Patent Publication Number: US-2007113351-A1

Title: Patient support apparatus having an air cell grid and associated method

Description:
TECHNICAL FIELD  
      The present invention relates to an apparatus for supporting a patient during a medical procedure and to a method of using the apparatus to support a patient. More particularly, the present invention relates to a surgical support surface for supporting a patient during a surgical procedure and to a method of use for the surgical support surface.  
     BACKGROUND OF THE INVENTION  
      A surgical support surface supports a patient on a surgical table. A typical surgical support surface includes a foam rubber interior and a plastic cover. When a patient lies on the typical surgical support surface, the pressure interface between the patient and the surgical support surface is concentrated at particular locations on the patient&#39;s body, such as at the patient&#39;s heals, sacrum, scapulas, and cranium. Pressure ulcers may occur at locations of high interface pressure between the patient and the surgical support surface. Additionally, when the surgical table is moved or tilted, areas of high interface pressure are subject to shear. It is desirable to minimize areas of high interface pressure between the patient and the surgical support surface and to prevent the occurrence of shear during movement of the surgical table.  
      U.S. Pat. No. 5,966,763 attempts to address the problem of high interface pressure between the patient and a surface pad. A vacuum bead bag is placed in the surface pad at a location for engaging the patient. The vacuum bead bag conforms to the contour of the patient to increase the surface area of contact between the patient and the surface pad. Once the vacuum bead bag conforms to the contour of the patient, the vacuum bead bag is rigidified for supporting the patient during the medical procedure.  
      In addition to minimizing areas of high interface pressure between the patient and the surgical support surface and preventing the occurrence of shear, it is also desirable for a surgical support surface to be radiolucent. Radiolucency of the surgical support surface enables x-rays of a patient to be taken while the patient is located on the surgical support surface.  
     SUMMARY OF THE INVENTION  
      The present invention relates to an apparatus for supporting a patient during a medical procedure. The apparatus comprises a bead bag that is filled with compressible beads. The bead bag forms a lower layer of the apparatus. The apparatus also comprises a layer of foam material that is located above the bead bag and an air cell grid that has a plurality of inflatable air cells. The air cell grid forms an upper layer of the apparatus and provides a soft surface upon which the patient lies. The bead bag, when subjected to a vacuum, becomes rigid for supporting the air cell grid against the patient for helping to maximize a surface area of contact between the patient and the apparatus.  
      According to another aspect, the present invention relates to an apparatus for supporting a patient during a medical procedure. The apparatus comprises an air cell grid having a plurality of inflatable air cells. Each air cell includes a base wall and an upper wall. The upper wall moves away from the base wall when the air cell is inflated into an expanded condition. The apparatus also comprises an electrical switch for indicating a collapsed condition of an associated air cell of the air cell grid. The electrical switch includes a first electrical contact that is located on the base wall of the associated air cell and a second electrical contact that is located on the upper wall of the associated air cell. The first and second electrical contacts come into engagement with one another in response to the associated air cell moving into the collapsed condition.  
      According to yet another aspect, the present invention relates to a method of supporting a patient on a support structure having an air cell grid that includes a plurality of inflatable air cells. In accordance with the inventive method, the air cells of the air cell grid are inflated into an expanded condition. The air cells of the air cell grid are vented to atmosphere while maintaining the air cells in the expanded condition. Air cells of the air cell grid are isolated from one another and from atmosphere. The patient is positioned on the support structure above the air cell grid. The air cells are then placed in fluid communication with one another to equalize air pressure throughout the air cell grid for helping to equalize an interface pressure between the patient and the support structure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The foregoing and other features of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, in which:  
       FIG. 1  is a perspective cutaway view of an apparatus constructed in accordance with the present invention;  
       FIG. 2  is a perspective cutaway view of a group of air cells of an air cell grid of the apparatus of  FIG. 1 ;  
       FIG. 3  is a top view of the group of air cells of  FIG. 2 ;  
       FIG. 4  is a view taken along line  4 - 4  in  FIG. 3 ;  
       FIG. 5  is a flow diagram illustrating a method in accordance with the present invention;  
       FIG. 6  is an exploded perspective view of a group of air cells constructed in accordance with an alternative embodiment of the present invention;  
       FIG. 7  is an exploded perspective view of a group of air cells constructed in accordance with a second alternative embodiment of the present invention; and  
       FIG. 8  is a sectional elevation view of a portion of an apparatus constructed in accordance with a second embodiment of the present invention. 
