Abstract:
A wearable infusion device delivers a liquid medicant to a patient. The infusion device comprises a base that contacts a patient&#39;s skin and a reservoir arranged to be filled with a liquid medicant to be delivered beneath a patient&#39;s skin. The reservoir has an outlet through which the medicant flows. The infusion device further comprises a flexible conduit communicating with the outlet of the reservoir, a pump that causes the medicant to flow down the conduit, an actuator that performs a function related to the operation of the device, and an enable mechanism that enables the actuator in response to the filling of the reservoir with the liquid medicant.

Description:
BACKGROUND OF THE INVENTION 
     Tight control over the delivery of insulin in both type I diabetes (usually juvenile onset) and type II diabetes (usually late adult onset), has been shown to improve the quality of life as well as the general health of these patients. Insulin delivery has been dominated by subcutaneous injections of both long acting insulin to cover the basal needs of the patient and by short acting insulin to compensate for meals and snacks. Recently, the development of electronic, external insulin infusion pumps has allowed the continuous infusion of fast acting insulin for the maintenance of the basal needs as well as the compensatory doses for meals and snacks. These infusion systems have shown to improve control of blood glucose levels, however, they suffer the drawbacks of size, cost, and complexity, which prevents many patients from accepting this technology over the standard subcutaneous injections. These pumps are electronically controlled and must be programmed to supply the desired amounts of basal and bolus insulin. 
     Hence, there is a need in the art for a simple, mechanically driven infusion device for both basal needs and boluses that is directly attached to the body and does not require any electronics to program the delivery rates. The insulin is preferably delivered through a small, thin-walled tubing (cannula) through the skin into the subcutaneous tissue similar to technologies in the prior art. The present invention, in its various embodiments, is directed to providing such a device. 
     SUMMARY OF THE INVENTION 
     The invention provides a wearable infusion device comprising a base that contacts a patient&#39;s skin, a reservoir arranged to be filled with a liquid medicant to be delivered beneath a patient&#39;s skin, the reservoir having an outlet through which the medicant flows, and a flexible conduit communicating with the outlet of the reservoir. The device further comprises a pump that causes the medicant to flow down the conduit, an actuator that performs a function related to the operation of the device, and an enable mechanism that enables the actuator in response to the filling of the reservoir with the liquid medicant. 
     The reservoir may be formed of flexible material and the enable mechanism may be responsive to the inflation of the reservoir upon being filled with the liquid medicant to enable the actuator. The reservoir may be an expandable structure and the enable mechanism may be responsive to expansion of the reservoir upon being filled with the liquid medicant to enable the actuator. The enable mechanism may comprise a follower that follows the expansion of the reservoir. The actuator may be displaced when performing the function related to the operation of the device, the device may further comprise a latch positioned to impede the displacement of the actuator, and the enable mechanism may reposition the latch when the reservoir is filled to permit the displacement of the actuator. 
     The enable mechanism may comprise a follower that follows the expansion of the reservoir and is coupled to the latch. The follower may comprise a bar extending across the reservoir. 
     The actuator actuates the pump to cause the medicant to flow down the conduit. The actuator may comprise at least one push button which, when depressed, causes the pump to cause the medicant to flow down the conduit. The device may further comprise a latch positioned to impede the displacement of the at least one push button, and the enable mechanism may reposition the latch when the reservoir is filled to permit the at least on push button to be depressed. 
     In another embodiment, a wearable infusion device comprises a base that contacts a patient&#39;s skin, a reservoir arranged to be filled with a liquid medicant to be delivered beneath a patient&#39;s skin, the reservoir having an outlet through which the medicant flows and being expanded upon being filled with the liquid medicant, and a flexible conduit communicating with the outlet of the reservoir. The device further comprises a pump that causes the medicant to flow down the conduit, an actuator that performs a function related to the operation of the device, and an enable mechanism that enables the actuator in response to expansion of the reservoir when the reservoir is filled with the liquid medicant. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further features and advantages thereof, may best be understood by making reference to the following description taken in conjunction with the accompanying drawings, in the several figures of which like reference numerals identify identical elements, and wherein: 
         FIG. 1  is a perspective view of an infusion device embodying the present invention; 
         FIG. 2  is a perspective view of the device of  FIG. 1  with its top cover removed and in a condition ready for having its reservoir filled with liquid medicant; 
         FIG. 3  is a perspective view of the infusion device of  FIG. 1  with its top cover removed after its reservoir has been filled with liquid medicant; 
         FIG. 4  is perspective view with portions cut away of the infusion device of  FIG. 1  illustrating the path of the liquid medicant within the device; 
         FIG. 5  is a top view of the device of  FIG. 1  with its reservoir removed to illustrate the manner in which the liquid medicant is caused to flow within the device; 
         FIG. 6  is a perspective view of the infusion device of  FIG. 1  with its reservoir removed illustrating further aspects of the pump thereof; 
         FIG. 7  is a perspective view of the infusion device of  FIG. 1  with portions cut away to illustrate a safety check valve in its opened position; 
         FIG. 8  is a perspective view similar to  FIG. 7  illustrating the safety check valve closed; 
         FIG. 9  is a perspective view of a reservoir which may be used in the infusion device of  FIG. 1  in accordance with an alternate embodiment; and 
         FIG. 10  is a perspective view with portions cut away of the reservoir of  FIG. 9  illustrating further aspects thereof according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIG. 1 , it illustrates an infusion device  100  embodying the present invention. The infusion device  100  may be useful, for example, in providing boluses of a liquid medicant, such as insulin, to be delivered beneath a patient&#39;s skin. 
