Abstract:
A sleeping monitoring system includes a first padding layer. A fluid bladder is beneath the first padding layer. A sensor is in fluid communication with the fluid bladder. The sensor is configured to output a vital sign signal.

Description:
FIELD OF THE INVENTION 
     The present invention pertains to a vital sign monitoring apparatus. 
     BACKGROUND 
     Historically, monitoring vital signs of a person has required expensive equipment, such as an electrocardiogram (EKG) or a ballistocardiograph (BCG). In addition to being prohibitively expensive for many situations (e.g., home use), both EKGs and BCGs can be too cumbersome for use outside of medical facilities. EKGs, for example, typically necessitate attaching electrodes to the bodies of users, while BCGs rely on large, heavy, and unaesthetic force-measuring platforms that users lie on. 
     In more recent times, devices including piezoelectric films or arrays of sensors have been developed to measure heart and respiration rates. A user can lie on the device, and the film or sensors can generate a signal indicate of the user&#39;s heart rate and/or respiration rate. However, these devices can also be expensive. 
     SUMMARY 
     Placing a sensor beneath a padding layer can provide more comfort than having a sensor occupy a top position on a mattress. However, when the sensor is placed beneath the padding layer, the padding layer can dampen pressure input to the mattress, thereby preventing the sensor from properly detecting pressure. For example, if the sensor is near a foot of the mattress and beneath the padding layer, a pressure exerted on the mattress resulting from a heart beat will not likely create a wave in the padding layer of sufficient strength to propagate all the way through the padding layer to the sensor. Using a fluid bladder beneath the padding layer can aid in the transmission of waves resulting from pressure exerting on the padding layer to the sensor. 
     Accordingly, one example of a sleep monitoring system includes a first padding layer. A fluid bladder is beneath the first padding layer. A sensor is in fluid communication with the fluid bladder, and the sensor is configured to output a vital sign signal. 
     In another example, a mattress for determining at least one vital sign of a person lying thereon is provided. The mattress includes a first foam layer and a second foam layer. A fluid bladder is between the first and second foam layers, and the fluid bladder defines at least one aperture extending between a top side of the fluid bladder that the first foam layer rests on and a bottom side that rests on the second foam layer. A sensor in fluid communication with the fluid bladder is configured to output a vital sign signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description herein makes reference to the accompanying drawings, wherein like reference numerals refer to like parts throughout the several views, and wherein: 
         FIG. 1  is an exploded perspective view of an example of a mattress including a sensing layer; 
         FIG. 2  is an end view of the mattress of  FIG. 1 ; 
         FIG. 3  is a plan view the sensing layer of  FIG. 1 ; 
         FIG. 4  is a plan view of another example of a sensing layer; 
         FIG. 5  is a side view of another example of a mattress including a sensing layer; and 
         FIG. 6  is an end view of the mattress of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     A bed  10  as shown in  FIGS. 1-2  can include a frame  12  and a mattress  14 . The frame  12  can be a standard sized bed frame, such as a frame for holding a twin, full, queen, or king mattress. The frame  12  can hold the mattress  14  off the ground, such as at a level allowing a user to easily mount and dismount the mattress  14 . While shown as a standard bed frame, the frame  12  can alternatively be a crib, hospital bed, or another support structure for the mattress  14 . Also, the mattress  14  can be set directly on the ground or a floor, in which case no frame  12  is necessary. 
     The mattress  14  can have a standard size (e.g., a twin, full, queen or king size) or be sized for use in a crib, on a hospital bed, or in another environment. The mattress  14  can include a bottom padding layer  16 , the sensing layer  18 , and a top padding layer  20 , with the sensing layer  18  sandwiched between the padding layers  16  and  20  as shown in  FIGS. 1 and 2 . The mattress  14  can be an integral, inseparable unit, or the mattress  14  can be formed by stacking separate layers  16 ,  18  and  20 . 
