Pressure monitoring system for infusion pumps

Abstract

A pressure monitoring system allows for more accurate and reliable measurement of the pressure inside of a tube in a pump. The pressure monitoring system prevents movement of the tubing or a change in size of the tubing due to external forces applied to the pump, eliminating inaccuracies due to handling of the pump during use.

Description

THE FIELD OF THE INVENTION

The present invention relates to pressure monitoring systems in pumps. More specifically, the present invention relates to a pressure monitoring system for medical pumps such as feeding pumps and infusion pumps which allows for more accurate pressure measurement in a fluid delivery tube while utilizing inexpensive components. The pressure monitoring system isolates the pressure measurement from environmental effects such as movement of the pump or, more importantly, external forces applied to the pump such as a user grasping the pump.

BACKGROUND

Medical pumps such as peristaltic pumps are commonly used to deliver fluids. In medical applications, peristaltic pumps and fluid delivery systems are used to deliver medication, nutrition, and other fluids to a patient. In these applications, it is important to monitor the pressure inside of the delivery tubing. Typically, pressure is measured and monitored before and after the pumping motor. This allows the pump to determine if a blockage is present in the tubing or if the pressure in the tubing is outside of a safe working range. Measuring the pressure may also enable the pump to more accurately determine the rate of fluid delivery.

It has been difficult to accurately measure the pressure in the delivery tubing. For medical applications, a disposable tubing set is loaded into the pump and used for a relatively short period of time. This requires that the pressure monitoring system does not interfere with the loading and unloading of the tubing. Existing pressure monitoring systems have experienced inaccuracies due to the inconsistent loading or placement of the tubing or due to external forces which are applied to the pump such as when a user grabs or moves the pump.

There is a need for a pressure monitoring system for fluid delivery pumps which more accurately measures the fluid pressure inside of the tubing. There is a need for such a system which overcomes inconsistencies in tubing placement, and which is not affected by environmental conditions such as movement or forces applied to the pump.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved pressure monitoring system.

According to one aspect of the invention, a pressure monitoring system is provided which allows the infusion tubing to be easily loaded and unloaded from the pump. The tubing is simply placed in a channel in the pump and the door is closed. No additional latch mechanisms are necessary.

According to another aspect of the invention, a pressure monitoring system is provided where the pressure readings are isolated from external forces acting on the pump, and acting on the pump door in particular. The pressure monitoring system thus provides a more consistent and reliable measurement of the pressure within the tubing.

These and other aspects of the present invention are realized in a pressure monitoring system as shown and described in the following figures and related description.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention are shown and described in reference to the numbered drawings wherein:

FIG. 1 shows a perspective view of a fluid delivery pump according to the present invention;

FIG. 2 shows a perspective view of the pump of FIG. 1;

FIG. 3 shows a partial cross-sectional view of the pump of FIG. 1;

FIG. 4 shows a partial cross-sectional view of the pump of FIG. 1; and

FIGS. 5 through 7 show partial cross-sectional views of the pressure monitoring channel of pump of FIG. 1.

It will be appreciated that the drawings are illustrative and not limiting of the scope of the invention which is defined by the appended claims. The embodiments shown accomplish various aspects and objects of the invention. It is appreciated that it is not possible to clearly show each element and aspect of the invention in a single figure, and as such, multiple figures are presented to separately illustrate the various details of the invention in greater clarity. Similarly, not every embodiment need accomplish all advantages of the present invention.

DETAILED DESCRIPTION

The invention and accompanying drawings will now be discussed in reference to the numerals provided therein so as to enable one skilled in the art to practice the present invention. The drawings and descriptions are exemplary of various aspects of the invention and are not intended to narrow the scope of the appended claims.

Turning now to FIG. 1, a perspective view of a pump 10 is shown. The present application applies to many types of pumps such as nutrition delivery and feeding pumps and I.V. or medication delivery pumps. For simplicity, the application simply refers to pumps or infusion pumps to indicate these types of pumps. The pump 10 is typically used for delivery of medical fluids, such as delivering medicine or nutritional solutions. Many of the controls or features of the pump 10 are known in medical peristaltic pumps, and are not discussed herein for clarity in discussing the invention. The pump 10 includes a door 14 which is closed after mounting an infusion cassette into the pump. The door 14 is used to ensure proper loading of the infusion cassette.

