Occlusion system and method for a flow control apparatus

A flow control apparatus having a flow monitoring system capable of detecting and identifying a downstream occlusion present within an administration feeding set loaded to the flow control apparatus is disclosed. A software subsystem is associated with the flow control apparatus and administration feeding set, the software system plots at least one discrete date point against a standard occlusion profile to detect if a downstream occlusion present within the administration feeding set.

FIELD OF THE INVENTION

The present invention relates to a flow control apparatus capable of identifying a downstream occlusion condition within an administration feeding set.

BACKGROUND OF THE INVENTION

Administering fluids containing medicine or nutrition to a patient is generally well known in the art. Typically, fluid is delivered to the patient by an administration feeding set loaded to a flow control apparatus, such as a pump, connected to a source of fluid which delivers fluid to a patient.

A flow control apparatus of the prior art may also be capable of monitoring and detecting fluid flow conditions that can occur within the loaded administration feeding set during operation of the flow control apparatus. Generally, prior art flow monitoring systems that are capable of monitoring and detecting flow conditions may rely on separate sensors being placed at the upstream and downstream sides of the administration feeding set in order to distinguish between an upstream or a downstream flow condition.

Therefore, there is a need in the art for an improved flow control apparatus having a flow monitoring system capable of identifying between an upstream flow condition and a downstream flow condition using a single sensor, thereby making it possible to monitor the flow of the fluid and recognize any problem that has occurred in the delivery of the fluid.

SUMMARY OF THE INVENTION

The present invention relates to a flow control apparatus comprising a flow control apparatus adapted to be loaded with an administration feeding set having an upstream side and a downstream side, a single sensor for detecting the presence or absence of fluid in the upstream side of the administration feeding set, and a software subsystem in operative association with the single sensor, wherein the software subsystem is capable of identifying between an upstream flow condition and a downstream flow condition present within the administration feeding set.

The present invention also relates to a flow control apparatus comprising a flow control apparatus adapted to be loaded with an administration feeding set, an administration feeding set having an upstream side and a downstream side with the administration feeding set loaded to the flow control apparatus, a single sensor for detecting the presence or absence of fluid in the upstream side of the administration feeding set, and a software subsystem in operative association with the single sensor, wherein the software subsystem is capable of identifying between an upstream flow condition and downstream flow condition present within the administration feeding set loaded to the flow control apparatus.

The present invention further relates to a method for monitoring fluid flow comprising engaging one end of an administration feeding set to at least one fluid source, loading the administration feeding set to a flow control apparatus, engaging another end of the administration feeding set, and identifying between an upstream flow condition and a downstream flow condition present within the administration feeding set loaded to the flow control apparatus.

The system and method is a downstream occlusion (DSO) triggering test that incorporates a standard occlusion profile to determine an occluded feeding tube. The DSO triggering test is invoked through software or user initiated. The DSO triggering test is based on relative rotor turn durations, in milli-seconds (ms), and consecutive rotor turns, measured in turns, as compared against a standard profile for the flow control apparatus.

As the flow control apparatus is running, the system is determining the time of a rotor revolution until the microprocessor receives the required number of encoder signals, which is representative of one complete rotor turn. The system tracks a number of relative revolution durations over apparatus' period of operation, as discrete data points and each data point is compared against the standard occlusion profile, as shown inFIG. 6BorFIG. 6C. The system can set an alarm based on an occlusion detected condition, or control will pass to step289inFIG. 4to determine an occlusion, when the system determines an increase in the relative rotor revolution duration time over one or more rotor turns, or if the duration time matches a standard occlusion profile.

In the first embodiment, a number of revolution times are stored in a revolution history buffer. The buffer, when filled, is averaged and compared against the next NewTime to determine an actual relative rotor duration time difference. This time difference or discrete data point is compared against the standard profile over one or more rotor turns. If compared over a number of rotor turns, and the system is trending higher, the occlusion detected sets the occlusion alarm, or the main control loop exits to step289inFIG. 4, to determine the occlusion. If the duration time selected to be a single discrete data point and it meets the standard profile at a single rotor turn, the occlusion detected condition sets the alarm on, to sound.

