Abstract:
An inflatable positioning device is provided. The device includes a pump, a tube extending from the pump, a valve intermediate the length of the tube and non-rectangular inflatable pillow connected to the end of the tube remote from the pump. The non-rectangular inflatable pillow is dimensioned for positioning portions of a patient&#39;s body during surgery.

Description:
[0001]    This application claims the benefit of U.S. Provisional Patent Appl. No. 60/118,293 filed Feb. 2, 1999.  
         [0002]    This application also is a divisional of appl. Ser. No. 09/495,596 now U.S. Pat. No. 6,327,724. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0003]    1. Field of the Invention  
           [0004]    The subject invention relates to inflatable positioning aids for an operating room that enable a patient to be conveniently and safely positioned during surgery.  
           [0005]    2. Description of the Prior Art.  
           [0006]    An anesthetized patient must be maintained substantially immovably in a position that enables convenient access by doctors during surgery. Additionally, the anesthetized patient must be positioned in a manner that maintains an open air passage for continuous unstressed breathing. Still further, the anesthetized patient must be positioned in a manner that will prevent long term pressure at a location that could impede blood flow or put pressure on nerves or vital structures.  
           [0007]    Doctors and other members of a surgical team continue to use fairly crude positioning devices during surgery. For example, patients may be propped into a selected position by rolled-up sections of blankets, sheets and gauze pads. However, these fairly crude positioning devices do not provide an acceptable degree of control, and do not facilitate repositioning intraoperatively. Furthermore, a roll of fabric, or the like, may create local pressure points that would not be appreciated by the surgical team and that could impede blood flow. A restriction of blood flow during a lengthy operation can cause serious damage to limbs, and hence can require a long term regimen of post-operative physical therapy. Nerve damage or damage to other organs may be permanent.  
           [0008]    The prior art has included several inflatable positioning aids. Most of the prior art inflatable positioning aids are very complicated structures that would be costly to manufacture. The complexities arise from having a plurality of angularly aligned internal or external panels that must be carefully secured to one another. The prior art requirement for the plurality of angularly aligned, intersecting and seamed panels adds to manufacturing and assembly costs and substantially complicates quality control inspections of the product.  
           [0009]    The assignee of the subject invention also has rights to an inflatable positioning aid. The assignee&#39;s inflatable positioning aid is described in copending Appl. No. 08/733,629 which was filed on Oct. 17, 1996, and includes: a generally rectangular inflatable pillow; a tube extending into the pillow; a hand pump for directing air through the tube and into the pillow; and a valve for selectively releasing air from the pillow.  
           [0010]    Despite the many advantages of the assignee&#39;s prior inflatable positioning aid, the need for further improvements has been recognized by the inventors herein. For example, certain types of surgery create unique positioning requirements that may not be met appropriately by a rectangular inflatable pillow.  
           [0011]    The subject invention relates to solutions to certain of those unique surgical positioning demands.  
         SUMMARY OF THE INVENTION  
         [0012]    The subject invention is directed to inflatable positioning aids for use during a medical procedure. More particularly, the subject invention relates to inflatable positioning aids that are uniquely configured to meet demands of certain medical procedures. These inflatable positioning aids may be used with a flexible tube, a hand pump for manually inflating the positioning aid and a valve for selectively deflating the positioning aid. The inflatable positioning aid also may be used with the tube, the valve and an adaptor that can be engaged with the flexible tube and with a source of compressed air for automatic inflation of the positioning aid. Such a source of compressed air commonly is present in an operating room. Thus, the use of a source of a compressed air enables very rapid inflation and avoids the need to have a person in the operating room mechanically pump air into the inflatable positioning aid.  
           [0013]    In all embodiments, the inflatable positioning aid is formed from a top panel and a bottom panel, at least portions of which are of substantially identical shape. Preferred embodiments of the inflatable positioning aids of the subject invention do not include end panels, side panels or internal panels that would complicate assembly and increase costs. Rather, the desired shape of the inflatable positioning aid is achieved by the careful selection of the non-inflated shapes of the top and bottom panels as described herein. In all embodiments, the inflatable positioning aid is assembled by positioning identically configured portions of the top and bottom panels in registration with one another and seaming the top and bottom panels to one another at selected locations.  
