Patent Publication Number: US-2005138728-A1

Title: Patient support for external counterpulsation cardiac assist device

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates generally to external counterpulsation cardiac assist, and more particularly, to a patient support for use with external counterpulsation cardiac assist.  
      2. Prior Art  
      In external counterpulsation cardiac assist device (APPLICATOR) applicators (hereinafter “applicator”) of the prior art, the limb pressure is generated by inflating balloon-like chambers that surround the limb. In addition, to keep the volume of the inflow air in check, the balloon-like chambers are encased in a relatively inextensible fabric to minimize the bulging out of the applicator assembly. A cross-section of a typical such arrangement is illustrated in  FIG. 1 .  
      The applicator  100  (alternatively referred to as an actuator) is used by laying the patient on a bed, “wrapping” the applicator around a limb or other body portion  101  (such as the legs, thighs, arms, or buttocks) and affixing the outer liner  104  by Velcro or other similar means such that the assembly stays tightly over the limb  101 . The applicators are generally constructed with an inner layer  102  and a relatively inextensible outer layer  104 . Between the inner and outer layers  102  and  104 , balloon-like members  106  are positioned. The balloon like members  106  are typically made from an elastic material and provide inner cavities or chambers. The applicator operates by pressurizing the balloon-like members  106  with air or other gases through an inlet and/or outlet  108 , preferably in synchronization with the patient&#39;s cardiac cycle.  
      Part of the limb  101  such as ankles, knees, feet, elbows, chest area, neck and the head are not covered since due to the absence of a considerable amount of muscle mass, no significant amount of blood can be displaced by the external pressure by the applicators. In the applicators of the prior art, the patient&#39;s leg, thighs, arms and buttock are supported by the outer layer  104  over the bed or table (collectively referred to herein as a tabletop). As the result, as the air pressure builds up in the chamber  106 , the outer layer  104  has a tendency to bulge out, thereby lifting the limb  100  above the top surface of the tabletop. This is the case even though relatively inextensible outer applicator layers are commonly used which make them resist radial extension but cannot prevent longitudinal bulging of the applicators. The aforementioned lifting following the pressurization of the applicator is illustrated in  FIGS. 2   a  and  2   b .  FIG. 2   a  illustrates the applicator during an evacuation cycle in which the chamber  106  is evacuated and  FIG. 2   b  illustrates a pressurization cycle on the right in which the chamber  106  is pressurized with air or any other suitable gas. As can be readily appreciated from the comparison between  FIGS. 2   a  and  2   b , the pressurization of the chamber  106  results in a lifting of the limb  100  by an amount H.  
      Appreciating that the applicator can operate at up to one cycle per heart beat cycle, i.e., in the order of about 60-80 times a minute, and that each time the patient&#39;s limb(s)  101  is effectively thrown up a considerable distance (H) above the top surface  112  of the tabletop  110 , the discomfort facing the patient becomes apparent. In fact, the length of time that the procedure can be continued is very much related to how long the patient can tolerate such highly stressful and rapid lifting, without excessive and harmful fatigue. In addition, patients also tend to tighten their muscles due to such rapid lifting, thereby reducing the effectiveness of the entire procedure.  
      A need therefore exists for means to alleviate patients from the stress and other harmful effects of the aforementioned lifting actions during the procedure.  
     SUMMARY OF THE INVENTION  
      Therefore it is an object of the present invention to provide a patient support for maintaining at least a portion of the patient above a tabletop during a positive pressure portion of the external counterpulsation cardiac assist procedure.  
      Accordingly, a patient support for external counterpulsation cardiac assist devices is provided. The patient support comprises: a base; and at least one support connected to the base for maintaining at least a portion of the patient above a tabletop during a positive pressure portion of the external counterpulsation cardiac assist procedure.  
