Abstract:
An apparatus for pumping fluid through tubing comprising a stop platen is disclosed. The stop platen is operatively arranged to depress a wall of the tubing along a section of a longitudinal axis of the tubing. The stop platen is narrower than the tubing along a transverse axis of the tubing. The invention further comprises a cabinet containing the stop platen, a door rotatably fixed to the cabinet, and locking means for preventing rotation of the door. The locking means are operatively arranged to be unlocked by a tubing occluder.

Description:
FIELD OF THE INVENTION 
   This invention relates to a pump for providing fluid for injection into a patient. More specifically it relates to a method and apparatus for an ambulatory infusion pump for pumping liquid through standard intravenous (IV) tubing. 
   BACKGROUND OF THE INVENTION 
   Infusion pumps for delivering fluid to a patient are well known in the art. Two general categories of infusion pumps known in the art are ambulatory pumps and large volume parenteral (LVP) pumps. These pumps deliver fluid to a patient through tubing at higher accuracies than gravity drip tubing delivery systems. 
   LVP pumps are relatively large infusion pumps that can provide a fluid to a patient for 24 hours or more on a single battery charge, or indefinitely from an AC power connection. They operate on standard IV polyvinyl chloride (PVC) tubing. This obviates the need for changing IV tubing sets when a decision has been made to change from a drip tubing delivery system to the more accurate infusion pump system. Most available LVP pumps completely collapse the PVC tubing during operation to ensure that there is no free flow to the patient or back flow to the fluid reservoir. This leads to very high power consumption when using standard tubing. Thus, a battery capable of powering the pump for 24 hours is very heavy and bulky. A patient receiving fluid from an LVP pump must stay within reach of a power cord, or push a wheeled stand with the LVP pump and battery mounted on it. In addition, fully collapsing the tubing deforms the tubing. The tubing cross section becomes more elliptical the longer the pump operates on it. Less fluid is discharged from the tubing as the cross section becomes more elliptical, leading to negative flow rate errors. The pump rate accuracy decays proportional to the amount of time an individual tubing set is used to deliver fluid to a patient. An example of an LVP infusion pump is shown in U.S. Pat. No. 4,653,987 (Tsuji et al.). 
   Ambulatory pumps are smaller infusion pumps that can be attached to a patient&#39;s belt, allowing them to move around without a bulky LVP pump. However, there are several drawbacks in comparison to the LVP pump. To reduce the weight to a level where a patient can carry the pump, the size of the battery is reduced considerably. The reduced battery cannot provide the power required to completely collapse standard PVC tubing. Instead, many ambulatory pumps require the use of special dedicated IV sets, or special silicon tubing threaded through a cassette to be inserted into the pump. This specialized equipment increases the cost of using the pumps. Even with special dedicated IV sets or silicon tubing and cassettes, many ambulatory pumps can only provide fluid to a patient for a few hours on a single battery charge. An example of an infusion pump that requires a dedicated IV set is shown in U.S. Pat. No. 5,772,409 (Johnson). An example of an ambulatory infusion pump that requires silicon tubing and cassettes is shown in U.S. Pat. No. 5,791,880 (Wilson). 
   Another problem with the infusion pumps currently in the art is the danger of free flow of fluid when the tubing is inserted or removed from the pump. An occluder is used to completely collapse the tubing while the tubing is outside the pump. The occluder is disengaged when the tubing is installed in the pump. The tubing is occluded again before the tubing is taken out of the pump. However, there is no means currently in the art to ensure that the tubing is occluded before the tubing is installed into or removed from the pump. Thus, the tubing may accidentally become unoccluded while the tubing is outside the pump, allowing fluid to flow freely to the patient. This overdose of fluid may be harmful or even lethal. 
   Clearly, then, there is a longfelt need for an ambulatory infusion pump that utilizes standard PVC tubing, operates for approximately 24 hours on one battery charge, and can prevent free flow of fluid into the patient. 
   SUMMARY OF THE INVENTION 
   The present invention comprises an apparatus for pumping fluid through tubing comprising a stop platen. The stop platen is operatively arranged to depress a wall of the tubing along a section of a longitudinal axis of the tubing. The stop platen is narrower than the tubing along a transverse axis of the tubing. The invention further comprises a cabinet containing the stop platen, a door rotatably fixed to the cabinet, and locking means for preventing rotation of the door. The locking means are operatively arranged to be unlocked by a tubing occluder. 
   A general object of the present invention is to provide an ambulatory pump that utilizes standard PVC tubing. 
