IV Drip Chamber Monitor

Abstract

A monitor for an IV drip chamber comprising a light emitting device, a photosensor, a housing with attached to an IV drip chamber and holds the light emitting device and photosensor on substantially o

Description

The present specification relates to IV drip chamber monitor, that is, a monitor which monitors the flow of IV solution through an IV drip chamber of an infusion system. An infusion system delivers IV (intravenous) solution contained in an IV bag to a patient via an IV tube and IV catheter. An IV flow regulator or pump controls the flow rate, and the flow rate can be observed through a drip chamber, which is a transparent plastic contained in line with the IV tubing, through which the drips of the IV solution can be observed. The flow rate can be reduced or interrupted through various causes, such as kinks in the IV tube or IV catheter, blockages or air bubbles in the same, or an empty IV bag. Such a reduction or interruption can lead to inadequate fluid or medication delivery, as well as increasing the risk of blood clots, infection and pain and discomfort. Visually monitoring the drip chamber may not be easy in low light levels; and when a large number of patients" drip chambers must be monitored, it is easy for staff to overlook a reduced or interrupted flow of IV solution. It is known to have monitors which strapped or connect to the drip chamber, and automatically monitor the flow rate through a drip chamber, and give a visual and / or aural alarm if there is a reduction or interruption of the flow rate. Such monitors are powered by large capacity (and hence inconveniently large size) of battery that can supply a stable voltage to the monitors.. Particularly where smaller batteries have been tried, it has been found that as the battery or batteries discharge and the output power drops, the variation in voltage can cause the monitoring of drips to become inaccurate, and either activate the alarm means unnecessarily, fail to activate the alarm means, or improperly monitor in an incorrect state. The object of the present invention is to ameliorate the reduction in monitoring accuracy to account for variation in output voltage, power or other variables which may drift over time. According to the present invention, there is provided a monitor for an IV drip chamber according to claim 1. The invention will now be described, by way of example, with reference to the drawings, of which Figure 1 is a perspective view of the general arrangement of the infusion system and the monitor; Figure 2 is a diagrammatic view of a droplet; Figure 3 is a diagrammatic view of a droplet relating it to the sensor readings; Figures 4 to 7 is a flow chart of the, sensor, calibration alarm system ; Figure 8 is a perspective view of the monitor from the front; Figure 9 is a perspective view of the monitor from the rear; Figure 10 is a plan view of the monitor; Figure 11 is a perspective view of the internal components of the monitor from the front; Figure 12 is a plan view of the internal components of the monitor; Figure 13 is a plan view of the internal components of the monitor from underneath; Figure 14 is a side elevation and detail of the drip chamber; Figure 15 is a perspective view and detail of the monitor being attached to the drip chamber; Referring to figure 1, a typical infusion system includes a drip chamber 15 which collects IV solution 12 from a bag spike 16 (and ultimately from an IV bag), the IV solution 12 then flowing through the IV tube 18 to a catheter (not shown) and into the vein of a patient. The drip monitor 14 is secured to the drip chamber 15 by monitor arms 13, and ideally includes a visual alarm (such as a flashing LED 10, which will be described in further detail below) and optionally an audible alarm. A suitable general configuration is disclosed in GB2586285. The drip monitor 14 includes an IR LED and Photo transistor / diode arranged such that, when fitted to the drip chamber 15, the IR LED may transmit IR light across the drip chamber to be received by the Photo transistor / diode when there is occluding the passage of the IR light beam in the drip chamber, but when a drop of IV solution 12 interrupts the beam, the Photo transistor / diode detects this (or more specifically the Photo transistor / diode no longer detects the beam of IR light from the IR LED, indicating that a drop has interrupted the beam; this will henceforth be referred to for simplicity as the Photo transistor / diode detecting a drop). The number of drips in a period time will depend on the intended flow rate of the IV solution for the infusion system, as well as the particular IV solution and the requirements of the patient. However, a typical correct drip rate would be in the order or 10-50 drips per minute, so that the period between any two drips should be in order of a few seconds. The absence of drips for a continuous period indicates that there is a problem with the infusion system, and an alarm should be triggered to alert carers. Suitable alarms are LED lights that may be illuminated either in a continuous or flashing mode, and / or a buzzer or other audible alert. A preferred alert regime is: Active State: The system is actively detecting drops continuously over and over again in a loop fashion and if a drop meanwhile is being detected, an alarm LED indicator is flashing. Also still in active state, the first warning buzzer will trigger after a 20 seconds lapses when no drop is being detected; that state should continue to a second warning buzzer after a further 20 seconds lapses. While in active state, any drop can still be possibly detected. Both buzzer warning states should emit a series of 3 one second (On-Off-On) beeps style. Sleep / lnactive Mode: the monitor enters the sleep / inactive mode when no drop is being detected after 40 seconds lapses i.e. after the second buzzer warning. The circuit is put into a sleep state with very low power consumption and the alarm LED is not possibly be turned On. The monitor will remain in this state until removed / unclipped from the drip chamber i.e. the switch button resets (which disconnects the power circuit fully, including the Microcontroller). With a known monitor, as described in GB2586285 (the description of which is hereby incorporated by reference), a side switch was provided for the monitor to be switched on and off. In the present invention, to exit the sleep mode, the monitor may be manually switched off for another auto-calibration to take place, conveniently by including a spring loaded button which is depressed by the drip chamber, such that when the monitor is removed from the drip chamber the monitor is switched off and reset. Each detected drop prompts the LED indicator to flash a light for a duration of 50-150 milliseconds, ideally 30 ms. The monitor is powered by a compact battery arrangement, ideally a single button battery such as standard CR1632- 3volts or CR2032-3volts; however, the performance of the system can adversely be affected by a voltage drop using such batteries. To compensate for this, the monitor continuously recalibrates its detection. In order for this recalibration feature to function properly, the monitor, as shown in illustration of the PCB board in Fig.ll, is powered by 2 stacked CR1216-3 volts coin batteries, and a solution for battery voltage drop has been found and presented, which will be the main element for a new patent