           [0014]    At least one of the panels of the positioning aid may include a non-inflatable flap extending beyond the periphery of the inflatable portions of the positioning aid. The flap is disposed at a location on which a portion of the patient will lie. Thus, the flap functions to hold the inflatable positioning aid at a specified location during inflation, and during a medical procedure.  
           [0015]    In one embodiment, the inflatable positioning aid defines a wedge-shape after inflation that enables the patient to be shifted from a perfectly horizontal supine position into a position where one side of a patient is elevated slightly. The inflated positioning aid to meet these requirements may be tapered from a first end defining a point or line of substantially zero cross-section to a second end defining a circle, oval or rectangle of larger cross-section. The cross-sectional difference between the first and second ends can be varied by the sizes and shapes of the panels and by the amount of air pumped into the inflatable portion of the positioning aid. Positioning aids of this type will have particularly utility in certain obstetric procedures, such as a caesarian section. In particular, during all childbirth, the uterus tends to compress the vena cava and/or the aorta, thereby impairing blood flow to the fetus (aorto-caval compression syndrome). The shifting enabled by the wedge-shape after inflation displaces the uterus and helps to avoid the compression of the vena cava and/or aorta. The inflatable positioning aid may have a non-inflatable flap extending from one end. The flap may be placed under the patient to prevent lateral shifting as the wedge-shape develops during inflation and to prevent shifting during childbirth.  
           [0016]    The subject invention also relates to a non-rectangular inflatable positioning aid intended for supporting the face in surgical procedures that require a patient to be in a prone position. In this position, it is often difficult to conveniently position the face in a manner that will ensure that the air passages remain open. Accordingly, a generally U-shaped inflatable positioning aid may be provided. The U-shaped inflatable portion of the positioning aid may have an inflatable connecting portion and a pair of inflatable arms. The opening between the pair of inflatable arms may be dimensioned to receive the nose and mouth of the patient. In certain embodiments, the opening between the arms may be substantially T-shaped, with the central portion of the T being dimensioned and configured for receiving the nose and mouth, and with the arms of the T being dimensioned and configured for receiving the eyes of the patient, to prevent excessive pressure on the eyes. The inflatable positioning aid of this embodiment may be made of a transparent material to enable the anesthesiologist to clearly see the face and eyes when the patient is in the prone position. Ends of the arms of the inflatable positioning aid remote from the connecting portion may be joined by a sheet member or strap for ensuring that the inflatable arms remain in selected positions relative to one another, and to prevent the inflatable arms from spreading in a manner that would urge the nose and mouth downwardly against the operating table. A non-inflatable flap may further extend from ends of the arms of the inflatable positioning aid remote the connecting portion. The non-inflatable flap will carry the weight of the torso of the patient and will ensure that the inflatable positioning aid does not shift significantly relative to the patient in response to forces generated during inflation or during the medical procedure. A similar configuration may be employed for back surgery. In this embodiment, the inflatable arms diverge in a V-shape. Additionally, the non-inflatable flap may extend from the inflatable connecting portion. The space between the inflatable arms may be positioned to align with the sternum, and the non-inflatable flap may be positioned under the hips.  
           [0017]    A third inflatable positioning aid is elongated and dimensioned to extend over substantially the entire torso of a patient. This third inflatable positioning aid includes a generally rectangular top panel and a rectangular bottom panel. The rectangular top and bottom panels may be secured to one another about the periphery of at least one panel. Additionally, an elongated central portion is rendered non-inflatable by securing the central portion of the top panel to the central portion of the bottom panel. Areas of the central portion that are not inflated may extend continuously from one longitudinal end of the rectangular inflatable positioning aid to a location near the opposed longitudinal end. This will create first and second spaced apart longitudinally extending inflatable portions. Additionally, the first and second longitudinally extending inflatable portions are connected to one another at a location in proximity to at least one of the ends. Thus, a single source of air can be employed to inflate both longitudinally extending sections of the inflatable position aid. The non-inflated central portion of this inflatable positioning aid preferably is disposed to substantially align with the spine of the patient. Thus, the spine will extend along the non-inflated groove and will not be subjected to pressure. Furthermore, this positioning aid provides two elongate inflatable supports that ensure uniform stable elevation without rocking or tilting that could occur with a single rectangular chamber under the back. An inflatable positioning aid of this type is particularly useful for heart surgery. To ensure that the inflatable positioning aid does not move, this embodiment may include first and second non-inflatable flaps extending respectively from the opposed longitudinal ends of the inflatable portion. The first non-inflatable flap may be positioned under the hips of the patient, and the second non-inflatable flap may be positioned under the head of the patient. Each flap may be a unitary extension of one panel.  
