EP0992230A2

EP0992230A2 - Medical pumping apparatus and related methods

Info

Publication number: EP0992230A2
Application number: EP99307963A
Authority: EP
Inventors: designation of the inventor has not yet been filed The
Original assignee: KCI Licensing Inc
Current assignee: KCI Licensing Inc
Priority date: 1998-10-08
Filing date: 1999-10-08
Publication date: 2000-04-12
Also published as: EP0992230A3

Abstract

A medical pumping system (10) for use with a therapeutic patient treatment system generally comprises a reservoir (12) for holding a compressed fluid, with a fluid outlet (13,14) and a valve (15,16) for controlling flow of fluid from the reservoir through the outlet; a compressor (11) for supplying pressurised fluid to the reservoir (12); and a controller (17) for controlling the supply of pressurised fluid to the reservoir (12) and for controlling the flow of fluid from the reservoir through the outlet (13,14). The controller (17) has associated therewith a sensor (25) for measuring the internal pressure of the reservoir, and is adapted to provide the reservoir with an initial quantity of fluid on an initial cycle of operation; to operate the valve (15,16) to release the initial quantity of fluid from the reservoir (12) through the valve; to measure the internal pressure of the reservoir (12) while the valve (15,16) is operated; and to provide the reservoir with an additional quantity of fluid, less than the initial quantity of fluid based upon a comparison of the internal pressure of the reservoir (P_eq), after the release of the initial quantity of fluid, with the target pressure (P_targ).

Description

FIELD OF THE INVENTION:

The present invention relates to medical pumping apparatus. More particularly, the invention relates to medical pumping apparatus for use in supplying a compressive fluid a therapeutic wrap.

BACKGROUND OF THE INVENTION:

Medical devices that apply cyclic pressure to a person's arms, legs, hands and/or feet are very old and well known in the art. Many of these devices have employed pulsating pads, pistons and plungers for improving circulation. Others have used hydraulic and pneumatic bladders for similar purposes. Additionally, new applications previously unknown are emerging in which cyclic pressure upon the extremities is being found to have beneficial effects. For example, the present Applicant's have invented a new and useful method and apparatus utilizing the application of cyclic pressure for the healing of diabetic and/or similar wounds in the feet or ether extreme areas. The shapes, sizes and compositions of such bladders, pads and the like are widely varied, depending largely upon their respective particular applications; most, however, are cyclically supplied with compressive gas from an auxiliary compressor unit.
In the present state of the art, the auxiliary compressor unit comprises a fluid reservoir, filled with gas by an associated compressor, and a mechanism for controlling the delivery of pressurized gas from the fluid reservoir to the device, which typically comprises some sort of foot wrap or the like. Such wraps are generally well known in the relevant arts, an exemplary wrap being commercially available from Kinetic Concepts, Inc. of San Antonio, Texas under the trade designation "PLEXIPULSE." In operation of the presently known state of the art compressor units, the associated compressor is either continuously ran or is ran until sonic predetermined pressure (often near the maximum pressure achievable, as will be better understood further herein) is reached in the reservoir. In the former case, the compressor "dead-heads," i.e. continues to operate without effect on reservoir pressure, and in the latter case the compressor is shut off for only that time beyond which the reservoir is pumped to the predetermined pressure.
In either case, pressurized gas delivered from the reservoir to the foot (or other) wrap is generally controlled in one of two timing-based methods. In the first control method, generally known as same-cycle adjustment, a valve interposed in a fluid communication line between the reservoir and the wrap is opened to allow inflation of the wrap. The pressure in the wrap is monitored while the valve is open to ensure that the wrap's internal pressure does not exceed some target pressure. Upon reaching the not to exceed pressure, the valve is closed. This operation is then repeated for each cycle of pressure application.
In the second control method, generally known as next-cycle adjustment, the valve to the wrap is opened for some determinable time period after which the valve is again closed. The pressure in The wrap is then measured. Based upon this measurement, the time period for which the valve is set to remain open is adjusted for subsequent cycles, i.e. the time period is enlarged if the measured pressure is less than desired and the time period is reduced if the measured pressure is greater than desired. Again, this operation is repeated for each cycle of pressure application.
While each of the four methods for delivery of pressurized fluid to a wrap is generally effective for provision of the desired pressure for the desired time, all nonetheless suffer significant shortcomings. For example, in each case more pressure ban is necessary is generated on each pressure cycle to fill the fluid reservoir. In continuously operated compressor methods the compressor needlessly operates to deliver the maximum possible reservoir pressure and in predetermined reservoir pressure methods the compressor needlessly operates to deliver a predetermined reservoir pressure that is necessarily excessive in order to ensure sufficient available pressure to obtain the desired wrap pressure. As a result, especially in the case of the continuously operated compressor, compressor life cycle is sharply reduced due to unnecessary operation. Additionally, the unnecessary operation needlessly contributes to the noise level in the patient's immediate vicinity. This can reduce patient compliance - especially in the home care scenario in which many of the previously described devices may be utilized. To further exacerbate this deficiency, the unnecessary operation of the compressor often results in the otherwise unnecessary utilization of cooling fans, again needlessly contributing to the noise level and potentially affecting patient compliance and/or comfort.
As another example of the deficiencies present in the current state of the art devices, it is bind that operation of the devices at higher than necessary pressures makes the devices more susceptible to leak development. Not only does this necessitate otherwise unnecessary repair costs, but it also subjects the patient to needless risk far ineffective treatment. This is again especially true of the home care scenario in which a patient is unlikely to easily recognize the malfunction or the resulting attenuation in therapeutic benefit.
With the foregoing deficiencies in mind, it is a primary object of the present invention to improve over the prior art by providing a compressor unit, specifically adapted for therapeutic applications of cyclic pressures, wherein the compressor unit is optimized to more efficiently and reliably deliver a desired pressure to a wrap device.
It is a further object of the present invention to contribute to patient comfort and compliance by providing a compressor unit that operates more quietly than those devices available in the prior art, and is therefore less intrusive to the patient.
It is yet another object of the present invention to provide a compressor unit with increased life cycle and mean time between failure as well as reduced component count, thereby helping to reduce the high costs now typically associated with most aspects of modern healthcare.
Finally, it is a specific object of the present invention to provide a compressor unit incorporating features for simplified operation, thereby helping to ensure that patients of the most varied ability are able to safely and effectively utilize the compressor unit in the home environment.

SUMMARY OF THE INVENTION:

In accordance with the foregoing objects, the present invention - a medical pumping system for use with a therapeutic patient treatment system - generally comprises a reservoir for holding a compressed fluid, with a fluid outlet and a valve for controlling flow of fluid from the reservoir through the outlet; a compressor for supplying pressurized fluid to the reservoir; and a controller for controlling the supply of pressurized fluid to the reservoir and for controlling the flow of fluid from the reservoir through the outlet. The controller has associated wherewith a sensor for measuring the internal pressure of the reservoir, and is adapted to provide the reservoir with an initial quantity of fluid on an initial cycle of operation; to operate the valve to release the initial quantity of fluid from the reservoir through the valve; to measure the internal pressure of the reservoir while the valve is operated; and to provide the reservoir with an additional quantity of fluid, less than the initial quantity of fluid based upon a comparison of the internal pressure of the reservoir, alter the release of the initial quantity of fluid, with a target pressure.
In at least one embodiment, the medical pumping system comprises a plurality of fluid outlets, wherein each fluid outlet has associated respectively therewith a valve for controlling flow of fluid from the reservoir therethrough. Further still, the controller may be adapted to release fluid from the reservoir alternately through each of the fluid outlets.
Preferably, the valve comprises a solenoid operated valve. The valve may have a vent, the vent preferably being adapted to release the pressure downstream the reservoir to the atmosphere. The system may also comprise a check valve, interposed between the compressor and the reservoir, to prevent back flow of pressurised fluid from the reservoir to the compressor. The sensor preferably comprises a solid state pressure transducer. Most preferably the transducer forms a component of the controller and may be integrated with the controller.
The medical pumping system further comprises a detector associated with the fluid outlet to provide the controller with information indicative of the connection of a medical wrap device. The information may be indicative of the connection of a particular medical wrap device. In one embodiment, the detector comprises a magnetic polarity sensor. In another embodiment, the controller further comprises a pressure feedback system, whereby the controller is adapted to determine the proper connection of a medical wrap device based upon the internal reservoir pressure following a release of fluid from the reservoir through the outlet. Either embodiment, or their substantial equivalent, may be utilised to monitor patient compliance, which, with the provision of a communications port, may be by remote interface with the pumping system.
In operation, pressurised fluid is preferably supplied to a medical wrap by supplying a reservoir with an initial quantity of fluid; releasing the initial quantity of fluid through an outlet, adapted for fluid communication with the medical wrap, from the reservoir; measuring the outlet pressure after releasing the fluid; and then supplying the reservoir with an additional quantity of fluid being based upon a comparison of the measured outlet pressure with a target pressure. The additional quantity of fluid is estimated to produce the target pressure at the outlet after a subsequent release of fluid from the reservoir through the outlet.
Preferably the method of operation further comprises the step of determining the proper connection of a medical wrap device based upon a comparison of the measured outlet pressure with an expected pressure value. The determining of the proper connection of a medical wrap device step may be adapted for use in determining patient compliance data.
The additional quantity of fluid may be a quantity less than said initial quantity of fluid.
Finally, many other features, objects and advantages of the present invention will be apparent to those of ordinary skill in the relevant arts, especially in light of the foregoing discussions and the following drawings, exemplary detailed description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS:

Although the scope of the present invention is much broader than any particular embodiment, a detailed description of the preferred embodiment follows together with illustrative figures, wherein like reference numerals refer to like components, and wherein:
Figure 1 shows, in perspective view, a medical pumping apparatus embodying the principles of the present invention, as housed in an easy to handle enclosure;
Figure 2 shows a pair of therapeutic foot wraps, such as those with which the present invention is adapted to operate;
Figure 3 shows, in functional block diagram, the pneumatic distribution system of the preferred embodiment of the present invention;
Figure 4 shows, in flow chart, an overview of the preferred method of the present invention;
Figure 5 shows, in a Cartesian representation, key pneumatic pressures during an initial and several subsequent cycles of operation of the present invention;
Figure 6 shows, in flow chart, an overview of one possible initialization sequence as implemented as part of the preferred method of the present invention; and
Figure 7 shows a detail of an alternate embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT:

