Patent Description:
The disclosure relates to flow detection systems and methods for operating an infusion pump which utilize a high-frequency acoustic, closed loop system to measure and control the volumetric flow rate of the infusion pump.

Infusion systems and methods often operate in an open loop configuration, without receiving feedback regarding the volume of fluid being delivered to the patient. These infusion systems and methods typically rely on tightly controlled tolerances to fabricate the individual components and assemblies of the infusion pumping system to maintain the accuracy of delivered medication over a prescribed time. The accuracy of the amount of the prescribed medication being delivered to the patient by current infusion systems and methods can vary over time due to the component degradation over the life of the infuser. Additionally, requirements for tight tolerances for the individual components of the pumping mechanism significantly increase the manufacturing and service cost of the infusion system. Other infusion systems and methods utilize varying ways of attempting to monitor the amount of the medication being delivered to the patient with one or more additional issues.

An infusion system is needed to reduce one or more issues associated with one or more of the current infusion systems and methods.

<CIT> discloses a system including an ultrasonic transducer sensor assembly coupled with a tubing of a medical pump to transmit and receive acoustic signals directed at or through the tubing. An inner diameter and wall thickness of the tubing is determined based on the signals, and a controller determines a fluid flow rate based on the determined inner diameter and a determined flow velocity. A flow velocity is determined from a difference in the propagation time of the signals; the propagation time in the upstream direction minus the propagation time in the downstream direction.

<CIT> discloses a breathing apparatus has a first delivery device for adding a volume of a substance to a gas flow, the delivery device having a gas inlet and a gas outlet. Propagation times of a sound pulse in the gas is used to determine the gas flow in a duct.

<CIT> discloses a method of detecting an occlusion for an infusion therapy. An output signal from a flowrate sensor for a pulsatile fluid flow has a frequency range, the pulsatile flow being through a fluid pathway to a patient. The signal strength of the range is compared to a threshold level to determine if an occlusion is present during the infusion therapy.

<CIT> discloses an acoustic access disconnect detection system for detecting when an access needle has become dislodged or when blood is leaking. The system includes an acoustic transmitter and an acoustic sensor placed upstream of an access site of a patient, the sensor suitable for generating and detecting an acoustic signal that is intended to pass unobstructed through the access site.

<CIT> discloses a system and a method for detecting the presence of air bubbles in an intravenous (IV) line supplying a medicinal liquid to a patient. An air bubble sensor includes an ultrasonic transmitter acoustically coupled to an ultrasonic receiver to detect the presence of a gas (e.g., air) in a portion of a tube comprising the IV line.

Advantageous embodiments are subject of the dependent claims. In one embodiment of the disclosure, an infusion system for automatically detecting and adjusting a volumetric flow rate delivered by an infusion pump is disclosed. The infusion system includes an infusion pump, a flow path, at least one upstream acoustic sensor, at least one downstream acoustic sensor, at least one processor, and at least one memory. The infusion pump is configured to pump infusion fluid. The infusion fluid is configured to be delivered by the infusion pump along the flow path. The upstream acoustic sensor is located at an upstream location of the flow path. The downstream acoustic sensor is located at a downstream location of the flow path. The downstream acoustic sensor is configured to detect an upstream acoustic signal emitted by the upstream acoustic sensor. The upstream acoustic sensor is configured to detect a downstream acoustic signal emitted by the downstream acoustic sensor. The processor is in electronic communication with the infusion pump, the upstream acoustic sensor, and the downstream acoustic sensor. The memory is in electronic communication with the processor. The memory includes programming code for execution by the processor. The programming code is configured to determine a volumetric flow rate of the infusion fluid along the flow path based on the upstream acoustic signal detected by the downstream acoustic sensor and on the downstream acoustic signal detected by the upstream acoustic sensor. The programming code is configured to determine the volumetric flow rate of the infusion fluid along the flow path based on a first phase delay of the upstream acoustic signal between the upstream acoustic sensor and the downstream acoustic sensor, and/or on a second phase delay of the downstream acoustic signal between the downstream acoustic sensor and the upstream acoustic sensor. The programming code is further configured to automatically adjust the infusion pump based on the determined volumetric flow rate, to achieve a desired volumetric flow rate of the infusion fluid along the flow path.

In an example of the disclosure, a method for automatically detecting and adjusting a volumetric flow rate delivered by an infusion pump is disclosed. In one step, infusion fluid is delivered with an infusion pump along a flow path. In another step, an upstream acoustic signal emitted by at least one upstream acoustic sensor, located at an upstream location of the flow path, is detected with at least one downstream acoustic sensor located at a downstream location of the flow path. In an additional step, a downstream acoustic signal emitted by the downstream acoustic sensor, located at the downstream location of the flow path, is detected with the upstream acoustic sensor located at the upstream location of the flow path. In another step, a volumetric flow rate of the infusion fluid along the flow path is determined, with at least one processor, over each stroke of the infusion pump based on the upstream acoustic signal detected by the downstream acoustic sensor and on the downstream acoustic signal detected by the upstream acoustic sensor. The processor determines the volumetric flow rate of the infusion fluid along the flow path over each stroke of the infusion pump by determining a first phase delay of the upstream acoustic signal between the upstream acoustic sensor and the downstream acoustic sensor, or by determining a second phase delay of the downstream acoustic signal between the downstream acoustic sensor and the upstream acoustic sensor. In still another step, the infusion pump is automatically adjusted, with the processor, over each pumping cycle of the infusion pump based on the determined volumetric flow rate to achieve a desired volumetric flow rate of the infusion fluid along the flow path.

