Abstract:
An intravenous infusion system that shows infusion flow rate, volume of medication infused, and alarming during malfunction. User intervention to adjust flow rates deviation is possible, using the data already stored in the system prior to the onset of making the adjustment. The system detects flow rate by measuring temperature dynamics in a section of the fluid path, unlike other systems that measures the electromechanical output of the pumping source if the counting of drops is not possible. This fundamental difference allows the invention to be used in any system that has a pumping source that provides a continuous fluid path as it measures actual flow of fluid in a segment of the fluid path, independent of pumping mechanism design.

Description:
TECHNICAL FIELD 
       [0001]    Embodiments of the invention relate to a system, apparatus, and methods for monitoring intravenous (IV) infusion, in particularly the flow rate and volume of infusion delivery to a patient. 
       BACKGROUND 
       [0002]    In infusion therapy, the patient could either be immobilized at bed site or ambulatory. In the former, infusion consist of an intravenous (IV) drip set with gravity means or with the aid of an electronic IV pump while in the latter the patient is ambulatory with a self powered pump like elastomeric or electronic pumps. The inadequacies in either situations relate to the lack of the flow rate display of a gravity IV drip set as well as flow rate drifts of such, hence necessitating frequent drip rate checks and roller clamp adjustments by a healthcare provider. In electronic pumps the flow rate display relates to the functioning of the driving mechanism of such pumps and not the monitoring of actual flow of medication to the patient. 
         [0003]    Therefore, improved infusion procedures that address these inadequacies are desirable. In conventional mechanical infusion apparatus like elastomeric, spring powered or gas powered pumps, flow adjustments are non-existent while in electrically driven pumps user/healthcare provider response relates to malfunctioning of the pumping mechanism itself. 
         [0004]    It is the object of this invention to provide monitoring of IV infusion by measuring the actual flow of medication independent of the driving mechanism of the source and using the techniques disclosed to enhance patient safety and caregiver efficacy. 
       SUMMARY 
       [0005]    According to one embodiment of the invention, a thermal pulse (or heat pulse) is emitted into the fluid or medication whose flow rate is determined by measuring the time taken for this thermal pulse and any change in its level to be detected by a thermal sensor (e.g. temperature sensor) located at a fixed position downstream in relation to the flow direction. This time duration and change in temperature and the fixed distance between the emitting and sensing locations provide the inputs to determine flow velocity. The volumetric flow rate of the fluid is then derived from the product of the flow velocity (V) and the cross-sectional area (A) for flow. Even when different types of fluids with different thermal coefficient are used, the impact arising from such variables has little or no influence as the measurement involves taking time duration between successive pulses. While flow rate is determined by time and temperature measurements, occlusion is detected by comparing the temperature detected by two temperature sensors located at one upstream location and another downstream location in relation to the fluid delivery channel or path. In the absence of occlusion, the temperature at the two locations will be different, specifically the temperature at the downstream site will be higher than the temperature at the upstream site due to the thermal pulse emitted between the two locations. The fluid absorbs thermal energy from the pulse and flows downstream, resulting in a higher temperature detected at the downstream location. On the other hand, the presence of occlusion causes minimal or no flow which results in a minimal temperature difference or substantially equal temperature readings at the two sensor locations. 
         [0006]    According to one embodiment of the invention, the section of the fluid delivery channel or path that is used in the above described measurements of flow rate and temperature difference is enclosed within an in-line Flow Cell, which can be inserted or attached to a control module (Flow Detection Unit) that measures and displays the appropriate flow status. The Flow Detection Unit comprises a thermal source that utilizes a Laser diode, infra-red (IR) diode or any heat generating means. The thermal source emits the thermal pulse(s) that transfers heat to the fluid in the channel of the Flow. Cell. The temperature sensors in the Flow Detection Unit measure the temperatures at the predetermined locations in the Flow Cell and provide these as input data for further processing by the microprocessor in the Flow Detection Unit. The algorithm programmed in the microprocessor will convert these temperature inputs into digital outcomes and display instantaneous flow rate, mean flow rate and/or volume delivered. 
