Patent Description:
In medical care facilities, infusion of medical fluids into a patient is a commonly performed patient care operation. A fluid infusion device, such as an infusion pump, is typically configured to infuse a fluid from a fluid source into a patient through a vascular access device (VAD) such as a syringe or a catheter. If an occlusion occurs between the pump and the VAD, fluid does not reach the vascular system as intended and blood may back up resulting in clotting and attendant risks.

Prior to starting a fluid delivery session, a caregiver typically sets up the infusion device to alert the caregiver when fluid pressure in a infusion line exceeds a pressure threshold so that the caregiver could take corrective action to avoid possible harm to the patient. Current methods of setting up infusion devices include the caregiver entering a 'care area profile', e.g. NICU, for which the pressure limits and associated rules have been pre-configured. In some pumps, these pre-configured values may be adjusted by the caregiver while in other pumps the pre-configured values are fixed and all have limited ranges. Certain pumps are pre-configured to acquire a value during power-on, which the caregiver may or may not be allowed to control to adjust, though this acquired value is over a defined range of pressure values. Caregivers may adjust pressure limits for several reason. For example, caregivers adjust pressure limits to minimize time to detection of an occlusion. This is important to avoid undue interruption of delivery of medication, to avoid exposure of the patient's vessels and tissue to a higher pressure than necessary and to avoid false alarms which would be issued due to occlusion, causing an interruption of medication delivery. While mathematical formulae for calculating a pressure threshold are known in the art, caregivers typically select the pressure threshold for alarm based on their experience or using "rule of thumb" calculations. Often, caregivers do not have access to parameters such as catheter and tubing resistance, fluid viscosity and so forth, so caregivers often use preset values, perhaps based on the location of care or a flow rate. If the pressure threshold is set too low, then the fluid delivery equipment may frequently and unnecessarily alert the caregiver. Such false alarms take the caregiver's valuable time away from other medical tasks, interrupt flow of medication and elevate risk of clot formation in the VAD. On the other hand, if the pressure threshold is too high, then increased fluid pressure may go unnoticed, thereby potentially harming the patient. Furthermore, a method sometimes used by caregivers is to set the pressure threshold simply to be a certain amount over the current pressure. This method may set the pressure threshold incorrectly high or low if the current pressure was erroneous, e.g., because there was an existing elevated pressure in the fluid line. <CIT> discloses a system and method to determine when fluid is not flowing properly from a secondary infusion source during a secondary infusion. The system includes an upstream pressure sensor and a processor programmed to receive signals from the sensor and analyze the signals to determine if secondary fluid flow is proper. The processor samples the output signals from the upstream pressure sensor and analyzes the sampled signals to determine if a pressure rise in the infusion line has occurred when the secondary infusion is initiated. If a pressure rise, indicating that fluid from the secondary container has begun flowing into the infusion line, has not been detected, the processor is programmed to provide a signal indicating that attention should be given to the infusion set up.

<CIT> discloses a fluid flow monitoring method and system for parenteral fluid delivery systems for use in situations, such as with sedentary patients, when wide pressure variations are not expected. The resistance of the fluid
delivery system is determined from the ratio of pressure differences at high and low fluid flow rates to differences in the high and low fluid flow rates. The resistance is used to develop a pressure limit from the sum of the pressure at low fluid flow rates and the product of the resistance and the high fluid flow rate. The pressure limit is compared with the pressure monitored and if the pressure monitored exceeds the calculated pressure limit, an alarm is actuated to warn medical personnel of an occlusion or other fluid flow fault. Additionally, if the noise level (pressure) excess predetermined limits during the periods of low and high fluid flow, the pressure monitoring is terminated.

<CIT> discloses a medication delivery monitoring device comprising: a user interface configured to receive input information; a sensor configured to measure a plurality of fluid state parameters of a fluid delivery channel through which the medication is delivered by a vascular access device (VAD) to an infusion site region of the patient; a processor configured to determine a state of the infusion site region based on the plurality of measured fluid state parameters and the input information; and an output device configured to provide a communication regarding the state of the infusion site region.