FIG. 2 shows a perspective view of the pump 10 with the door 14 removed. An infusion cassette 18 is mounted in the pump. The infusion cassette 18 includes a cassette body 22, an inflow tubing 26, an outflow tubing 30 and a pump tubing 34. The pump tubing 34 is typically flexible silicone tubing. The cassette body 22 provides connectors to attach the inflow tubing 26 to the first end of the pump tubing 34 and the outflow tubing to the second end of the pump tubing. The pump tubing thus forms a loop which is stretched around the pump rotor 38. It will be appreciated, however, that the pressure monitoring system of the present invention may also be used in other pumps such as linear peristaltic pumps.

The cassette 18 is typically loaded into the pump 10 by placing the loop of pump tubing 34 over the pump rotor 38, stretching the pump tubing, and placing the cassette body 22 into a nesting area 42. The pump includes pressure monitoring channels 46. The pressure monitoring channels 46 receive the pump tubing 34 to monitor the pressure therein. It is typically desired to monitor the pressure inside the tubing both upstream and downstream from the pump rotor 38. This allows the pump 10 to more accurately determine the fluid delivery rate and allows the pump to determine if a blockage or overpressure situation has occurred.

FIG. 3 shows a partial cross-sectional view of the pump 10 taken through the pressure monitoring channels 46. For clarity, not all structures are shown. The pump tubing 34 is loaded into the pressure monitoring channels 46. The pump door 14 is shown open and in a first shape. Pressure sensors 50 are located in the bottom of the channels 46. Piezoelectric crystals are typically used for the sensors 50, but other types of pressure sensors could be used. Variances in the pressure within the pump tubing 34 change the amount of force applied to the pressure sensors, providing a signal which may be used to calculate the pressure inside of the tubing 34. The sidewalls 54 of the pressure monitoring channels 46 may contact the tubing 34 in order to constrain the tubing. In this case the sidewalls 54 would be slightly narrower than the outer diameter of the tubing to limit the movement or expansion of the tubing and to slightly compress the tubing. Alternatively, the sidewalls 54 may be spaced apart from the tubing slightly to allow the tubing to more freely press against the pressure sensors 50.

The pump door 14 has pedestals 58 formed thereon which are formed in alignment with the pressure monitoring channels 46. The pedestals 58 extend downwardly from the inside of the door 14. The bottoms of pedestals 58 have a tubing contacting surface 62 and channel contacting surfaces 66. When the door 14 is closed, the tubing contacting surface 62 contacts the top of the tubing 34 and compresses the tubing slightly, pressing the tubing against the pressure sensor 50. When the door 14 is closed, the channel contacting surfaces 66 contact the top of the channels 46 and rest against the channel, preventing the pedestals 58 from moving towards the tubing 34 and further compressing the tubing. The door 14 is pivotably attached to the pump 10 via a hinge 70 and is secured close with a latch or catch 74.

FIG. 4 shows the pump door 14 in the closed position and having a second shape. When the pump door 14 is closed, the projections 58 are pushed down against the tubing 34 and the pressure monitoring channels 46. The projections 58 are made slightly taller than the available distance between the closed pump door 14 and the channels 46, causing interference when closing the pump door. Thus, the projections 58 contact the pressure monitoring channels 46 before the pump door 14 is completely closed and the pump door is bent as shown in order to close the latch 74 and secure the pump door in a closed position. The bend in the door 14 is exaggerated to illustrate the bending of the door. In use, a slight interference and a slight bend in the door 14 is sufficient to ensure that the projections 58 are always disposed in contact with the channels 46. The portion of the pump door 14 adjacent the projections 58 is bowed outwardly relative to the rest of the pump door. This bending of the door biases the projections 58 against the pressure monitoring channels 46 and maintains contact and pressure therebetween. The contact and applied pressure between the channel contacting surfaces 66 of the projections 58 and the pressure monitoring channels 46 prevents the projections 58 from moving relative to the channels 46 when the pump is in use, moved, or grasped by a user, preventing erroneous changes in the pressure reading. Thus, the tubing 34 is held in a consistent position and is consistently held against the pressure sensor 50 with a small amount of preload. This allows for more reliable pressure monitoring.