         [0007]    According to another embodiment of the invention, the Flow Cell comprises a bar code that can be read as it is swiped along a slot in the housing of the Flow Detection Unit. The bar code is encoded to provide specific input data for the microprocessor or MCU in the Flow Detection Unit, which obviates the need for manual input by the user of such data, hence promoting plug and play simplicity. The barcode, which can be preprinted on the Flow Cell, can also contain unique identification such that when the Flow Cell is swiped in the Flow Detection Unit, the patient data tagged to the barcode is scanned/read by the Flow Detection Unit, which displays patient data for nurse verification. This provides for positive identification of patient to the IV pump, i.e. medication prescribed to the patient. Barcode can also be tagged with a desired flow rate of the medication for the patient. In the situation where patient and medication data are managed in a server with wireless connectivity, such information could be sent to the Flow Detection Unit by remote means. This allows further means of verifying that correct medication is administered to the patient as the Flow Detection Unit is attached to the Flow Cell through which medication flows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Embodiments of the invention will be readily understood by the following detailed description in conjunction with the accompanying drawings. 
           [0009]      FIG. 1  is a schematic view of the intravenous (IV) infusion monitoring system in accordance with one embodiment of the invention. 
           [0010]      FIG. 2  is a perspective view of the Flow Detection Unit and Flow Cell in accordance with one embodiment of the invention. 
           [0011]      FIG. 2A  is a perspective view of the Flow Detection Unit with Flow Cell attached in accordance to one embodiment of the invention. 
           [0012]      FIG. 2B  is an unassembled perspective view of the Flow Detection Unit with its associated components in accordance with the one embodiment of the invention. 
           [0013]      FIG. 2C  is a perspective view of the Flow Detection Unit in use with the flow cell in accordance with one embodiment of the invention. 
           [0014]      FIG. 3A  and  FIG. 3B  are perspective views of the Flow Cell in accordance with one embodiment of the invention. 
           [0015]      FIG. 3C  and  FIG. 3D  are side views of the Flow Cell illustrated in  FIG. 3A  and  FIG. 3B . 
           [0016]      FIG. 3E  is a cross-sectional view of the Flow Cell illustrated in  FIG. 3C  along A-A. 
           [0017]      FIG. 3F  is a perspective view showing a Flow Cell according to another embodiment of the present invention. 
           [0018]      FIG. 3G  is a perspective view showing a Flow Detection Unit and the Flow Cell of  FIG. 3F . 
           [0019]      FIG. 4A  is a perspective view of a Flow Cell in accordance with yet another embodiment of the invention. 
           [0020]      FIG. 4B  is a side view of the Flow Cell illustrated in  FIG. 4A . 
           [0021]      FIG. 4C  is a cross-sectional view of the Flow Cell taken along line B-B in  FIG. 4B . 
           [0022]      FIG. 4D  is a cross-sectional view of the Flow Cell taken along line A-A in  FIG. 4B . 
           [0023]      FIG. 4E  is a perspective view of a Flow Detection Unit in use with the flow cell shown in  FIG. 4A  in accordance with one embodiment of the invention. 
           [0024]      FIG. 5A  is a perspective view of the Flow Cell shown in  FIG. 4A  coupled to a flow regulating mechanism and a clamping mechanism in accordance with one embodiment of the invention. 
           [0025]      FIG. 5B  is a top view of the Flow Cell shown in  FIG. 5A  with a partial cross-sectional view of the clamping mechanism. 
           [0026]      FIG. 5C  is a side view of the Flow Cell illustrated in  FIG. 5A . 
           [0027]      FIG. 5D  is a cross-sectional view of the Flow Cell viewed from the line A-A in  FIG. 5C . 
           [0028]      FIGS. 6A and 6B  are examples of temperature vs time graphs of the temperature profiles in the Flow Cell. 
           [0029]      FIGS. 6C and 6D  are examples of temperature vs. time graphs of the temperature difference in the Flow Cell. 
           [0030]      FIG. 6E  is an example of temperature vs. time graphs of temperature difference measured with the Flow Cell and Flow Detection Unit shown in  FIG. 2B . 
           [0031]      FIG. 7  is a block diagram of the Flow Detection Unit in accordance with an embodiment of the invention. 
           [0032]      FIG. 8  is a flow diagram illustrating the functions of the Flow Detection Unit in accordance with an embodiment of the invention. 
           [0033]      FIGS. 9A and 9B  are flow diagrams illustrating the instantaneous flow rate mode in accordance with an embodiment of the invention. 
           [0034]      FIGS. 10A to 10C  are flow diagrams illustrating the mean flow rate mode in accordance with an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    In the following description, numerous specific details are set forth in order to provide a thorough understanding of various illustrative embodiments of the invention. It will be understood, however, to one skilled in the art, that embodiments of the invention may be practiced without some or all of these specific details. In other instances, well known intravenous delivery processes and mechanisms have not been described in detail in order not to necessarily obscure pertinent aspects of embodiments being described. 