    
    
     DESCRIPTION OF EMBODIMENTS  
       FIG. 1  is a perspective cutaway view of an apparatus  10  constructed in accordance with the present invention. The apparatus  10  is a surgical support surface for supporting a patient (not shown) during a surgical procedure. Alternatively, the apparatus  10  may be used for supporting a patient during a medical procedure other than surgery. For example, the apparatus  10  may be used in an emergency vehicle, such as an ambulance, in which medical procedures are performed on a patient while transporting the patient to a medical facility.  
      The apparatus  10  illustrated in  FIG. 1  is to be positioned on a surgical table (not shown) below a patient. The apparatus  10  includes a pliable elastic cover  12  that defines an upper surface  14  and a lower surface (not shown) of the apparatus  10 . The lower surface of the apparatus  10  lies on the surgical table and the upper surface  14  of the apparatus supports the patient. The apparatus  10  functions to maximize the surface area of contact between the patient and the upper surface  14  so as to minimize areas of high interface pressure between the patient and the apparatus. Additionally, the apparatus  10  provides stability for retaining the patient in position during movement of the surgical table so as to minimize the occurrence of shear on the patient.  
      As shown in  FIG. 1 , the apparatus  10  includes a bead bag  18 . The bead bag  18  is a pliable plastic bag in which is stored a plurality of compressible beads  20 . A valve  24 , shown schematically in  FIG. 1 , extends through the bead bag  18  for allowing airflow into and out of the bead bag.  FIG. 1  illustrated the valve  24  extending outwardly through the cover  12  of the apparatus  10 . When subjected to a vacuum, the bead bag  18  stiffens, i.e., becomes more rigid. Under a partial vacuum, the bead bag  18  becomes moldable and has a stiffness sufficient to remain in its molded condition. The bead bag  18  becomes rigid when the vacuum is increased. When rigid, the bead bag  18  is no longer moldable.  
      The bead bag  18  forms a lower layer of the apparatus  10 . Only the portion of the cover  12  that defines the lower surface of the apparatus  10  extends between the bead bag  18  and the surgical table. The bead bag  18  has a length and a width that are substantially equal to a length and width of the apparatus  10 . In one embodiment, the bead bag  18  has a width of approximately three feet and a length of approximately seven feet. A depth of the bead bag  18 , measured vertically between a lower surface (not shown) of the bead bag and an upper surface  26  of the bead bag when the bead bag is at atmospheric pressure, i.e., in a non-molded condition, is approximately one and a half to two inches. It should be understood that the dimensions of the bead bag  18  might be varied depending upon the intended use of the apparatus  10 . Also, the dimensions of the bead bag  18  may vary as a result of molding of the bead bag during use.  
      A layer of highly resilient foam material  30  overlies the upper surface  26  of the bead bag  18 . The layer of foam material  30  preferably is formed from polyurethane. The layer of foam material  30  has a length and a width that are substantially equal to the length and width of the bead bag  18  and, in one embodiment of the invention, has a depth that is approximately three-quarters of an inch.  
      An air cell grid  36  overlies the layer of foam material  30 . The air cell grid  36  includes a plurality of air cells  38 . All of the air cells  38  of the air cell grid  36  may be interconnected with one another with a separate valve (not shown) associated with each air cell. In an exemplary embodiment of the apparatus  10 , the air cells  38  are formed in groups with the groups of air cells being interconnected, as is described below.  