application. The monitor recalibrates accordingly, even under the voltage drop conditions, so that when there is a drop being detected within the IR detecting field, detection is carried out as indicated from the alarm LED turning ON. If no drop is detected within the IR range, the alarm LED remains off, indicating that no calibration has taken place. This is following by a sleeping mode function which preserves battery power when no drops are being detected after some specific time. When in the sleeping mode function, the micro-controller may consume only 500nA (Nano Amperes) of current. For this draw of current, it is estimated that the monitor could have a running time 210,000 hours, equivalent to more than 23 years, with a typical coin cell battery, excluding the self-discharge of the battery. This saves power when compared to keeping an alarm LED turned on fora duration of minutes (e.g. 5 minutes) such as described in GB2586285, and the buzzer is optional and reserved for particular modes of alarm. For such a device using one or two small coin batteries, recalibration regime set out below, has been found that with a single CR1632-3V coin battery may last for 60 hours, and two of such batteries more than 100 hours. With reference to the monitor described in GB2586285, It has been found however that voltage drop, and power instability can cause false alarm indications. Therefore the monitor adopts a conditional loop calibration configuration to compensate continuously for any recent voltage drop and power instability output from the IR LED Phototransistor that may cause faulty reading during IV drop detection, resulting unwanted alarm indication. Of course, conventionally accepted in IR sensor detection of prior art disclosure, it is the insignificant small-scale difference of voltage fluctuations at the phototransistor’s output that sends a signal pulse to the microcontroller for comparing with pre stored reading variable, hence a calibration takes place when a drop intercepts the IR beam. Since Coin-batteries have limited capacity of supply power range of 1.5 - 3 nominal voltage which are often intended to operate rather in electronic items such as wristwatches - for example, using very low-current consumption - or maybe on pulse use basis so that they are able to operate over a longer period of time. Relevant to the current invention the current monitor uses coin battery power to supply the IR sensors, microcontroller, and the alarm LED indicator under voltage fluctuation occurrences, and that the monitor's sensors must operate differently in transmitting and receiving IR signals in adaptation to however these fluctuations. In effect, components in use such as the microcontroller will keep resetting itself when using voltage below the nominal operating range by means of burning the brownout BOD fuse inbuilt in the microcontroller - of course if this feature is enabled. To achieve this monitor's adaptation to voltage drop requires a dynamic way of IR detection to compensate for the unstable power for the duration of the IV drip infusion process. The present monitor then detects the drops over longer period of time, and the monitor adapts proportionally with any voltage drop when they are occurred. Power surges or fluctuations which would otherwise affect the IR phototransistor's correct detection are overcome by the monitor's auto recalibrating during the entire detection process. Dynamic auto calibration configuration When IR Diode emits an IR beam onto the surface of the IR LED phototransistor and a liquid drop falls through the drip chamber to cut the IR beam, the light falling on the phototransistor is reduced, increasing the resistance of the phototransistor; the variation in resistance can be sampled to obtain a signal dependent on the IR light reaching the phototransistor, which in turn can be used to indicate whether a drop of IV solution is present at that instant moment between the IR LED and the IR phototransistor. As previously mentioned, variation in voltage affects the reliability of the detection. A reduction in voltage may reduce the amount of light the IR LED produces, reducing the readings or preventing to get valid readings obtained from the phototransistor. Further, the phototransistor may, for example, be arranged with a fixed resistor to form a voltage divider circuit, and the output of the voltage divider can input into a microcontroller to calculate a value dependent on the amount of light falling on the phototransistor. If the voltage across the voltage divider circuit drops, the apparent resistance of the phototransistor may appear to increase, giving an inaccurate value of the light calculated as hitting the phototransistor. Referring to Fig.2, the proportion of light 25 from the IR LED 20 hitting the phototransistor 22 is dependent on the projected area of a drop 24, that is, the two dimensional area that the droplet covers when viewed in the axis between the IR LED and the IR phototransistor when the reading is obtained; for example, if the droplet has almost passed the beam 25, or the droplet is small, or is extended in shape, a higher light reading will be obtained than if the droplet is centred in the beam, or is large, or is spherical ('high' here is arbitrary, the reading could equally be counted as 'low'), thus occluding more of the beam from the LED 20 (indicated by dashed lines 26). The voltage output from the IR photorsensor's potential divider will be at a maximum when no drop is present between the IR phototransistor and the IR LED. Referring to Fig.3, each voltage output is converted-to a digital reading value by the microcontroller, and a series of such readings (a group of sensor-values while IR phototransistor detects) are being stored in a successive rolling array such that when an array is full then the previous array gets deleted and a new array is then being added to the device memory. Alternatively, each new reading can be added to the array and the oldest reading deleted (i.e. a rolling array in the more traditional sense). Sensor values from the IR photosensor are being produced while the monitor is in IR detection to an IV drop, hence sensor readings are being of varied values depending on the varied state of IR light occlusion, e.g. if there is or there is no drop; if there is a drop, then it has varied dimensions, thus producing varied rate of IR beam. Also relevant to current detecting of IV drop, the monitor gets an (initial base-value) from IR photodiode reading of the environment which gets calibrated only once; then again with every sizeable drop the monitor gets a new (base-value) from assigning the lowest sensor value of an array of value readings taken from the IR phototransistor. Both aforementioned (base-value from the initial calibration stage and the array's sensor-values in the running loop) are base-value, respectively; but each is taken in a different time, hence termed differently, as follows: First basic-value is taken from the initial reading of the IR LED phototransistor (this could be any value), whether or not there is a drop in between IR sensors, and / or even, in the very moment, a drop now is in just across the IR central axis and / or has any bigger value than is wanted to obtain. This initial base-value, after being subtracted by a sensor-value, gets adjusted automatically when a new base-value is assigned in the next array of a drop being detected. The IR phototransistor's