In an example of the disclosure, a non-transitory computer readable medium is disclosed. The non-transitory computer readable medium is configured to, using at least one processor, automatically detect and adjust a volumetric flow rate of infusion fluid delivered by an infusion pump. The non-transitory computer readable medium includes programming code to command the processor to determine, over each stroke of the infusion pump, the volumetric flow rate of the infusion fluid delivered by the infusion pump along a flow path. The programming code is configured to determine, over each stroke of the infusion pump, the volumetric flow rate based on an upstream acoustic signal emitted by at least one upstream acoustic sensor, located at an upstream location of the flow path, which is detected by at least one downstream acoustic sensor located at a downstream location of the flow path. The programming code is further configured to determine, over each stroke of the infusion pump, the volumetric flow rate based on a downstream acoustic signal emitted by the downstream acoustic sensor and detected by the upstream acoustic sensor. The programming code is configured to automatically adjust the infusion pump over each pumping cycle of the infusion pump, based on the determined volumetric flow rate, to achieve a desired volumetric flow rate of the infusion fluid along the flow path.

In certain embodiments, an infusion system can automatically control an infusion pump. The infusion system can include an infusion pump that can pump infusion fluid along a flow path. The infusion system can also include a first acoustic sensor positioned at a first location along the flow path, the first acoustic sensor can detect a first acoustic signal. The infusion system can further include a second acoustic sensor positioned at a second location downstream from the first acoustic sensor along the flow path. The second acoustic sensor can detect a second acoustic signal. The infusion system can also include a controller that can determine a first volumetric flow rate of the infusion fluid based on the detected first acoustic signal and the detected second acoustic signal. The controller can also control the infusion pump to pump infusion fluid at a second volumetric flow rate based on the detected first volumetric flow rate.

The infusion system of the preceding paragraph can have any sub-combination of the following features: wherein the first acoustic signal originated from the second acoustic sensor and the second acoustic signal originated from the first acoustic sensor; wherein the first acoustic sensor comprises a first transducer and the second acoustic sensor comprises a second transducer; wherein the first acoustic sensor comprises a first transmitter and a first receiver and the second acoustic sensor comprises a second transmitter and a second receiver; wherein the first receiver and the second receiver each comprise at least one noise cancelling component; wherein the first volumetric flow rate of the infusion fluid is calculated over each stroke of the infusion pump; wherein the first volumetric flow rate is determined based on a first phase delay associated the first acoustic signal; wherein the first volumetric flow rate is determined based on a second phase delay associated the second acoustic signal; wherein the first volumetric flow rate is determined based on a length between the first location and the second location; wherein the first volumetric flow rate is determined based on a first time it takes the first acoustic signal to travel between the second acoustic sensor and the first acoustic sensor; wherein the first volumetric flow rate is determined based on a first time it takes the second acoustic signal to travel between the first acoustic sensor and the second acoustic sensor.

In certain examples, a method of controlling an infusion pump can include detecting a first acoustic signal from a first acoustic sensor positioned at a first location along the flow path. The method can further include detecting a second acoustic signal from a second acoustic sensor positioned at a second location downstream from the first acoustic sensor along the flow path. The method can also include determining a first volumetric flow rate of the infusion fluid based on the detected first acoustic signal and the detected second acoustic signal. Moreover, the method can include changing the first volumetric flow rate to a second volumetric flow rate based on the determined first volumetric flow rate.

The method of the preceding paragraph can have any sub-combination of the following features: wherein the first acoustic signal originated from the second acoustic sensor and the second acoustic signal originated from the first acoustic sensor, wherein the first acoustic sensor comprises a first transducer and the second acoustic sensor comprises a second transducer; wherein the first acoustic sensor comprises a first transmitter and a first receiver and the second acoustic sensor comprises a second transmitter and a second receiver; wherein the first receiver and the second receiver each comprise at least one noise cancelling component; wherein the first volumetric flow rate of the infusion fluid is calculated over each stroke of the infusion pump; wherein the first volumetric flow rate is determined based on a first phase delay associated the first acoustic signal; wherein the first volumetric flow rate is determined based on a second phase delay associated the second acoustic signal; wherein the first volumetric flow rate is determined based on a length between the first location and the second location; wherein the first volumetric flow rate is determined based on a first time it takes the first acoustic signal to travel between the second acoustic sensor and the first acoustic sensor; wherein the first volumetric flow rate is determined based on a first time it takes the second acoustic signal to travel between the first acoustic sensor and the second acoustic sensor.

These and other features, aspects and advantages of the disclosure will become better understood with reference to the following drawings, description and claims.

The following detailed disclosure describes one or more modes of carrying out the invention. The disclosure is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the disclosure, since the scope of the disclosure is best defined by the appended claims. It is noted that the figures are purely for illustrative purposes and are not to scale. It is further noted that any portions of the embodiments of the below disclosure may be, in varying embodiments, combined in part or in full, one or more components may be added, or one or more components may be removed.