       FIG. 2  is a perspective cutaway view illustrating an exemplary group  44  of air cells  38 . The group  44  illustrated in  FIG. 2  includes four air cells  38 . The air cells  38  in the group  44  are formed in a two-by-two array. The group  44  of air cells  38  preferably is molded from vinyl. The vinyl enables each air cell  38  of the group  44  to be inflated into an expanded condition but prevents ballooning of the air cells. As shown in  FIG. 3 , the group  44  also includes four molded air channels  46 . The molded air channels  46  are disposed between laterally adjacent air cells  38  and longitudinally adjacent air cells of the group  44 .  
      A valve  48  ( FIG. 4 ) is associated with the group  44  of air cells  38 . The valve  48  has open and closed conditions. In the open condition, air may flow through the valve  48  and into or out of the air cells  38  of the group  44 . In the closed condition, air is prevented from entering or exiting the group  44  of air cells  38 . Thus, the valve  48 , when in the open condition, may be used for interconnecting the group  44  of air cells  38  with other groups of air cells in the air cell grid  36  and, when in the closed condition, may be used for isolating the group  44  of air cells  38  from other groups of air cells in the air cell grid  36 .  
      With reference again to  FIG. 1 , groups of air cells  38  are arranged laterally and longitudinally adjacent to one another to completely cover the length and width of the layer of foam material  30 . The valves of the groups of air cells  38 , such as valve  48  of group  44 , are interconnected with one another. Preferably, conduits (not shown) located within the apparatus  10  and under the air cell grid  36  interconnect the valves. An air valve  52  ( FIG. 1 ) also connects to the conduits for enabling airflow into and out of the air cell grid  36 .  FIG. 1  illustrates the air valve  52  extending outwardly from the cover  12 . Alternatively, each group of air cells  38  of the air cell grid  36  may include a conduit that extends outside of the cover  12  of the apparatus  10  and valves for interconnecting the groups of air cells may be located outside of the cover  12 .  
      As shown in  FIG. 4 , each air cell  38  of the air cell grid  36  includes a base wall  56  and an upper wall  58 . A common sheet of material may form the base walls  56  of all of the air cell  38  of the group  44 . The upper wall  58  of each air cell  38  is affixed to the base wall  56 . Preferably, the upper wall  58  of each air cell  38  is molded to its associated base wall  56 .  
      The base wall  56  of each air cell  38  is substantially planar and has a generally square configuration. An air channel  60  extends through a base wall  56  of one of the air cells  38  in the group  44 . The air channel  60  is in fluid communication with the valve  48  and enables airflow into and out of the air cells  38  of the group  44 .  
      The air cells  38  each have a fully expanded condition. The air cells  38  are illustrated in  FIGS. 2-4  in the fully expanded condition. When in the fully expanded condition, each air cell  38  has a height of approximately two and a half inches.  
      When an air cell  38  is in the fully expanded condition, the upper wall  58  includes a generally square base portion  64  and a domed upper portion  66 . The base portion  64  ( FIG. 2 ) includes four sidewalls  68 .  FIG. 4  only illustrates two of the sidewalls  68  of each air cell  38 . Each sidewall  68  extends upwardly from the base wall  56  at an acute angle relative to the base wall  56 .  FIG. 4  illustrates the angle between the sidewall  68  and the base wall  56  as angle α. Preferably, angle α is approximately 85 degrees. However, it will be understood by those skilled in the art that the angle α may be different based on the material used and its thickness. The sidewalls  68  extend upwardly from the base wall  56  for approximately one-half of the height of the air cell  38 . The domed upper portion  66  of the air cell  38  connects the four sidewalls  68 . When the air cell  38  is in the fully expanded condition, the domed upper portion  66  of the air cell  38  is located at its farthest distance away from the base wall  56 .  