sensor-valuesmay vary asthe power fluctuates affecting the IR beam, hence they are dynamic, i.e. running arrays may have varied values in proportional with the power when it drops; however, detection should still be carried out as long as any assigned base-value makes a desirable difference set to be made from any sensor-value in any given array (This is explained in the software description later). As of the assignment of a new basevalue, when the microcontroller checks the time counter, since when it is running and if more than, for example 200ms, it starts taking sensor-value readings from the IR phototransistor's and storing them in an array of, for example 10 values, out of which a minimum value is assigned as a new base-value when a drop is detected. This new base-value, is used for re calibrating the monitor within the assigning of looping arrays, when meets some pre set conditions of the same array. This assignment of new base-value repeats with every new drop along the IV drop detection. The new basic-value could be any value too as long as it is the minimum value in an array, i.e. whether an IV drop occlusion to the IR beam making detectable or undetectable of IR values along the detection. If a pre determined rate of occlusion to the IR beam is obtained at any moment now, this should lead to a detection being carried out and hence turning alarm LED on, hence makes it the principle of this monitor's IR detection. A 200ms time slot per array is calculated and well suited for IV drop detection taking into account the drop's falling speed and shape in the IR sensing field. Auto recalibration is taking place regardless of how fast or slow the falling IV drop is, hence taking 10 value readings, for example, are well managing within an array. After the initial calibration stage of base-value is finished. In effect, while the monitor is active within a specified time, at any moment when an IV drop or any other object occludes the IR beam, this produces varied sensor reading values. The sensor-value readings are then each getting subtracted from (an assigned new base-value within the same array). This results varied values which some are bigger, equal or smaller than a preset value selected according to a desired sizeable drop, a preset sensor value, for example 4, (a value which suitably corresponds to the narrow part of a drop intersecting the beam), referred to in 24, see Fig.2. Hence detection is predetermined by how much difference the IR beam is occluded, although this difference could be from any point across the intercepting drop. Referring to a rolling array's sensor-values illustrated in Fig.3, for example 8, would be a detectable sensor value to make a difference with a base-value (the lowest assigned) if this new base-value is to be 4 in this case, as in the following equation ( 8 - 4 = 4 >4 ), where >4 is a preset sensor value. Therefore, 8 is calibration-trigger potential and is a detectable value, hence is able to turn the alarm LED. In the same way and example, any sensor value under 8 makes a difference (after subtracted from the new base-value) results a value less than (the preset sensor value 4), make undetectable values, hence does not recalibrate the monitor, nor does it turn on the alarm LED. Any sensor value above 8 here is a potential variable which can be a detectable to do a re calibration. The preset sensor value 4 used in the present IV drop detection system is assessed from the top end or the tale of the drop wherein projects in curved surface all the way to the top end, which gives a lower value than the wider middle part when measured horizontally in our configuration. This preset sensor value can be varied to vary the monitor's sensitivity to the drop being detected. When arrays are arranged in sequential arrangements running one after another in slots of 200ms, within which a recalibration takes place. Each array of 200ms slot possibly taking 10 sensor values; this is well estimated and performs well in proportional with calculating any IV drip rate factor. Similarly, if at any moment, while the monitor is still in the same active mode, the rolling sensor values can be sampled to any object whose dimensions being put across the IR beam, hence each of the sensor values in a given array get subtracted (one by one) by the new base-value, until they are all calculated. Or in other terms, the configuration for the monitor is recalibrating 10 times per array in 200ms i.e. equals to 50 times per a second: a total of each calibration making sensor-value in any given array while occlusion is remained still within IR detecting field, hence the monitor continuously recalibrates for a maximum total limit of 100 times for 2 seconds detections which is displayed in alarm LED's turning ON constantly. This dynamic Auto Conditional Calibration should take place in such a way that is, as though transforming one unreliable received IR signal and be compensated for by the other IR sensor readings. In other terms, instead of transmitting only one IR signal, which as it has previously shown in our experiments, that is becoming unreliable in triggering calibration due to the voltage being reduced while in detection and its effects on the IR phototransistor, it is now compensated through a conditional treatment of several readings by the same way of a falling drop cutting the IR beam whose values are recorded as in variables. Hence, the IR transmitting signal received by the IR phototransistor has been purposefully reconfigured; it functions differently from that of the conventional way of a drop intercepting IR light which is then taking the converted photosensor value, generated from the IR phototransistor's pulsing current, and later comparing it with the initial pre stored value in the microcontroller. Also, different from prior art HIVALE Patent Number US5088990A “I.V. alert system” in drop detection, our method provides an approach that lies in the fact that reliance solely on the drop's interception of the IR photo-sensing beam, and / or to provide a stable power source such as larger batteries for higher or more constant voltage, or use of a mains power source is no longer necessarily required. Nor is the circuit dependent on a power consistency factor in powering up the IR Diode emitter and the IR phototransistor. The present drop detection is adopted for a conditional treatment of the IR emitting beam and for it to happen certain factors are estimated such as: the external environmental lighting effects, the drop shape, drop's falling speed within a timeframe assigned to take the variable readings across each falling drop in the form of rolling array assignments. Thus, the present IR sensor instrument to detect IV drop provides two elements which are being taken advantage of: - First element is only one value reading amongst a larger number obtained by IR photodiode can trigger a calibration, hence detection followed by alarming, regardless how fluctuating and the voltage surge range across the IR receiver and the IR emitter affecting the IR beam strength and quality, i.e. producing shorter or longer, weaker or stronger IR beams. Since the photodiode's resistance and output voltage change in correspondence to the IR light received - Second element is the advantage of adopting for dynamically generating varied values within an array or range (such as a rolling array or a sequence of graded IR readings to be in proportional with the