         [0036]    Embodiments of the invention relate to an infusion monitoring and measurement system that supports mobile or ambulatory and bed side mode of infusion based on any mechanical or electrical source of pumping fluid source. In an embodiment of the invention, a control module (Flow Detection Unit), which is a tablet or pod like device, displays data and alarms to provide effective monitoring of a typical infusion procedure and allows appropriate user response. In another embodiment, a flow section of the fluid path (Flow Cell) is attachable to the Flow Detection Unit to enable measurement and monitoring of the fluid flow, volume of fluid delivered and other related parameters. 
         [0037]    The Flow Detection Unit comprises at least one thermal or heat source such as a laser diode or Infra Red (IR) diode or any heat generating means, at least one thermal sensing means, and electronic processing circuits to ascertain flow rates and occlusion, and in certain application modes prompts the user or healthcare provider to take specific actions in order to achieve desired flow of medication or fluids to the patient. In one embodiment, the Flow Cell is an in-line component of the fluid delivery path between the fluid source and the patient. The Flow Cell allows thermal energy/thermal signal emitted from the Flow Detection Unit to be transferred to the fluid or medication that flows through the flow cell. In one embodiment, certain portions of the Flow Cell include heat transmission paths, e.g. contacts or conductive probes, which facilitate the heating or temperature measurement of the fluid or medication by the Flow Detection Unit. The Flow Cell may function as an interface on the fluid delivery path which allows specific measurement of the fluid (by the Flow Detection Unit) while it is delivered to the patient, hence making it amenable as a single use or disposable component that could be easily assembled with the entire fluid delivery apparatus. In one embodiment, the Flow Cell is bar-coded to allow automatic input of relevant data related to the fluid delivery apparatus used, for example flow rate and volume to be infused or even unique patient or pump or medication related identification. 
         [0038]    One advantage of the re-usable main body Flow Detection Unit and a single use in-line installed Flow Cell allows all current disposable mechanical pumps including and not limited to spring powered, gas powered or elastomeric pumps to be equipped with a safety feature indicating flow rates and occlusion that is not available presently. The implication is significant as the use of such pumps, which is well received for its ease of use could be expanded to include infusion of medication with narrow therapeutic tolerances. Without such means to show the flow status, and where appropriate prompting user intervention the use of such medication with such pumps would be limited, and even hazardous. Furthermore, unlike monitoring systems in most electronic pumps that focuses on the proper functioning of the pump itself, the Flow Cell and Flow Detection Unit monitors the actual flow rate of infusion and in some embodiments allow the necessary adjustment to the flow orifice to achieve the desired flow. 
         [0039]    For example, the Flow Detection Unit provides a display of flow rates, such as instantaneous and mean rate of infusion, and the volume delivered as means of alerting the healthcare provider to undesirable deviations. It may also alert the healthcare provider when occlusion is detected. The Flow Detection also allows user/healthcare provider to make adjustments to correct the flow rates as a means of addressing the risks associated with any non-action. 
         [0040]    In addition, the Flow Detection Unit supports positive identification of patient/drug patency. Conventionally, drugs to be infused are prepared in the pharmacy while the filled apparatus are attached to patients by a separate healthcare provider. Patient and intended medication data stored in the Flow Detection Unit by means of a barcode wand or hand held scanner in the pharmacy can be subsequently used as positive identification means when the infusion monitoring is initiated. For example, the nurse will be able to identify the correct matching of medication in the pump to the patient when the Flow Detection Unit displays patient data that is tagged to the barcode on the Flow Cell. This helps to reduce incorrect infusion of medication to the patient. Barcode could also be tagged with a desired or nominal flow rate data for the medication to be administered to the patient. As an interface between the Flow Detection Unit and the fluid delivery path, the Flow Cell is not necessarily an integral part of the delivery system. It could be configured as an in-line component of an extension tube that could be connected to any infusion delivery system to support monitoring of infusion described in this invention. 
         [0041]    Referring to  FIG. 1  and  FIG. 2 , a Flow Cell  200  according to one embodiment of the present invention forms a segment of a fluid path of a fluid delivery system, e.g. an intravenous infusion system, from a fluid source  201  to a final receiving point, e.g. a patient  20 . The fluid source  201  can be an electrical fluid pump or a mechanical fluid pump (e.g. spring powered, gas powered or elastomeric fluid pumps) In one embodiment, the Flow Cell  200  includes a first plate  246  and a second plate  247  connected to each other. In the context of a patient receiving medication, the Flow Cell  200 , when inserted into an opening or slot  103  in the Flow Detection Unit  100 , enables the flow rate of infusion to be detected and shown on a display screen  108  of Flow Detection Unit  100 . The display screen  108  could be a Liquid Crystal Display (LCD) or Organic Light-Emitting Diode (OLED) display with or without in-screen navigational options for displaying flow rates, flow rate deviations, volume delivered and visual alarms for occlusions or unacceptable deviations in flow rates, etc. The Flow Detection Unit  100  can also include an audio alarm that activates when unsafe flow rates or occlusion are detected. 