<FIG> illustrates an embodiment of a box diagram of an infusion system <NUM>. The infusion system <NUM> can include an infusion pump or infuser <NUM> and an infusion set <NUM> that is inserted in, and is acted upon by the infusion pump <NUM>. The infusion set <NUM> can include, among other elements, an inlet tube <NUM>, an outlet tube <NUM> and a cassette <NUM>. The infusion system <NUM> can also include an infusion pump <NUM> with an infusion pumping mechanism <NUM>, a pump cassette <NUM>, an infusion set <NUM> that has an internal flow path <NUM>, at least one upstream acoustic sensor <NUM>, at least one downstream acoustic sensor <NUM>, at least one hardware processor <NUM>, at least one memory (also referred to herein as a non-transitory computer readable medium) <NUM>, programming code <NUM>, a proximal air-in-line sensor <NUM>, a proximal pressure sensor <NUM>, a distal pressure sensor <NUM>, and a distal air-in-line air sensor <NUM>. Signals from the infusion pumping mechanism <NUM> and the sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are acquired, conditioned if necessary, and sent to the hardware processor <NUM> by signal acquisition electronics <NUM> to monitor proper operation of fluid delivery. The hardware processor <NUM> can be programmed to execute programming code <NUM> or various algorithms stored in the memory <NUM> and can control operation of the pumping mechanism <NUM> through the driving electronics. The programming code or instructions can be implemented in C, C++, JAVA, or any other suitable programming languages. In some embodiments, some or all of the portions of the programmed instructions can be implemented in application specific circuitry <NUM> such as ASICs and FPGAs.

The infusion system <NUM> is configured to automatically detect and adjust a volumetric flow rate of infusion fluid <NUM> delivered by the infusion pump <NUM> along the flow path <NUM>. In other embodiments, the infusion system <NUM> may include varying components varying in number, size, type, orientation, configuration, location, or function. For instance, in another embodiment the infusion system <NUM> may not utilize a pump cassette <NUM> (for example, see <FIG> and the description below).

As shown collectively in <FIG> and <FIG>, the infusion pump <NUM> is operatively coupled to the pump cassette <NUM>. In other words, the cassette <NUM> is inserted in the infusion pump <NUM>. The infusion pump <NUM> is configured to operate on the cassette <NUM> to pump the infusion fluid <NUM> from a source or reservoir <NUM>, which can be a bag, vial or other container, through the inlet tube <NUM>, at least one internal passageway of the cassette <NUM>, and through the outlet tube <NUM> along the flow path <NUM>, which may lead to a patient <NUM>. In other embodiments, the flow path <NUM> may be a flow path outside the pump cassette <NUM> or the pump cassette <NUM> may not be present at all and the flow path <NUM> may be any flow path over which the infusion fluid <NUM> flows. The upstream acoustic sensor <NUM> is coupled with the pump cassette <NUM> and located at an upstream location 14a of the flow path <NUM> at or integrated with the proximal pressure sensor <NUM> which is coupled with the pump cassette <NUM>. In other embodiments, the upstream acoustic sensor <NUM> may be located at or integrated with the proximal air-inline sensor <NUM> or located or integrated with varying components of the infusion system <NUM>. The upstream acoustic sensor <NUM> may include one or more ultrasonic sensors or other types of acoustic sensor. Upstream and downstream are relative terms used herein to indicate the position of the sensors along the flow path. In an embodiment, the upstream sensor encounters the flow of fluid from the reservoir <NUM> before the downstream sensor.

In an embodiment, the downstream acoustic sensor <NUM> is coupled with the pump cassette <NUM> and located at a downstream location 14b of the flow path <NUM> at or integrated with the distal air-in-line sensor <NUM> which is coupled with the pump cassette <NUM>. In other embodiments, the downstream acoustic sensor <NUM> may be located at or integrated with the distal pressure sensor <NUM> or located or integrated with varying components of the infusion system <NUM>.

The downstream acoustic sensor <NUM> may include one or more ultrasonic sensors or other types of acoustic sensors. In an embodiment, the downstream acoustic sensor <NUM> is configured to detect an upstream acoustic signal emitted by the upstream acoustic sensor <NUM>. The upstream acoustic sensor <NUM> can also be configured to detect a downstream acoustic signal emitted by the downstream acoustic sensor <NUM>. In one embodiment, the upstream acoustic sensor <NUM> and the downstream acoustic sensor <NUM> may take turns, synchronized with the pumping mechanism of the infusion pump <NUM>, transmitting their respective upstream acoustic signal and downstream acoustic signal. The hardware processor <NUM> can calculate the flow rate of the infusion fluid by integrating the phase delay measurement between the upstream and downstream signals over each periodic pumping interval. The pumping mechanism <NUM> operates in a periodic manner, the flow measurement is obtained by the sensors <NUM> and <NUM>, and the flow is calculated by integration of the phase delay measurement over each individual periodic pumping interval as seen in <FIG>. The flow measurement obtained by the sensors <NUM> and <NUM> can be synchronized with the period interval of the pumping mechanism <NUM> by the hardware processor <NUM> which determines the phase delay between the upstream and downstream signals over each stroke of the pumping mechanism <NUM> (shown in <FIG>) and uses the phase delay to determine the volumetric flow rate of the infusion fluid over each stroke of the pumping mechanism <NUM>. Moreover, the hardware processor <NUM> (shown in <FIG>) is configured to make flow rate adjustments to the infusion fluid over each pumping cycle based on the determined flow rate over each stroke of the pumping mechanism <NUM>. Furthermore, the hardware processor <NUM> (shown in <FIG>) may average the determined flow rates over a multitude of pump cycles and adjust the flow rate of the infusion fluid accordingly. In such manner, rapid update rate fluid delivery pumping correction can be achieved utilizing periodic sampling over the pumping period.