      The relative angle between the base wall  56  and the sidewall  68  helps with the radiolucency of the apparatus  10 . When the air cell grid  36  of the apparatus  10  is loaded with the weight of the patient, it is unlikely that a large portion of any of the sidewalls  68  of the air cells  38  will extend in a direction perpendicular to an upper surface of the surgical table. An x-ray is usually taken at an angle perpendicular to the upper surface of the surgical table. Since it is unlikely that a large portion of any of the sidewalls  68  of the air cells  38  will extend in the direction of the x-ray, resistance to the x-ray passing through the air cell grid  36  is minimized. As a result, the apparatus  10  provides sufficient radiolucency for allowing x-rays of a patient positioned on the apparatus.  
      The cover  12  of the apparatus  10  completely surrounds the bead bag  18 , the layer of foam material  30 , and the air cell grid  36 . The cover  12  is preferably made from a material that is easily cleaned and that is non-absorptive.  
      As shown schematically in  FIG. 1 , the apparatus  10  also includes a control unit  74 . The control unit  74  may be battery operated or may include an electrical cord for receiving electrical power. Alternatively, the control unit  74  and its associated compresses may be manually operated to either compress air or to pull a vacuum. The control unit  74  includes an air outlet port  76  and a vacuum inlet port  78 . Conduit  77  connects the air outlet port  76  of the control unit  74  to the valve  52 . Conduit. 79  connects the vacuum inlet port  76  of the control unit  74  to the valve  24 . The control unit  74  also includes an air inlet port  82  for connection to a compressed air source (not shown) and a vacuum outlet port  84  for connection to a vacuum source (not shown). Alternatively, the control unit  74  may include a pump (not shown). The air outlet port  76  and the vacuum inlet port  78  may be connected to the pump for providing compressed air and vacuum, respectively.  
      The control unit  74  also includes a control knob  86  that is rotated for performing particular steps associated with the use of the apparatus  10 . By way of example,  FIG. 5  illustrates a process  500  for using the apparatus  10  for supporting a patient during a medical procedure. Various steps of the process  500  may be associated with rotational positions of the control knob  86 .  
      The process  500  of  FIG. 5  begins at step  502  at which the control unit  74  is powered on. At step  504 , the air cells  38  of the air cell grid  36  are inflated into a fully expanded condition. To inflate the air cells  38  to the fully inflated condition, the control unit  74  controls the supply of compressed air into the air cell grid  36 . The valve associated with each group of air cells  38 , such as valve  48  of group  44 , is opened to allow the air pressure within each air cell to increase. The increased air pressure within the air cells  38  expands the air cells into the fully expanded condition. From step  504  the process  500  proceeds to step  506 .  
      At step  506 , the air cells  38  of the air cell grid  36  are vented to atmosphere. To vent the air cells  38  to atmosphere, the valve associated with each group of air cells  38  remains in the open condition and the valve  52  is connected to atmosphere. When the air cells  38  are vented to atmosphere, the air pressure within each air cell substantially equalizes with the atmospheric air pressure. Since, at this time, no forces other than atmospheric pressure are being applied to the air cells  38 , the air cells remain in the fully expanded condition.  
      At step  508 , the valve associated with each group of air cells  38  is closed so that the. groups of air cells are isolated from one another. When isolated from one another, the air cells  38  within each group, such as the air cells of group  44 , remain in fluid communication with one another through the air channels  46 . From step  508  the process  500  proceeds to step  510  at which the patient is positioned on the apparatus  10 . The patient may be positioned in any position on the apparatus  10 . Generally, for surgical procedures, the patient is either in a supine position or in a side-lying position.  
      At step  512 , a partial vacuum is pulled on the bead bag  18 . When subjected to the partial vacuum, the bead bag  18  becomes moldable and remains in its molded position. At step  514 , the medical personnel mold the bead bag  18  to provide support to areas of the patient that are commonly subject to low interface pressure, such as the lumbar region of the spine when the patient is in the supine position, the perineum, and the lateral aspects of the thorax and the thighs. After the bead bag  18  is molded at step  514 , the bead bag  18  is rigidified at step  516 . To rigidify the bead bag  18 , the vacuum on the bead bag  18  is increased. The process  500  proceeds from step  516  to step  518 .  