The next NewTime or rotor revolution time can be filtered (as described in the detailed specification). The DSO Triggering test is used to identify an occlusion state or condition sooner than the procedure, described inFIG. 4, and DOS Triggering operates as a stand alone occlusion detection (as shown inFIG. 10), or the main control loop can exit to step289atFIG. 4, as described in an alternative embodiment below inFIG. 11.

The standard profile is stored as computer instructions. The instructions can be a quadratic equation or a data table of points. The profile is loaded into flash memory at the start of the pump. Alternatively the standard profile may be constructed during a pumping operation, such as flushing, by tallying a series of relative rotor durations by consecutive rotor turns and storing them in an array or buffer location. The program may also save this alternative standard profile to an EEPROM for later use.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, an embodiment of the flow control apparatus according to the present invention is illustrated and generally indicated as10inFIGS. 1-5. Flow control apparatus10comprises a flow monitoring system12that is capable of detecting and identifying between upstream and downstream flow conditions present within an administration feeding set14. The administration feeding set14includes tubing56that is loaded to the flow control apparatus10for delivery of fluid to a patient by engaging a valve mechanism26and mounting member74of the administration feeding set14to the flow control apparatus10. As used herein, the term load means that the valve mechanism28and mounting member74are engaged to the flow control apparatus10and tubing56is placed in a stretched condition between the valve mechanism28and mounting member74such that the administration feeding set14is ready for operation with flow control apparatus10.

Referring toFIGS. 1 and 2, an exemplary flow control apparatus10according to the present invention comprises a housing20adapted for loading administration feeding set14to the flow control apparatus10. Flow control apparatus10comprises a main recess124covered by a main door136and includes first and second recesses58and60for providing sites that are adapted to load the administration feeding set14to the flow control apparatus10when engaging the valve mechanism28and mounting member74to first and second recesses58,60, respectively. Preferably, a means for driving fluid, such as a rotor26, is rotatably engaged through housing20and adapted to engage tubing56such that tubing56is placed in a stretched condition between first and second recesses58,60when the administration feeding set14is loaded to the flow control apparatus10.

As used herein, the portion of tubing56of administration feeding set14leading to rotor26is termed upstream, while the portion of tubing56leading away from rotor26is termed downstream. Accordingly, rotation of rotor26compresses tubing56and provides a means for driving fluid from the upstream to the downstream side of the administration feeding set14for delivery to a patient. The present invention contemplates that any flow control apparatus having a means for driving fluid may be used, such as a linear peristaltic pump, bellows pump, turbine pump, rotary peristaltic pump, and displacement pump. In addition, the present invention contemplates that a means for preventing fluid flow in the administration feeding set14is preferably valve mechanism28; however any means that can prevent fluid flow through the administration feeding set14may be used.

Referring toFIG. 1, flow control apparatus10further comprises a user interface40that assists the user to operatively interface with the flow control apparatus10. A display70, in operative association with a plurality of buttons138positioned along an overlay66, assist the user to interact with a microprocessor62to operate the flow monitoring system12according to the present invention.

Referring toFIG. 3, flow control apparatus10further comprises a microprocessor62in operative association with a single sensor32. A software subsystem36is operatively associated with microprocessor62and is further associated with flow monitoring system12and a means for preventing fluid flow, such as valve mechanism28, that provides a means for the flow control apparatus10to detect and identify between upstream and downstream flow conditions present in the administration feeding set14during operation of the flow control apparatus10. As noted above, flow control apparatus10includes single sensor32for detecting whether fluid is present or absent in tubing56at the upstream side of the administration feeding set14. The single sensor32is located on housing20of the flow control apparatus10and is positioned to detect the presence or absence of fluid in the upstream side of the administration feeding set14. In an embodiment shown inFIG. 2, single sensor32is incorporated in a recessed sensor track42and is adapted to securely receive tubing56therein when the administration feeding set14is loaded to the flow control apparatus10.