           [0018]    A fourth inflatable positioning aid in accordance with the subject invention is intended for positioning the neck and head when the patient is in a supine position. More particularly, this inflatable positioning aid may include a generally toroidal section dimensioned and configured for supporting the back of the head and an elongate portion for positioning under the neck. The elongate portion may be substantially tangential to the toroidal portion. Additionally, the toroidal portion and the elongate portions may be separately controllable. Thus, the valve employed in this embodiment may differ from the valve employed in other embodiments in that air pressure may be selectively added to or withdrawn from either of the two separate sections of the inflatable support in accordance with the particular needs of the patient.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a top plan view of a patient supported by the wedge-shaped inflatable positioning aid in accordance with the first embodiment of the subject invention.  
         [0020]    [0020]FIG. 2 is a cross-sectional view taken along line  2 - 2  in FIG. 1.  
         [0021]    [0021]FIG. 3 is a cross-sectional view taken along line  3 - 3  in FIG. 1.  
         [0022]    [0022]FIG. 4 is a top plan view of a second embodiment of the subject invention.  
         [0023]    [0023]FIG. 5 is a side elevational view of the inflatable positioning aid shown in FIG. 4.  
         [0024]    [0024]FIG. 6 is a top plan view of a third embodiment.  
         [0025]    [0025]FIG. 7 is a cross-sectional view taken along line  7 - 7  in FIG. 6.  
         [0026]    [0026]FIG. 8 is a top plan view of a fourth embodiment of an inflatable positioning aid that is particularly useful for heart surgery.  
         [0027]    [0027]FIG. 9 is a cross-sectional view taken along line  9 - 9  in FIG. 8.  
         [0028]    [0028]FIG. 10 is a top plan view of a fifth inflatable positioning aid in accordance with the subject invention.  
         [0029]    [0029]FIG. 11 is a side elevational view of the positioning aid shown in FIG. 10.  
         [0030]    [0030]FIG. 12 is a top plan view of an adaptor to enable use of the inflatable positioning aids with a supply of compressed air.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    An inflatable positioning apparatus in accordance with a first embodiment of the subject invention is identified generally by the numeral  10  in FIGS.  1 - 3 . The inflatable positioning apparatus  10  includes a tube  12 , a pump  14  and a valve  16 . In addition to the valve  16 , the pump  14  is provided with two one-way valves (not shown). The first one-way valve is operative to permit air to flow from the pump  14  to the tube  12  each time the pump  14  is manually squeezed. However, this first one-way valve prevents a return flow of air from the tube  12  into the pump  14 . The second one-way valve permits air flow from the ambient environment into the pump  14  as the pump  14  resiliently expands from the squeezed condition to the expanded condition. This second one-way valve, however, prevents an outflow of air from the pump to the ambient environment. The tube  12 , the pump  14  and the valve  16  all may be of prior art design.  
         [0032]    The positioning apparatus  10  further includes an inflatable pillow  18  connected to the end of the flexible tube  12  remote from the pump  14 . The inflatable pillow  18  is formed from substantially trapezoidal top and bottom sheets  20  and  22  each of which has long and short parallel edges and a pair of non-parallel edges. The longer of the parallel edges of each of the top and bottom sheets  20  and  22  are substantially identically dimensioned, and the non-parallel edges converge at substantially identical angles from the longer parallel edge of each sheet  20  and  22 . However, the top sheet  20  preferably is longer than the bottom sheet  22 , such that the distance between the parallel edges on the top sheet  20  is greater than the distance between the parallel edges on the other of bottom sheet  22 . With these relative shapes, the two sheets  20  and  22  can be such that the longer parallel edges of the sheets  20  and  22  will register with one another and the non-parallel edges of the bottom sheet  22  will register with portions of the non-parallel edges of the top sheet  20 . However, the top sheet  20  will extend beyond the shorter parallel edge of the bottom sheet to define a non-inflatable flap  24 .  