      At step  518 , the groups of air cells  38  are interconnected, i.e., placed in fluid communication with one another, so that the air pressure throughout the air cell grid  36  equalizes. To interconnect the groups of air cells  38 , the valve associated with each group of air cells  38  is placed in the open condition and the valve  52  remains in the closed condition. When the valve of each group of air cells  38  is opened, the air pressure throughout the air cell grid  36  will equalize. Ideally, when the groups of air cells  38  are interconnected to equalize the air pressure throughout the air cell grid  36 , the distance between the patient and the molded and rigidified bead bag  18  will be relatively constant over the entire area of contact between the patient and the apparatus  10 .  
      When the air pressure throughout the air cell grid  36  is equalized, the surface area of contact between the upper surface  14  of the apparatus  10  and the.patient is maximized. As a result, areas of high interface pressure between the patient and the apparatus  10  are minimized.  
      At step  520 , the medical procedure is performed. The medical procedure may involve moving or tilting of the surgical table. The apparatus  10  of the present invention minimizes movement of the patient during the movement of the surgical table. Also, the use of the layer of foam material  30  between the generally soft air cell grid  38  and the rigidified bead bag  18  helps reduce shear on the patient. The layer of foam material  30  also provides a baseline level of support for the patient should a failure occur to the air cell grid  36 .  
      After the medical procedure is performed, the patient is removed from the apparatus  10  at step  522 . At step  524 , the valves  24  and  52  of the apparatus  10  are opened and the bead bag  18  and the air cell grid  36  are vented to atmosphere. When the bead bag  18  is vented to atmosphere, the bead bag  18  becomes soft and returns to its original non-molded condition. After the bead bag  18  and the air cell grid  36  are vented to atmosphere, the process  500  ends at step  526 .  
      To prevent areas of high interface pressure between the patient and the apparatus  10 , it is desirable to ensure that each air cell  38  of the air cell grid  36  remains at least partially expanded while the patient is being supported on the apparatus  10 . When an air cell  38  “bottoms out,” i.e., collapses so that the upper wall  58  and the base wall  56  of the air cell  38  come into contact with one another, an area of high interface pressure between the patient and the apparatus  10  may occur. To help prevent the bottoming out of air cells  38 , some or all of the air cells  38  of the air cell grid  36  may be constructed to include an integral electrical switch for indicating a bottoming out or collapsed condition of the air cells.  
       FIG. 6  is an exploded perspective view of a group  44 ′ of air cells  38 ′ constructed in accordance with an alternative embodiment of the present invention. The group  44 ′ of air cells  38 ′ of  FIG. 6  may be used in the apparatus  10  illustrated in  FIG. 1 .  
      The base walls  56 ′ of the air cells  38 ′ of the group  44 ′ are formed from a single sheet  90  of material. A first electrically conductive grid  92  is located on an upper surface  96  of the sheet  90 . The first electrically conductive grid  92  that is illustrated in  FIG. 6  includes four electrical contact  94 . One electrical contact  94  is associated with the base wall  56 ′ of each air cell  38 ′ of the group  44 ′. The first electrically conductive grid preferably is screen-printed on the sheet  90 .  
      A second electrically conductive grid (not shown) is also associated with the upper walls  58 ′ of the air cells  38 ′ of the group  44 ′. The second electrically conductive grid preferably is screen-printed on the sheet upper walls  58 ′.  FIG. 6  illustrates an electrical contact  100  of the second electrically conductive grid located on an interior surface of each upper wall  58 ′ of the group  44 ′. The electrical contact  100  on the upper wall  58 ′ of each air cell  38 ′ extends generally perpendicularly to the electrical contact  94  on the base walls  56 ′ of the air cell so that a bottoming out of any portion of the air cell will cause the electrical contacts  94  and  100  to engage one another.  