<CIT> discloses determining flow parameters in a fluid delivery assembly by monitoring pressure responses and processing those responses along with information regarding the fluid flow. In one aspect, a processor controls the
pump to pump flow quantities in accordance with a pseudorandom code. Portions of the resulting pressure signal sensed are then decoded in accordance with pseudorandom code. An estimate of the equilibrium pressure is generated from the decoded pressure values, while a summation of the pressure samples is generated from the undecoded pressure signals. The resistance to fluid flow of the system is determined from the estimated equilibrium pressure and pressure summation. For
low flow rates, a processor controls the pump to pump fluid in a series of fluid boluses, with each fluid bolus delivered in the beginning of a separate timeslot. The equilibrium pressure is measured at the end of each timeslot, and summation of the pressure samples is generated from the pressure signals. For high flow rates, the pump is controlled to vary the flow rate and the change in pressure is divided
by the change in flow to directly determine the resistance. A resistance display continuously displays the resistance of the system. The pseudorandom coding and decoding can be used to filter out pressure-response crosstalk caused by multiple fluid infusion segments feeding into a common line.

<CIT> describes a method for infusing a fluid in programmed pulses. The programmed pulse is a small volume of fluid, such as a drug, in relatively short bursts. Fluid properties relevant to streaming for the particular fluid to be infused are determined. The relevant fluid properties include static fluid properties, such as a fluid density, specific weight, specific gravity, viscosity, elasticity, or kinetic properties. Programmed pulse variables are determined, which may include the pressure at which the fluid will be infused. Program pulse variables may include fluid delivery pressure.

The fluid delivery pressure is observed to prevent an overpressure condition. An overpressure condition refers to a condition in which the fluid delivery pressure exceeds a working pressure or pressure limit. If an overpressure condition is observed, the fluid delivery may be adjusted or the infusion may be stopped.

A more exact method for setting fluid pressure thresholds for alerting a healthcare professional when infusing a medical fluid into a patient is needed.

A system for infusing a fluid according to claim <NUM> is provided. Furthermore a fluid pump according to claim <NUM> is provided. Furthermore a machine readable medium according to claim <NUM> is provided. Dependent claims provide preferred embodiments.

In certain aspects of the present disclosure, a method of infusing a fluid is provided. The method includes receiving values of one or more infusion parameters for an infusion of a fluid. Based on the received infusion parameter values, a pressure threshold for the infusion of the fluid is calculated. During the infusion, fluid pressure is sensed. An indication is
provided if a value of the sensed fluid pressure contravenes or is greater than the occlusion pressure threshold.

In certain aspects of the present disclosure, a fluid pump includes a pressure sensor for sensing fluid pressure during an infusion of a fluid, a display, a memory and a processor. The processor is configured to receive values of one or more infusion parameters. The processor is also configured to calculate, based on the received infusion parameter values, an occlusion pressure threshold for the infusion of the fluid. The processor is also configured to receive, during the infusion, a fluid pressure signal from the pressure sensor. The processor is also configured to provide and indication responsive to whether a value of the received fluid pressure signal contravenes the pressure threshold.

In certain aspects of the present disclosure, a machine-readable medium encoded with instructions for performing an infusion of a fluid is provided. The instructions comprise code for receiving values of one or more infusion parameters. The instructions also comprise code for calculating, based on the received infusion parameter values, an occlusion pressure threshold for the infusion of the fluid. The instructions also comprise code for receiving, during the fluid infusion, a fluid pressure signal from a pressure sensor. The instructions also comprise code for providing an indication responsive to whether a value of the received fluid pressure signal contravenes the pressure threshold.

The foregoing and other features, aspects and advantages of the embodiments of the present disclosure will become more apparent from the following detailed description and accompanying drawings.

The disclosed arrangements and methods overcome the above discussed limitations, at least in part, by providing methods and systems for automatically calculating a occlusion pressure threshold for monitoring fluid pressure in an infusion fluid tube for alerting a caregiver.

Certain configurations of the present disclosure overcome the above limitations by providing a processor in a fluid infusion device configured to perform pressure threshold calculations based on infusion parameters obtained from a caregiver and/or communicating with other medical equipment. Using the infusion parameters, the processor calculates flow resistance due to the tubing and equipment used for the infusion. Flow resistance of the delivery fluid pathway, in conjunction with other measured and available parameters, is used in the computation of the occlusion pressure limit. In certain configurations, after the processor calculates a pressure threshold, the processor presents the calculated pressure threshold to a caregiver, obtains a confirmation or an alternate threshold value from the caregiver and monitors fluid line pressure of an ongoing infusion session based on the occlusion pressure threshold.

In certain configurations, the processor calculates a pressure threshold and monitors a multi-channel or a multi-segment infusion system. An occlusion pressure threshold is calculated by consideration of the "common" flows through all common segments of the infusion system, such as when multiple pumps infuse through a common catheter, as well as considering the fluid resistance of any intervening components and a fluid flow resistance of a vascular access device (e.g., a catheter) employed in the infusion system.

