mean "including but not limited to", and are not intended to (and do not) exclude other moieties, additives, components, integers or steps.

The use of the terms "include," "includes", "including," "have," "has," or "having" should be generally understood as open-ended and non-limiting unless specifically stated otherwise.

The use of the singular herein includes the plural (and vice versa) unless specifically stated otherwise. In addition, where the use of the term "about" is before a quantitative value, the present teachings also include the specific quantitative value itself, unless specifically stated otherwise. As used herein, the term "about" refers to a ±<NUM>% variation from the nominal value unless otherwise indicated or inferred.

Further aspects and embodiments of the invention are set forth in the following description and claims.

The present invention is further described by way of example only with reference to the accompanying Figures in which:.

<FIG> shows a plan view of a preferred embodiment of the apparatus of the present invention, shown generally at <NUM>, including a patient transfer board <NUM> and a surround <NUM>. The patient transfer board <NUM> includes a plurality of transducers provided under the upper sheet. No transducers are provided under the surround <NUM>. The surround is provided along the lateral sides of the patient transfer board. The corners of the surround <NUM>, <NUM> are rounded. Four handles are provided at spaced intervals along each side of the surround.

<FIG> shows a schematic representation of a preferred transducer arrangement of the apparatus of the present invention. Each unit area of the upper surface of the apparatus of <NUM>,<NUM><NUM> includes at least one transducer. Each transducer is spaced no more than <NUM> from another of the transducers.

The accuracy of the apparatus of the present invention including the transducer arrangement illustrated in <FIG> was tested by applying the weight of a human adult across the majority of the length and the majority of the width of the patient transfer board as shown in <FIG>. This was repeated with a human adult of different weight. The apparatus provided an accurate measurement of the weight in both cases: <NUM> applied, <NUM> measured and <NUM> applied, <NUM> measured.

The accuracy of the apparatus of the present invention including the illustrated transducer arrangement was then tested where the weight of a human adult was applied to one side of the patient transfer board, above around half of the transducers provided, as shown in <FIG>. This was repeated with a human adult of different weight. The apparatus provided an accurate measurement of the weight in both cases: <NUM> applied, <NUM> measured and <NUM> applied, <NUM> measured.

The weight of a human adult was then applied to an area over just three transducers, as shown in <FIG> and then repeated with a human adult of different weight. The apparatus provided an accurate measurement of the weight in both cases: <NUM> applied, <NUM> measured and <NUM> applied, <NUM> measured. Finally, the weight of a human adult was applied to an area over just one transducer, as shown in <FIG>, and then repeated with a human adult of different weight. The apparatus nonetheless provided an accurate measurement of the weight in both cases: <NUM> applied, <NUM> measured and <NUM> applied, <NUM> measured.

Typically, the apparatus of the present invention may be produced according to the steps detailed below. A lower panel of the patient transfer board is provided, suitably formed from a rectangular piece of carbon fibre or plastic. A surround is provided on either side of the patient transfer board, and is glued or mounted into place. The surround may be formed from expanded polystyrene foam, and typically has a width of around <NUM>. The surround slopes towards the horizontal, so that the height of the apparatus at the outer lateral boundary is at a minimum. The corners of the composite may be rounded, and handles may be provided. A plurality of transducers is provided on the lower panel of the patient transfer board, generally through gluing or mounting transducer supports to the lower panel and then gluing or mounting the transducers onto the supports. Spacer disks may be used on an upper surface of the transducers. End caps may be provided at both ends of the lower panel, to protect the inner workings of the patient transfer board, and to ensure the finished apparatus is suitable for medical use. The transducers are each connected to one or more summing means, typically through wires. Where more than one summing means is provided, the summing means are connected, typically in series. Weight distribution plates are generally provided on the upper panel of the patient transfer board in the same layout as the transducers. The lower and upper panels may be covered with a protective sheet, for instance formed from vinyl. The upper panel is then provided on top of the lower panel, and secured into place. The apparatus is then calibrated. <FIG> illustrates the patient transfer board of the present invention in use. The patient is provided initially on a trolley which is placed next to a bed. All brakes on the trolley and on the bed are applied. The patient is rolled onto their side, the patient transfer board is provided, bridging the gap between the trolley and a bed. The patient is rolled onto one side of the patient transfer board, and then slid fully onto the patient transfer board, so that their entire weight is supported by the patient transfer board. A measurement of their weight is taken before the patient is slid to the other side of the patient transfer board. The patient may then be rolled off the patient transfer board onto the bed. Alternatively, the patient transfer board may facilitate transfer from a bed to a trolley, another bed, or may be used to obtain a measurement of the weight of the patient before the patient is transferred back to the bed or trolley upon which they were initially provided.

A first prototype was prepared using a carbon fibre base, an array of transducers in load cell layout A as illustrated in <FIG> and a carbon fibre top. A second prototype was provided using a carbon fibre base, an array of transducers in load cell layout B as illustrated in <FIG> and a carbon fibre top.