FIG. 5 shows an enlarged view of a single projection 58 and pressure monitoring channel 46 with the pump door 14 in the closed position. The channel contacting surfaces 66 are biased towards and pressed against upper surfaces 78 of the pressure monitoring channel 46. Thus, the contact between the channel contacting surfaces 66 and upper channel surfaces 78 prevents the projection 58 from moving further towards the tubing 34 and further compressing the tubing if a person grabs the pump 10. The tubing contacting surface 62 presses against the tubing 34 and compresses the tubing slightly. In this configuration, the tubing 34 is contacted on four sides by the projection 58, channel side walls 54, and pressure sensor 50. As discussed above, the channel side walls 54 may be slightly wider than the tubing such that the tubing contacts the projection 58 and pressure sensor 50. Because the tubing 34 is loaded consistently, more accurate and consistent pressure readings are obtained. If the tubing 34 is constrained on all sides, expansive force due to pressure within the tube may be more fully directed towards the pressure sensor 50. If the tubing 34 is not contacted by the side walls 54, the tubing may more easily seat against the pressure sensor 50 and eliminate friction with the side walls as a source of error.

FIG. 6 shows an alternate configuration where the tubing contacting surface 62 and the channel contacting surfaces 66 are at or near the same height, or in the same plane. In this configuration, the pressure monitoring channel 46 is made slightly shallower so that the tubing 34 protrudes slightly from the channel 46 before the pump door 14 is closed, causing the tubing contacting surface 62 to press the tubing 34 downwardly when the door 14 is closed. As discussed above, the door 14 is slightly bent when fully closed to bias the projection 58 towards the channel 46 and maintain pressure between the channel contacting surfaces 66 and upper surfaces of the channel 46.

FIG. 7 shows an alternate configuration where the pressure sensor 50 is separated from the tubing 34. A rigid intermediate connecting member 82 is placed therebetween to transfer force between the tubing 34 and the pressure sensor 50. The connecting member 82 is coupled to the pump 10 by a flexible membrane 86, allowing the connecting member to move relative to the pump body and transfer force from the tubing to the pressure sensor 50. The membrane 86 seals around the connecting member 82 and isolates the pressure sensor 50 from the exterior of the pump, making the pump easier to clean and less likely to become damaged due to liquid spills around the pump. The pressure sensor configuration of FIG. 7 functions with the projection 58 as discussed above.

The pressure sensor configuration shown is advantageous in allowing for more consistent pressure measurements. The tube 34 is held against the pressure sensor 50 with a consistent amount of preload by the projection 58. The projection 58 is held against the channel with a consistent amount of preload by the slightly bent door 14, but is prevented from moving further towards the channel 46 and tube 34 by the channel contacting surfaces 66. In this manner, the tube 34 is held in a consistent position where it is unaffected by external influences such as movement of the pump or pressure placed on the pump door. Thus, the pressure sensing is more accurate where the pump is used in an ambulatory (carried with the person) application, where the pump is moved about with a hospital bed, or where a person must move the pump around.

It will be appreciated that various aspects of the invention may be combined together. Thus, for example, in accordance with principles of the present invention, a pressure monitoring system for a pump may include: a pump having a pressure monitoring channel; a tubing disposed in the pressure monitoring channel; a pressure sensor disposed in communication with the tubing to monitor the pressure in the tubing; a pump door; and a projection disposed on the inside of the pump door, the projection engaging the tubing and the pressure monitoring channel when the pump door is closed, and wherein closing the door causes a portion of the door adjacent the projection to bend outwardly and thereby bias the projection towards the pressure monitoring channel. The pressure monitoring system may also include the projection having a channel contacting surface which contacts the channel when the door is closed to thereby prevent further movement of the projection towards the channel; the channel contacting surface contacting an upper surface adjacent the channel; and/or the projection having a tubing contacting surface on the bottom thereof, the tubing contacting surface contacting the tubing and compressing the tubing when the door is closed; or combinations thereof.

In accordance with one aspect of the invention, a pressure monitoring system may include: a pump having a channel therein for receiving a flexible tubing; a tubing disposed in the channel; a pressure sensor disposed in communication with the tubing; a pump door; a projection on the pump door; and wherein, when the pump door is closed: the projection is moved adjacent the channel; the projection compresses the tubing into the channel; the projection contacts a pump surface to stop movement of the projection towards the tubing; and the projection is biased towards the tubing. The pressure monitoring system may further include a portion of the door adjacent the projection being bent outwardly when the door is closed to thereby bias the projection towards the tubing; the projection having a tubing contacting surface for contacting the surface and a channel contacting surface which contacts the channel to thereby stop movement of the projection towards the tubing; the projection having first and second channel contacting surfaces, and the first channel contacting surface contacting a first side of the channel and the second channel contacting surface contacting a second side of the channel opposite the first side; and/or channel contacting surface contacting a surface adjacent the top of the channel; or combinations thereof.