In order for single sensor32to detect the presence or absence of fluid in the tubing56of the administration feeding set14it is required that tubing56be engaged and retained within sensor track42. In one embodiment, the engagement and retention of tubing56within sensor track42is achieved by activating flow control apparatus10when tubing56is empty of fluid and engaged around the flow control apparatus10such that a vacuum is created that decreases the outer diameter of tubing56as air is evacuated from the administration feeding set14, thereby placing tubing56in a deflated state. In this deflated state, the user may easily insert tubing56within sensor track42when loading the administration feeding set14to the flow control apparatus10.

Further, with tubing56empty of any fluid, a valve mechanism28connected to tubing56is engaged to the first recess58, the tubing56then wrapped around rotor26, and a mounting member74engaged to second recess60such that administration feeding set14is loaded to flow control apparatus10and the portion of tubing56between first and second recesses58and60is in a stretched condition. Valve mechanism28is then operated to allow fluid flow communication through tubing56such that air is evacuated from the administration feeding set14. Thus, when the rotor26is made operational during this priming procedure a vacuum is created within tubing56forcing it to collapse due to the flexible nature of tubing56and lack of fluid contained in the administration feeding set14. This temporary collapse of tubing56coupled with the tensile forces applied from operating rotor26allows tubing56to be easily retained within sensor track42.

In addition, when the flow control apparatus10is operational and the tubing56engaged within sensor track42, fluid flow through tubing56increases the outer diameter of tubing56relative to the inner diameter of the sensor track42. Once the tubing56is engaged within sensor track42and the remaining portions of the administration feeding set14are engaged to flow control apparatus10, the flow monitoring system16becomes operational.

Microprocessor62controls and manages the operation of the various components of the flow control apparatus10. Preferably, single sensor32comprises an ultrasonic transmitter assembly90that transmits an ultrasonic signal through the portion of tubing56seated in the sensor track42to provide a means for detecting the presence or absence of fluid in the upstream side of the administration feeding set14when the signal is received by a receiver assembly92. Upon receipt of the ultrasonic signal, receiver assembly92detects whether fluid is present or absent within tubing56along sensor track42based on the characteristics of the ultrasonic signal received by the microprocessor62. The receiver assembly92then communicates with the microprocessor62. Based on the characteristics of the received ultrasonic signal communicated to microprocessor62software subsystem36determines whether fluid flow within the administration feeding set14is normal or a flow abnormality exists.

Software subsystem36determines through a series of decision points and steps whether normal flow or abnormal flow conditions exist within tubing56, and if an abnormal flow condition does exist, whether it is a bag empty condition, upstream occlusion, or a downstream occlusion.

Referring to the flow charts inFIGS. 4 and 4A, the various decision points and steps executed by software subsystem36to perform an intermittent test procedure A by flow monitoring system12are illustrated. Software subsystem36directs flow control apparatus10to perform various operations related to detecting and distinguishing between upstream and downstream flow conditions present in the administration feeding set14. During normal operation, single sensor32transmits ultrasonic signals through tubing56engaged within sensor track42for detecting the presence or absence of fluid in the administration feeding set14. During operation of flow control apparatus10software subsystem36decides at predetermined times whether to initiate an intermittent test procedure A to determine whether a downstream occlusion exists. Intermittent test procedure A comprises terminating fluid flow communication through the administration feeding set14by valve mechanism28, transmitting and detecting an ultrasonic wave for determining the presence or absence of fluid by single sensor32and a repetition of these steps, if necessary.

In particular, at step289software subsystem36decides whether to perform the intermittent test procedure A as illustrated inFIG. 4A. If so, the microprocessor62instructs flow control apparatus10to the OFF condition at step290in order to terminate operation of flow control apparatus10such that rotor26no longer drives fluid through tubing56. At step292, microprocessor62then places valve mechanism28in the blocking position that prevents fluid flow through tubing56.