In certain embodiments, the pump computes the fluid flow resistance from data obtained by interaction with a user. If the user interface provides means to input a catheter type or model, the system stores pre-computed fluid flow resistance values for these devices. To calculate fluid flow resistance of a segment of infusion line, the processor uses infusion parameters such as the internal diameter (or bore) of the infusion line, the length of the fluid line and the viscosity of the fluid being infused. These and other infusion parameters are either input to the processor by a user or obtained by the processor from a database. Alternatively, the pump may dynamically measure the fluid resistance. In brief terms, this is performed by dynamically modulating the flow rate of the pump around the nominal flow rate programmed by a caregiver. For example, if the programmed flow rate is <NUM>/h, the instantaneous flow rate may vary by <NUM>%. From measurements of pressure (dynamic changes) during these variations, the dynamic fluid flow resistance is computable in principle as the partial derivative of pressure with respect to the flow. , discloses some techniques for dynamic fluid resistance measurements.

In accordance with certain configurations, occlusion pressure threshold calculations are made by automatically identifying infusion connectors being used, obtaining flow resistance information for the identified infusion connectors from a database, optionally computing fluid flow resistance dynamically and calculating a working pressure in the fluid line. Once a working pressure is thus calculated, the occlusion pressure threshold for alarm is set to be a certain percent or a certain noise margin over the working pressure.

<FIG> is a block diagram representation of a patient care system <NUM>, in accordance with certain configurations of the present disclosure. A patient <NUM> is connected to a fluid delivery apparatus <NUM> for infusion of one or more fluids via vascular access device (VAD) <NUM> using a fluid line <NUM>. In certain configurations the patient <NUM> is also be connected to an additional fluid delivery apparatus <NUM>. The fluid delivery apparatus <NUM>, <NUM> are communicatively coupled to a server <NUM> via a hospital network <NUM>. The server <NUM> is configured to gather and provide information related to ongoing patient treatments in the hospital. In certain configurations, the server <NUM> is centrally located in a medical facility. In certain configurations, the server <NUM> is located at a caregiver's station. Other possible locations of the server <NUM> are also within the scope of the present disclosure.

<FIG> is a block diagram representation of a portion of the fluid delivery apparatus <NUM>, in accordance with certain configurations. The fluid delivery apparatus <NUM> comprises a durable portion <NUM> and a disposable portion <NUM>. A pressure sensor <NUM> is positioned on the durable portion <NUM>. The pressure sensor <NUM> is configured to sense outflow fluid pressure in the disposable portion <NUM>. The pressure sensor <NUM> is communicatively coupled to a processor <NUM> to provide sensed pressure readings to the processor <NUM>. In certain configurations, the durable portion <NUM> is a modular fluid delivery system such as the ALARIS SYSTEM® infusion pump by CareFusion Inc. In certain configurations, the disposable portion <NUM> is a disposable IV set for attaching to an infusion pump such as a ALARIS SYSTEM® infusion pump.

Still referring to <FIG>, the fluid delivery apparatus <NUM> further includes a display <NUM>. The display <NUM> provides a user interface (e.g., text and/or graphics) for the processor to communicate with a user. In certain configurations, the display <NUM> is also an input device such as a touch-screen. The display <NUM> is communicatively coupled with the processor <NUM>. The durable portion <NUM> also has one or more user input means <NUM> such as a keyboard, a barcode reader, a radio frequency identification (RFID) reader, and so on, as are well known in the art. A user can program infusion parameters or enter commands using user input means <NUM> to control the operation of the processor <NUM>.

Still referring to <FIG>, the processor <NUM> is further coupled to a memory <NUM>. The memory <NUM> stores, for example, program code for execution by the processor <NUM>, data used by the processor <NUM> for the pressure threshold calculations further described below, and so on. The processor <NUM> is also coupled to a communication module <NUM>, which is configured to establish a communication link with the hospital network <NUM>. The communication module <NUM> uses a wired or wireless communication technology such as the Ethernet or the IEEE <NUM> standard. In certain embodiments, the memory <NUM>, is used to store a variety of data in a 'library' for use by the computation system. For instance, the memory <NUM> is programmed with the fluid resistance characteristics of the vascular access devices <NUM> and tubings (e.g., fluid lines <NUM>) typically used in a hospital. Further, the memory <NUM> may contain subsets of these data aggregated by area of care - a so-called 'profile' - allowing automatic selection and presentation to the caregiver of only those devices used in that area along with other aspects of that care area. For instance, a profile for the Neonatal Intensive Care unit would contain the VAD's <NUM> and tubings <NUM> typical to that area and area-specific rules such as the `noise margin pressure' to be applied in the computation of occlusion pressure limits. This 'noise margin pressure' accounts for, among other things, normal fluctuations of pressure due to anticipated movement, breathing, caregiver activity and similar which add to the pressure required to drive fluid through the resistance of the outflow pathway. It ALSO accounts for measurement uncertainty in the pressure sensor and BIAS due to hydrostatic pressure offset due to elevation differences between sensor and patient blood vessel.