         [0042]    The Flow Detection Unit  100  with the Flow Cell  200  may be dimensioned to be attachable to the patient  20  so that it allows easy access to the caregiver, e.g., a physician or nurse, to adjust the rate of infusion when needed, to reset an alarm button  104  or merely to monitor the flow status on display screen  108 . In one embodiment, the Flow Detection Unit  100  starts automatically when Flow Cell  200  is inserted or secured thereto, an in-built proximity switch will initiate the MCU in the Flow Detection Unit  100  to perform the preprogrammed logic. 
         [0043]    Referring to  FIG. 2B  and  FIG. 2C , the Flow Detection Unit  100  comprises a thermal source  109  and first, second, third and fourth thermal sensors  110 ,  111 ,  112  and  113 . The use of more thermal sensors enables time and amplitude data to be recorded at more positions along the fluid channel. This in turn increases the permutations in the development of the algorithm for flow rate detection. The thermal source  109  is a flexible resistive heater, but it could be any source generating thermal energy, e.g. a laser diode, an IR diode or the like. In one embodiment, the thermal source  109  is positioned in substantially equidistant between the first and second thermal sensors  110  and  111 . However, it is also possible that the distances from thermal source  109  to thermal sensors  110  and  111  are not substantially equidistant. If this is the case, an algorithm used to determine the measurement/monitoring results could be developed to compensate for the impact of such non-equidistance positioning relationship between thermal source  109  and first and second thermal sensors  110  and  111 , in the data recorded. The thermal sensors  110 ,  111 ,  112  and  113  are radiation or temperature sensing means that uses, for example IR sensors, laser sensors, film based resistance temperature detectors (RTD) sensors, negative/positive temperature coefficient (NTC/PTC) thermistors or any thermocouple. 
         [0044]    During operation, when Flow Cell  200  is inserted into the slot  103  of the Flow Detection Unit  100 , the thermal source  109  and thermal sensors  110 ,  111 ,  112  and  113  are aligned to the windows portions  249 ,  250 ,  251 ,  252  and  253 , respectively, that are disposed along the flow direction of the fluid through the Flow Cell  200  ( FIG. 2B  and  FIG. 3B . The window portions  249 ,  250 ,  251 ,  252  and  253  may be openings formed on one or both of first and second plates  246  and  247 , transparent panels and/or other suitable configurations that allow thermal radiation to be transmitted between the fluid in the Flow Cell  200  and the thermal source  109  and sensors  100 ,  111 ,  112  and  113  through first and second plates  246  and  247 , without substantial thermal energy losses. The slot  103  ( FIG. 2 ) provides simplicity and ease of use for attaching Flow Cell  200  to Flow Detection Unit  100 , thus obviating the need for additional protective means to prevent unintended visual and physical exposure to the radiation waves from the thermal source  109 . 
         [0045]    In one embodiment, the Flow Cell  200  may be bar-coded and together with a bar code reading feature, hence the need for manual user inputs may be obviated. In an embodiment of the invention, the Flow Detection Unit  100  comprises a barcode reading/scanning means  114  to read a barcode  312  on the Flow Cell  200  as the Flow Cell  200  is inserted into and swiped along the slot  103 . The barcode  312  can be encrypted by a commercially available printer, a laser marking system or other means onto the Flow Cell  200 . In one embodiment, the barcode reading means  114  is a photocell comprising emitter and receiver elements for sensing the barcode  312  as the Flow Cell  200  is swiped along the slot  103 . The orientation of the barcode reading means  114  in relation to the slot  103  may differ from the illustrations in the context and in the drawings, depending on the barcode position marked on the Flow Cell  200 . Upon reading the barcode  312 , the barcode scanning means  114  generates an input signal to a microprocessor or micro-controller unit (MCU)  130  in the Flow Detection Unit  100 . The input signal can be used to, for example, set the reference value for calculation of flow rates, infused volume as well as the interval frequency of the thermal pulses (or heat pulses) to be emitted by thermal source  109 . 