After fluid flow has been prevented through the administration feeding set14by valve mechanism28, a baseline signal is taken by the single sensor32at step294for providing microprocessor62with a reading of the signal when the flow control apparatus10is reactivated at step296. After re-activation, any fluid present within tubing56should be driven through tubing56by operation of rotor26and delivered to the patient as long as no occlusion is present along the downstream side of the administration feeding set14. After a short period of time placement of valve mechanism28in the blocking position that terminates fluid flow should cause tubing56to run dry of any remaining fluid unless a downstream occlusion is present which would effectively prevent fluid from being delivered to the patient as fluid is forced to remain within tubing56due to the occlusion. Software subsystem36, after a predetermined amount of time, permits any excess fluid to drain from tubing56at step298. At step300, single sensor32then transmits another ultrasonic signal through tubing56and takes a second reading to determine if fluid is present or absent within the administration feeding set14. If fluid remains within the administration feeding set14, software subsystem36then determines that a downstream occlusion is present and sounds an alarm.

Once intermittent test procedure A is completed, software subsystem36reaches a decision point302which determines whether or not a downstream flow condition, such as an occlusion along the downstream side of the administration feeding set14is present within tubing56. If no fluid remains in tubing56at decision point302, software subsystem36determines that no downstream occlusion is present. At step304, microprocessor62re-sets the counter and places flow control apparatus10in an OFF condition at step306. Valve mechanism28is then placed in either a feeding or flushing position that permits fluid flow through tubing56at step308. After actuation of valve mechanism28to the feed or flush position flow control apparatus10is placed in the ON condition at step310and the flow monitoring system12has software subsystem36return to step289.

If at decision point302an occlusion along the downstream side of the administration feeding set14is possible then decision point312is reached. Decision point312counts the number of occurrences that single sensor32detects the presence of fluid within tubing56which is referred to as Do, while a pre-set maximum number of occurrences that flow monitoring system12allows for detection of a possible downstream occlusion being referred to as Do(max). If the Dois not greater than Do(max) at decision point312software subsystem36will determine that no downstream occlusion exists and valve mechanism28is placed in a position that permits fluid flow through the administration feeding set14in a manner as previously described above in steps304,306,308, and310. However, if Dois greater than Do(max) a downstream occlusion may exist and software subsystem36will direct microprocessor62to activate an alarm68.

Preferably, alarm68may be audible, visual, vibratory or any combination thereof. In an embodiment of the present invention it is anticipated that a certain type of alarm68may represent a specific abnormal flow condition being present within administration feeding set14and identifiable to the user by its own unique visual, audible and/or vibratory alarm68. For example, alarm68having different sounds could indicate different types of upstream and downstream flow conditions, such as a downstream occlusion, a bag empty condition, or an upstream occlusion. These unique alarms68allow for flow monitoring system12to signal the presence of several different abnormal flow conditions.

The detection of the upstream flow conditions present within administration feeding set14, such as upstream occlusion or a bag empty condition, is determined by the presence or absence of fluid within tubing56by single sensor32at a detection point positioned on the upstream side of administration feeding set14. However, unlike the detection of a downstream occlusion along the administration feeding set14the detection of an upstream flow condition, such as an upstream occlusion or bag empty condition, in the administration feeding set14does not require that the intermittent test procedure A be performed. Instead, the detection of these upstream flow conditions is accomplished during the normal operation of flow control apparatus10while valve mechanism28is in the feeding or flushing position that permits fluid flow through the administration feeding set14.

Flow monitoring system12also detects and distinguishes between upstream flow conditions, such as normal flow, bag empty, and upstream occlusion conditions when the intermittent testing procedure A is not being performed by software subsystem36. Specifically, at decision point289if software subsystem36does not initiate intermittent test procedure A for detecting downstream flow conditions software subsystem36will function to detect and distinguish between the conditions of normal flow, bag empty, and upstream occlusion.