     The bottom padding layer  14  can be a firm layer for providing support. For example, the bottom layer  14  can include firm high density foam (e.g., visco-elastic polyurethane foam sometimes referred to as memory foam), another type of foam, a conventional mattress, a box spring, a fluid bladder, a straw-filled pad, a feather-filled pad, a sawdust-filled pad, a spring-based pad, and/or another material that offers flexibility and/or softness. A top side  22  of the bottom layer  14  can partially define a recess  24  sized to receive the sensing layer  18 . The recess  24  can have a depth less than a height of the sensing layer  18  when inflated to a normal pressure as shown in  FIG. 2 . The recess  24  can have one open end  26  at a foot of the mattress  12  as shown in  FIG. 1 . The open end  26  can allow a cord, hose, or other structure to easily access the sensing layer  18 , and the open end  26  can be on a different side of the mattress  12  than shown in  FIGS. 1 and 2 . 
     The top padding layer  20  can be a comfort layer, which can be softer (i.e., less firm) than the bottom padding layer  14 . The top layer  20  can include high density foam (e.g., memory foam), another type of foam, a conventional mattress, a fluid bladder, a straw-filled pad, a feather-filled pad, a sawdust-filled pad, a spring-based pad, and/or another material that is offers flexibility and/or softness. A bottom side  28  can partially define the recess  24 . Alternatively, the recess  26  can be entirely defined by just one of the bottom layer  16  and the top layer  20 . Also, depending on the thickness of the air bladder  18  and the firmness of the bottom and top layers  16  and  20 , among other considerations, the bladder  18  can fit between layers  16  and  20  without the need for the recess  26 . 
     The sensing layer  18  as shown in  FIG. 3  includes a fluid bladder  30 , a pressure sensor  32  configured to sense a fluid pressure within the fluid bladder  30 , and a controller  34 . The sensing layer  18  is also shown coupled to a control unit  38  and a pump  39 . However, instead of using the pump  39  to inflate the bladder  30 , another inflation mechanism can be provided. For example, the bladder  30  can be self-inflating by including a foam or other material within the bladder  30 . As another example, compressed gas (e.g., compressed air or CO 2 ) can be used to inflate the bladder  30 . Also, as is explained below in greater detail, the pressure sensor  32  can detect pressure changes caused by, for example, a pulse and/or breath of a user on the mattress  14 , and the controller  34  can determine the user&#39;s heart rate, respiration rate, and/or other vital signs based on the detected pressure changes. 
     The fluid bladder  30  can hold air or another fluid, such as water, gel, another gas, or a combination thereof. The fluid bladder  30  can be sized to extend over a large portion of the top side  22  of the bottom layer  16 , such as substantially the entire top side  22  of the bottom layer  16  as shown in  FIG. 1 . Alternatively, the bladder  30  can cover a smaller area of the top side  22  than as shown, such as an area of the top side  22  above which the torso of a user is expected to be positioned. Thus, the size of the fluid bladder  30  can allow the fluid bladder  30  to sense pressure changes over a wide range of positions of the user on the mattress  14 . That is, even if the pressure sensor  32  is far from a source of a pressure change (e.g., a beating heart or inhaling or exhaling lungs of the user), the pressure change can create a wave within the bladder  30  propagating the pressure change to the sensor  32 . 
     Also, the bladder  30  can be shaped to achieve a balance between allowing air to pass across the bladder  30  and providing the bladder  30  with a large area such that pressure changes are not dampened too greatly before reaching the bladder  30 . Allowing air to pass across the bladder  30  can be beneficial for multiple reasons. First, passing air can dissipate heat from the top layer  20 , thereby reducing a feeling of warmth common among foam mattresses. Second, passing air can remove moisture, thereby reducing the likelihood of mold growth within the mattress  14 . 
     To achieve this balance, the bladder  30  as shown in  FIG. 3  defines a plurality of apertures  36  arranged in a grid pattern. The apertures  36  can allow heat and moisture to pass across the bladder  30 . Due to the arrangement of the apertures  36 , the bladder  30  defines transverse and lengthwise paths shown, respectively, by lines  35   a  and  35   b  in  FIG. 3 . Waves caused by pressure changes input to the top layer  20  can propagate along the paths  35   a  and  35   b  to the sensor  32 . Thus, the bladder  30  as shown in  FIG. 3  can both allow moisture to pass between the layers  16  and  20  and can prevent pressure input to the top layer  20  from being dampened before reaching the sensor  32 . 