   Another object of the present invention is to provide an ambulatory pump with high accuracy, preferably better than ±5% accuracy. 
   It is a further object to provide an ambulatory pump that can deliver fluid to a patient at a high volume flow rate, for example 500 ml/hour, for at least 24 hours. 
   It is yet another object to provide an ambulatory pump that prevents the free flow of fluid into the patient when the tubing is installed and removed. 
   These and other objects, features and advantages of the present invention will become readily apparent to those having ordinary skill in the art upon a reading of the following detailed description of the invention in view of the drawings and claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which: 
       FIG. 1  is a side view of a first embodiment of the present invention, with the platens arranged to allow fluid flow from a reservoir; 
       FIG. 1   a  is a perspective view of an occlusion platen; 
       FIG. 1   b  is a perspective view of a pump platen with a stop platen thereon; 
       FIG. 2  is a side view of a first embodiment of the present invention, with the platens arranged to allow fluid flow to a patient; 
       FIG. 3  is a side view of a first embodiment of the present invention, with the platens arranged to pump fluid to a patient; 
       FIG. 4  is a side view of a first embodiment of the present invention, with the platens arranged at the end of a pump cycle; 
       FIG. 4   a  is a cross sectional view of the tubing and the pump platen showing the dimensions of the stop platen and the tubing; 
       FIG. 4   b  is a cross sectional view of the tubing and the pump platen, with the stop platen completely collapsing a portion of the width of the tubing; 
       FIG. 5  is a perspective view of the preferred embodiment of the present invention; 
       FIG. 6  is an exploded view of the preferred embodiment of the present invention; 
       FIG. 7  is an electrical schematic of the motor drive circuit of the preferred embodiment of the present invention; 
       FIG. 8  is a front perspective view of the preferred embodiment of the present invention, a section of tubing, and an occluder, with the door of the present invention closed, and the tubing unoccluded; 
       FIG. 9  is a front perspective view of the preferred embodiment of the present invention, a section of tubing, and an occluder, with the door of the present invention closed, and the occluder being inserted in the keyhole of the present invention; 
       FIG. 10  is a front perspective view of the preferred embodiment of the present invention, a section of tubing, and an occluder, with the door of the present invention open; 
       FIG. 11  is a front perspective view of the preferred embodiment of the present invention, a section of tubing, and an occluder, with the door of the present invention open, and the tubing installed in the pump; 
       FIG. 12  is a front perspective view of the preferred embodiment of the present invention, a section of tubing, and an occluder, with the door of the present invention closed, and the tubing installed in the pump; 
       FIG. 13  is a front perspective view of the preferred embodiment of the present arranged to pump fluid through the tubing; 
       FIG. 14  is a front perspective view of the preferred embodiment of the present invention, a section of tubing, and an occluder, with the door of the present invention opened, and the tubing installed in the pump; 
       FIG. 15  is a front perspective view of the preferred embodiment of the present invention, a section of tubing, and an occluder, with the door of the present invention open, and the tubing uninstalled from the pump; 
       FIG. 16  is a front perspective view of the preferred embodiment of the present invention, a section of tubing, and an occluder, with the door of the present invention closed, and the tubing occluded. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   It should be appreciated that, in the detailed description of the invention which follows, like reference numbers on different drawing views are intended to identify identical structural elements of the invention in the respective views. 
   A first embodiment of the present invention is shown in  FIG. 1  and generally designated  10 . Apparatus  10  is an infusion pump comprising pump base  20  with tubing base  31  fixed thereto. Tubing  21  is routed over tubing base  31  underneath occlusion platens  22  and  29 , and pump platen  25 . Occlusion platen  22  is fixed to platen support  55 . Occlusion platen  29  is fixed to platen support  55 . Pump platen  25  comprises stop platen  26 , and is fixed to platen support  55 . Motor  42  is fixed to pump base  20 . Motor  42  drives camshaft  38 . Camshaft  38  is supported by shaft supports  40  and  41 . Cams  35 ,  36 , and  39  are all fixedly mounted on camshaft  38 . As camshaft  38  rotates when driven by motor  42 , cams  35 ,  36 , and  39  are rotated at the same rate. Cam  35  is operatively arranged to cyclically drive occlusion platen  29  between a first, unoccluding position and a second, occluding position. The first position is shown in  FIG. 1 , wherein occlusion platen  29  is not in contact with tubing  21 . As cam  35  is rotated by shaft  38 , platen support  55  is driven down by cam  35 . This drives occlusion platen  29  towards tubing  21 . Occlusion platen  29  is driven to a second position, shown in  FIGS. 2 ,  3 , and  4 , where occlusion platen  29  occludes tubing  21 . As the shaft continues to rotate, cam  35  moves away from platen support  55 . Spring  52 , shown on  FIGS. 5 and 6 , provides upward force on platen support  55  to lift occlusion platen  29  back to the first, unoccluded position. Cam  39  drives occlusion platen  22  through a similar cycle. Occlusion platen  22  is driven from a first, unoccluded position to a second, occluded position. However, occlusion platen  22  occludes tubing  21  at substantially different times than occlusion platen  29 . Occlusion platen  22  is shown occluding tubing  21  in  FIGS. 1 and 4 . Spring  52 , shown on  FIGS. 5 and 6 , provides upward force on platen support  55  to lift occlusion platen  22  back to the first, unoccluded position when cam  39  moves away from platen support  55  due to the rotation of shaft  38 . 