Referring to <FIG>, an example occlusion pressure limiting setting and monitoring operation of a fluid delivery apparatus <NUM> is explained next. <FIG> depicts a graphical representation <NUM> of fluid pressure (vertical axis <NUM>) as a function of time (horizontal axis <NUM>). Prior to starting a fluid infusion to a patient, the fluid delivery apparatus <NUM> calculates a working fluid pressure (reference number <NUM>). As further explained below, the working fluid pressure is calculated from fluid delivery parameters of the tubings and connectors used, including length and the inner diameter, viscosity of the fluid to be delivered and flow rate. The fluid delivery apparatus <NUM> then calculates a "noise margin" <NUM> and adds the noise margin <NUM> to the working pressure <NUM> to arrive at a occlusion pressure threshold <NUM>. The occlusion pressure threshold <NUM> represents an alarm limit so that during infusion, if fluid pressure sensed by the fluid delivery apparatus <NUM> (shown as curve <NUM>) exceeds the occlusion pressure threshold (e.g., at time <NUM>), then the fluid delivery apparatus <NUM> provides an indication.

In certain embodiments, the fluid delivery apparatus <NUM> also performs signal processing operations on the sensed fluid pressure (curve <NUM>) to produce a processed sensed fluid pressure (represented by curve <NUM>) and the above discussed indication may be provided when the processed sensed fluid pressure (curve <NUM>) exceeds the occlusion pressure threshold <NUM>. It will be appreciated by one of skill in the art that while <FIG> depicts situations where the occlusion pressure threshold is used to monitor whether a value of sensed fluid pressure exceeds the threshold, similar concepts are applicable to situations where a second pressure threshold is used to monitor the fluid pressure falling below the threshold value, such as, for example, when the VAD <NUM> inadvertently leaves a vein.

In certain embodiments, further explained in detail below, the fluid delivery apparatus <NUM> also adjusts the occlusion pressure threshold as a function of the sensed fluid pressure <NUM> (or <NUM>). For example, if a certain patient's sensed fluid pressure <NUM> shows a certain amount of fluctuations (e.g., periodicity or intensity of pressure swings, as depicted in the time interval <NUM>), the fluid delivery apparatus <NUM> changes the occlusion pressure threshold accordingly. In <FIG>, the occlusion pressure threshold is shown changed to a higher value (curve <NUM>) after time period <NUM>, in response to swings in the sensed fluid pressure during period <NUM>.

<FIG> is a flow chart representation of a method <NUM> of infusing a fluid, in accordance with certain configurations. The method includes operation <NUM> wherein, the processor <NUM> receives values of one or more infusion parameters for an infusion of a fluid. As used herein, the term "infusion parameter" refers to one of several operational parameters that are used in fluid pressure calculations, including, but not limited to, information regarding type and dimensions of infusion equipment and tubings, clinical information about a patient, information about other ongoing infusions for the patient, information about fluid line topology (e.g., number of channels or manifolds), and so on. In some embodiments, as shown in box <NUM>, before starting a patient infusion, "static" parameters such as patient weight, age, catheter type and location are entered and used in the initial computation of occlusion pressure limit along with "dynamic" parameters such as flowrate (e.g., as further described below with respect to box <NUM>) are entered by a user and received at the processor <NUM>.

Still referring to <FIG> and operation <NUM>, in certain configurations, the processor <NUM> obtains one or more of the infusion parameters automatically; by wirelessly sensing (e.g., RFID) certain infusion equipment or by querying from another computer in communication with the hospital network <NUM>, such as the server <NUM>. In certain configurations, the processor <NUM> obtains the infusion parameters by prompting a user for manual entry of certain infusion parameters via, for example, the input means <NUM>. In certain configurations, the processor <NUM> obtains the necessary infusion parameters using a combination of automatic and manual entries of the infusion parameters.