         [0033]    The sheets  20  and  22  both are formed from a nylon material with a thickness in the range of 70-400 denier, and preferably about 200 denier. Each sheet  20  and  22  has an inner surface  26  laminated with a layer of urethane that has a thickness of approximately 3.5 mil. Each sheet  20  and  22  further may have a kiss coat of urethane on its outer surface  28  to a thickness that may be in the range of 0.25-0.50 inch.  
         [0034]    One of the sheets  20  or  22  has a fitting  30  mounted thereto at a location in proximity to the longer parallel edge. The fitting  30  may include a flange and a cylindrical portion extending from the flange. The cylindrical portion is passed through an aperture formed in the sheet  20  or  22  such that the flange abuts the inner surface  26  of the sheet  20  or  22 . The flange of the fitting  30  then is welded or adhered in position. The sheets  20  and  22  then have their respective inner surfaces  26  placed in opposing relationship to one another such that the longer parallel edges of the sheets  20  and  22  are registered. In this condition, the non-parallel edges of the bottom sheet  22  will register with portions of the non-parallel edges of the top sheet  20 , and the shorter parallel edge of the bottom sheet  22  will extend transversely across the top sheet  20 . The registered sheets  20  and  22  then are subjected to an RF welding apparatus which welds the bottom sheet  20  to the top sheet  22  around the periphery of the bottom sheet  20 . In particular, the RF welding apparatus applies pressure and radio frequency energy which causes the urethane lamination on the inner surfaces  26  to bond the two sheets  20  and  22  together around the periphery of the bottom sheet  20 . Thus, an inflatable region is defined between the sheets and within the area bounded by the periphery of the bottom sheet  20 .  
         [0035]    With this construction, as shown in FIGS.  1 - 3 , the inflatable pillow  18  includes a long parallel welded seam  32 , a short parallel welded seam  34 , and a pair of non-parallel welded seams  36  and  38  that converge toward one another from the long parallel welded seam  32  toward the short parallel welded seam  34 . Additionally, the inflatable pillow  18  includes the non-inflatable flap  24  that extends beyond the short parallel seam  34 . The kiss coating of urethane on the outer surfaces  28  provides a fluid repellency to the inflatable pillow. In particular, the kiss coating of urethane seals the nylon material of the sheets  20  and  22  and at least partly smoothes out the peaks and valleys inherently present in the nylon. As a result, fluids, such as blood or sweat that may be generated during the medical procedure will be repelled.  
         [0036]    Air may be inserted into the inflatable pillow  18  under the action of the pump  14  to cause the pillow  18  to assume a substantially wedge-shape. As shown in FIG. 3, the wedge-shaped pillow  18  has a small end at the seam  34  and a large end at the seam  32 . The direction of more air into the pillow  18  will cause the volume of the large end of the pillow  18  to increase more than the volume of the small end, thereby enabling the pillow to support a patient at a correspondingly greater angle of tilt. The angle of tilt can be adjusted easily merely by releasing air from the inflatable pillow  18  or adding air thereto.  
         [0037]    Forces exerted on the wedge-shaped pillow  18  by the weight of the patient will urge the pillow laterally, and thereby could cause the patient to move into a less tilted position. To prevent the lateral movement of the pillow  18 , the non-inflatable flap  24  is positioned under the patient, and the weight of the patient on the non-inflatable flap  24  prevents the lateral movement of the wedge-shaped pillow  18 . A similar tilting effect can be achieved by employing an inflatable pillow with rectangular top and bottom panels and a rectangular flap. The inflated wedge shape and the tilting of the patient can be achieved by positioning the seam between the inflatable pillow and the non-inflatable flap at a selected weight bearing location under the patient, such as under one buttocks.  
         [0038]    A second inflatable positioning apparatus is illustrated in FIGS. 4 and 5 and is identified generally by the numeral  40 . The assembly  40  includes a flexible tube  42 , a pump  44  and a valve  46  all of which are similar or identical to the tube, pump and valve described above and illustrated in FIGS.  1 - 3 . The inflatable positioning assembly  40  further includes an inflatable pillow  48  having a substantially U-shape, or Ω-shape as shown most clearly in FIG. 4. The inflatable pillow  48  is formed from two sheets of urethane coated nylon, as described above with respect to the first embodiment. More particularly, the pillow  48  includes an inflatable connecting portion  50  and first and second inflatable legs  52  and  54  extending from the connecting portion  50 . A non-inflatable connecting strap  56  extends between the inflatable legs  52  and  54  at locations furthest from the inflatable connecting portion  50 .  