   Cam  36  drives pump platen  25  from a first position to a second position as shaft  38  rotates. The first position is shown in  FIGS. 1 ,  2 , and  4   a.  The pump platen is not in contact with tubing  21 . As shown in  FIG. 4   a,  width d of stop platen  26  is less than width w of tubing  21 . In  FIG. 4   a,  tubing  21  is in a state of rest. That is, tubing  21  is not being compressed by stop platen  26 . As shaft  38  rotates, cam  36  drives platen support  55  to a second position, shown in  FIGS. 3 ,  4 , and  4   b.  In the second position, pump platen  25  depresses tubing  21 . Stop platen  26  completely collapses a section of the width of tubing  21 , as shown in  FIG. 4   b.  Stop platen  26  prevents pump platen  25  from occluding tubing  21 . Stop platen  26  does not occlude tubing  21  because stop platen  26  is narrower than tubing  21 , as shown in  FIG. 4   a.  Occlusion by the pump platen is undesirable because it would require significantly more power than partially occluding the tubing, as shown in  FIGS. 3 ,  4 , and  4   b.  Further, the tubing does not deform as readily when partially deflected by the pump platen, as compared to the deformation caused by occluding the tubing. 
   In a preferred embodiment, the platens are spring loaded, to allow the platens to be overdriven. This ensures tubing  21  is occluded by the occlusion platens or partially occluded by the stop platen, regardless of the dimension of tubing  21 . This improves the accuracy of the pump when using tubing of varying dimensions. Otherwise expensive, complicated measurement devices are needed to ensure that the tubing is deflected the appropriate amount by each platen. Springs  51 , shown in  FIGS. 5 and 6 , accomplish this spring loading. 
   As shown in  FIGS. 1–4 ,  1   b,    4   a,  and  4   b,  the preferred embodiment of stop platen  26  is a platen that extends the length of the pump platen, and is centered along the width of the pump platen. However, it should be readily apparent to one skilled in the art that many other configurations of stop platens could be used and these modifications are intended to be within the spirit and scope of the invention as claimed. For example, the stop platen could extend only a portion of the length of the pump platen, or it could be located away from the center of the pump platen. A stop platen shorter than the pump platen could be off center along either the length or width of the pump platen, or both. 
     FIG. 1  shows platen  22  occluding tubing  21 , and platens  25  and  29  above tubing  21 . This is the first position in the pump cycle, which allows fluid from a reservoir (not shown) in flow communication with end  14  of tubing  21  to flow into the tubing proximate the pump platen.  FIG. 2  shows platen  29  occluding tubing  21 , and platens  22  and  25  above tubing  21 . This position allows fluid to flow to a patient (not shown) in flow communication with end  12  of tubing  21 .  FIG. 3  shows platen  29  occluding tubing  21 , platen  25  depressing tubing  21  until stop platen  26  completely collapses the central portion of the width of tubing  21 , and platen  22  above tubing  21 . This configuration forces the fluid in tubing  21  towards end  12  of the tubing.  FIG. 4  shows platens  22  and  29  occluding tubing  21 , and platen  25  depressing tubing  21  until stop platen  26  completely collapses the central portion of the width of tubing  21 . This is the end of the cycle. Platens  25  and  29  move up again to return to the first configuration of the pump cycle shown in  FIG. 1 . 
     FIGS. 1–6  show a single pump platen  25 . However, it should be readily apparent to one skilled in the art that a plurality of pump platens may be used, and these configurations are intended to be within the spirit and scope of the invention as claimed. 
     FIG. 1   a  is a perspective view of occlusion platen  29 .  FIG. 1   b  is a perspective view of pump platen  25  with stop platen  26  thereon. 