Software subsystem36in operative association with flow monitoring system12determines whether or not a normal upstream flow condition exists within administration feeding set14during operation of flow control apparatus10. This operation occurs at a decision point314and is determined based upon the presence or absence of fluid as detected by the single sensor32. Specifically, if single sensor32detects the presence of fluid within tubing56then the flow is detected by software subsystem36at decision point314. A normal upstream flow condition exists because a flow condition is not present that would occlude or obstruct fluid flow on the upstream side of the administration feeding set14that would cause fluid to become absent as detected by the single sensor32. If flow is present at decision point314this normal flow condition would be displayed on user interface40at step315. Accordingly, alarm68would not be activated since the patient would receive the correct dosage of fluid during flow conditions.

Flow monitoring system12only activates alarm68at decision point314if a bag empty condition or an occlusion along the upstream side of the administration feeding set14is detected as evidenced by the absence of fluid in tubing56during operation of the flow control apparatus10. Software subsystem36distinguishes between bag empty condition and an upstream occlusion at decision point316. As depicted inFIGS. 5A and 5B, a comparison is performed at decision point316in order to ascertain whether a bag empty condition or an upstream occlusion is present within administration feeding set14.

As further shown, the graphs illustrated inFIGS. 5A and 5Bprovide predetermined baselines that represent the relative signal strengths of the ultrasonic signal received by the receiver assembly30B for a bag empty condition and upstream occlusion, respectively, which provide a basis for distinguishing between these two upstream flow conditions based upon a comparison of a plurality of readings taken by single sensor32against the respective predetermined baseline criteria representative of these two flow abnormalities. In particular, software subsystem36compares the change of the signal strength from the plurality of sensor readings generated by single sensor32over time against the predetermined baseline criteria for these particular flow conditions. This provides a comparison with readings taken by single sensor32that permits the software subsystem36to distinguish between a bag empty and an upstream occlusion. For example, in a bag empty condition, the change between the subsequent readings would decrease more rapidly over time, while in an upstream occlusion the signal change would decrease more slowly over time. It should be noted that while the graphs inFIGS. 5A and 5Bdepict an example of a preferred baseline criteria, other baseline criteria which may distinguish these two flow abnormalities may be utilized.

Upon the determination that a bag empty condition is present at decision point316based upon signal comparison against the predetermined criteria as described above, software subsystem36activates alarm68. If the software subsystem36determines at decision point316that an upstream occlusion is present, software subsystem36would also direct the activation of an alarm68indicative of such a flow abnormality.

Accordingly, the flow monitoring system12is capable of detecting and distinguishing between upstream and downstream flow conditions including at least four separate flow conditions that occur within an administration feeding set14. The ability of the flow monitoring system12to detect and distinguish between upstream and downstream flow conditions is accomplished preferably by a single detection point by single sensor32positioned at the upstream side of the administration feeding set14.

FIG. 6Aillustrates the flow control apparatus10operating within a proper tolerance. The discrete data points (described below) are the stars (‘*’). The data points varying above and below a set point of 100 ms of the flow control apparatus10. A tolerance band of +/−30 ms, for example, represents system noise, which can falsely trigger an occlusion indicator within the tolerance band. The tolerance band can be set other values depending on the motor or the required sensitivity. A sensitive application can be a syringe pump, requiring a tighter or lower tolerance. The standard occlusion profile is a straight line; however, a profile can be different to match the flow control apparatus10pumping characteristics.

To determine an occlusion or predict the occurrence of an occlusion, at least one discrete date point (described below), must be above the higher or lower limit of the tolerance band. The dashed line is the normal operation of the flow control apparatus10varying above and below the horizontal line at a 100 ms set point. The set point can change resulting in a change in the normal operation, tolerance band, and even the standard occlusion profile changes.