For example, in certain embodiments VADs <NUM> and tubings <NUM> may by divided into categories based on the flow resistance (e.g., a Reynolds number value). A marking (e.g., a barcode label or an RFID) is placed on the VAD <NUM> or the tubing <NUM>, identifying the category of flow resistance. During the operation, the marking is read into the processor <NUM> manually or automatically, thereby allowing the processor <NUM> to perform the calculations described herein to determine the pressure thresholds discussed herein. In some embodiments, the flow characteristics are identified as a value directly usable by the processor <NUM>. In some embodiments, the flow characteristics are identifies in terms of the physical dimensions and the processor <NUM> derives the working pressure values and thresholds, as further described below. Furthermore, in some embodiments, the processor <NUM> is provided with an identity of the fluid being pumped (e.g., fluid composition included <NUM>% Dextrose and <NUM> % lipid). As described in greater detail below, in some embodiments, the processor <NUM> uses fluid temperature signals received from a fluid temperature sensor to accurately determined viscosity of fluid being pumped.

Still referring to <FIG> and operation <NUM>, in certain configurations, the processor <NUM> prompts a user to input information regarding the topology of the infusion system. For example, the processor <NUM> asks the user to input the number of channels used for infusion and configurations of any manifolds used. The processor <NUM> asks the user to input lengths of the fluid line segments upstream and downstream of the manifolds. The processor <NUM> further asks the user to input information related to a type of tubings and VADs used for infusion (e.g., a make/model identification of a catheter or a syringe). In certain configurations, the processor <NUM> displays a selectable list of tubings <NUM> and VADs <NUM> from which the user can select the tubings <NUM> and VADs <NUM> being used. Upon selection by the user, the processor <NUM> retrieves, from a database stored in the memory <NUM>, information regarding the flow resistance of the tubings <NUM> and VAD <NUM> selected.

Still referring to <FIG> and operation <NUM>, in certain configurations, the processor <NUM> asks the user for patient-specific information. The patient-specific information includes the patient's clinical profile including, for example, the patient's age, anticipated activity level, acuity to interruption of specific medication, etc. The patient-specific information further includes information about any other medical equipment currently connected to the patient, and associated facts. In certain configurations, the processor <NUM> prompts the user to input the identity of the patient, for example, by scanning the patient's wristband. Using the received patient identity, the processor <NUM> then obtains the patient-specific information needed for the calculation of the occlusion pressure threshold by communicating with the server <NUM>.

Still referring to <FIG> and operation <NUM>, in certain configurations, the processor <NUM> requests from the user, information regarding the fluid to be infused. In certain configurations, the processor <NUM> prompts the user to input the drug name and/or viscosity of the fluid solution being infused. In certain configurations, the processor <NUM> prompts the user to scan a barcode label attached to the drug vial, and then retrieves viscosity information from a drug database stored in the memory <NUM>.

Still referring to <FIG>, the method <NUM> includes an operation <NUM> of calculating, based on the received infusion parameter values, an occlusion pressure threshold for the infusion of the fluid. The infusion parameters can be broadly divided into two categories, patient-dependent infusion parameters and patient-independent infusion parameters. The patient-dependent infusion parameters include a patient's clinical profile such as the patient's age and sensitivity to interruption of medication delivery. The patient-independent infusion parameters include parameters that affect the fluid mechanics of the infusion path, including flow rate, types and geometries of the fluid lines and connectors and viscosities of fluids being infused.

As indicated in Eq. (<NUM>) below, the alarm threshold pressure value is proportional to the product of the Flow_Rate and a resistance of the flow tubing, plus a NoiseMargin.

The first component "Flow_Rate," in Eq. (<NUM>) above is generally patient-dependent and widely variable though in general increasing with patient weight. The second component "Resistance" is a quality of the fluid pathway dominantly influenced by the minimum tubing diameter and secondarily by the tubing path length as well as the viscosity of the fluid.

Still referring to <FIG> and operation <NUM>, the processor <NUM> uses the flow rate and the resistance to determine the estimated 'working pressure' produced. In the case where there can be determined, such as via user input, that more than one pumping channel is infusing through a common lumen, the 'flow rate" will be the sum of the flows from each channel. To determine the occlusion pressure limit, the working pressure is computed and added to a 'NoiseMargin' which is required to accommodate for elevation differences when the patient may be higher than the pump, for venous pressure and for transient pressures produced by either physiology such as coughing, Valsalva or Mueller maneuvers and tubing movement during ambulation.