         [0039]    The connecting portion  50  and the legs  52  and  54  are dimensioned and configured to define an opening  58  therebetween. The opening  58  includes a nose and mouth receiving portion  59  extending substantially parallel to the inflatable legs  52  and  54 . Additionally, the opening  58  includes an eye-receiving portion  60  extending transverse to the inflatable legs  52  and  54  and substantially parallel to the inflatable connecting portion  50 .  
         [0040]    The inflatable pillow  48  can be used during surgical or chiropractic procedures that require the patient to assume a prone (face down) position. The unique shape of the inflatable pillow  48  ensures that the air passages will remain open and that the eyes will be substantially free of pressure. The condition of the air passages and the eyes can be checked by forming the inflatable pillow  48  from a substantially transparent nylon with a substantially transparent coating of urethane thereon. The transparency would enable the anesthesiologist to visually observe the face of the patient. In this embodiment, non-inflatable flaps  62  may extend from ends of the inflatable legs  52  and  54  remote from the inflatable connecting portion  50 . The flaps  62  are dimensioned to be positioned under the chest of the patient and to prevent shifting of the inflatable pillow  38  during inflation and during the medical procedure.  
         [0041]    A third embodiment of a positioning apparatus is illustrated in FIGS. 6 and 7, and is identified generally by the numeral  70 . The apparatus  70  includes urethane coated nylon top bottom panels  72  and  74  which are welded to one another about peripheral regions. The top panel  72  and portions of the bottom panel  74  registered therewith are of generally V-shape, such that the apparatus  70  has first and second inflatable arms  76  and  78  that diverge from an inflatable base portion  80 . Portions of the arms  76  and  78  remote from the base portion  80  are connected to one another by an inflatable connecting tube  82  that limits the amount of divergence of the inflatable arms  76  and  78  during inflation and during the medical procedure and that helps to stabilize the apparatus  80 . A non-inflatable flap  84  extends unitarily with the top or bottom panel  72 ,  74  away from the inflatable connecting portion  80 . The non-inflatable flap  84  can be positioned under the hips of a patient lying face down in a prone position. The inflatable arms  76  and  78  of the positioning device  70  can be positioned under the torso such that the space between the inflatable arms  76  and  78  substantially aligns with the sternum of the patient. Inflation of the device will slightly elevate the torso of the patient from the hips, and will cushion the weight of the patient that would otherwise be placed directly on the chest. The inflatable positioning aid  70  is particularly useful for back surgery.  
         [0042]    A fourth inflatable positioning aid is identified generally by the numeral  90  in FIGS. 8 and 9. The inflatable positioning aid  90  is intended primarily for heart surgery that requires the chest of the patient to be opened. The inflatable positioning aid  90  has rectangular top and bottom panels  92  and  94  formed from a urethane coated nylon, as in the first embodiment. Inflatable portions of the positioning aid  90  are secured to one another along opposed parallel longitudinal side edges  96  and  98  and along opposed parallel top and bottom ends  100  and  102 . Additionally, the top and bottom panels  92  and  94  are secured to one another along a central connection portion  104  that extends from the bottom end  100  to a location near the top end  102 . However, the central connection portion  104  is spaced from the top end  102  of the inflatable portion of the positioning aid  90 . With this design, the inflatable positioning aid  90  defines first and second elongated inflatable portions  106  and  108  which are joined to one another at an inflatable connecting portion  110  near the top end  102 .  
         [0043]    The inflatable position aid  90  further includes a bottom flap  112  that extends from the bottom end  100  and a top flap  114  that extends from the top end  102 . The bottom flap  112  may be disposed beneath the hips of the patient, while the flap  114  may be disposed beneath the head of the patient. Thus, this elongate inflatable positioning aid  90  is secured at both of its longitudinal ends to prevent shifting during inflation or during surgery. As shown most clearly in FIG. 9, central connecting portion  104  defines a groove extending longitudinally along a major portion of the length of the inflatable positioning aid  90 . The groove is aligned with the spine to prevent the weight of the patient from exerting pressure on the spine during a lengthy surgery in which the chest of the patient is opened to access the heart. Additionally, the central connecting portion effectively defines two spaced apart inflatable chambers that stabily elevate both sides of the patient and that prevent tilting or rocking of the patient.  