It is noted that the movement of infusion fluid into an IV line is modulated by numerous items. The items that modulate the fluid flow are complex including but not limited to plunger movement, pump valve operation, bag height, and patient relation to the pump chamber. Many of the dynamic changes are periodic in nature as depicted in <FIG>. This periodicity can be utilized to create a more rapid update rate for average flow. To have a reading of average flow by conventional means it may require averaging the readings over several periodic periods. However, by gating the averaging by the periodic period the average can be known in one periodic period. This can allow the control of fluid delivery to be corrected much more quickly. In some embodiments, this is much more accurate for determining the flow rate than conventional methods. In such manner, the hardware processor of the infusion system can calculate the phase delay over each stroke to determine the flow rate over each stroke and by subsequently adjusting the flow rate over each pumping cycle based on the determined flow rate, the infusion system has superior flow rate accuracy over conventional systems and methods. This allows for the use of the infusion system over a much longer period of time as diaphragm deterioration and other deterioration of the components of the infusion system may be accounted for in real-time during each pumping cycle of the pumping mechanism by adjusting the flow rate of the infusion fluid accordingly.

In another embodiment, the upstream acoustic sensor <NUM> and the downstream acoustic sensor <NUM> may continuously transmit their respective upstream acoustic signal and downstream acoustic signal or the measurements may occur over a given number of periodic intervals. One skilled in the art will recognize that the terms "upstream" and "downstream", as used herein, are terms that describe the location of one component of the system with respect to one or more other components of the system. The flow path <NUM> can be thought of as a river where fluid is normally flowing from the source <NUM> to the patient <NUM>. In an embodiment, the upstream acoustic sensor <NUM> is located between the pumping mechanism <NUM> and the reservoir <NUM> or upstream of the pumping mechanism <NUM>, and the downstream acoustic sensor <NUM> is located between the pumping mechanism <NUM> and the patient <NUM> or downstream of the pumping mechanism <NUM>. The upstream acoustic sensor <NUM> is located upstream along the normal flow path <NUM> from the downstream acoustic sensor <NUM>. One skilled in the art will also appreciate that the upstream and downstream acoustic sensors <NUM> and <NUM> could be referred to as proximal and distal acoustic sensors respectively.

<FIG> and <FIG> illustrate two different possible configurations and placements of acoustic sensors <NUM> and <NUM> against or adjacent to a cassette <NUM> as shown relative to the inlet tube <NUM> and the outlet tube <NUM>. The acoustic sensors <NUM> and <NUM> are non-invasive ultrasonic transducers 16T and 18T. The transducers 16T and 18T have double function of emitters and receivers. The transducers 16T and 18T contact the cassette <NUM> by means of coupling elements. The coupling elements 16C and 18C are made of a compliant material and ensure good acoustic contact. In one embodiment, the transducers 16T and 18T with their coupling elements 16C and 18C are part of the pump <NUM> (shown in <FIG>).

<FIG> illustrates one embodiment of a cross-section view through a portion of an infusion system <NUM> in which the disclosure could be implemented showing the flow path <NUM>, the one upstream acoustic sensor <NUM>, and the one downstream acoustic sensor <NUM>. The upstream acoustic sensor <NUM> includes a first transducer 16T that includes a transmitter 16E and a first receiver 16R which are shown in greater detail with their accompanying electronics in <FIG>. The first receiver 16R includes a noise cancelling component such as a noise cancelling microphone <NUM>. Similarly, the downstream acoustic sensor <NUM> includes a second transducer 18T that includes a transmitter 18E and a second receiver 18R which are shown in greater detail with their accompanying electronics in <FIG>. The second receiver 18R can also include a noise cancelling component such as a noise cancelling microphone <NUM>. In additional embodiments, the upstream acoustic sensor <NUM> and the downstream acoustic sensor <NUM> may further vary.

<FIG> illustrates another embodiment of a cross-section view through a portion of an infusion system <NUM> in which the disclosure could be implemented showing the flow path <NUM>, the upstream acoustic sensor <NUM>, and the downstream acoustic sensor <NUM>. The upstream acoustic sensor <NUM> can include a first transducer 16T, and the downstream acoustic sensor <NUM> includes a second transducer 18T. The first transducer 16T and the second transducer 18T may each include or be connected to a noise cancelling component such as noise cancelling microphones <NUM> and <NUM>. In additional embodiments, the upstream acoustic sensor <NUM> and the downstream acoustic sensor <NUM> may further vary.

In another embodiment shown in <FIG>, the existing cassette <NUM> is enhanced by the addition of a straight rigid tube 12T with a precise internal bore. The tube 12T can be part of the cassette <NUM> as an extension of its outlet port. The transducers 16T and 18T make contact with the tube 12T or are coupled to the tube 12T by the coupling elements 16C and 18C.

In another embodiment shown in <FIG>, the infusion system <NUM> may or may not include a cassette, but includes in the flow path <NUM> a straight rigid tube 12T that has a precisely dimensioned internal bore. If the system <NUM> includes a cassette (shown in <FIG> as cassette <NUM>), the rigid tube 12T is located downstream of the cassette and is connected to or integrated with an outlet tube (shown in <FIG> as outlet tube <NUM>). If the system does not include a cassette, the tube 12T can be located downstream of whatever pumping mechanism (shown in <FIG> as pumping mechanism <NUM>) exists. In the case of gravity flow where no pumping mechanism exists other than gravity, the tube 12T can be located between the source (shown in <FIG> as source <NUM>) and the patient (shown in <FIG> as patient <NUM>), downstream of a conventional clamp or valve (not shown) for controlling the flow of the infusion fluid <NUM>. The infusion fluid <NUM> enters the tube 12T through an inlet and flows to an outlet. The upstream transducer 16T is coupled to the tube 12T adjacent to the inlet by a coupling element 16C. The downstream transducer 18T is coupled to the tube 12T adjacent to the outlet by a coupling element 18C.