         [0046]    In one embodiment, the display screen  108  is activated to request user for inputs of flow rate and fill volume when the barcode reading means  114  failed to generate input signals for MCU  130  after reading the barcode  312 , or in a situation when wireless transmission of such data from a server to the Flow Detection Unit  100  failed. In one embodiment, the Flow Detection Unit  100  comprises a membrane switch  107  or any other forms of user input/control means, such as a scroll wheel which allows user to select predetermined values shown in the display screen  108 . Alternatively, the display screen  108  may show in-screen options that allow user selection, i.e. touch-screen features to allow user input or selection. 
         [0047]    In one embodiment, the Flow Detection Unit  100  includes a housing  102  having a top lid  120  and a bottom shell  121 . For clarity purposes and to illustrate other components of Flow Detection Unit  100 , the top lid  120  is not shown in  FIG. 2C . In one embodiment, the Flow Detection Unit  100  comprises a power source  131  for the MCU  130 , display screen  108 , alarm button  104  and any associated electrical components. For example, the power source  131  can be a Lithium polymer or Lithium Ion cells or any other commercially available batteries. The power source  131  can be retained within the bottom shell  121  by a hinged cover  122  over an opening  123 . Alternatively, the power source  131  could be connected to a universal serial bus (USB) port for charging on board. 
         [0048]    In an embodiment of the invention, the power source  131  can be coupled to an electrical port  116 , for example a USB port, which may be used to recharge the power source  131 . The electrical port  116  can also be configured to serve as a communication port to store data in the MCU  130 , for example, from a pen scanner. In another embodiment, the electrical port  116  receives data from a scanning wand or any equivalent barcode input, where the data could be patient and medication information that are automatically stored in the MCU  130 . These data could be retrieved using the membrane switch  107  and used as positive identification purposes for patient-drug patency. 
         [0049]    In an embodiment of the invention, the Flow Detection Unit  100  may be equipped with wireless connectivity means  105 , e.g. a blue tooth or wifi device etc., to allow data exchange between itself and a remote server  35  wirelessly ( FIG. 2A ). In one application, the server could send patient and medication data to the Flow Detection Unit  100  when the Flow Cell  200  is swiped or attached to it. This feature allows the caregiver to confirm that the infusion system comprising the Flow Cell  200  as a segment of the fluid channel carries the correct medication to the patient. Likewise, any adverse events pertaining to infusion irregularities or any event that may require imminent attention could be communicated remotely to the server, hence allowing care givers to plan and schedule work ahead. The possibilities arising from wireless connectivity associated with the means of monitoring status of infusion as described in this invention is encompassing for anyone ordinarily skilled in the art. 
         [0050]    The Flow Cell  200  forms a segment of the fluid path from the fluid source  201  to the patient  20 , either as an integral part of the infusion system or as a separate standalone component that is connected to the infusion system. In a preferred embodiment, the Flow Cell  200  is flat paneled in shape. Referring to  FIGS. 3A-3E , the flow Cell  200  includes a tubular member, e.g. a soft flexible tube  243 , a first plate  246  and a second plate  247 . Soft flexible tube  243  defines a fluid channel  241  therethrough. First and second plates  246  and  247  are constructed with substantially rigid material. When assembled together, first and second plates  246  and  247  form a space therebetween which is narrower than an external diameter of soft flexible tube  243 . Accordingly, first and second plates  246  and  247  press against soft flexible tube  243  disposed between plates  246  and  247 . As plates  246  and  247  are rigid, soft flexible tube  243  is compressed into a thin channel shaped configuration from its original round cross sectional geometry in the section where plates  246  and  247  and soft flexible tube  243  are in contact. The rigid plates  246  and  247  are held firmly together by means of claws  254 ,  255  and  256  and adjacent openings or slots  257 ,  258  and  259  such that these features will engage each other to produce a locking action when the plates  246  and  247  are firmly pressed against each other. The positions and number of claws and slots may vary from those shown in the drawings and maybe subject to tool design considerations suitable for manufacturing. Connection of first and second plates  246 ,  247  by the claws and openings also enables easy assembly and when necessary, also allows first and second plates  246 ,  247  to be detached from each other for, e.g. checking or replacement of soft flexible tube  243 . Compressed by plates  246  and  247 , the cross section of the soft flexible tube  243  along a direction perpendicular to the fluid path it communicates is approximately a thin rectangular space  242  with a thickness of about 0.05 to 0.35 mm and is created between the inner walls of the soft flexible tube  243 . Second plate  247  may have a slightly raised section  248  facing first plate  246 . Raised section  248  is to provide uniform compression displacement onto the soft flexible tube  243 . The soft flexible tube  243  is typically constructed from materials that allow transmission and detection of infrared radiation through its walls. The plates  246  and  247  could also be part of a clamp shell or hinged-like contraption as a means to achieve a thin channel-like cross section in the soft flexible tube  243  such that the fluid channel created allows thermal radiation to be transmitted to and from the fluid in a manner and extent that data could be recorded and used to develop an algorithm for flow rate determination. Window portion  249  formed on first plate  246  may be the type of thin panel to give improved proximity or an opening to allow direct access and physical contact between the heat source  109  and the soft flexible tube  243 . Window portions  250 ,  251 ,  252  and  253  formed on second plate  247  may also be the types of thin panels or openings at locations adjacent to the thermal sensors  110 ,  111 ,  112  and  113  in the Flow Detection Unit  100 , to allow direct access and physical contact between thermal sensors  110 ,  111 ,  112  and  113  and soft flexible tube  243 . 