The concept of the present invention is monitoring, in software, the drag on the motor through a series of software calculations. Other prior art systems monitor directly the current or voltage use of the motor with software, to indicate an occlusion. These prior art systems suffer from not being flexible or accurate, in some high performance cases such as medical, to properly determine the presence or absence of an occlusion. The term consecutive rotor turns is meant to be one or more discrete data points in. succession, as determined by the program or user input (always possible with the LED screen atFIG. 1at element138). In other words, a rotor revolution turn can be skipped; however, the test will continue using the next available rotor revolution turn. The rotor revolution turn information could use rotor turn1,3,5, and6to determine the presence of a downstream occlusion. The DSO Trigger test can cause the downstream occlusion test inFIG. 4or sound an occlusion alarm68.

FIG. 6Billustrates the standard occlusion profile plot. The plot is relative rotor turn duration, typically in mill-seconds (ms), plotted against the consecutive rotor turns measured in turns. The profile is independent of flow rate or the flow of a material or substance through the administration feeding set14. Generally, a flow rate is based on the time between rotor turns and is dependent on the rotor26shaft speed and encoder counts.

An encoder (not shown) is attached to the rotor26shaft (not shown) and measured by the microprocessor62. The number of signals from the encoder to the microprocessor62, overtime indicates the speed. The number of encoder counts indicates a complete rotor turn. The DSO triggering test is measuring the relative revolution duration time of a rotor turn against a standard occlusion profile for the purpose of identifying an occlusion condition, not the flow rate. Once an occlusion detected condition is identified, the system sets the DSO Trigger variable (not shown), to TRUE and sets an occlusion alarm68, or in the alternative embodiment exits to step286inFIG. 4at step1130A (described below), to perform the downstream occlusion test.

FIG. 6Cshows a temporary occlusion. The rotor revolution measured is plotted against the standard profile and compared against the rotor history of previous turns, filtered or otherwise, as shown inFIG. 6C. An increase in relative rotor revolution over one rotor turn may reduce at the next rotor turn at or near the tolerance band. This would represent a solid temporarily becoming lodged in the tubing, and if the number of NewTime readings is set at 1, the system may false alarm68. Solids exist in formulae fed to a patient. The scale inFIG. 6Chas been changed. This illustrates a design choice depending on the motor and other factors, such as sensitivity, accuracy and frequency of alarming required.

Referring toFIG. 7, the preferred embodiment of the invention for the flow control apparatus10is shown. This embodiment uses, among other things, an average of the rotor history file (determined at step940C), to obtain the necessary repeatability and sensitivity required. An exemplary operation of the main control loop720is shown for the downstream occlusion trigger test or DSO Triggering test. A positive DSO Triggering without chaining (described below) triggers an occlusion alarm68.

At step700, the DOS trigger test is started. The test operates concurrently with the occlusion routine shown inFIG. 4. At step710, the rotor history file is reset. The rotor history buffer or array is set to zero. The rotor history file or buffer has a number of, filterer or unfiltered, rotor revolution times, called NewTime below. At step730, the user may manually invoke the DOSTriggering test. This is accomplished by depressing a key on the front of the flow control apparatus10, or just entering the Running Mode screen inFIG. 1at138.

The DOCInterval time (not shown) sets the frequency at which the DSO Triggering test is run. For example, a DOCInterval set at 30 seconds means every 30 seconds the downstream occlusion test is executed. At step740, the main control loop720determines if the flow control apparatus10is priming and resets the rotor history buffer to zero at step740A. This means the main control loop can execute an occlusion check more quickly or less frequently, than the occlusion detection inFIG. 4above.

At step750, the main control loop720stops the flushing750activity, if flushing, and skips one rotor revolution because flushing occurs at high rate of speed. The one rotor revolution allows the system to stabilize. NewTime is the time of a rotor revolution, as discussed below. At750A, the rotor revolution information is skipped, not the revolution itself.