     However, the bladder  30  can have a different shape from illustrated while still achieving similar functionality. For example,  FIG. 4  shows a bladder  40  including longitudinal slots  42  for allowing moisture to pass the bladder  40 . The bladder  40  also includes longitudinal connectors  44  for allowing waves to propagate to the sensor  32  in the bladder  40 . The sizes of the slots  42  and connectors  44  can be a trade off between providing a large area for the passage of moisture and providing the bladder  40  with a large area to prevent pressure changes from being dampened before reaching the bladder  40 . As another example in which the shape of the bladder  30  can different from as shown in  FIG. 3 , the fluid bladder  30  can include multiple discrete compartments, in which case each compartment can include one of the pressure sensors  32 . For example, if the mattress  14  is large enough for two users, the mattress  14  can include two discrete compartments, each including its own sensor  32 , for separately detecting the vital signs of the two users. However, the pressure detected by a single sensor  32  can indicate vital signs of multiple users, and the controller  34  can perform a pattern recognition algorithm or other calculation to determine the users&#39; respective vital signs as explained in more detail below. 
     As shown in  FIG. 6 , the sensing layer  18  can be subject to a shearing force is a lateral force applied to the top padding layer  20 . As a result, the sensing layer  18  can be deformed to the shape shown in phantom at  18 ′. The height  31  of the fluid bladder  30  can be great enough such that when the sensing layer  18  undergoes an expected amount of deformation, the top of the sensing layer  18  does not contact the bottom of the sensing layer  18 . Contact between the top and bottom of the sensing layer  18  can allow force to be transmitted directly from the top padding layer  20  to the bottom padding layer  16 , in which case the pressure sensor  32  may not accurately detect pressure changes in the fluid bladder  30 . The height  31  can also be based on the expected weight of the top padding layer  20  and any users that rest thereon, as well as the expected pressure within the fluid bladder  30 . Under normal conditions (e.g., a normal user weight and a normal top layer  20  weight), the fluid bladder  30  portion of the sensing layer  18  can have an approximately 1.0″ height. 
     As mentioned above, the pressure sensor  32  can be configured to sense a fluid pressure within the fluid bladder  30 . For example, the pressure sensor  32  can be inside the bladder  30 . As another example, the pressure sensor can be in a portion of the pump  39  in fluid communication with the bladder  30 , and thus in a portion of the pump  39  having a pressure corresponding to a pressure in the bladder  30 . The sensor  32  can include a semiconductor pressure sensor or another type of pressure sensor. Additionally, other types of sensors, such as a temperature sensor, can also be included. The sensor  22  can output a pressure signal α to the controller  34 . 
     Further, the pressure signal a can indicate the whether or not a person is lying on the bladder  30 , the heart rate of a person lying on the bladder  30 , the respiration rate of a person lying on the bladder  30 , other movement (e.g., rolling or limb movement) of a person lying on the bladder  30 , the temperature of the fluid in the bladder  30 , and vital signs because all these can be factors of the pressure within the fluid bladder  30 . 
     The controller  34 , which can include a memory and a CPU for executing a program stored on the memory, can control the pump  39  to produce pressurized air. For example, the controller  34  can control the pump  39  in response to the pressure signal a such as by instructing the pump  39  to inflate the bladder  30  when the controller  34  determines the pressure in the bladder  30  is below a set amount. While the controller  34  is shown as inside the bladder  30 , the controller  34  can alternatively be part of the control unit  38  or otherwise located outside the bladder  30 . The controller  34  can be hard-wired to the sensor  32  and/or pump  39 , in wireless communication with the sensor  32  and/or pump  39  using, e.g., a standard wireless protocol (IEEE 802.11, Bluetooth, etc.), or the controller  34  can communicate with the sensor  32  and/or pump  39  in another way. 