         [0051]    The soft flexible tube  243  has an inlet  243   a  for coupling to the fluid source  201  via inlet tube  204 , and an outlet  243   b  for coupling to outlet tube  205 . On the sidewall of soft flexible tube  243 , there are defined thermal conductive portions  243   c ,  243   d ,  243   e ,  243   f  and  243   g . When soft flexible tube  243  is sandwiched between first and second plates  246  and  247 , thermal conductive portion  243   c  is in alignment with, and become at least partially overlapped to, window portion  249 . Similarly, thermal conductive portions  243   d ,  243   e ,  243   f  and  243   g  are also in alignment with, and become at least partially overlapped with, window portions  250 ,  251 ,  252  and  253 , respectively. This structure allows thermal signals to transmit between Flow Detection Unit  100  and Flow Cell  200  through thermal conductive portions  243   c ,  243   d ,  243   e ,  243   f  and  243   g , when Flow Cell  200  is attached to Flow Detection Unit  100  and that thermal source  109 , first, second, third and fourth thermal sensors  110 ,  111 ,  112  and  113  face respective window portions,  249 ,  250 ,  251 ,  252  and  253 . 
         [0052]    Outlet tube  205  can be coupled to a patient  20  through common means like a patient connector and catheter. The inlet  243   a  and outlet  243   b  are also means to allow improved manufacturability when the soft flexible tube  243  and the fluid tubes  204  and  205  are of different dimensions (primarily inner and/or outer diameters) or materials. The soft flexible tube  243  and fluid tubes  204  and  205  could also be connected directly without separately formed inlet  243   a  and outlet  243   b.    
         [0053]    According to another embodiment of the present invention, as shown in  FIG. 3F , there is provided a Flow Cell in the form of a tubular member  270  to enable thermal signal transmission with an external device, e.g. a Flow Detection Unit, for flow rate measurement, detection and monitoring in a fluid delivery system e.g. an intravenous infusion system. Tubular member  270  includes a sidewall  273  surrounding a fluid channel  271 . Tubular member  270  may form a segment of a fluid path of a fluid delivery system, e.g. an intravenous infusion system. Tubular member has an inlet  273   a  at one end of sidewall  273 , and an outlet  273   b  at opposite end of sidewall  273 , and allows fluid to flow through fluid channel  271  from inlet  273   a  to outlet  273   b . Sidewall  273  has a first portion  273   c  and a second portion  273   d  adjacent to first portion  273   c . First portion  273   c  is to allow a first thermal signal to transmit into fluid channel  271 , and second portion is to allow a second thermal signal to transmit out from fluid channel  271 . It should be appreciated that although shown in  FIG. 3F  as separate regions on sidewall  273 , first portion  273   c  and second portion  273   d  may also join together as one region. 
         [0054]      FIG. 3G  shows a flow detection unit  170  for flow rate detection using tubular member  270  shown in  FIG. 3F . Flow detection unit  170  includes a housing  171 , a thermal source  173   c , a thermal sensor  173   d  and a controller e.g. a microprocessor  172  disposed in housing  171 . Microprocessor  172  is coupled to thermal source  173   c  and thermal sensor  173   d . In use, tubular member  270  is placed proximate to flow detection unit  170  by, e.g. attaching to housing  171  of flow detection unit  170  such that thermal source  173   c  is aligned with first portion  273   c , and thermal sensor  173   d  is aligned with second portion  273   d . When activated, thermal source  173   c  emits a first thermal signal into fluid channel  271  through first portion  273   c . Meanwhile or subsequently, thermal sensor  173   d  receives a second thermal signal from fluid channel  271  through second portion  273   d . First and second thermal signals, the time instant at which the thermal signals are emitted/received as well as the time intervals taken in between may then be recorded by microprocessor  172  for determining the flow rate based on methods as hereinafter described. 