drop size when intercepting the IR beam) which is demarcated by specific time slots (for example, 200ms). Values are assigned for each array having a number of potential variables to trigger a recalibration or basically a calibration. These variables are arranged so that the lowest value should successively (random or orderly) produce a detecting calibration-trigger value first before the second lowest value (larger than preceding). A new array's value rolls over each time the preceding array is deleted. An array is comprised of, for example, 10 reading variables to allocate, hence triggering a recalibration within an array taking up 200ms from taking and assigning the variables. Thus, there comes a solution of restricting a drop detection by the varied IR sensor values within a time limit helps eliminating false alarm (which as it has previously shown in our experiments,) such as the alarm LED's turning constantly ON during IV drop detection when IR sensors often do not retain reliable power. Each recalibration array is limited to 10 sensor values in our example, this could be varied. Or in other terms, a rolling array in IR detection is meant to be used as a secondary safeguard measure to provide for the aforementioned first element: A benefit for limiting -the alarm LED from remaining ON when resulted unwanted indication under voltage drop, specifically experienced in the monitor disclosed in GB2586285 application- only to that time segment, before another cycle of recalibration takes place. Although this should not happen now because of the conditional treatment for the IR detection (First Element) should take place in the first place. Algorithm Description for the IV drop detection by the monitor Denoting for comprehensive monitor functions as in Fig.11-13 (2x CR1216-3volts - coin batteries exemplary model) showing components in relation to program coding software Fig.4-7 which works in the following steps: 1. Putting / clipping the drip detector 14 instrument around drip chamber 15 by means of the gripping arm brackets DI, D2, D3 gripping arm dimensions, Fig.9. If possible, precisely in between the two defining lines 100, Fig. 15, outstanding on the outer surface of a drip chamber 15 positioned on the upper part just under the dripping nozzle, so that monitor detects IV drops. In this case, the instrument is well above, if any, rebounding small drops from the reservoir. 2. Interposed is a spring-loaded switch button 108, Fig 8-10, extruded in between the opposing grip arm brackets 104, is pressed by the force of the push-in drip chamber 15, Fig. 15. Herein, spring-loaded switch button 108 makes a full contact of the electrical circuit when taking full flush position with enclosure surface D9, Fig. 10. The arm brackets can be adjusted to accommodate for various drip chamber diameters by means of its flexible feature to grip around different drip chambers from 14mm- 19mm outer circumferential standards. Drip Sensor Monitor detectability is based on the configuration steps according to the following firmware block diagram Figs. 4-7. Instrument runs immediately after starting the Microcontroller as in Figs 4-7 incorporating parts comprising instrument's electronic layout. During IV droplet detection, when drip sensor monitor detects no occlusion from the IR photosensor's digitally converted readings from the arrays or specifically when sensor values that make a difference from an assigned sensor value is less than 4, in this case no drop is being detected (LED Alarm is remained OFF); or, otherwise if a difference made is equal or more than 4, the monitor gets in the calibrating readings of array and a drop gets detected (LED Alarm is turned ON). The monitor remains in non-detecting as long as the difference aforementioned remained less than 4, i.e. either no drop is intercepting yet to make a difference equal or more than 4. or drops are too tiny to be making such a difference, such as any rebounding micro drop or drops that may be produced by a falling IV drop when falling in the bottom reservoir inside the IV drip chamber. Moreover, the preset sensor value of 4, Fig.2 has been found to disregard these small rebound drops generated from falling drops. So, while the monitor's detectability can be increased i.e., >3, >2, this may cause the IR phototransistor to pick up these small rebounding drops, and further may cause detectability of dust particles, and / or be too sensitive to external light. For adjusting the sensitivity. Increase the sensitivity >3, >2. If reduce the sensitivity >5, >6, >7. Referring to the monitor's detection of IV drops while in active mode, as referred to in Fig.4 -6, the IR LED and phototransistor are operated by the microcontroller. The steps of the operation of the monitor which runs only once after the starting of the microcontroller in the following: When the monitor is first switched on 30 (as described below), the necessary variables and libraries are set up 32, followed by the initial setup 34 which setting the pin configurations, and power supply for the IR LED and photodiode, taking the first reading of Calibration Value: basevalue = reading the photodiode pin &the current environment. The initial calibration stage takes less than 1ms. After the initial calibration stage is over, the next stage from 35 runs in a continuous loop for as long as the monitor is active. A sensor value is read from the phototransistor 36 and the difference is checked with the first base value calculated 38. If the difference 40 is smaller than e.g. 4 (i.e. the preset sensor value as previously discussed), the alarm LED indicator LED 42 turns off, simultaneously with setting the waitingtosleep counter to 1, the monitor should remain in non detecting state for as long as a desired preset IR occlusion by the IV drop does not take place for the next 40 seconds. The monitor then enters a low power / sleep mode after a period of 40 seconds lapses (20 seconds in between 2 sound alarm warnings). Whereas if the difference 44 is greater than or equal to 4 (the preset sensor value), the alarm LED indicator 45 is turned on for e.g. 30 milliseconds to indicate a drop has been detected, this happens simultaneously with making waiting-to-sleep counter &warning-count counter equals to 0. While monitor is still in active mode, at the same time the microcontroller's counter 46 tracks the time in 200ms. If less than 200ms is counted since last checked, no action is taken, whereas if counter 46 is checked to more 200ms, the current phototransistor (sensor values) e.g. 10 readings start to be gradually stored in an array 52 and be calculated, outcome result should remain constant unless there is a considerable change of sensor-values from any given array, now in case of a falling drop intercepting the IR beam, micro-controller gets varied sensorvalues, as in the array 70 - Fig.3. From these sensor-values the lowest value is calculated and assigned as new base-value 54. And now this assigned new base-value is taken to be subtracted from each of the array's sensor values in the equation: A recalibrating Value if ( SensorVal- BasicVal) >4, where 4 is a preset sensor value. Depending on an occlusion (a drop) that produces varied sensor values, and that if a value from (subtracting the current sensor values from the new base-value) bigger than or equal to a preset 4 (the preset sensor value), this recalibrates the monitor. Hence this sensor value is a detectable