Still referring to <FIG> and operation <NUM>, the processor <NUM> uses the flow rate of infusion to calculate the pressure threshold. In a typical medical infusion situation, the infusion flow rates are in the range where flows can be assumed to be laminar. Therefore, the well known Hagen-Poiseuille equation for cylindrical lumens can be used by the processor <NUM> in calculating the occlusion pressure threshold described by Eq. <NUM>. If the processor <NUM> determines that the flow rate of the infusion is such that the Hagen-Poiseuille equation is not applicable, the processor <NUM> uses additional NoiseMargin to increase the pressure threshold. For example, the operation allowance is calculated using: <MAT>
where:.

The NoiseMargin partially depends on the patient and partially depends on other clinical information, further described below. The operational parameter is added to increase the NoiseMargin for an occlusion alarm threshold to reduce the possibility of false alarms. In certain configurations, the NoiseMargin depends on a patient's clinical profile. For example, if the patient is a child (e.g., in the neonatal unit), then a higher NoiseMargin value is used. Another example of the patient's clinical profile includes information related to the reason a drug is being infused. For example, certain drugs are infused at different flow rates, depending on the clinical reason for which the drug is being infused. For example, dopamine is infused at low levels for renal use, intermediate levels to increase cardiac output and blood pressure and high levels to increase vascular resistance. Therefore, in certain configurations, a lower NoiseMargin value is used when a particular drug is used for a particular clinical reason and where the programmed flow rate is low. For example, a lower NoiseMargin is used when dopamine is infused at low infusion rates since a quicker time to alarm is needed. This selection considers the potential for false alarms.

In some embodiments, the exact value of the dynamic fluid viscosity µ is determined using a temperature of the fluid as well as information as to the fluid type. The fluid temperature is obtained from, e.g., a signal received from a fluid temperature sensor.

In some embodiments, a technique of flow-rate-variable-filtering may be used to mitigate against false alarms at low flow. In this technique, the pressure sensor's signal is passed through a digital low-pass filter whose low-pass corner or cut-off frequency is a function of the flowrate. More specifically, the lowpass filter corner frequency is typically proportional to the flow rate so that as lower flow rates are used the filter acts to beneficially reduce the instantaneous rate of change of its output suppressing abrupt changes in pressure that may be causes by noise sources while responding with sufficient speed to detect an occlusion in a timely manner since the lower the flow, the slower the time-rate of increase of the pressure due to actual occlusion dynamics.

In certain configurations, the processor <NUM> is configured to generate an estimation of the time-to-alarm (TTA) value. The TTA value indicates to a caregiver an estimate of the time required to detect a full occlusion based on the present flow rate, pressure value, pressure limit and compliance of the tubing pathway as determined from inputs to the computer. The accuracy of this estimate is limited by the amount of information known e.g. the characteristics of all portions of the path may not be known. In some implementations, the system may dynamically estimate the compliance of the un-occluded system. The TTA is calculated using the following equation: <MAT>.

In Eq. (<NUM>), the variables are as follows.

This estimate of the TTA is presented to the caregiver to enable them to anticipate the impact of medication interruption should it occur and to, if desired, make overriding adjustments to the occlusion pressure limit set by the algorithm described.

Still referring to <FIG> and operation <NUM>, if in operation <NUM>, the processor <NUM> determines that the infusion configuration includes multiple channels and/or manifolded connectors, e.g., from the received inputs, then the processor <NUM> calculates the pressure threshold by taking into account the pressure drop in each of the manifolded tubes. The formula in Eq. (<NUM>) is used for calculating alarm threshold when multiple channels are used for fluid infusion.

In Eq. (<NUM>) above, the variable i is over all the flow rates in tubes <NUM> and <NUM>. The processor <NUM> also calculates the NoiseMargin term in Eq. (<NUM>) as previously described herein. After the processor <NUM> has calculated each term, the sum of all the pressure values is used to determine the alarm threshold pressure value.

In some embodiments, the fluid flow path resistance might be measured using one of several well known techniques, omitted here for brevity.

Still referring to <FIG>, the method <NUM> further includes an operation <NUM> of sensing, during the infusion, a fluid pressure value. In certain configurations, the pressure sensor <NUM> senses the pressure of fluid in the disposable <NUM>. In certain configurations, the processor <NUM> may perform a zero offset calculation (e.g., a baseline pressure to offset elevation difference between the fluid source and the patient). In certain configurations, the processor <NUM> samples pressure sensory measurements of the pressure sensor <NUM> at a predetermined frequency (e.g., <NUM> to <NUM> times per second). The pressure sensor <NUM> can use one of several well-known pressure sensing mechanisms such as a pressure sensing membrane, a piezo-electric element, and so on. In certain configurations, the processor <NUM> stores the sensed pressure data from the pressure sensor <NUM> in the memory <NUM>. In certain configurations, the processor <NUM> performs data processing operations such as low pass filtering described in detail previously regarding the flowrate-variable-corner-frequency, noise removal and trend calculations on the sensed pressure data.