Taking as an example the embodiment in <FIG>, <FIG> shows one embodiment of the flow sensor circuits which may be utilized to monitor the flow rate of the infusion fluid <NUM>. In this case, the transducers 16T, 18T can be transducers or can each include separate emitters or transmitters 16E, 18E and receivers 16R, 18R. The transmitter and receiver function can be accomplished by the same transducer or by separate transducers performing each a single function. The transmitters 16E and 18E can emit ultrasonic signals and the receivers 16R and 18R receive the ultrasonic signals from the transmitters 18E and 16E. The receivers 16R and 18R can include noise cancelling components such as noise cancelling microphones <NUM> and <NUM>. The microcontroller <NUM> (also referred to as a hardware processor herein which could include one or more hardware processors) commands a frequency generator <NUM> to generate a voltage signal with the programmed frequency f. A driver <NUM> amplifies the signal and sends it to the emitter 16E of one of the transducers 16T. The emitter 16E generates an ultrasonic signal S that propagates through the fluid <NUM> and is detected by the receiver 18R at the other end of the tube, which generates a voltage signal proportional to the received ultrasonic signal R. The emitted signal S and the received signal R are fed to a phase comparator <NUM> that generates a signal proportional to the phase difference between the two signals. A signal conditioning stage <NUM> amplifies and filters the signal and sends it to an analog to digital converter <NUM> that converts it to a digital phase signal received by the microcontroller <NUM>. The microcontroller <NUM> controls the switches 314A, 314B, 314C, 314D that select the propagation direction of the ultrasonic signal. In this embodiment the signal S is emitted alternatively with and against the flow direction. When the signal S is to be emitted with the direction of fluid flow, the normally closed switches 314A and 314B are closed and the normally open switches 314C and 314D are open; and when the signal S is to be emitted in the opposite direction, against the direction of fluid flow, the microcontroller <NUM> opens switches 314A and 314B and closes switches 314C and 314D. The transmitter and receiver transducers can be piezoelectric, electromagnetic, or microelectromechanical systems (MEMS) based in construction.

Taking as an example the embodiment of FIG. <NUM>, <FIG> shows another embodiment of the flow sensor circuits which may be utilized to monitor the flow rate of the infusion fluid <NUM>. In this case the transducers 16T and 18T still contain separate emitters 16E and 18E and receivers 16R and 18R, but the transducers 16T and 18T are operated continuously. In other words, the case of simultaneous transmission with separate transmitter and receiver transducers is illustrated. There are two separate channels, one for the acoustic signal propagating against the flow and one for the acoustic signal propagating with the flow. The programmed frequencies f<NUM> and f<NUM> of the signals S1 and S2 in the two channels are different, so they can be separated by the phase comparators 308A and <NUM>. The microcontroller <NUM> commands a frequency generator 304A to generate a voltage signal with the programmed frequency f<NUM>. A driver 306A amplifies the signal S1 and sends it to the emitter 16E of one of the transducers 16T. The emitter 16E generates an ultrasonic signal that propagates through the fluid <NUM> and is detected by the receiver 18R at the other end of the tube, which generates a voltage signal proportional to the received ultrasonic signal R <NUM>. The emitted signal S1 and the received signal R1 are fed to a phase comparator 308A that generates a signal proportional to the phase difference between the two signals. A signal conditioning stage <NUM> OA amplifies and filters the signal and sends it to an analog to digital converter 312A that converts it to a digital phase signal received by the microcontroller <NUM>. The microcontroller <NUM> further commands a frequency generator <NUM> to generate a voltage signal with the programmed frequency f<NUM>. A driver <NUM> amplifies the signal S2 and sends it to the emitter 18E of one of the transducers 18T. The emitter 18E generates an ultrasonic signal that propagates through the fluid <NUM> and is detected by the receiver 16R at the other end of the tube, which generates a voltage signal proportional to the received ultrasonic signal R2. The emitted signal S2 and the received signal R2 are fed to a phase comparator <NUM> that generates a signal proportional to the phase difference between the two signals. A signal conditioning stage <NUM> OB amplifies and filters the signal and sends it to an analog to digital converter <NUM> that converts it to a digital phase signal received by the microcontroller <NUM>. The transmitter and receiver transducers can be piezoelectric, electromagnetic, or microelectromechanical systems (MEMS) based in construction.