At step760, a stopped rotor is started at step810(FIG. 8). At step830, a rotor revolution timer is started to measure the rotor revolution time, which is stored in NewTime. A rotor revolution time is measured using the system clock (not shown). The clock duration is measured after a fixed number of encoded signals are received at the microprocessor for a rotor revolution or a number of rotor revolutions, as specified in the DSO Triggering test. The clock duration is independent of the rotor turn.

An occlusion will drag the rotor, which will take the rotor26longer to make a revolution, as measured by the number of encoder signals returned to the microprocessor62. The number of encoder signals is fixed at the time of manufacture for the flow control apparatus10. So if a hundred encoder signals are needed per a rotor revolution, once the microprocessor receives the hundredth signal, the system clock time is measured and stored in memory. The difference of the start time, at step830and stop time at step910is stored in NewTime. This NewTime represents the rotor revolution duration for one rotor revolution. At step820A, the system can still proceed to measure the rotor revolution time or NewTime, if the system overrides the failed conditions at step820.

At step820, a set of pre-existing conditions can be checked to determine if the current rotor turn is appropriate to measure for a rotor revolution time. This improves accuracy and helps avoid false occlusion alarms. The critical conditions may be the flow control apparatus10is not flushing, not priming, in a normal flow as opposed to super bolus mode, or no other system error exists. Once the conditions820are satisfied, the revolution timer830is started. The microprocessor62runs the timer830, until the required number of encoder signals (as discussed in the preceding paragraph) are received.

At step770, the end of a rotor26revolution is determined, and if YES, the program exits to step900in FIG.9. The command to stop the rotor is given at step910. At step920, a set of pre-existing conditions may be checked. The conditions are the same as in step820. Additional conditions are rotor is off, or the current rotor revolution is not immediately following the downstream occlusion test because the measure is not reliable for averaging. If YES, the conditions are verified and control passes to step930. If NO, at step920A it is determined if the there is an override (Still Continue?), to use the rotor revolution for a NewTime, otherwise the rotor revolution information is discarded at step920B and control returns to the main control loop at step720.

At step930, a NewTime is computed. The Revolution timer is stopped and stored in NewTime. Alternatively, the system clock time is stored in a buffer or temporary memory position. Then the clock time, at step830, is subtracted from the clock time at step930and this difference is stored in NewTime, as discussed above in step910.

At step940, if the rotor history is filled, control passes to step950. Otherwise, control is passed to step940A and the buffer position is incremented. The rotor history position is updated with NewTime and control passes to step940B. At940B, if the rotor history array is filled, control passes to step940C. At step940C, a rotor history average is determined. The average is used to determine a discrete data point plotted onFIG. 6B, as shown. The discrete data point is NewTime less the rotor history average, provided the different is not greater than a Filter Error for NewTime (described below in step950A). The discrete data point is the actual relative rotor revolution duration time, during flow control apparatus10operation. The data point is plotted on,FIG. 6B, to determine if an occlusion is happening.

Returning to step940B, in this embodiment, the array is updated if there are still unfilled positions, which means the HistoryCount variable (not shown) is not zero. The HistoryCount variable is preset, when the history buffer is reset. The HistoryCount is not necessarily reset every time the downstream occlusion test is run.

The HistoryCount variable is counted down to determine the number of non-zero rotor revolution NewTimes' are stored in the history buffer, for averaging. The average of the rotor history buffer or file is used to determine if the system is trending in relative rotor revolutions. Trending higher indicates the system is occluded downstream, as illustrated inFIG. 6B. At step940D, the rotor history buffer or array is not full, so exit to step720.

An occlusion can occur for a variety of conditions. Material may settle from the feed solution at low feed rates. The sediment may collect and occlude the feeding set14. The set14may become pinched as the patient rolls or moves.