     FIG. 5  is a perspective view of the preferred embodiment of the present invention, designated  50 .  FIGS. 1–4  show motor  42  mounted in line with camshaft  38  so that the platens are visible. To reduce the volume of the pumping assembly, the preferred embodiment locates the motor parallel to the camshaft, coupling them with gears  45  as shown in  FIGS. 5 and 6 . It should be readily apparent to one skilled in the art that many mechanical configurations are possible, and these modifications are within the spirit and scope of the invention as claimed. 
     FIG. 6  is an exploded view of the preferred embodiment of the present invention in perspective. Springs  52  provide an upward force on the platen supports to return them to an upper position when each cam moves away from the platen supports. Springs  52  are connected between the platen supports and the pump base  20 . Springs  51  spring load the platens so that they may be overdriven. This enables the pump to be used with tubes of differing dimensions, as discussed above. 
     FIG. 7  is an electrical schematic of the preferred embodiment of the pump. Circuit  60  shown in  FIG. 7  is designed to provide power to motor  63  (corresponding to motor  42  of  FIGS. 1–6 ) to pump the fluid over a wide range of flow rates at high accuracy. In a preferred embodiment, the pump will deliver 0.1–500 ml/hr±2%. This is achieved at a low rate, for example, one revolution per hour, by the following process. N-type field effect transistor (FET)  64  is turned off and P-type FET  61  is turned on, charging capacitor  62 . P-type FET  61  is then turned off. Capacitor  62  is discharged through motor  63  by turning on N-type FET  64 . This discharge process allows a small motor movement. The amount of energy in capacitor  62  is controlled by the amount of time P-type FET  61  is turned on. This process is repeated to pump fluid through the tubing at the desired low rate. 
   For pumping at a high rate, for example, one revolution per second, P-type FET  61  is turned on and N-type FET  64  pulse width modulates motor  63  with a variable duty cycle. The motor has an average input power based on the duty cycle. The variable power allows higher speed positioning within the tolerances allowed. Power supply  65  is the battery. In a preferred embodiment, capacitor  62  is a 470 μF capacitor, and resistor  66  is 0.1 ohms. 
   In the preferred embodiment, pump assembly  50  is mounted in cabinet  70 , as shown in  FIGS. 8–16 . Cabinet  70  comprises keyhole  73 , case  74 , display  75 , keypad  76 , and door  78 . Also shown in  FIG. 8  is tubing  21  with an occluder  80 . Occluder  80  has a first end  81 , a second end  82 , and a slit  83 . To occlude tubing  21 , tubing  21  is routed through slit  83  proximate first end  81 . Slit  83  is narrowest where the slit is closest to end  81 . Slit  83  is wider proximate second end  82 . Fluid flows freely through tubing  21  when the tubing is located proximate second end  82 . Thus, tubing  21  is shown unoccluded in  FIG. 8 . Fluid may flow freely through the tubing to a patient. 
   Free flow of fluid through the tubing is prevented with the present apparatus as follows.  FIG. 9  shows occluder  80  being inserted into slot  73  of the present invention. Second end  82  must be inserted to open door  78 , as first end  81  is too thick to fit into keyhole  73 . As occluder  80  is inserted into keyhole  73 , tubing  21  is forced towards first end  81 , as shown in  FIG. 10 . Thus to open door  79 , tubing  21  must be occluded by occluder  80 . Door  78  unlocks as shown in  FIG. 10 , exposing the pump assembly. Door  78  is unlocked when hooks  72  disengage loops  71 . Tubing  21  is routed along tubing channel  79 , between the tubing base and the platens, as shown in  FIG. 11 . Door  78  is closed, as shown in  FIG. 12 . Occluder  80  is removed from keyhole  73 , and tubing  21  is moved through slot  83  until it is unoccluded. This is shown in  FIG. 13 . The pump may now operate to deliver fluid to a patient. 
   To remove the tubing from cabinet  70 , occluder  80  is again inserted in keyhole  73 . This forces tubing  21  to first end  81 , occluding the tubing. Door  78  opens, as shown in  FIG. 14 . The tubing is removed from the pump in  FIG. 15 .  FIG. 16  shows the tubing outside the pump and pump door  78  closed. Tubing  21  is still occluded. In the above-described manner, the present invention requires the tubing to be occluded before the door can be opened. This will prevent medical personnel from forgetting to occlude the tubing before it is removed from the pump. 
   Thus, it is seen that the objects of the present invention are efficiently obtained, although modifications and changes to the invention should be readily apparent to those having ordinary skill in the art, and these modifications are intended to be within the spirit and scope of the invention as claimed.