calibrating-trigger leading to turn alarm LED on (hence IR detection conditionally treated). Also from the same array, if any value results from (subtracting the current sensor value from the new base-value) is less than 4 (the preset sensor value), no action is taken, as these sensor value readings are being in less values (considerably small) to make a difference more than or equal to the preset sensor value, hence regarded are not calibrating-trigger readings such asthose values that are less than 8 in the example of Fig.3. This should continue in loop with every array as long as the monitor is still in active mode. While the monitor is still in active detecting mode, the micro-controller checks If the waiting-to-sleep counter 55 is above 20 seconds 58 &warning-count is zero, a warning buzzer 60 is activated in three beeps lasting 1 second (On-Off-On) each and set the warning-count to 1, whereas if the waiting-to-sleep counter &warning-count 55 is less than 20 seconds 56, no action is carried out. While monitor is still in active mode and no drop detection event has occurred, i.e. if the waiting-to-sleep counter 62 checked is above 40 seconds &warning-count is already set to 1, this leads to this action to happen: if less than 40 seconds 64, no action is carried out; whereas if the waiting-to-sleep counter 65 is above 40 then 66 is activated in three beeps lasting 1 second (On-Off-On) each. This 66 happens simultaneously with turning off power for IR LED, Phototransistor and buzzer, and go-to-sleep function is triggered. When go-to-sleep mode 68 is activated the following take place: set the sleep mode and power down, turn off the analog to digital converter, turn off Timer 0 and 1, serial interface, trigger sleep enable function, trigger sleep CPU function. Structure and Turning Monitor Off Mechanism Referring to Fig. 14 and 15, a drip chamber 10 may be provided with circumferential projections 100 or lines to indicate the correct position of the drip indicator 14. As previously stated, the IV drip monitor 14 is pressed onto the drip chamber 10 where it remains secured. To remove the drip chamber, the operation is simply reversed. Referring to Fig. 8-10, the drip monitor 14 comprises a body 101 having two projecting generally parallel arms 102. Inside these arms 102, are two generally parallel arm brackets 104. These arm brackets 104 are resilient, so that when the monitor 14 is oriented so that the drip chamber 10 faces the opening between the arm brackets 104, and the monitor 14 is pressed onto the drip chamber 10, they open to accommodate the drip chamber 10 but grip the outer circumference of the drip chamber 10. The arm brackets can accommodate a range of diameters of drip chambers. The arms 102 bear the IR LED diode 105 and IR photosensor LED 106, the arm brackets 104 including apertures 116 so that there is an uninterrupted path between the LED diode 105 and IR photosensor LED 106. - The body 101 of the drip monitor 14 includes a spring-loaded micro detector switch connector 108, Fig.8-10, located at the rear surface of the region 109 between the arms 102 which is depressed when the drip monitor 14 is correctly pressed onto the drip chamber 15, but in a released state when the drip monitor 14 is not connected to a drip chamber 15. The body also includes an alarm LED 110. - Referring to figures 11 to 13, the body 101 of the drip indicator 14 houses a coin battery 112 constrained by a connector tab 113 (or potentially more than one battery, though as discussed one battery is preferred), a processor 114, and optionally a piezoelectric buzzer 115. - Referring to Fig. 10 turning the monitor completely off manually by removing the monitor from the drip chamber at any time during (Active or Sleep Mode) to let (the spring-loaded button of the micro detector switch that is pressing against drip chamber's surface to re set its normal stationary position, by disconnecting the electrical circuit. - The drip monitor with micro switch detector connector in between the arm brackets is quicker to set up than a side actuated micro switch. Given the instrument's immediacy use feature (clip to turn ON and unclip to turn OFF, Fig. 15) that lies in the way of readily to use in a convenient fashion. - The instrument can be clipped around the drip chamber immediately after unpacked to turn ON right away when the spring-loaded connector button 108, that is extruded between the gripping arm brackets 104 shown in Figs. 8 -10, gets pressed by a pushing drip chamber 15 to move it in flush with the enclosure; whereas a side-actuated micro connector switch (such as disclosed in GB2586285) needs to apply a short finger press to turn instrument ON manually and also (when unusually by applying a short press during monitor being in active / detection mode to reactivate a manual recalibration) under voltage drop condition. This re application of short presses which was necessary when monitor's phototransistor's reading of IR emission varied (affected by power surge) and led to wrong visual indication. - Micro detector switch connector is repositioned in between the clipping arm brackets for easiness and convenience, and against any inadvertent press by IV set tubes if packed within. Unlike instrument with the side-actuated micro switch connector which needs a long press to turn OFF; the instrument having a micro detector switch connector in between the gripping arm brackets will turn OFF completely by unclipping it from the drip chamber as the spring-loaded button will re set its normal stationary extruded position, hence disconnecting the electrical circuit. This latter feature is helpful in case of instrument users forget to turn OFF the instrument, however a sleep / inactive mode is configured to take place. The invention as per its further embodiment presents a software program which puts the circuit into sleep mode (inactive at very less power consumption). The sleep current is only 500nA (500 Nano Amperes) which is [Estimated running time 210000 hours equivalent to more than 23 years with a typical coin cell battery. Excluding the self-discharge of the battery]. Specifically, the monitor employs a conditional loop calibration configured to calibrate on a condition when only there is a drop / artefact being detected in the IR field. The monitor is designed to work with, for example, one or two CR1216 -3 volts coin-batteries 112, Fig.11, though other batteries could be employed, including a single battery. This produces a no load battery voltage of 6.6 Volts with series resistance of lk ohms, and results in running time approximately for 11 hours. Drop Detection failing issues took place with battery voltage drop in the 3xLR44 - 4.5 volts coin batteries submitted in patent application GB1912958.4: When the monitor disclosed in GB1912958.4 is started off after pressing the side-actuated switch's push button N3, to correspond now in function with current monitor in rear switch 108, Figs 8-10 to initiate a calibration of the current light, followed by the auto-calibration loop function to allow continuous measure of the reading from the phototransistor and then compare it with the pre-stored value; it has been found that without the conditional auto calibration loop, the Alarm LED 110, Fig.10 may become turned ON constantly and remained turned ON at fault, instead of blinking with every single falling drop, this due to fluctuating voltage affecting the IR beam. This resulted in