         [0055]    Housing  171  may have a first plate  280  on which thermal source  173   c  and first thermal sensor  173   d  are fixed, and a second plate  281  opposite to first plate  280 . First plate  280  is fixed to housing  171 , second plate  281  is movable relative to first plate  280 . When second plate  281  is at a position away from first plate  280 , e.g. with a distance d greater than an external diameter of tubular member  270 , tubular member  270  can be placed between first plate  280  and second plate  281 . When second plate  281  move towards first plate  280 , i.e. by decreasing distance d, tubular member  270  will be clamped between first and second plates  280 ,  281  such that tubular member  270  is fixed to housing  171 . At this position, first portion  273   c  is aligned with thermal source  173   c , and second portion  273   d  is aligned with first thermal sensor  173   d  such that, a first thermal signal from thermal source  173   c  can be emitted into tubular member  270  through first portion  273   c , and a second thermal signal from tubular member  270  through second portion  273   d  can be received by second thermal sensor  173   d.    
         [0056]    Flow detection unit  170  may include a second thermal sensor  173   e  disposed at the opposite side of first thermal sensor  173   d  about thermal source  173   c . Tubular member  270  includes a third portion  273   e  between inlet  273   a  and first portion  273   c . When tubular member  270  is clamped between first plate  280  and second plate  281 , third portion  273   e  is aligned with second thermal sensor  173   e  such that a third thermal signal from tubular member  270  through third portion  273   e  can be received by second thermal sensor  173   e.    
         [0057]    In a further embodiment, as shown in  FIGS. 4A-4E , a Flow Cell  200 ′ is tubular in shape and comprises a housing  208  having an inlet  214 , an outlet  215 , and a fluid channel  213  in fluid communication with the inlet  214  and outlet  215 . Housing  208  is formed of rigid material, by injection molding for instance. Housing  208  includes a sidewall  217  defining the channel  213 , and with three window portions  209 ,  210 ,  211  formed on sidewall  217 . The window portion  209  allows thermal energy to be transmitted to the fluid flowing through channel  213 , at the window portion  209  of the channel  213 . The window portions  210  and  211  allow the detection of respective thermal energy levels (i.e. temperature) of the fluid at the window portions  210  and  211 . When the Flow Cell  200 ′ is attached to a Flow Detection Unit, e.g. a Flow Detection Unit  100 ′ shown in  FIG. 4E , the window portions  210 ,  211  and  209  are substantially aligned to the thermal sensors  110 ,  111  and thermal source  109  respectively ( FIG. 4E ). In one embodiment, the housing  208  of the Flow Cell  200 ′ includes a protrusion or handle  219  that eases the insertion or removal of the Flow Cell  200 ′ into/from the slot  103  of the Flow Detection Unit  100 ′. 
         [0058]    In one embodiment where the thermal source  109  utilizes an IR diode, the Flow Cell  200 ′ can be made from materials with minimal IR absorption characteristics. In other words, Flow Cell  200 ′ can be made of materials that allow a large percentage of the IR radiation to be transmitted to the fluid. For example, the window portions  209 , 210 ,  211  are made of polyethylene materials. Alternatively, the entire Flow Cell  200 ′ can be made of polycarbonate materials. In another embodiment, the window portions  209 ,  210 ,  211  are each formed as a recess on the sidewall  217  such that the window portions  209 ,  210 ,  211  have smaller thickness than the other portions of the sidewall  217 . The smaller thickness helps to reduce the absorption of radiation by the window portions  209 ,  210 ,  211 . 
         [0059]    If a laser diode is used as the thermal source  109 , heat transfer probes  209   a  (only one is shown) may be used to improve the transfer of heat to the fluid in the channel  213 , as shown in  FIG. 4C . The probes are made of good heat conducting material, e.g. stainless steel, and at least one probe is integrated into each of the window portions  209 ,  210 ,  211 , for example by insert molding techniques. The probe  209   a  extends across the thickness of portion  209  such that it has an exposed surface in contact or in close proximity to the thermal source  109  when the heat pulse is emitted, and an opposite surface in contact with the fluid path so that the fluid receives the heat pulses. Similarly, probes at the portions  210  and  211  has an exposed surface in contact or in close proximity to the thermal sensors  110  and  111 , and opposite surfaces in contact with the fluid to conduct heat from the fluid to the thermal sensors  110  and  111 . 