     Additionally, the controller  34  can analyze the pressure signal a to determine a heart rate, respiration rate, and/or other vital signs of a user lying or sitting on the mattress  12 . As explained above, when a user lies on the top layer  20 , each of the user&#39;s heart beats and breaths can create a force on the top layer  20  that is transmitted to the bladder  30 . As a result of the force input to the bladder  30  from a heart beat or breath, a wave can propagate through the bladder  30  to the sensor  32 . The sensor  32  can detect the wave, and the pressure signal a output by the sensor  32  can thus indicate a heart rate or respiratory rate of a user. As a result, the bladder  30  can prevent waves from being dampened by foam prior to reaching the sensor  32 . 
     To overcome a DC offset in the pressure signal α, the pressure signal α can pass through a circuit splitting the signal into a DC coupled path and an AC coupled path, and the AC coupled path can be amplified and filtered. The controller  34  can perform a pattern recognition algorithm or other calculation based on the amplified and filtered pressure signal α to determine the user&#39;s heart rate and respiratory rate. For example, the algorithm or calculation can be based on assumptions that a heart rate portion of the signal α has a frequency in the range of 0.5-4.0 Hz and that a respiration rate portion of the signal α has a frequency in the range of the range of less than 1 Hz. The controller  34  can also be configured to determine other characteristics of a user based on the pressure signal α, such as blood pressure, tossing and turning movements, rolling movements, limb movements, weight, or the identity of the user. Further, the controller  34  can receive signals from other sensors (e.g., a temperature sensor). The controller  34  can output a status signal β indicating the characteristics of the user (e.g., heart rate and respiratory rate) to the control unit  38 . 
     The control unit  38  can include a transmitter, a display screen, and controls. The transmitter can relay the status signal β to a database or other source. The transmitter can be a wireless transmitter operating using a standard wireless protocol (e.g., IEEE 802.11, RF, Bluetooth, or 3G), though the transmitter can alternatively be hardwired to the remote source using a phone line, Ethernet line, or other connection. As a result, the database can store sleep information produced as a result of the status signal β, and the user can be alerted to sleep issues based on long-term sleep trends or provided with other communications regarding the user&#39;s sleep (e.g., an alarm warning of apnea), fitness level, cardiovascular condition, or other health information. 
     The display screen can display information relayed in the status signal β, such as a sleep score based on the user&#39;s heart rate, respiratory rate, amount of time spend in REM sleep, total time in bed, and other considerations. 
     The controls can be used to control the operation of the sensor  32  and/or controller  34 . For example, the controls can be used to increase the pressure in the bladder  30 , instruct the sensor  32  and/or controller  34  to operative in a privacy mode in which data is not detected, retained, displayed, transmitted, and/or analyzed, or to communicate with the database to obtain sleep information (e.g., sleep trends, sleep scores from previous nights, sleeping tips). The database can alternatively or additionally be accessible using a computer, e.g., via the internet. 
     The pump  39  can be a rotary type pump or another type of pump. The pump  39  can be fluidly coupled to the bladder  30  via a hose. However, the pump  39  can alternatively be integral with the mattress  14  such that a hose is not necessary. 
     The mattress  14  can have a different configuration from as shown in  FIGS. 1-2 . As such, while the bottom layer  16 , sensing layer  18 , and top layer  20  are shown as being discrete structures, alternative configurations are possible. For example,  FIG. 5  illustrates a foam mattress  60  including a top portion  62  and a bottom portion  64  connected by a linking portion  66 . The mattress  60  defines an envelop  68  for receiving the sensing layer  18 . As additional examples, the sensing layer  18  can be sealed within the mattress  14  during the manufacture of the mattress  14 , or the sensing layer  18  and top layer  20  can be integral. Also, in another example, the bladder  30  can be positioned between a foundation (e.g., the frame  12 ) and the bottom layer  16  of the mattress  14 . 
     While the invention has been described in connection with what is presently considered to be the most practical example, it is to be understood that the invention is not to be limited to the disclosed example but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.