unwanted re pressing on the side-actuated connector's push button to re calibrate often. A conditional calibration of the presented application is a dynamic feature and is running continuously along IR detection specified by a dynamic time range within which a drop may be detected, see Fig. 3 for reference. Re calibrating the monitor adopts an inventive way of continuously storing some dynamically changing IR photosensor's reading values as variables - termed as (SensorValues) - comprised in the form of an array of time-spaced readings taken during IR detection. When a drop intercepts between the IR LED and the IR Phototransistor LED - when device is active - a varied of IR readings are obtained across the drop. These IR variables of arrays are continuously taken and stored in the microcontroller, as soon as a new array is filled then the previous array gets deleted during IR detection. Conditional Calibration helps solving one major failing issue which is a false indicating visual alarm which often occurred because of battery's variation in surge or effect on the IR LED phototransistor's photosensitivity which may fluctuate as IR phototransistors are vulnerable to electrical surges and electromagnetic energy. This overcomes the problems of the monitor described in the previous patent application GB1912958.4, as issue was only discovered at a later stage. Therefore, instead of relying on an unreliably transmitted IR signal - between IR LED diode as emitter and IR phototransistor as receiver-affected by a power surge or fluctuating voltage, which led to wrong photosensor readings (which was then taken for triggering a calibration from the microcontroller) when a drop intercepted IR beam; the monitor now takes a form of successive arrays of possibly varying photosensor values which are obtained from across the vertical surface of an intercepting drop's varying dimensions from different positions when occluding the IR beam, illustrated in Fig. 2-3. As the drop intercepts, hence ideally a minimum of 10 varied IR transmitted signals are obtained by the IR LED phototransistor 106, which are then converted and stored (either in random or orderly) as digital values ( now termed as sensor-values) in the form of rolling arrays, from which a lowest value (termed as new base-value) is assigned amongst the 10 readings (termed as sensor-values) in the present configuration, the new "base-value" is then subtracted from each sensor-value so that result will be more / equal than the preset sensor value (the value of which calibrates the sensitivity of the sensor) of 4 (in this example). The lowest calibrating sensor-value which is variably selected based on estimating a drop size proportionality, hence measured suitably to be sufficiently detectable (in the case of IV drop the IR beam detection at the top narrow part of a drop measures mostly at the lowest). The adjustable preset sensor value 4 is a preset that determines which array's sensor reading value the monitor should recalibrate at. The monitor's auto-calibration is believed to depend on factors such as the variation of which part of the intercepting drop's projecting surface occludes the IR beam, the varying dimensions of the drip, varying levels of ambient light, as well as variation in the IR LED, IR phototransistor, and other circuit variation. A preset sensor value (the value determines the sensitivity of the monitor) of 4 is suitably selected to meet an achievable calibration when subtracting base-value from the sensor-value as in the following formula: A calibrating Value if ( SensorVal - BasicVal) >4. However, this value may vary with other components and set-up, depending on the system and configuration, but can be found by experimentation. To avoids the monitor being prevented a conflict between the auto sleep / inactive mode and the continuous run-in-loop recalibration, which otherwise prevents the monitor from entering sleep / inactive mode through the loop calibration when waking it up before going into sleep mode / inactive. And also to allow the monitor to perform a wakeup step after going into a sleep / inactive mode, since microcontroller is now using voltage below the nominal operating range of 2.7-5.5V. To overcome this problem, the term (BOD which means Brown Out Detection is enabled: A "brown out" of a microcontroller is a partial and temporary reduction in the power supply voltage below the level required for reliable operation. Many microcontrollers have a protection circuit which detects when the supply voltage goes below this level and puts the monitor into a reset state to ensure proper startup when power returns. By default, the brown-out detection (BOD) is usually not enabled within micro-controller. To enable the brown-out detection some of the fuse settings must be changed via burning the fuses within the micro-controller. 1.8v enabled in BOD from the tool's menu of Arduino UNO in ISP MODE, in our experiment. Fig.3 shows an array 70 of signals from the IR phototransistor is comprised of 10 sensor value readings taken whilst a drop vertically falls across the IR beam, varying due to the drop shape as it cuts down the beam (a 3mm beam diameter would be typical) and various other factors. These values from the array are converted into digital variable values by the microcontroller 114 Figs.11 and 12. In order to calibrate monitor, a particular IR reading (the lowest value) of the array is assigned to recalibrate IR sensor reading of the phototransistor. Each new array with sensor readings 70 replaces the preceding deleted array 72. Hence a conditional calibration takes place according to the following logical formula set out in the configuration:. A calibrating Value if ( SensorVal - BasicVal) >4. This configuration is providing a solution for the electrical fluctuation, surges and electromagnetic energy issue caused by the installed coin batteries. It makes it a conditional type of calibration in such that there is no calibration taking place unless there is some drop or an artefact in the path of the IR transmitting beam between the IR LED diode and IR photo diode. For a conditional "continuously run-in-loop calibration" to function, the monitor configures a program here, describes works on a principle based on two linked dynamic elements required: 1- Drop / artefact intercepts or occludes IR beam; and 2- Drop / artefact detected are bound by limiting time slot or array assignment. The time of detection is dynamic i.e. detection corresponds with the drop / artefact's time taken to intercept the IR sensing beam. For example, a fallen intercepting IV drop's turns the alarm IR LED ON for 30ms array, whereas an object being put still in intercepting the IR sensing beam should turn the Alarm LED ON longer i.e. (from recalibrating a total of 100 sensor-values of the next arrays in an apparent display of turning Alarm LED ON for 2 seconds - (10 per sensor values x 200ms), before turns OFF. Specifically in the case of IV drop in IR detection as used by our drip monitor: A recalibration should only take place when there is a drop occludes IR beam and being detected, hence detection is displayed via the alarm being turned ON; alarm is turned OFF when no drop / no occlusion being detected, hence no alarm is indicated. As such by adopting the application of dynamic limiting arrays of IR beams in drop detection helps preventing any IR beam under fluctuating power. As explained in the following