      The electrical contacts  94  and  100  are electrically coupled to the control unit  74  ( FIG. 1 ). When the electrical contacts  94  and  100  come together, i.e., engage one another, an electrical signals is sent to the control unit  74  indicating that an air cell  38 ′ has bottomed out. The control unit  74  may include an alarm for indicating to the medical personnel performing the medical procedure that an air cell  38 ′ has bottomed out. Additionally, or alternatively, the control unit  74  may include an automatic inflation mode that is responsive to the electrical signal indicative of a bottomed out condition for controlling the supply of compressed air and the valve  52  of the apparatus  10  for providing air into the air cell grid  36  to inflate the air cells  38 ′. When the electrical contacts  94  and  100  disengage as a result of inflation of the bottomed out air cell  38 ′, the control unit  74  discontinues inflation of the air cell grid  36  and closes the valve  52  associated with the air cell grid.  
       FIG. 7  is an exploded perspective view of a group  44 ″ of air cells  38 ″ constructed in accordance with a second alternative embodiment of the present invention. The group  44 ″ of air cells  38 ″ of  FIG. 7  may be used in the apparatus  10  illustrated in  FIG. 1 .  
      The base walls  56 ″ of the air cells  38 ″ of the group  44 ″ are formed from two sheets of material. A lowermost layer  104  is formed from an electrically conductive material. In one embodiment of the invention, the lowermost layer  104  is formed from an electrically conductive vinyl. An insulating layer  106  overlies the lowermost layer  104 . The insulating layer  106  is electrically non-conductive. A plurality of cutouts  108  extends through the insulating layer  106 . A cutout  108  is associated with the base wall  56 ″ of each air cell  38 ″ of the air cell grid  36 . Each cutout  108  in the insulating layer  106  is square and extends over a large portion of the base wall  56 ″ of the associated air cell  38 ″. The portion  110  of the lowermost layer  104  that is open through an associated cutout  108  at the base wall  56 ″ of each cell forms an electrical contact  112 .  
      The upper wall  58 ″ of each air cell  38 ″ is formed from an electrically conductive material. In one embodiment of the invention, the upper wall  58 ″ is formed from an electrically conductive vinyl. The upper wall  58 ″ also forms an electrical contact  114 .  
      The electrical contacts  112  and  114  are electrically coupled to the control unit  74  ( FIG. 1 ). When the electrical contacts  112  and  114  come together, an electrical signals is sent to the control unit  74  indicating that an air cell  38 ″ has bottomed out.  
       FIG. 8  is a sectional elevation view of a portion of an apparatus  10 ′ constructed in accordance with a second embodiment of the present invention. Structures of the apparatus  10 ′ of  FIG. 8  that are the same as or similar to those described with reference to the apparatus  10  of  FIG. 1  are indicated in  FIG. 8  with the same reference numbers as used with regard to  FIG. 1 .  
      The cover  12  of the apparatus  10 ′ of  FIG. 8  is formed from a gas impenetrable material. The apparatus  10 ′ enables the interface temperature between the patient and the apparatus  10 ′ to be regulated. The cover  12  includes spaced inlet and outlet ports (not shown). The inlet port is adapted to receive a conduit for blowing low-pressure air into the cover  12 . The outlet port may be vented to atmosphere or may be connected to low-pressure vacuum source. The air blown into the cover  12  flows through gaps formed between adjacent air cells  38  in the air cell grid  36  and exits the cover  12  through the outlet port.  FIG. 8  schematically illustrates the flow of air through the gaps formed between adjacent air cells  38  of the air cell grid  36  with arrows. The temperature of the air being blown into the cover  12  may be controlled so as to control the interface temperature between the patient and the apparatus  10 ′.  
      From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. For example, the air cell grid  36  may be regionalized so as to provide support for specific portions of the patient&#39;s body. For example, the air cell grid  36  may include a torso region, a lower limb region, etc. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.