Again taking as an example the embodiment of <FIG>, <FIG> shows another embodiment of the flow sensor circuits which may be utilized to monitor the flow rate of the infusion fluid <NUM>. In this case, the transducers 16T and 18T perform both functions of emitting and receiving the ultrasonic signals. The transducers 16T and 18T transmit simultaneously and are operated continuously. There are still two separate channels. The frequencies f1, f2 of the signals S1 and S2 in the two channels are different, so they can be separated by the phase comparators 308A and 308B. The voltage at the terminals of each of the transducers 16T and 18T is the sum of the emitted signals S1 and S2 voltages from the drivers 306A and 306B and the voltages generated by the transducers 16T and 18T, which is proportional to the received signals R2 and R1. Difference amplifiers 316A and 316B subtract the emitted signals S1 or S2 from this sum, outputting the received signals R2 or R1 respectively. The microcontroller <NUM> (also referred to as a processor herein which could include one or more processors) commands frequency generator 304A to generate a voltage signal with the programmed frequency f<NUM>. A driver 306A amplifies the signal S1 and sends it to the transducer 16T. The transducer 16T generates an ultrasonic signal that propagates through the fluid <NUM> and is detected by the transducer 18T at the other end of the tube, which generates a voltage signal of the sum of the received ultrasonic signal R1 and the signal S2 transmitted by the transducer 18T. Difference amplifier 316A subtracts the emitted signal S2 from this sum, outputting the received signal R1. The emitted signal S1 and the received signal R1 are fed to a phase comparator 308A that generates a signal proportional to the phase difference between the two signals. A signal conditioning stage 310A amplifies and filters the signal and sends it to an analog to digital converter 312A that converts it to a digital phase signal received by the microcontroller <NUM>. The microcontroller <NUM> further commands frequency generator 304B to generate a voltage signal with the programmed frequency f<NUM>. A driver 306B amplifies the signal S2 and sends it to the transducer 18T. The transducer 18T generates an ultrasonic signal that propagates through the fluid <NUM> and is detected by the transducer 16T at the other end of the tube, which generates a voltage signal of the sum of the received ultrasonic signal R2 and the signal S1 transmitted by the transducer 16T. Difference amplifier 316B subtracts the emitted signal S1 from this sum, outputting the received signal R2. The emitted signal S2 and the received signal R2 are fed to a phase comparator 308B that generates a signal proportional to the phase difference between the two signals. A signal conditioning stage 310B amplifies and filters the signal and sends it to an analog to digital converter 312B that converts it to a digital phase signal received by the microcontroller <NUM>. The transmitter and receiver transducers can be piezoelectric, electromagnetic, or microelectromechanical systems (MEMS) based in construction.

As shown in <FIG> (and as further detailed in other embodiments herein using the same or different reference numbers), the hardware processor <NUM> is in electronic communication with the infusion pump <NUM>, the upstream acoustic sensor <NUM>, the downstream acoustic sensor <NUM>, the one memory <NUM>, the proximal air-in-line sensor <NUM>, the proximal pressure sensor <NUM>, the distal pressure sensor <NUM>, and the distal air-in-line air sensor <NUM>. The memory <NUM> contains the programming code <NUM> which is configured to be executed by the processor <NUM>. The programming code <NUM> is configured to determine the volumetric flow rate of the infusion fluid <NUM> along the flow path <NUM> based on the upstream acoustic signal detected by the downstream acoustic sensor <NUM> and on the downstream acoustic signal detected by the upstream acoustic sensor <NUM>, and to automatically adjust the infusion pump <NUM>, based on the determined volumetric flow rate, to achieve a desired volumetric flow rate of the infusion fluid <NUM> along the flow path <NUM>.

In the embodiments of <FIG>, <FIG> and <FIG>, the hardware processor <NUM> executing the programming code <NUM> (shown in <FIG>) can determine the volumetric flow rate of the infusion fluid <NUM> along the flow path <NUM> based on a first phase delay of the upstream acoustic signal between the one upstream acoustic sensor <NUM> and the downstream acoustic sensor <NUM>, or on a second phase delay of the downstream acoustic signal between the downstream acoustic sensor <NUM> and the upstream acoustic sensor <NUM>.

In the embodiment of <FIG>, the hardware processor <NUM> executing the programming code <NUM> is configured to determine the volumetric flow rate of the infusion fluid <NUM> along the flow path <NUM> by using the algorithm Q = V * A. In the algorithm, Q includes the volumetric flow rate, V includes a velocity of the infusion fluid <NUM> generated by the infusion pump <NUM>, and A includes a cross-sectional area of the flow path <NUM>. Moreover, V = (L / <NUM>) * (<NUM>/ti - <NUM>/tz), wherein L includes a length between the upstream location 14a and the downstream location 14b, t<NUM> includes a first time it takes the upstream acoustic signal to travel from the one upstream acoustic sensor <NUM> to the downstream acoustic sensor <NUM>, and t<NUM> includes a second time it takes the downstream acoustic signal to travel from the downstream acoustic sensor <NUM> to the one upstream acoustic sensor <NUM>. In other words, t<NUM> - t<NUM> can be thought of as the transit time of the signal or delta t. The distance between the sensors divided by delta t is the speed of the flow stream. The speed times the area of flow path equals the volumetric flow rate.

<FIG> illustrates a graph <NUM> of one embodiment of two acoustic pressure function curves <NUM> and <NUM> plotting time on the X-axis and pressure on the Y-axis to show the phase delay between the pressure function curves <NUM> and <NUM>. Acoustic pressure function curve <NUM> includes the pressure wave at the origin of the upstream acoustic sensor <NUM> or 16T of Figure <NUM>. Acoustic pressure function curve <NUM> includes the pressure wave at distance x from the origin of the downstream acoustic sensor <NUM> or 18T of <FIG>. There is a delay time tx between the two acoustic pressure function curves <NUM> and <NUM>. The two acoustic pressure function curves <NUM> and <NUM> represent periodic variations in time and space of the pressure in the liquid. It can be assumed that the pressure at the source is a simple sinusoidal function represented by P(<NUM>,t) = P<NUM> sin(<NUM>*π*f*t), where P<NUM> includes pressure amplitude, f includes frequency of the sound wave, and t includes time.

At the distance x, the wave <NUM> is delayed by the time tx or, to express it in another way, the argument of the sine function is changed by the phase angle ϕ so that.