illustration of the block diagram Fig.4 -7: As a first step, when the drop intercepts the IR beam:- • An environmental reading measurement from the IR LED Photo Diode is taken and stored as a Base-Value in the micro controller; this stage is a simple calibration. • The IR transmitting beam is getting variably intercepted (shortened and lengthened) by a falling drop across which an array of a minimum of 10 variable measurement readings are taken from 10 points; • A preset sensor value of 4 is a value at which the assigned base-value of an array is subtracted from the lowest sensor-value reading of the current array, ideally varied values produced when an IV drop intercepts IR beam. A variable IR sensor-reading is a calibrating Value if ( SensorVal - BasicVal) >4. Wherein, 4 is a preset sensor value. - BaseValue = (Wall [i.e. the internal diameter measured from wall to wall] of Drip Chamber with a drop - if initial, basevalue adjusts later in loop by a new BaseValue - or without drop within IR beam); - SensorValue = (Wall [i.e. the internal diameter measured from wall to wall] of Drip Chamber + Intercepting Drop); - SensorValue (with obstacle [i.e. the drop]) >Basevalue (with no obstacle ); - Initial or Re Calibration Value if (sensorValue - basevalue) >4; -4 is an adjustable preset sensor value for drop size detectability (Increase the monitor sensitivity >3, >2, >1; To reduce the sensitivity >5, >6, >7. Experiment testing the monitor's dynamic detectability of IVdrop The current monitor integrates another type of dynamic time-based variable attribute in IV drop detection, should the batteries become unable to retain a constant voltage during operation. A continuous checking is performed by sensor running-arrays 70, Fig.3 obtaining varied readings from the IR photosensor when a drop falls Fig.l. An array is checked in 200ms during which drops / artefacts are being detected in the IR detecting field whether they are moving objects such as that of a fast-moving drop or a still object. So based on this time checked in background, a successful dynamic treatment of the IV drop is carried out, aiming to restrict the detection error to that particular array or sensor values within 200ms, and this be compensated and corrected by another cycle or loop. In testing this dynamism feature of the monitor, in the event of initiating a constantly deliberate occlusion of the IR beam, a series of continuous recalibrations take place, alarm LED turns ON constantly, and this will be restricted to a maximum of 2 seconds only - a collection of 10 consecutive calibrating sensor-values in an array (200ms x 10 = 2 sec) - which is the result (subtraction of new base-value) from each sensor-value in each of 10 arrays to recalibrate. Applying the conditional recalibrating treatment helps overcome a locked alarm signal, should the voltage fluctuate before instrument adjusts itself in adaptation with the new ( high / low) voltage powering the IR transmitter. Once an array is fully calibrated, it gets deleted and a new array is replacing to run in loop again. A desired correct visual alarm for the monitor is to detect and indicate which is flashing, for example, 30 milliseconds when a drop intercepts IR beam inside the drip chamber, where 30 milliseconds is integrated within the loop. This has been tested to confirm the element of the dynamically changing time-range fragmentation in the IR photo-sensing field is when press switch connector button 108, Fig. 15, to turn on monitor 14 and placing an artefact such a finger in the IR sensing field between the IR diode emitter and the IR LED phototransistor. The monitor should trigger an instant consecutive series of recalibrations for a duration of 2 seconds, that is indicated via the alarm LED 110, before the alarm LED indicator turns off while the finger is yet within the IR beam. Now if removing the finger and placing it back still within the IR beam for half of previous time, now alarm LED 110 should indicate for only one second, this establishes the fact that the time period is dynamically changing. This occurs provided that - each of 10 sensor-value variables in an array is applied in the logic formulation: CalibrationVal if ( SensorVal - BasicVal ) >4, hence in an order, each sensor-value recalibrates to follow one after another successively in a series of 10 consecutive recalibrations. When an array is full, it is then deleted and another array follows to refill. In a similar manner, a maximum of 2 seconds of alarm LED 110 turning constantly ON when the dripping of IV liquid, for example, becomes a constant runlet stream in the drip chamber 15 before the alarm LED 110 starts flashing for 30 milliseconds again with every falling drop once the drip stream interrupts into intermitting drops. Hence, this way of only trigger-to-recalibrate when specific size of an artefact treatment satisfies the concept of time assignment (in particular IR error prevention) within which calibration is carried out dynamically. Therefore, calibration should only take place when a drop / artefact is within IR detecting field in a moving or still mode. In other words, any detected artefact should take as much time, either placed still or moved, to occluding the IR beam but should be limited to no more than 2 seconds. This time-based fragmentation concept can ideally be applicable in detecting moving objects such as that of detecting drops in the use of IV infusion since a drop is pulled downwards by the gravity force, at a fast speed estimated in milliseconds counting frame than that of a still artefact when put deliberately to intercept the IR detecting field. The time-based concept serves a crucial and useful tool in object detecting which, in our case, a falling drop defined to be a fast-moving object and has a disproportionate formation by the definition of physics, which is cutting through IR field when battery power retention is of paramount element along the operating process against the fluctuating effects. The IV drip sensor monitor takes the shape of a horseshoe or the letter (J and is powered by a single / multiple coin battery. It is used to detect drops in the IV drip infusion for patients, utilising the IR LED diode as emitter and the IR phototransistor as receiver. The instrument detects across each intercepting drop of the IR beam, and when this happens the IR occlusion across a drop produces varied lengths of IR beam from different locations or points while intercepting. These varied lengths, taken by the IR LED phototransistor, are being converted in the micro-controller and stored in the form of digital values called sensor-values. A minimum of, for example 10, of these sensor-values being gradually taken and put in an array in such that when an array is full within a specific period, 200ms for example, the preceding array is deleted. When a drop intercepts the IR sensor beam, a lowest value amongst the sensor-values is assigned as base-value, then each of the sensor values in (randomly or orderly) gets subtracted from the assigned base-value within the same array. This results values either [equal or higher] or lower than a preset sensor value that is selected to correspond with the monitor's detectability of a drop, or in other terms, any result from applying the equation: if (sensorvalue - basevalue) >4 is now detectable, hence is a calibration-trigger. Otherwise, any sensor-value, after applying aforementioned equation, results <4, is a