      Preferably, the at least one support comprises a padded portion fabricated of a soft material. The at least one support further preferably comprises a fixing means for fixing the at least a portion of the patient thereto. Preferably, the fixing means comprises a strap having a first end fixed to the at least one support and a corresponding buckle fixed to the at least one support.  
      In a first embodiment of the patient support, the base is the tabletop. In which case, the patient support preferably further comprises moving means for movably fixing the at least one support to the tabletop such that the at least one support can be movably positioned under the portion of the patient to be maintained above the tabletop. The moving means preferably comprises the at least one support having a slide portion which is slidably arranged in a corresponding slot on a top surface of the tabletop. Preferably, the at least one support further has a locking means for locking the at least one support at a predetermined position corresponding to the portion of the patient to be maintained above the tabletop. Preferably, the locking means comprises a locking shaft having a keyed portion on one end and a threaded portion on another end, the keyed portion being slidingly disposed in a corresponding keyway in the tabletop, the locking means further comprising a threaded knob threadingly engaged with the threaded portion, wherein tightening of the knob on the shaft causes the keyed portion to engage a lower surface of the tabletop to thereby lock the at least one support thereon.  
      Where the base is a tabletop, the patient support preferably further comprises height adjustment means for movably fixing the at least one support to the tabletop such that a height of the at least one support above the tabletop can be adjusted. Preferably, the height adjustment means comprises at least one rod connected to the at least one support, the at least one rod being slidingly disposed in a corresponding bore in the tabletop. Preferably, the patient support further comprises a locking means for locking the rod at a predetermined height. The locking means preferably comprises the at least one rod having at least one groove and a detent housed in the tabletop for operatively engaging with the at least one groove.  
      The patient support preferably further comprises biasing means for biasing the at least one support above the tabletop. The biasing means preferably comprises a constant tension spring corresponding to each of the at least one supports, the constant tension spring having a portion disposed in the tabletop and a portion connected to the at least one support.  
      In a second embodiment of the patient support, the base is raised above the level of the patient and tabletop. In such an embodiment, the at least one support preferably comprises a sling, the sling having a tensioning member and balancing means for maintaining the sling in a balanced position to maintain the at least a portion of the patient above the tabletop. Preferably, the tensioning member is a cable attached at a first end to the sling and at a second end to the balancing means. The balancing means is preferably a constant tension spring attached to the second end. Alternatively, the balancing means is a counterweight attached to the second end.  
      Also provided is a patient table for use with external counterpulsation cardiac assist. The patient table comprises: a tabletop having a top surface; and at least one support connected to the tabletop for maintaining at least a portion of the patient above the top surface of the tabletop during a positive pressure portion of the external counterpulsation cardiac assist procedure.  
      The at least one support preferably comprises a padded portion fabricated of a soft material. Preferably, the at least one support further comprises a fixing means for fixing the at least a portion of the patient thereto. The fixing means preferably comprises a strap having a first end fixed to the at least one support and a corresponding buckle fixed to the at least one support.  
      The patient table preferably further comprises moving means for movably fixing the at least one support to the tabletop such that the at least one support can be movably positioned under the portion of the patient to be maintained above the tabletop. The moving means preferably comprises the at least one support having a slide portion which is slidably arranged in a corresponding slot on the top surface of the tabletop. Preferably the at least one support further has a locking means for locking the at least one support at a predetermined position corresponding to the portion of the patient to be maintained above the tabletop. Preferably, the locking means comprises a locking shaft having a keyed portion on one end and a threaded portion on another end, the keyed portion being slidingly disposed in a corresponding keyway in the tabletop, the locking means further comprising a threaded knob threadingly engaged with the threaded portion, wherein tightening of the knob on the shaft causes the keyed portion to engage a lower surface of the tabletop to thereby lock the at least one support thereon.  
      The patient table further comprising height adjustment means for movably fixing the at least one support to the tabletop such that a height of the at least one support above the tabletop can be adjusted. The height adjustment means preferably comprises at least one rod connected to the at least one support, the at least one rod being slidingly disposed in a corresponding bore in the tabletop. The patient table preferably further comprises a locking means for locking the rod at a predetermined height, wherein the locking means comprises the at least one rod having at least one groove and a detent housed in the tabletop for operatively engaging with the at least one groove.  