Still referring to <FIG>, the method <NUM> includes an operation <NUM> of indicating if the sensed and processed fluid pressure value contravenes the alarm threshold. The processor <NUM> periodically checks, by comparing the processed pressure data with the alarm threshold value, whether the measured fluid pressure contravenes the occlusion pressure threshold. Depending on the mode of operation, the contravening either indicates that the processed pressure data has fallen below a threshold value or is greater than an occlusion threshold value. For example, in certain embodiments, when the processor <NUM> determines that the processed fluid pressure has exceeded the occlusion alarm threshold, the processor <NUM> indicates this event to the user. In certain embodiments, when the processor <NUM> determines that the fluid pressure has dropped below an alarm threshold (e.g., because the VAD <NUM> has inadvertently left the vein), the processor <NUM> indicates this event to the user. In certain configurations, the mode of indication is pre-selected by the user from among various possible modes of indication. In one mode, the processor <NUM> alerts a user by issuing an audio alarm. In another mode, the processor <NUM> indicates the excess pressure event by flashing a light or an indicator on the display <NUM>.

In another mode, the processor <NUM> transmits an alarm signal to the server <NUM>, or another device (e.g., a computer at a caregiver station) communicatively connected to the processor <NUM>. In yet another mode, the processor <NUM> pauses the fluid delivery. In certain configurations, the fluid delivery is resumed after the sensed pressure falls below the alarm threshold. In certain configurations, resumption of fluid delivery requires manual intervention by a caregiver. In certain configurations, a caregiver intervenes by communicating control messages to the processor <NUM> via the hospital network <NUM>. In certain configurations, a caregiver can intervene using user input means <NUM> (e.g., keys on a front panel of the durable portion <NUM>). The above modes may be separate or combined, such that, for example, an alarm and pausing of delivery may be performed together.

Still referring to <FIG>, in certain configurations, multiple alarm thresholds are used for indicating alarms of different degrees. For example, in certain configurations, a first alarm is indicated when the sensed fluid pressure is above a first (lower) alarm threshold and a second indication is issued if the sensed fluid pressure is above a second (higher) alarm threshold. For example, in certain configurations, the first alarm is an audible alarm while the second indication includes stopping the fluid delivery operation until manual intervention by a caregiver.

The process <NUM> depicted in <FIG> is recurrent in several possible ways, as indicated by box <NUM>. For example, each time a parameter change is made, the occlusion pressure limit may be recomputed, for example, if the flow rate is changed, the occlusion pressure limit must be recomputed as indicated by Eq. (<NUM>). In an optional embodiment, the pump is able to continuously dynamically measure the actual fluid pathway flow resistance. Such a measurement involves multiple measures of pressure as the flow rate is instantaneously deliberately 'modulated' typically above and below the mean programmed flow rate and other comparable methods such as pressure pulse integration may be used. By continually measuring the flow resistance of the path, the pump is able to determine a more accurate occlusion pressure limit setting. Further, it may not require the entry of all parameters discussed above with respect to steps <NUM> and <NUM>. In some use cases, these parameters may not be known thus the ability to determine the critical normal flow resistance assists in providing the automation of occlusion pressure limit setting.

With reference to <FIG>, the process of calculating the occlusion pressure threshold for the infusion of the fluid according to certain configurations is described below. At box <NUM>, resistance of the fluid pathway used for an infusion operation is computed by the processor <NUM>. The resistance is calculated, e.g., by computing Eq. (<NUM>) as previously described. At box <NUM>, the total flow through a common infusion pathway, based on the configuration of the infusion system, is computed to calculate a theoretical working pressure for the entire infusion system. A working pressure value is calculated at box <NUM>, using the previously described techniques. In step <NUM>, noise margin pressure is computed, as previously described.

Referring now to <FIG>, a block diagram representation of a multi-channel fluid delivery system in accordance with certain configurations disclosed in the present disclosure is depicted. Three fluid pumps 402a, 402b and 402c are connected through three fluid channel segments 404a, 404b, 404c having resistances 406a, 406b, 406c through manifold <NUM>. The fluid line segment between manifold <NUM> and vascular access device <NUM> has a fluid resistance <NUM> and the VAD <NUM> has a resistance. As previously discussed, in certain configurations, where the topology of the infusion network is provided to the infusion system, the working pressure threshold can be computed using the following formula <MAT>.