non detectable value, hence not calibrating the monitor. By this way of treating the IV drop through the aforementioned conditional detection, a recalibration for the IV drop monitor is carried out. In effect, the monitor is managed to adjust in correspondence to the battery power fluctuations. Two elements necessary for the monitor to adopt in order to carry out detection and resulting recalibration: First, only by interposing an artefact / drop temporarily or still within the IR detecting beam. Second, that interposition is bound by a limiting time period within which a recalibration takes place, should it meet a condition with regards to a (preset sensor value). Monitor's sensitivity to detect an IV drop is determined by a preset sensor value or a preset sensitivity selected for the monitor at which rate to recalibrate. Each time a recalibration is carried out an alarm indication is given out via the monitor's alarm LED to flash for (30ms, for example) within the time assigned for an array. Integrated also is (optional) a buzzer to alarm acoustically. The buzzer may ideally be a piezo-electric buzzer, which can be fabricated at a small size and thin shape. The instrument starts on via a micro switch connector's button (be pressed ON / Released OFF) extruded between the two curved gripping arms / brackets as in Fig. 8 -10. The monitor comprised from the following dimension measurements Fig.8 DOI, D02, D03, D04, D05 and Fig.9 DI, D2, D3, D4 and Fig.10, D8, D9, DIO, Dll, wherein D6, D7 and D14 show battery lid hinge, battery opening clipping, battery lid respectively. This is to show how small the monitor can be, however, monitor can also be slimmer in height if one coin battery or no buzzer is utilised: As the monitor may be reliably powered with compact disposable batteries, it avoids the use of photovoltaic cells to generate electricity from sunlight and store the resulting electrical energy in batteries or either they are rechargeable batteries. While the day-to-day operating cost of a photovoltaic system is low, these systems typically have a high installation cost, and the batteries have a finite life, requiring expensive periodic replacements. Battery systems also are typically oversized, as the life of the batteries is optimised by avoiding discharges of more than 20 percent of the stored energy from the batteries. A major problem with such past monitors is that the batteries need to be replaced periodically by opening the monitor. This requires some sort of openable closure, which may allow dirt, water, and moisture into the monitor, which may cause the battery to short out and also can affect the performance of monitor. These solutions are limited and restricted to their conventional systems. The monitor as described above provides an assembly that is a simple, quick to set up, easy-to-use ergonomic design. The intrinsic shape and look of it - such as a flexible ring with an open-end design - helps giving it a high degree of usability of its peculiar intention that is quickly acquired by the simple common sense of human's intellect. The monitor can be pressed against the drip chamber in an inverted way i.e either side of the surface top to bottom or opposite. The device can be supplied packaged with an IV infusion pack, and a user's instruction manual may be printed on the IV infusion pack to help save additional catalog cost. The monitor is cost effective due to the simple design and the very few elements composing the whole embodiment design. It is also easily recyclable and re-usable due to its simple enclosure mechanism - the battery compartment may be conveniently designed to replace the batteries in the easiest and practical way. Another characteristic is the rechargeable feature the monitor adopts which makes it environmentally friendly and economically cost-effective especially for hospital and caregiving centres. The invented monitor is to be used by professional and non-professional caregivers. Recommended as a supplementary, but not essential part, within the Intravenous Drip Infusion Pack is the following monitor item: A relatively small ring shape enclosure in compacted in solid e.g. plastic material with an open end cavity as in - (FIG.l) of the attached drawings - to be pushed onto the dripping chamber cylinder similar to a saddle clip over varied standards of drip chamber's outer body. It can conveniently be powered by a small single coin battery resting on a small PCB, a tiny press-button switch to work as monitor starter on the side (A suitable general configuration is disclosed in GB2586285, which is incorporated herein by reference) or extruded in between the opposing grip arm bracket. Many variations are possible without departing from the scope of the present invention as defined in the appended claims.

Claims

21 03 251. A monitor for an IV drip chamber comprisinga light emitting devicea photosensora housing attachable to an IV drip chamber, the housing holding the light emitting device and photosensor on substantially opposite sides of an IV drip chambera power supplysuch that a drop of IV solution falling between the light emitting device and the photosensor intercepts the light beam between the light emitting device and the photosensora first state when an obstruction such as a drop to the photosensor is detected, and a second state when obstruction to the photosensor is not detected characterised in that the follow steps are carried outthe value of the output from the photosensor is dependant on and varies with the amount of light intercepted from the light emitting device and is capable of producing more than one valuea sequence of values of the photosensor being stored in an arraya base value representing the value of the photosensor when no droplet or the lowest value if a droplet is present is subtracted from the lowest value of the sequence of values, and if this resulting value is equal or more than a preset value, the monitor is actuated to the first stateand these steps are repeated while the monitor is active.

2. A monitor for an IV drip chamber according to claim 1, wherein the monitor is actuated to the second state if the resulting value is less than a preset value, and these steps are repeated while the monitor is active.

3. A monitor for an IV drip chamber according to claim 2, wherein the monitor is in-the second state enters sleep state after a pre-set time representing a sleep state where the functionality of the a light emitting device and / or photosensor are suspended to conserve power.

4. A monitor for an IV drip chamber according to claim 1, wherein a sleep state is entered from the second state when an obstruction to the photosensor is not detected for a preset time period where operation is suspended and battery power reduced.

5. A monitor for an IV drip chamber according to claim 1, wherein the preset value is selected from the values 1, 2, 3, 4, 5, 6, or 7.

6. A monitor for an IV drip chamber according to either claim 2 or 3, wherein the sleep state may be exited by user activation.

7. A monitor for an IV drip chamber according to any previous claim, wherein the monitor includes arms to secure the IV drip chamber, and a button on the inside surface of the monitor which is depressed by the IV drip chamber when the monitor is secured to the IV drip chamber, a change in the actuation of the button deactivating the sleep state.21 03 25

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