      The patient table preferably further comprises biasing means for biasing the at least one support above the top surface of the tabletop. Preferably, the biasing means comprises a constant tension spring corresponding to each of the at least one supports, the constant tension spring having a portion disposed in the tabletop and a portion connected to the at least one support.  
      Still yet provided is a method for supporting a patient during external counterpulsation cardiac assist. The method comprising: applying at least a positive pressure cycle to at least a portion of the patient; and supporting the at least a portion of the patient above a tabletop during the positive pressure portion of the external counterpulsation cardiac assist procedure.  
      The method preferably further comprising movably fixing at least one support to the tabletop such that the at least one support can be movably positioned under the portion of the patient to be maintained above the tabletop. The method preferably further comprising locking the at least one support at a predetermined position corresponding to the portion of the patient to be maintained above the tabletop.  
      The method preferably further comprising movably fixing at least one support to the tabletop such that a height of the at least one support above the tabletop can be adjusted. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These and other features, aspects, and advantages of the apparatus and methods of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:  
       FIG. 1  illustrates a section al view of an APPLICATOR of the prior art shown disposed about a patient&#39;s limb.  
       FIGS. 2   a  and  2   b  illustrate a comparison of the APPLICATOR of the prior art while undergoing a positive pressure cycle ( FIG. 2   b ) and an evacuation cycle ( FIG. 2   a ) thus showing a height H that a person&#39;s limb is lifted during the positive pressure cycle.  
       FIGS. 3   a  and  3   b  illustrate a side view and front view, respectively, of a first variation of the patient supports and table of the present invention.  
       FIG. 4  illustrates an isometric view of another variation of the patient supports and table of the present invention.  
       FIG. 5  illustrates a sectional view of the patient supports and table of  FIG. 4  as taken along line  5 - 5  therein.  
       FIG. 6  illustrates a sectional view of the patient supports and table of  FIG. 4  as taken along line  6 - 6  therein.  
       FIG. 7  illustrates yet another variation of the patients support and table of the present invention.  
       FIG. 8  illustrates a preferred implementation of still yet another variation of the patient supports and table of the present invention.  
       FIG. 9  illustrates an alternative implementation of the patient supports and table of  FIG. 8 .  
       FIG. 10  illustrates a partial front view of the implementations of the patient supports and table of  FIGS. 8 and 9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring now to  FIGS. 3   a  and  3   b  a table having a tabletop  110  and a top surface  112  is shown. The tabletop is given by way of example only and not to limit the scope or spirit of the present invention. For example, the supports of the present invention are equally applicable to beds. Hereinafter, “table” and “tabletop” are collectively used to refer to tables, beds, and any other structure, such as a sling, which are used to support a patient in a lying or partially lying position. Although, the tabletop  110  is shown as not having any supporting structure, those skilled in the art will appreciate that the same can be supported by legs, a stand rails, or the like.  
      The patient support and table are particularly suited in external counterpulsation cardiac assist (ECPCAD) procedures for at least the reasons set forth above. The patient support comprises a base and at least one support  114  connected to the base for maintaining at least a portion of the patient above tabletop  110  during a positive pressure cycle of the external counterpulsation cardiac assist. Although, the base, in the preferred implementation, is a tabletop  110 , as will be discussed below, the base does not have to be the tabletop, but can be positioned above the top surface  112  of the tabletop. Furthermore, the support  114  is described as being “connected” to the tabletop  110 , however, such is intended to describe not only a fixation of the support on the tabletop  110  but also a placement of the support on the top surface  112  of the tabletop  110 , as is shown in  FIGS. 3   a  and  3   b.    