Although those of ordinary skill in the art will readily recognize many alternative embodiments, especially in light of the illustrations provided herein, this detailed description is exemplary of the preferred embodiment of the present invention, the scope of which is limited only by the claims appended hereto.
Referring to Figures 1 and 3, the pumping unit 10 of the present invention generally comprises a compressor 11; a fluid reservoir 12 in fluid communication with one or more outlets 13, 14 through a corresponding number of valves 15, 16; and a controller 17 for controlling the pressurization of the fluid reservoir 12 and the subsequent release of fluid therefrom to the fluid outlets 13, 14. The pumping unit 10 is specifically adapted to operate with one or wore medical wrap devices 18, 19, such as those shown in Figure 2. In Figure 2, there is depicted a right foot wrap 18 and a left foot wrap 19, each adapted to provide wound healing therapy to patients exhibiting diabetic ulcers and like wounds of the feet. The depicted wraps 18, 19 are described in detail in Applicant's co-pending U.S. patent application entitled WOUND HEALING FOOT WRAP, filed on even date herewith and naming David M. Tumey and L. Tab Randolph as inventors; by this reference, the fell disclosure of said application is incorporated herein as though now set forth in its entirety. Although the principles of the present invention are described herein with reference to these diabetic wound healing type wraps 18, 19, it should be noted that the principles of the present invention may also be adapted, within the realm of ordinary skill in the art, for use in other applications of positive pressure. For example, the pumping unit of the present invention may be adapted for utilization with foot and/or leg wraps for the prevention of deep venous thrombosis (DVT), such as described in Applicant's co-pending U.S. patent application Serial No. 08/039,574 filed March 25, 1993, or with gradient compression leg wraps for the treatment of venous stasis ulcers, such as described in Applicant's co-pending U.S. patent application Serial No. 09/103,910 filed June 24, 1998. By this reference, the full disclosures of U.S. patent applications Serial No. 08/039,574 and 09/103,910 are incorporated herein as though now set forth in their respective entirety. In any case, the details of the interaction between the medical pumping unit of the present invention and the chosen medical wrap will be better understood further herein.
As shown particularly in Figure 1, the compressor 11, reservoir 12, valves 15, 16, 26, controller 17 and other associated components of the medical pumping unit are preferably housed in an easy to handle enclosure 20 of hardened or molded plastic, which may have a user control panel 21 mounted directly thereto. In the preferred embodiment of the present invention the pumping unit 10 includes a single push-button ON-OFF 22 switch and a display panel 21 to indicate proper operation or an alarm condition. Such an alarm condition may include, for example, the disconnection of a medical wrap device 18, 19 from one or more of the fluid outlets 13,14 , an opened or damaged wrap device 18, 19 or a kink in a wrap supply hose 23.
Referring now to the pneumatic diagram of Figure 3 in particular, the pumping unit 10 of the present invention is shown to comprise a conventional compressor 11, as is well know to those of ordinary skill in the art, in fluid communication with a fluid reservoir 12. In the preferred embodiment of the present invention, the fluid reservoir 12 is simply implemented with a plastic bottle. As shown in the figure, the reservoir 12 is also preferably supplied with pressurized fluid from the compressor 11 through a one-way check valve 24. For reasons that will be better understood further herein, this provides a simple manner in which the reservoir 12 may be pumped to a determinable pressure after which the compressor 11 may be shut off. In the preferred embodiment of the present invention, the controller board 17 includes a pressure sensor 25 in the form of a solid state pressure transducer. The sensor 25 is in fluid communication with the reservoir 12, whereby the reservoir's internal pressure may be known to the controller board 17 at any given time. Finally, the reservoir 12 is shown to be in fluid communication with at least one, but preferably two, front panel air outlets 13, 14 through a plurality of solenoid actuated valves 15, 16. In the two outlet configuration shown, one outlet is designated as the left outlet 13 and the other outlet is designated as the right outlet 14. Likewise, one solenoid valve is designated as the left valve 15 and one other as the right valve 16. As shown in the figure, a third valve - the initialization and safety valve 26 - is provided for reasons detailed further herein. Each valve 15, 16, 26 comprises a vent 27, 28, 29 in addition to a pneumatic flow control valve, whereby each may be used to release pressure to atmosphere.
In operation of the present invention as shown in the process flow chart of Figure 4, the reservoir 12 is initially filled to some predetermined pressure P₁, whereafter the compressor 11 is shut off 30. The left or right valve 15, 16 is then opened for the entire compression cycle, typically on the order of two to three seconds, allowing the reservoir pressure to equilibrate with the corresponding wrap pressure, in effect causing the properly applied wrap to exert a therapeutic force upon the desired region of a patient's body 31. The resultant equilibrium pressure P_eq is then measured 32 by the pressure sensor 25 and compared with the desired target pressure P_targ (determined on the basis of the therapy to which the patient is to be subjected) 33 in order to determine the pressure P₂ at which the reservoir 12 should be filled for the next cycle 34, 35. In particular, if P_eq is found to be less than P_targ, P₂ is set to a pressure x greater than P ₁ 36. On the other band, if P_eq as found to be greater than P_targ, P₂ is set to a pressure x less than P ₁ 37. As will be appreciated by those of ordinary skill in the art, many formulations may be contrived in order to adjust the magnitude of the difference between P₂ and P₁ (x) according to the magnitude of the difference between P_eq and P_targ. For example, a large variation between the measured equilibrium pressure P_eq and the desired target pressure P_targ will generally dictate a greater adjustment in pressure from P₁ to P₂ than would a lesser variation between the measured equilibrium pressure P_eq and the desired target pressure P_targ. The implementing engineer, however, will readily see many more sophisticated formulations that will allow the equilibrium pressure P_eq to be quickly brought, and thereafter maintained, within the realm of the target pressure P_targ.