P(x,t) = P<NUM>sin[<NUM>*π*f*(t-tx)] = P<NUM>sin(<NUM>*π*f*t +ϕ). Using an electronic circuit called a phase discriminator, which is known in the art, to measure the phase angle between the two waves, the delay time between the wave <NUM> emitted and the wave <NUM> received at a certain distance may be calculated as being tx = - ϕ I <NUM>*π*f. In order to reduce the size of the measurement apparatus, shorter time measurements may be required due to the short distance between the transmitter and receiver. These shorter time measurements over the shorter distances can be accomplished through the use of the phase discriminator. In order to increase the resolution of the fluid flow without restricting the area of the flow channel a differential measurement is used. This measurement is done by determining the phase delay between the transmitter and receiver of a continuous signal. To convert this phase angle measurement to fluid speed it is necessary to take the period of the repetitive signal times the angle, according to the tx equation shown above.

For example, in the case of a short distance between the transmitter and receiver (less than a full cycle), given a predetermined/designed oscillator frequency f = <NUM> and a measured phase delay angle of <NUM> degrees, the method might determine:
<MAT>
<MAT>.

Thus, this method allows a small time delay to be measured. Utilization of signal phase shift allows measurement of a very small time delay. Advantageously, this can translate into accurate measurements over very short distances too. This is accomplished by utilizing a carrier signal phase shift between the signal emitted by the transmitter source to the signal at the receiver. The process described herein can be further illustrated in <FIG> and <FIG>.

The determined time delay can be used to determine the velocity V of the fluid, which in turn can be used to determine the volumetric flow rate Q. An illustration of velocity computation follows with a hypothetical numerical example where: V = (L) * (<NUM>/t<NUM>-<NUM>/t<NUM>); tx = (<NUM>/t<NUM>-<NUM>/t<NUM>); and L=distance between transmitter and receiver.

In a phase approach, over longer distances than the example above, several full cycles may exist between the transmitter and the receiver due to the distance or length L between them. For purposes of illustration below we will utilize <NUM> full cycles, plus a partial cycle that is measured as a phase delay. Assuming L is predetermined or designed to equal. <NUM>, the frequency of the carrier is <NUM>, and φ = <NUM> deg (measured):
Given the above tx will be:.

Area, A, is the cross sectional area of the flow path (in this example the flow path is a tube or tubing with an inside diameter of. <NUM> meters) <MAT>.

This gives the volumetric flow rate Q = V * A <MAT>.

In the above equation, Q includes the volumetric flow rate, V includes a velocity of the infusion fluid <NUM> generated by the infusion pump <NUM>, and A includes a cross-sectional area of the flow path <NUM>.

So to review and summarize, the overall time propagation of the sound waves <NUM> and <NUM> will be affected by the flow of the fluid through the tubing and/or channel. There will be a difference in the delays since the propagation occurs faster downstream than upstream so that t<NUM> = L / C+V, and t<NUM> = L / C-V, wherein t<NUM> includes the time of sound propagation downstream, t<NUM> includes the time of sound propagation upstream, L includes a length of sound propagation path in the fluid channel, C includes sound velocity in the fluid, and v includes a velocity of fluid generated by the infuser. If the times are known, the following equation can be used <NUM>/t<NUM> - <NUM>/t<NUM> = (<NUM>*V)/L. From this equation, the following equation can be obtained V = (L/<NUM>) * (<NUM>/t<NUM> - <NUM>/t<NUM>). If the cross section area of the flow path A is known, the volumetric flow rate Q can be calculated using the equation Q = V*A. In the embodiment of <FIG>, the hardware processor <NUM> executing the programming code <NUM> can determine the volumetric flow rate of the infusion fluid <NUM> along the flow path <NUM> based on the phase delay by using the equations above.

<FIG> illustrates one embodiment of a set of graphs in which two different frequencies are transmitted, received, and processed by two different transducers respectively. The graphs depict the varying phase delays of the differing frequencies.

<FIG> illustrates a flowchart of one example of a method <NUM> of automatically detecting and adjusting a volumetric flow rate delivered by an infusion pump. <FIG> can also be thought of as a block diagram of closed loop control using flow sensing transduces. The method <NUM> may utilize any of the infusion systems disclosed herein. In other examples, the method <NUM> may utilize varying infusion systems. The method can start at node <NUM>. In step <NUM>, the infusion parameters including desired fluid flow rate, duration and dose are programmed by the user. Initially prompted by a start command from a user, in step <NUM>, the hardware processor coordinates the pump in pumping fluid according to the programmed parameters. In step <NUM>, the fluid flow is measured as described above and further explained with reference to <FIG> below. In step <NUM>, the measured value is converted to engineering units (cm/s, m/s, etc.) expressing the measured actual flow rate of the fluid. Scaling based on the physical dimensions of the tube or flow channel and time offsets may be utilized. In step <NUM>, the actual delivered volume is calculated based upon the measured flow rate and in step <NUM>, the actual delivered volume is compared to the programmed or desired volume based upon the programmed delivery flow rate. If the actual flow rate is equal to the desired flow rate and thus the delivered volume is correct, then the method proceeds to step 416A and the pump can continue as is or be stopped if the full programmed volume to be infused has been reached. If the actual flow deviates or is not equal to the desired flow and thus the delivered volume is incorrect, the method proceeds to step <NUM> where an adjustment to the pumping parameters such as the programmed or desire flow rate is determined. In optional step <NUM> the adjustment or the new program parameter can be evaluated for acceptability by a processor against a limit or range of limits in a memory. The limits can be hard coded into the pump or included in a user-customizable drug library that can be downloaded to the processor or memory of the pump over a network. If the adjustment or adjusted program parameter is outside the acceptable range or exceeds an acceptable limit, then an optional alarm is generated in step <NUM>. The alarm can be communicated visually, audibly, by other perceptible means or merely relayed electronically to a remote device. If the adjustment or adjusted program parameter such as a new desired flow rate is within the acceptable range or limit, the method moves back to step <NUM> and the method continues with the pump processor being automatically programmed to pump the fluid according to the newly adjusted program parameter such as a new flow rate. In other examples, one or more steps of the method <NUM> may be changed in substance or order, one or more steps of the method <NUM> may not be followed, or one or more additional steps may be added.