In according with an aspect of the invention, a pressure monitoring system may include a channel; a flexible tube disposed in the channel, the flexible tube being expandable due to pressure; a pressure sensor disposed in communication with the tube; a projection disposed in contact with the channel and in contact with the tube to hold the tube in the channel. The pressure monitoring system may also include: the projection having a channel contacting surface which contacts the channel to prevent movement of the projection towards the channel; the projection having a tube contacting surface which holds the tube in the channel; the tube contacting surface pressing the tube against the pressure sensor; the tube contacting surface extending into the channel; the channel being part of a pump; the projection being formed as part of a pump door; the projection having an interference fit between the pump door and the channel, causing the pump door to bend when the pump door is closed; the projection being biased towards the channel; and/or a channel contacting surface and preventing movement of the projection towards the channel; or combinations thereof.

There is thus disclosed an improved pressure monitoring system. It will be appreciated that numerous changes may be made to the present invention without departing from the scope of the claims.

Claims

1. A pressure monitoring system for a pump comprising: a pump having a pressure monitoring channel defined by opposing sidewalls, each sidewall having an upper surface;a tubing disposed in the pressure monitoring channel between the opposing sidewalls;a pressure sensor disposed in communication with the tubing to monitor the pressure in the tubing;a pump door having an inside surface and an outside surface, the door including a closure mechanism configured to releasably secure the pump door relative to the pump;a projection disposed on the inside surface of the pump door; wherein, in an open position, the pump door has a first shape;wherein, in a closed position, the projection is configured to contact the upper surfaces such that the pump door is bent outwardly into a second shape and thereby bias the projection towards the pressure monitoring channel;wherein, when the door is closed, the projection is configured to engage both the tubing and the upper surfaces of the opposing sidewalls.

2. The system of claim 1, wherein the projection has a channel contacting surface and wherein the channel contacting surface contacts the upper surfaces when the door is closed to thereby prevent further movement of the projection towards the channel.

3. The system of claim 2, wherein the projection has a tubing contacting surface on the bottom thereof, the tubing contacting surface contacting the tubing and compressing the tubing when the door is closed.

4. A pressure monitoring system comprising: a pump having a channel therein, the channel defined by opposing sidewalls, each sidewall having an upper surface;a tubing disposed in the channel between the opposing sidewalls;a pressure sensor disposed in communication with the tubing;a pump door having a first shape in an open position;a projection on the pump door; andwherein, when the pump door is closed: the projection is moved adjacent the channel;the projection compresses the tubing into the channel;the projection contacts the upper surfaces of the sidewalls to stop movement of the projection towards the tubing; andthe projection is biased towards the tubing;wherein a portion of the door adjacent the projection is configured to bend outwardly into a second shape when the door is placed in a closed position to thereby bias the projection towards the tubing.

5. The system of claim 4, wherein the projection comprises first and second channel contacting surfaces, and wherein the first channel contacting surface contacts a first side of the channel and the second channel contacting surface contacts a second side of the channel opposite the first side.

6. A pressure monitoring system comprising: a channel defined by opposing sidewalls, each sidewall having an upper surface;a flexible tube disposed in the channel, the flexible tube being expandable due to pressure;a pressure sensor disposed in communication with the tube;a projection disposed in contact with the channel and in contact with the tube to hold the tube in the channel; a door having a first shape in an open position;a closure mechanism configured to releasably secure the door relative to the pump;wherein in a closed position, the projection has a channel contacting surface which is configured to contact the upper surfaces of the sidewalls to prevent movement of the projection towards the channel, and which is configured to cause the door to bend outwardly into a second shape.

7. The system of claim 6, wherein the projection has a tube contacting surface which holds the tube in the channel.

8. The system of claim 7, wherein the tube contacting surface presses the tube against the pressure sensor.

9. The system of claim 7, wherein the tube contacting surface extends into the channel.

10. The system of claim 6, wherein the channel is part of a pump.

11. The system of claim 10, wherein the projection is formed as part of the door.

12. The system of claim 6, wherein the projection is biased towards the channel.