     The device  100  generally includes a base  110 , a top cover  120 , and a cannula port  130 . The base  110  prior to application to the patient&#39;s skin, carries a first tab member  112  and a second tab member  114 . The first tab member  112 , when removed, exposes a layer  116  of antiseptic material such as alcohol which may be rubbed against the skin of the patient in the area in which the device  100  is to be adhered. Once the antiseptic has been applied to the patient&#39;s skin, the second tab  114  is removed exposing an adhesive layer on the base  110  which is then used to adhere the device to the skin of the patient. Once the device is adhered to the skin of the patient, a cannula may be introduced into the device and beneath the skin of a patient through the cannula port  130 . 
     As may be seen in  FIG. 2 , the device  100  further includes a pair of actuator push buttons  120  and a reservoir  140  arranged to contain the liquid medicant. As will be seen hereinafter, concurrent pressing of the actuator push buttons  120  causes the liquid medicant within the reservoir  140  to flow down a flexible conduit  150  and eventually beneath the skin of a patient. Each of the push buttons  120  are spring loaded by an associated spring  122  and  124  which return the push buttons  120  to their starting positions. 
     The reservoir  140  as shown in  FIG. 2  does not yet contain the liquid medicant. A latch mechanism  160  precludes the push buttons  120  from being pressed when the reservoir  140  is empty. To that end, it will be noted that a follower bar  162  extends across the reservoir  140  and terminates at a latch member  164 . A dog  166  is coupled to the push buttons  120  and engages the latch member  164  to preclude the actuator buttons  120  from being pushed when the reservoir is empty. 
     Referring now to  FIG. 3 , when the reservoir is filled as illustrated in  FIG. 3 , the follower bar  162  follows the expansion of the reservoir  140 . To that end, the reservoir  140  is preferably formed of flexible material, such as plastic, and will expand upon being filled. The follower bar  162  follows the filling of the reservoir  140  to raise the latch member  164 . When the reservoir is full, the latch member  164  is raised to such an extent that the dog  166  may pass thereunder to permit the push buttons  120  to be pressed to cause pumping of the liquid medicant to the patient. Again, the springs  122  and  124  assist in returning the push buttons  122  to a starting position. 
     The reservoir  140 , as may be noted in  FIG. 3 , includes a plurality of raised portions  142  formed along its perimeter. This reservoir shape causes air pockets to be formed within the reservoir that traps air isolated from the reservoir outlet  144 . Accordingly, the device  100  is intended to be worn with its major axis  102  horizontal. In such an orientation, air within the reservoir  140  may be trapped in the air pockets, such as air pocket  146 . 
     Referring now to  FIG. 4 , it illustrates the fluid flow path of the liquid medicant upon being pumped responsive to the pressing of the actuator buttons  120 . The fluid flow path is shown in dashed lines in  FIG. 4 . As may be noted, the fluid flow from reservoir  140  begins at the outlet  144  along a flexible conduit  148 . The fluid medicant is propelled by a pump, such as a linear peristaltic pump  170  to be described hereinafter. It first flows through a valve  180  which may be provided to isolate the pump  170  from the reservoir  140  when the pump  170  pumps the fluid medicant. The valve  180 , under some circumstances, is optional, as for example when a linear peristaltic pump of the type described herein is employed as will be fully described hereinafter. 
     The fluid continues to flow along the flexible conduit  148  to eventually arrive at the cannula  200 . It is then delivered to the patient beneath the patient&#39;s skin. 