The resulting reservoir and wrap pressures for several typical cycles of this process are depicted in the plot of Figure 5. In the exemplary plots shown, the initial reservoir pressure 38 turns out to be too low to achieve the desired wrap pressure 39. As a result, the controller 17 instructs the compressor 11 to fill the reservoir 12 to a slightly higher pressure 40 for the subsequent cycle. This time, the wrap pressure 41 is found to be above the desired target pressure 39 and the controller 17 adjusts the set pressure for the reservoir 12 to a slightly less pressure 42. Finally, achieving the desired wrap pressure 43, the controller 17 instructs the compressor 11 to fill the reservoir 12 to the same pressure 42 for subsequent cycles.
In subsequent compression cycles, it is only necessary to operate the compressor 11 for the replacement of that pressure which has been lost in previous compression cycles. In this manner, and as is shown in the plot of Figure 5, the compressor operation time is minimized, resulting in a corresponding reduction in noise generated and increase in compressor life cycle. In fact, Applicant's initial findings indicate a three to four fold increase in compressor life cycle - a dramatic improvement over the prior art devices. Further, this improvement was found to be possible without requirement for a cooling fan, which also contributes to the noise reduction enabled by the present invention. As an unexpected result, the elimination of the cooling fan actually further increases the compressor life cycle by eliminating the forced flow of typically very dirty air found in the home environment. Finally, because the system 10 is also able to operate at minimum required pressures the incidence of leaks is reduced, which results in an increased mean time between failure.
As has been stated, it is a specific object of the present invention to provide a medical pumping unit 10 of this type that is simple to operate, thereby facilitating home care for those of most varied ability. To this end, and especially for use by the elderly and/or physically challenged, it is desired that the pumping unit be of one-button 22 type operation. In the past, however, pumping units 10 have required significant adjustment by a physician or highly trained technician in order to ensure delivery of the desired therapy. Further, it is necessary to tell the prior art devices whether to pump the right side, left side or both. As a result of this need to program a desired pumping protocol, such one-button type operation has not been previously realized.
Referring now to Figure 6, there is shown the setup feature of the preferred embodiment of the present invention. This setup feature eliminates the need to program a desired pumping protocol, allowing the pumping unit 10 to very robustly determine which side to pump and even, if desired, what type of therapeutic function to provide. As shown in the figure, the reservoir 12 is at power-up first vented 44 through the initialization and safety valve vent port 29. This ensures a known reference pressure in the reservoir 12 with respect to atmosphere. After venting, two cycles of air are blown through the right side outlet 45 (or left) without venting to atmosphere therebetween. After the second cycle, the equilibrium pressure is measured 46. If a pressure is present, a wrap is indicated and the pumping unit automatically configures to pump to the right (or left) side 47. The reservoir is then vented again 48 through the initialization and safety valve vent port 29 and the process is repeated for the remaining side to wit two cycles of air are blown through the left side outlet 49 (or right) without venting to atmosphere therebetween. After the second cycle, the equilibrium pressure is measured 50. If a pressure is present, a wrap is indicated and the pumping unit automatically configures to pump to the left (or right) side 51. The system is then vented a final time, after which is commenced 52 the normal pumping routine as depicted in Figure 4.
Not only is this setup method well suited for use with existing wraps 18, 19, and hoses 23 without further modification, but it is also robust enough to distinguish between a properly and improperly applied wrap and between a foot wrap, for example, and a calf wrap. These distinctions, of course, are based upon the volume of air released and equilibrium pressure thereafter detected and, with the benefit of this disclosure, are well within the realm of one of ordinary skill in the art.
The preferred embodiment of the present invention is also provided with a communications interface 53, such as an RS-232 standard communication port. This feature allows remote programming of the pumping unit 10 for such purposes as providing software upgrades. The communications port 53 also allows built in test type diagnostic data to be downloaded for checkout and maintenance of the pumping unit 10. Patient compliance data, which is available through the system's ability to distinguish between a properly and improperly applied wrap, may also be monitored through the communication port 53. Finally, warning indicators, such as the need for service or physician intervention, may be automatically transmitted.
While the foregoing description is exemplary of the preferred embodiment of the present invention, those of ordinary skill in the relevant arts will recognize the many variations, alterations, modifications, substitutions and the like as are readily possible, especially in light of this description, the accompanying drawings and claims drawn thereto. For example, and with reference to Figure 7, a sensor 54 may be inserted within the wrap's hose connector 55 in order to identify the type of wrap. One such sensor could be a simple magnet, presenting either a North pole or South pole. While the detection of no magnetic field at a corresponding sensor 56 on the pumping unit would indicate the absence of any wrap, detection of a North pole might indicate a foot wrap and detection of a South pole could indicate a calf wrap. In any case, because the scope of the present invention is much broader than any particular embodiment, the foregoing detailed description should not be construed as a limitation of the scope of the present invention, which is limited only by the claims appended hereto.