         [0044]    The fifth embodiment of the inflatable positioning aid is identified by the numeral  120  in FIGS. 10 and 11. The positioning aid  120  is formed from top and bottom panels, as in the previous embodiments. However, the panels are configured to define a toroidal head support  122  and a bar-shaped neck support  124  configured such that interior portions of the head support  122  and neck support  124  do not communicate with one another. However, the head support  122  and neck support  124  are connected along a connection line that extends substantially tangentially to the toroidal head support  122  and substantially parallel to the longitudinal axis of the bar-shaped neck support  124 .  
         [0045]    The inflatable positioning apparatus  120  further includes a single pump  126  communicating with a flexible tube  128 . The end of the tube  128  remote from the pump  126  communicates with a valve  130  that is operative to selectively direct air to either a tube  132  or a tube  134 . The tube  132  extends from the valve  130  to the toroidal head support  122 . The tube  134  extends from the valve  130  to the bar-shaped neck support  124 . By manually adjusting the valve  130 , air from the pump  126  can be directed to either the toroidal head support  122  or the bar-shaped neck support  124 . Similarly, by manually adjusting the valve  130 , air can be released selectively and independently from the toroidal head support  122  or the bar-shaped neck support  124 .  
         [0046]    The inflatable positioning apparatus  120  can be employed by positioning the back of the head of a patient centrally within the toroidal head support  122  and by positioning the bar-shaped neck support  124  directly beneath the neck of the patient. The pump  126  and the valve  130  then can be used to selectively direct air to the toroidal head support  122  or the bar-shaped neck support  124  for inflating the respective supports appropriate amounts to cushion the head and to position the head and neck of the patient.  
         [0047]    The preceding embodiments have schematically illustrated a manual inflation pump  14  in the form of a resiliently deflectable hollow bulb for directing air into the inflatable positioning aid. As an alternate to the manual inflation, the inflatable positioning aid may include an adaptor that enables connection of the inflatable positioning aid to a supply of compressed air that typically can be found in the operating room. The adaptor is identified generally by the numeral  140  in FIG. 12, and includes a short section of flexible tubing  142  with connections  144  and  146  at opposed ends thereof. The connection  144  is a Luer lock connector and includes a tapered nipple  148  and an internally threaded nut  150  surrounding the tapered nipple  148 . The tapered nipple  148  is dimensioned to be received in the outlet  152  of the three-way valve  16 . The internally threaded nut  150  is dimensioned to surround the outlet  152  and threadedly engage Luer lock projections on the outlet. The fitting  146  is a quick connect/disconnect fitting for connection to a supply of compressed gas  154 , such as the types of fittings used for connecting a facial mask to a supply of nitrous oxide or oxygen. Such quick connect/disconnect fittings are sold, for example, by Colder Products Company of St. Paul, Minn. A chain  156  is mounted to the adaptor  140  at a location near the fitting  148 . The chain  156  is provided with a conventional wire wrap that enables the adaptor  140  to be mounted in proximity to the supply of compressed gas.  
         [0048]    The adaptor  140  is used by threadedly connecting the fitting  144  to the outlet  152  of the valve  16 . The fitting  146  then is connected to the supply of compressed gas. The valve on the supply of compressed gas may be opened in the conventional manner to permit inflation of any of the inflatable positioning aids shown in FIGS.  1 - 11  herein. Typically the inflatable positioning aid will be over-inflated slightly. The valve  16  then is adjusted to close the outlet  152 , and the adaptor  140  is separated either from the valve  16  or from the supply of compressed air. The doctor or other medical technician then may slightly open the valve  16  to permit a controlled escape of air from the inflatable positioning aid. The valve  16  then is closed when the proper degree of inflation is achieved. The adaptor  140  may be reconnected to further increase the amount of inflation at any time during the surgery.  
         [0049]    While the invention has been described with respect to certain embodiments, it is apparent that various changes can be made without departing from the scope of the invention as defined by the claims.