      In the first embodiment of the present invention, as illustrated in  FIGS. 3   a  and  3   b , the supports  114  are provided under one or more of the exposed segments of the body, i.e., the feet, ankles, knees, back, neck and the head. The function of the supports  114  is to hold the limb/body above the top surface  112  of the tabletop  110 , providing enough clearance to clear the inflated applicator&#39;s  100 , thereby preventing the aforementioned up and down movement of the body/limb during the procedure.  FIG. 3   a  illustrates two applicator&#39;s  100 , a first positioned on the thigh and a second positioned on the shin. In this configuration, a first support  114  is positioned at the knee and a second support is supported at the ankle. It is assumed that the rest of the body is either supported on the tabletop  112  or on further supports (not shown). As is illustrated, in  FIGS. 3   a  and  3   b , the upper surface of the supports  114  are preferably curved to conform to the shape of the portion of the patient to be supported. The upper surface is preferably a complex curve.  FIG. 3   a  shows surface  114   a  having a convexity to support the convexity of the joints while surface  114   b  has a concavity to conform to the cylindrical shape of the leg.  
      Preferably, the support surfaces  114   a ,  114   b  are made of sufficiently soft padded material and hold the limb or other body portion securely to prevent it from slipping off the supports  114 . Although not preferred, a strap  116  and mating buckle  118  may be provided to retain the limb or other body portion on the support  114 . The height of the supports  114  is sufficient to maintain the outer portions of the applicator  100  above the top surface  112  of the tabletop  110 . In terms of the previously described prior art, the supports  114  should maintain the body portion to be supported above the top surface  112  of the tabletop  110  at a height greater than H.  
      Referring now to  FIG. 4 , there is shown a second embodiment of the present invention. In the second embodiment, the tabletop  200  has supports  202  having means for adjusting both the position of the supports  202  on the tabletop  200  and the height of the supports  202  above the top surface  204  of the tabletop  200 . The means for adjusting the supports  202  under the body provides for the most comfortable height and positioning of the supports  202 . Although the supports  202  are shown adjusting in a lateral direction (A), it will be appreciated by those skilled in the art that other directions of adjustment are possible and may be desired.  
      Referring now to  FIG. 5 , the means for movably fixing the supports  202  to the tabletop  200  is such that the supports  202  can be movably positioned under the portion of the patient to be maintained above the tabletop  200 . The moving means preferably comprises the supports  202  having at least one, and preferably two slide portions  206 , each of which are slidably arranged in a corresponding slot  208  on a top surface  204  of the tabletop  200 . The slide portions  206  are preferably cylindrical shafts. The slots  206  are preferably arranged in the direction of adjustment along the tabletop  200 , in the illustrated example, in the A direction. The slide portions  206  are prevented from falling into the slots  208  by a slide plate  210 . The slide plate  210  is sized such that it has a larger dimension than the widest dimension of the slots  210  such that it slides on at least a portion of the top surface  204  of the tabletop  200 . The slide plate  210  has bores  212  corresponding to each of the slide portions  206  and is either fixed therein to fix the height of the supports  202  above the top surface  204  of the tabletop  200 , or as will be discussed below, the slide portions  206  can be movingly disposed in the bores  212  to provide a height adjustment of the supports  202 .  
      The supports  202  preferably further have a locking means for locking the supports  202  at a predetermined position corresponding to the portion of the patient to be maintained above the tabletop  200 . The locking means preferably comprises a locking shaft  214  disposed in a bore  216  of the slide plate  210 . The locking shaft  214  has a keyed portion  218  on one end and a threaded portion  220  on another end. The keyed portion  218  is slidingly disposed in a corresponding keyway  222  in the tabletop  200 . A threaded knob  224  is provided and is threadingly engaged with the threaded portion  220  of the locking shaft  214 . When the threaded knob  224  is tightened on the locking shaft  214 , the keyed portion  218  engages a lower surface  226  of the tabletop  200  to thereby lock the support  202  to the tabletop in a predetermined position along direction A.  