After the rotor history buffer is full at step950, the NewTime is filtered for an abnormal condition. An abnormal condition can occur if a person interferes with the rotor26or the rotor26jams. A person pinching the tubing14will cause an occlusion alarm68

If the system is filtering (at step950A), the filter switch is the absolute value of NewTime less the average of the rotor history buffer (AvgRotorHistory) greater than a Filter error. The Filter error is set in the program to be about 100 ms, and the Filter error depends on the flow control apparatus10. The Filter error can be varied depending on the sensitivity of the flow control apparatus10. At step950B, an error or abnormal condition sets the NewTime to the current average of the rotor history file, previously determined at step940A. No error or abnormal condition, the program determines the average history, at step960, and passes controls toFIG. 10.

InFIG. 10, the system is identifying at least one NewTime that meets the standard profile inFIG. 6B. For improved accuracy, three NewTime values that meet the standard profile over three consecutive rotor turns will result in an occlusion detected condition. The first test step is to ensure the system is not chaining at step1000.

At step1000inFIG. 10, the system is checked for chaining. Chaining is too many downstream occlusion checks within DOCInterval is occurring. For example, five downstream occlusion tests are caused within ten minutes, the system is chaining. At step1000A, the downstream occlusion is disabled the system is reset and control passes to the main control loop at step720.

At step1010, the NewTime is determined to be consistent with the standard downstream occlusion profile and NewTime is above the upper tolerance, inFIG. 6B. At step1060, step1010is not True or NO. At step1010, the current rotor revolution is not matching the standard profile, so step1010exits to step1060. At step1060, the main control loop determines if the previous rotor revolution, to the current rotor revolution or NewTime, is consistent with the standard occlusion profile. If YES, then the main control loop detected two inconsistent rotor revolutions and will reset the rotor history file at step1020. This is shown inFIG. 6C, with the temporary occlusion.

One skilled in the art will recognize, one inconsistent reading may introduce too many alarms, but a higher number may not alarm quickly enough. The number of inconsistent rotor revolutions, at step1060may be set with a counter, incremented or decremented, after step1060. If the counter condition is meet, then the rotor history file is reset a step1020.

At step1040, NewTime, is converted to a discrete data point as NewTime less AvgRotorHistory. At step1050, the discrete data point is compared to the standard occlusion profile, atFIG. 6B, over one or more consecutive rotor turns, as determined by the system Until the number of consecutive discrete data points are plotted, the system will exit to the main control loop at step1050A.

At step1030, the standard occlusion profile is complete, if at least one or more NewTime data points match the standard occlusion profile, for the one or more consecutive rotor turns. Referring toFIG. 6B, at rotor revolution turn one (1), the discrete data point at step1040matches the relative duration for the rotor turn at 110 ms or, outside of the tolerance band. The system does not consider this point possibly occluding. If a second discrete data point is used, this point is plotted at approximately 135 ms, at the second consecutive rotor turn. This point falls outside the tolerance band and indicates a possible occlusion is occurring. A third consecutive rotor turn may be required, at 140 ms, to set the DSO Triggering test to TRUE and to sound the occlusion alarm at step1030A. The number of discrete data point matched to the standard occlusion profile, ofFIG. 6, is dependent on the accuracy or number of false occlusion alarms, the user will tolerate for the flow control apparatus.

In an alternative embodiment inFIG. 11, the standard profile is determined complete at step1130and the main control loop exits to step289inFIG. 4, at step1130A. This provides for another level of occlusion detection, which uses the standard profile, but actually determines the occlusion condition based onFIG. 4. Like steps have not been described betweenFIG. 10andFIG. 11. For example, step1020is the same as step1120. The reader is requested to refer to the description of the corresponding step inFIG. 10, forFIG. 11.

Although flow control apparatus10described above is an exemplary embodiment, the present invention contemplates that the flow monitoring system12may be used with any suitable flow control apparatus.

It should be understood from the foregoing that, while particular embodiments of the invention have been illustrated and described, various modifications can be made thereto without departing from the spirit and scope of the invention.