       FIGS. 5 and 6  show the peristaltic pump of the device  100  in greater detail. Here it may be seen that the peristaltic pump comprises a pair of pressure members  172  and  174 . The pressure members  172  and  174  are disposed on opposite sides of the flexible conduit  148 . The direction of fluid flow is indicated by the arrows  149  in a direction away from the reservoir (not shown). The pressure members  172  and  174  are spaced apart such that they become increasingly closer together in an upstream direction with respect to the fluid flow. Hence, when the pressure members  172  and  174  act upon the flexible conduit  148 , they will serve to first pinch the flexible conduit closed and then, upon exerting additional pressure, squeeze the conduit to force the liquid medicant in the downstream direction. 
     As previously mentioned, the valve  180  is optional. If the pump utilized is not a pump as illustrated herein that first closes off the conduit, the valve  180  may be coupled to the actuator buttons  120  so that the valve  180  closes the conduit  148  before pressure is exerted on the flexible conduit  148  by the pump. To that end, the valve  180  includes a first valve member  182  and a second stationary valve member  184 . Valve member  182  pivots about pivot point  186  upon the pressing of the actuator buttons  120  to pinch the flexible conduit closed against the stationary member  184 . 
     In  FIG. 6 , it may be more clearly seen that each pressure member  172  and  174  is integrally formed with an associated one of the actuator buttons  120 . More specifically, each pressure member may be formed as one piece with its actuator button  120 . Because the device  100  is intended to be disposable, the actuator buttons and hence the pressure members  172  and  174  may be formed of plastic. 
     Once the actuator buttons  120  are pressed and the peristaltic pump  170  causes the liquid medicant to flow down the flexible conduit  148 , the actuator buttons  120  are returned to their starting positions by their respective springs  122  and  124 . At this point in time, the flexible conduit  148  is charged with fluid to cause the fluid medicant to exit the cannula  190  as illustrated in  FIG. 4 . To guard against back pressure within the cannula  190  and flexible conduit which would otherwise lessen the amount of liquid medicant received by the patient, a check valve  190  is provided. The check valve  190  is downstream from the pump  170  and performs at least two functions. Firstly, the check valve  190  when closed precludes back flow of the medicant and assures that the medicant within the flexible conduit from the check valve to the cannula  200  is eventually diffused into the patient. It also precludes unintended leaking of the liquid medicant into the patient in between actuations of the push buttons  120 . 
     With particular reference to  FIGS. 7 and 8 , in  FIG. 7 , it will be noted that the valve  190  is formed by a closing member  192  which is coupled to an actuator push button  120  at an attachment point  194 . When the actuator buttons  120  are concurrently pressed, the closure member  192  slides to the position indicated in  FIG. 7  to an opened position to permit fluid flow through the flexible conduit  148 . As may be seen in  FIG. 8 , when the actuator buttons  120  are released, the closure member  192  is caused to move in a direction towards the flexible conduit  148  and eventually pinches the flexible conduit  148  closed between the closure member  192  and a stationary wall  196 . Once the valve  190  is closed as shown in  FIG. 8 , liquid medicant will not be permitted to inadvertently drip from the reservoir, flow through the conduit, and be delivered to the patient. 
     Referring now to  FIGS. 9 and 10 , they show an alternative flexible reservoir which may be used in the infusion pump according to the invention. The flexible reservoir  240  is formed of flexible sheet material including a sheet  242  and a sheet  244 . The sheet materials  242  and  244  are sealed along a peripheral seal line  246 . As may be clearly noted in  FIGS. 9 and 10 , the reservoir  240  is shaped to form raised portions  248  on one side of the reservoir and raised portions  250  on the opposite side of the reservoir. The raised portions  248  and  250  may be pointed regions having concave sidewalls. For example, pointed regions  248  have concave sidewalls  249  and pointed regions  250  have concave sidewalls  251 . 
     When the reservoir  240  is deployed in an infusion device, such as infusion device  100  of  FIG. 1 , it may be disposed so that the raised regions  250  and  248  are along a pane having a substantially vertical component. With the reservoir  240  being disposed such that the raised regions  250  are above the raised regions  248 , air pockets, such as air pocket  253  will be formed within the reservoir  240 . The air pocket  253  is isolated from the outlet  256  to assure that no air will become entrapped in the liquid medicant being delivered to the patient. 
     Hence, as may be seen from the foregoing, the present invention provides a simple, mechanically driven infusion device that provides boluses of liquid medicant, such as insulin, and which may directly attached to the body of a patient. The device does not require any electronics to deliver or program the delivery of the medicant. The liquid medicant, such as insulin, may be delivered through a small cannula into the subcutaneous tissue of the patient as is common in the art. 
     While particular embodiments of the present invention have been shown and described, modifications may be made, and it is therefore intended in the appended claims to cover all such changes and modifications which fall within the true spirit and scope of the invention as defined by those claims.