The accuracy of the weight measurement provided by the prototypes was tested, initially on a hard surface (the floor), and then on a soft surface (a mattress). Four different positions of the weight on the prototypes was tested, the four different loadings illustrated in <FIG>.

The accuracy of the weight measurement provided by the prototypes was then tested when the base of the prototype was positioned to span two mattresses butted against each other. The mattresses were of differing hardness and density and were of different heights so that there was a step from one to the other.

A calibrated, body shaped load was weighed on the prototypes. For each load tested, the head of the body shaped load was placed in the same position on the prototypes.

The following loads were weighted: <NUM>, <NUM>, <NUM> and <NUM>. Each test was repeated five times. The accuracy of the weight measurements of the prototypes was checked and recorded and the results are provided in Table A.

The results provided in Table A evidence the accuracy and reproducibility of devices including two different load cell layouts. The greatest percentage variation to applied load is significantly higher for Layout A (<NUM>%) than for Layout B (<NUM>%, or <NUM>% during retest).

Patient transfer boards having the load cell layout <NUM>, <NUM> and <NUM> as illustrated in <FIG> were prepared.

<NUM> load cells were used in each layout together with a single controller box to collate and sum the outputs from the <NUM> sensors. Each load cell was supported by a custom U shaped support in <NUM> Plywood. Each load cell had a 5mmx12mm hexagonal steel nut glued to the top as the load support. The top panel had a <NUM> square (the same dimensions as the load cell itself) steel plate fixed to it directly above each load cell as load spreading support. The hexagonal support nut locates to the centre of each spreader plate.

All <NUM> load cells were delivered with <NUM> wires for connection, wires were checked so that all <NUM> load cells had the same length of wires. Each load cell was individually checked according to the manufacturer's specification for resistance value and then calibrated. The load cells were soldered in parallel to a circuit board according to instructions from Zemic and a single set of outputs was taken from the circuit board into the T1 controller. Each individual load cell was calibrated and the T1 controller calibrated for the system using values for all the load cells. A single <NUM> plywood base panel was cut, with dimensions <NUM> x <NUM>. The positions of load cells for each layout were marked accurately on the base panel. A single <NUM> MDF top panel was cut, with dimensions <NUM> x x500mm. The positions of load spreader plates for each layout were marked accurately on the top panel. <NUM> Plywood load cell supports were glued to the underside of each load cell. Metal hex load supports were glued to the top of each load cell. For each layout to be tested the load cell assemblies and spreader plates were stuck in position using re-positionable double sided tape.

Each layout was tested with a known load (person) which weighed approximately <NUM>. The weight of the person used with layout <NUM> was slightly more than the weight of the person used with layout <NUM> and <NUM>. Actual accurate weights of the subject were measured using NAWI calibrated scales prior to each test. For each layout and calibrated load, a test was performed three times in <NUM> different positions (the four different loadings illustrated in <FIG>) on the patient transfer board and the average of the measured weights recorded. Each layout was tested on a hard substrate (carpeted floor) and on a soft substrate (mattress) and results recorded.

Table <NUM> shows the test results for testing the patient transfer boards of <FIG> on a hard substrate (carpeted floor). Layout <NUM> shows the best results with an average variance across all load tests of <NUM>%. While Layout <NUM> had an average variance of <NUM>% and Layout <NUM> an average variance of <NUM>%. Layout <NUM> did not return reliable results for the load condition where the load was in one corner of the scales, this was due to the fact that the top and bottom panels touched each other and the load cell assembly could not find a resting measurement value.

Table <NUM> shows the test results for testing of the patient transfer boards of <FIG> on a soft substrate (Mattress). Layout <NUM> shows the best results with an average variance across all load tests of <NUM>%, while Layout <NUM> had an average variance of <NUM>%. Layout <NUM> was not useful as it was impossible to get results for two of the positions. The two which did produce results showed an average variance of <NUM>%.

Layout <NUM> is the best for accuracy on both hard and soft substrates.

Layout <NUM> does not return reliable results for some load conditions and as such would not pass regulatory test requirements.

Layout <NUM> demonstrates a larger difference in average variance than Layout <NUM> between hard and soft substrates.

Claim 1:
An apparatus to weigh a patient comprising a patient transfer board configured to support a patient in a supine position, wherein an upper surface of the patient transfer board is configured to receive the supine patient, the upper surface having a width and a length;
the patient transfer board comprising a plurality of transducers provided beneath the upper surface, said transducers configured to determine a weight of the patient,
the apparatus comprising summing means configured to provide the summed weight sensed by the plurality of transducers,
wherein the plurality of transducers includes at least <NUM> transducers, and each transducer is <NUM> or less from another of the transducers;
the transducers are provided at three or more positions across the width of the patient transfer board;
characterized in that <NUM>% or more of the transducers are provided within the <NUM>% of the length closest to each end of the patient transfer board.