With reference to <FIG>, in one example the flow measurement step <NUM> and others from <FIG> are disclosed in greater detail as the steps of a flow measurement and automatic adjustment process <NUM>. In step <NUM>, infusion fluid is delivered with an infusion pump along a flow path of a pump cassette. In step <NUM>, an upstream acoustic signal emitted by the upstream acoustic sensor, coupled with the pump cassette and located at an upstream location of the flow path, is detected with the downstream acoustic sensor coupled with the pump cassette and located at a downstream location of the flow path. The upstream acoustic sensor may include at least one ultrasonic upstream acoustic sensor. In other examples the upstream acoustic sensor may vary. In one example, step <NUM> may include detecting the upstream acoustic signal emitted by the upstream acoustic sensor by receiving the upstream acoustic signal with a first noise cancelling component such as a first noise cancelling microphone.

In step <NUM>, a downstream acoustic signal emitted by the downstream acoustic sensor, coupled with the pump cassette and located at the downstream location of the flow path, is detected with the upstream acoustic sensor coupled with the pump cassette and located at the upstream location of the flow path. The downstream acoustic sensor may include one or more ultrasonic upstream acoustic sensor. In other examples, the downstream acoustic sensor may vary. In one example, step <NUM> may include detecting the downstream acoustic signal emitted by the downstream acoustic sensor by receiving the downstream acoustic signal with a second noise cancelling component such as a second noise cancelling microphone. In step <NUM>, a volumetric flow rate is determined, with the hardware processor, of the infusion fluid along the flow path based on the upstream acoustic signal detected by the downstream acoustic sensor and the downstream acoustic signal detected by the upstream acoustic sensor.

In one example, step <NUM> may include determining, with the hardware processor, the volumetric flow rate of the infusion fluid along the flow path by determining a first phase delay of the upstream acoustic signal between the upstream acoustic sensor and the downstream acoustic sensor, or by determining a second phase delay of the downstream acoustic signal between the downstream acoustic sensor and the upstream acoustic sensor. This may be done using an algorithm executed by the hardware processor <NUM>.

In another example, step <NUM> may include determining, with the processor, the volumetric flow rate of the infusion fluid along the flow path by using the algorithm Q = V *A, wherein Q includes the volumetric flow rate, V includes a velocity of the infusion fluid generated by the infusion pump, A includes a cross-section area of the flow path, and V = (L / <NUM>) * (<NUM>/t<NUM> - <NUM>/t<NUM>), wherein L includes a length between the upstream location and the downstream location, t<NUM> includes a first time it takes the upstream acoustic signal to travel from the upstream acoustic sensor to the downstream acoustic sensor, and t<NUM> includes a second time it takes the downstream acoustic signal to travel from the downstream acoustic sensor to the upstream acoustic sensor.

In step <NUM>, the infusion pump is automatically adjusted, with the hardware processor, based on the determined volumetric flow rate to achieve a desired volumetric flow, rate of the infusion fluid along the flow path. In other examples, one or more steps of the method <NUM> may be changed in substance or order, one or more steps of the method <NUM> may not be followed, or one or more additional steps may be added. It is noted that the method <NUM> may utilize any of the system or method examples disclosed herein. One or more embodiments of the disclosure allows for improved accuracy of determining flow much infusion fluid is being delivered to the patient while decreasing manufacturing cost of the infusion system. It should be understood, of course, that the foregoing relates to exemplary embodiments of the disclosure and that modifications may be made without departing from the scope of the disclosure as set forth in the following claims.

The disclosed apparatus and systems may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

Depending on the embodiment, certain acts, events, or functions of any of the algorithms, methods, or processes described herein can be performed in a different sequence, can be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the algorithms). Moreover, in certain embodiments, acts or events can be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially.

Claim 1:
An infusion system (<NUM>) configured to automatically control an infusion pump, the infusion system comprising:
an infusion pump (<NUM>) configured to pump an infusion fluid along a flow path (<NUM>);
a first acoustic sensor (<NUM>) positioned at a first location along the flow path, the first acoustic sensor configured to detect a first acoustic signal;
a second acoustic sensor (<NUM>) positioned at a second location downstream from the first acoustic sensor along the flow path, the second acoustic sensor configured to detect a second acoustic signal;
wherein the first acoustic signal is emitted from the second acoustic sensor parallel to the flow path and the second acoustic signal is emitted from the first acoustic sensor parallel to the flow path, and
a controller (<NUM>) configured to: determine a first volumetric flow rate of the infusion fluid based on the detected first acoustic signal and the detected second acoustic signal, and adjust the infusion pump based on the detected first volumetric flow rate to achieve a desired volumetric flow rate,
wherein the first volumetric flow rate is determined based on;
measuring a phase angle between the emitted first acoustic signal and the detected first acoustic signal by a phase discriminator (<NUM>) to determine a first phase delay of the first acoustic signal, between the first acoustic sensor and the second acoustic sensor; or
measuring a phase angle between the emitted second acoustic signal and the detected second acoustic signal by a phase discriminator (<NUM>) to determine a second phase delay of the second acoustic signal, between the second acoustic sensor and the first acoustic sensor.