Where the "k" resistance values are comprised as follows:.

Referring to <FIG>, the real time adjustment of occlusion pressure threshold in certain embodiments is explained further. Fluid pressures sensed for two patients A and B are shown as curves <NUM> and <NUM> respectively, plotted along the horizontal axis <NUM> (time) and the vertical axis <NUM> (pressure). In the depicted example, at the onset of a fluid infusion, both patients A and B in this example are calculated to have the same theoretical fluid pressure (curve <NUM>), the same noise margin (<NUM>) and therefore the same occlusion pressure <NUM>. During infusion, the monitored fluid pressure of patient A is shown to have more fluctuations that the monitored fluid pressure for patient B. In some embodiments, patient A's occlusion pressure may be adjusted upwards (curve <NUM>), while no change is made to patient B's occlusion pressure threshold (curve <NUM>). Such a patient-specific adjustment to the occlusion pressure, in one aspect, helps mitigate the possibility of false alarm triggering. As previously discussed, the monitored fluid pressure for patients may be filtered with an appropriate lowpass filter (or Kalman filter) before making patient-specific adjustments to the occlusion pressure limits.

It will be appreciated that the methods and systems disclosed herein provide for automatic calculation and setting of pressure alarm thresholds for fluid pumps. In certain configurations, the alarm setting calculations are based on user input and/or automatically obtained information regarding connecting tubing geometries and a patient's clinical profile. The calculated alarm thresholds are used for alerting a caregiver to the presence of an occlusion by monitoring fluid pressure during an infusion session.

The automatic calculation of occlusion alarm thresholds, as provided by the present disclosure, improves the effectiveness of the occlusion alarm system by providing a threshold tuned to the specific conditions of the infusion rather than using a preset value or depending on general guidelines employed by the caregiver in manually operating the pump. Further in some embodiments the system is able to automatically adjust the occlusion pressure threshold during the course of the infusion session. This is achieved by the recomputation based on changing flow rates and, in one embodiment, by the continual measurement of the fluid pathway flow resistance.

It will further be appreciated that alarm thresholds can be automatically adapted to clinical conditions of a patient through communication between the fluid pump processor <NUM> and the hospital server <NUM>. Such clinical conditions include, for example, the ward a patient is in, a patient's age, other ongoing infusions for the patient, and so on.

It will further be appreciated that, in certain configurations, the pressure threshold is programmed such that an 'alert' is issued upon detection of excess pressure, which then converts to a non-resetting alarm if the pressure fails to fall below a certain computed value such as a percentage of the alarm threshold in a defined period following the initiation of the alert state. In certain configurations, the pump operation is temporarily inhibited while the alarm and/or alert conditions exist.

It will further be appreciated that the automatic calculation of alarm thresholds disclosed herein therefore leads to better patient care by maintaining an optimized occlusion pressure limit that strikes a best balance between rapid detection and risk of false alarms.

Although embodiments of the present disclosure have been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being limited only by the terms of the appended claims.

All elements, parts and steps described herein are preferably included. It is to be understood that any of these elements, parts and steps may be replaced by other elements, parts and steps or deleted altogether as will be obvious to those skilled in the art.

Claim 1:
A system for infusing a fluid comprising a processor (<NUM>) configured for:
receiving (<NUM>) values of one or more infusion parameters for an infusion of a fluid prior to starting a fluid infusion to a patient, the infusion parameters comprising the internal diameter of the infusion line, the length of the fluid line or the viscosity of the fluid being infused;
calculating (<NUM>) an occlusion pressure threshold for the infusion of the fluid prior to starting a fluid infusion to a patient, the calculation being based on received infusion parameter values;
receiving (<NUM>) from a sensor a fluid pressure signal during the infusion;
providing (<NUM>) an indication responsive to whether a value of the sensed fluid pressure contravenes the occlusion pressure threshold; and
adjusting the occlusion pressure threshold responsive to:
a static operational parameter comprising patient medical information; and
a dynamic operational parameter comprising statistical characteristics of the value of the sensed fluid pressure,
wherein the calculating (<NUM>) the occlusion pressure threshold includes calculating a theoretical working pressure value and adding a noise margin pressure value to the theoretical working pressure value,
wherein the calculating (<NUM>) the theoretical working pressure includes calculating the theoretical working pressure based on an amount of total flow infusing through a common infusion pathway, a flow resistance value of the common infusion pathway and flow resistance values of any separate portions of the infusion pathway specific to a given pump.