Claims

A medical pumping system for use with a therapeutic patient treatment system, said pumping system comprising:

a reservoir for holding a compressed fluid, said reservoir having a fluid outlet, said fluid outlet having associated therewith a valve for controlling flow of fluid from said reservoir through said outlet;

a compressor for supplying pressurized fluid to said reservoir,

a controller for controlling the supply of pressurized fluid to said reservoir and for controlling the flow of fluid from said reservoir through said outlet, said controller having associated therewith a sensor for measuring the internal pressure of said reservoir; and

said controller being adapted to:

provide said reservoir with an initial quantity of fluid on an initial cycle of operation;

operate said valve to release said initial quantity of fluid from said reservoir through said valve;

measure the internal pressure of said reservoir while said valve is operated for the release of said initial quantity of fluid; and

provide said reservoir with an additional quantity of fluid, said additional quantity of fluid being less than said initial quantity of fluid, and said additional quantity of fluid being based upon a comparison of the internal pressure of said reservoir after the release of said initial quantity of fluid with a target pressure.
The medical pumping system as recited in claim 1, said reservoir having a plurality of fluid outlets.
The medical pumping system as recited in claim 2, wherein each said fluid outlet has associated respectively therewith a valve for controlling flow of fluid from said reservoir therethrough.
The medical pumping system as recited in claim 2 or claim 3, wherein said controller is further adapted to release fluid from said reservoir alternately through each said fluid outlet.
The medical pumping system as recited in any preceding claim, said pumping system further comprising a check valve interposed between said compressor and said reservoir, said check valve being adapted to prevent back flow of pressurised fluid from said reservoir to said compressor.
The medical pumping system as recited in any preceding claim, wherein said controller is further adapted to automatically determine the proper connection of a medical wrap device.
The medical pumping system as recited in claim 6, wherein said controller further comprises a pressure feedback system whereby said controller is adapted to determine the proper connection of a medical wrap device based upon the internal reservoir pressure following a release of fluid from said reservoir through said outlet.
The medical pumping system as recited in claim 7, wherein said controller is further adapted to utilize said pressure feedback system to monitor patient compliance.
The medical pumping system as recited in any preceding claim, said pumping system further comprising a communications port for remote interface with said pumping system.
A method for supplying pressurized fluid to a medical wrap, said method comprising the steps of:

supplying a reservoir with an initial quantity of fluid;

releasing said initial quantity of fluid through an outlet from said reservoir, said outlet being adapted for fluid communication with the medical wrap;

measuring the outlet pressure after said releasing step; and

supplying said reservoir with an additional quantity of fluid being based upon a comparison of the measured outlet pressure with a target pressure, said additional quantity of fluid being estimated to produce said target pressure at said outlet after a subsequent release of fluid from said reservoir through said outlet.