      Referring now to  FIG. 6 , the tabletop further comprises a height adjustment means for movably fixing the support  202  to the tabletop  200  such that a height (h) of the supports above the top surface  204  of the tabletop  200  can be adjusted. The height adjustment means preferably comprises at least one rod, preferably the slide portions  206  connected to the support  202 . The slide portions  206  being slidingly disposed in a corresponding bore  208  in the tabletop  200  and also in the bores  212  of the slide plate  210 . The slide portions  206  preferably being connected to the support  202  by way of a threaded fastener  228 .  
      A locking means is provided for locking the supports  202  at a predetermined height (h) above the top surface  204  of the tabletop  200 . Preferably, the locking means comprises each of the slide portions  206  having at least one groove  230 , and preferably a plurality of grooves  230  disposed along a length of the slide portions  206 . A detent  232  is slidingly housed in either the tabletop  200  or preferably, the slide plate  210  for operatively engaging and disengaging with the grooves  230 . A release means, such as handle  234  pulls the detent from the groove  230  to release the detent  232  from the groove  230  and allow adjustment of the height of the support  202 . Such release means are well known in the art, particularly in the art of automobile headrests. After release of the detent  232  the support  202  can be raised or lowered such that the detent  232  aligns with another groove  230  corresponding to a desired height. After such, the handle  234  is pushed forward to engage the desired groove  230  and thereby lock the support  202  at a desired height. Although the release means is shown as being manually operated, automatic release means can also be employed.  
      Referring now to  FIG. 7 , there is illustrated another version of the supports  300  for supporting a patient above a top surface  304  of a tabletop  302 . Supports  300  being similar to the previously described supports  114 ,  202  but has a biasing means for biasing the support  300  above the tabletop  302 . The biasing means preferably comprises a first cupped collar  306  disposed in the support  300  and a second cupped collar  308  disposed in the tabletop  302 . The second cupped collar  308  further having a portion slidingly disposed in the first cupped collar  306 . Preferably a pair of the first and second cupped collars  306 ,  308  are provided. A constant tension biasing spring  310  is disposed in a cavity  312  defined by the first and second cupped collars  306 ,  308  to bias the support  300  away from the top surface  304  of the tabletop  302 .  
      Referring now to  FIGS. 8-10 , there is shown another embodiment of the present invention where the base is raised above the level of the patient and the top surface  404  of the tabletop  402  and one or more of supports  400  hold the limb sufficiently above the bed surface by an overhanging support, i.e., by placing the exposed segment (e.g., foot, ankle, knee, etc.) into a sling type of support  400  to support the limb/body above the top surface  404  of the tabletop  402 , providing enough clearance to clear the inflated Applicator&#39;s  100 . Preferably more than one sling is provided, strategically positioned about the APPLICATOR  100 .  
      The support  400  preferably comprises a sling portion  406  and first and second sling bars  408 ,  410 . The sling portion preferably being a fabric such as canvas and having first and second loops  412 ,  414  in which the first and second sling bars are disposed. The support  400  further has a tensioning member, such as a cable  416 . The cable  416  being attached to the sling rods  408 ,  410  at a first end. Preferably, an end of the cable  416  is looped around each of the sling bars  408 ,  410  and clamped as is known in the art. A hole  418  is provided in the sling portion  406  to accommodate the fastening of the cable  416  to the sling rods  408 ,  410 .  
      The cable  416  is routed over at least one, and preferably two pulleys  420  connected to the ceiling or other structure. The cable  416  is connected at another end to a balancing means for maintaining the support  400  in a balanced position to maintain the patient above the tabletop  402 . In a first variation shown in  FIG. 9 , the balancing means is a constant tension spring  422  attached at one end to the cable  416  and at another end to the floor or other structure. In a second variation shown in  FIG. 8 , the balancing means is a counterweight  424  attached to the cable  416 , such that the counterweight  424  hangs freely from the cable  416 .  
      While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.