         [0060]    In one embodiment, the Flow Cell  200 ,  270  or  200 ′ may include a clamping mechanism  220  at one end, for example at the inlet  214 , and a flow rate regulating mechanism  230  at the other end, for example the outlet  215  ( FIGS. 5A-5D ). The clamping mechanism  220  offers a means of stopping fluid flow from the fluid source  201  to the patient  20 , while the flow regulating mechanism  230  provides a means of adjusting the flow rate of the fluid. In an embodiment of the invention, the flow regulating mechanism  230  includes a barrel  232  inside which a rotatable axle  231  is disposed. A fluid tube can be coupled to the opening  234  of the flow regulating mechanism  230 . Rotation of the axle  231  about its axis will move a stem  233  (solid or hollow) into the fluid tube in a longitudinal direction such that the effective lumen of the fluid tube will vary, hence modifying the flow rate of the fluid passing through it. This action of rotating the axle  231  could be done manually or by means of an actuating mechanism, for example a robotic arm interface that receives signals from the MCU  130  of the Flow Detection Unit  100  to effect the necessary rotation. The adjustment in the flow rate can be made automatically and optimized using data of the infusion stored in the Flow Detection Unit  100 . 
         [0061]    In an embodiment of the invention, the clamping mechanism  220  includes a tubular construction  225  with a silicone or pliable material as an over sleeve  226 . The tubular construction  225  can be made from any hard plastics. In one embodiment, the over sleeve  226  is secured in position with respect to the tubular construction  225  by O Rings  228   a  and  228   b  ( FIG. 5D ) made of elastic material or any constrictive means such that the fluid path along the axis of the Flow Cell  200  is not compromised due to leakages. The O Rings  228   a ,  228   b  can be protected by retainers  222   a  and  222   b  which may be designed to be part of a single molded piece. The clamping function is achieved by a lever  223  which includes a protrusion  229  on its underside. When the lever  223  is pushed towards the over sleeve  226 , the protrusion  229  will press against the wall of the over sleeve  226 . There is a notch  227  that permits the protrusion  229  to extend into the tubular construction  225  and cause a partial or full blockage of the fluid flow. The lever  223 , when pushed downwards, is held in place by a catch  224 . The lever  223  can be released by pushing the catch  224  away from the lever  223 . To avoid accidental activation of the lever  223 , there are side shields  221   a  and  221   b  formed on both sides of the lever  223 . 
         [0062]    The use of the clamping mechanism  220  and flow regulating mechanism  230  allows the function of stopping or regulating flow to be grouped within close proximity to the Flow Cell  200 , hence offering convenience for the healthcare provider. However, it can be appreciated that the Flow Cell  200  can be used without the clamping mechanism  220  or flow regulating mechanism  230 . 
         [0063]      FIG. 6A  to  FIG. 6D  illustrate an exemplary temperature vs. time graphs according to embodiments of the present invention, e.g. for the temperature readings by the thermal sensors  110  and  111  of Flow Detection Unit  100  shown in  FIG. 4E . Taken from a direction of flow of the fluid to be measured, thermal sensor  110  is situated in a downstream position in relation to the thermal source  109 , while thermal sensor  111  is situated upstream in relation to thermal source  109 . 
         [0064]    The temperature readings detected at thermal sensor  110  (represented by line T 2 ) and at thermal sensor  111  (represented by line T 1 ) vary according to the thermo diffusion of the fluid heated by thermal source  109  and also the flow of fluid passing through the thermal sensors  110 ,  111  locations in the channel  213 . In  FIG. 6A , the temperature T 2  is higher than T 1  as the fluid passing thermal sensor  110  would have predominantly being heated by thermal source  109 , while the temperature T 1  would represent the temperature of fluid at thermal sensor  111  before it is heated by thermal source  109 . Measuring the difference in the temperatures T 2  and T 1  allows the confirmation of flow of fluid. In a similar fashion, the minimal or lack of temperature difference between T 2  and T 1  is an indication of no flow or an occurrence of occlusion (see  FIG. 6B  and  FIG. 6C ). 
         [0065]    Further referring to  FIG. 6C , a temperature difference threshold level representing a predetermined quantum in the differential in temperatures between T 2  and T 1  could be used to determine flow or no flow situations. This threshold level could also be used, in conjunction with the thermal pulse duration of the thermal source  109  to determine the flow rate of the fluid passing through the channel  213 . The fluid passing through the channel  213  or alternatively thin rectangular space  242  acts as a carrier of thermal energy or heat emitted by the thermal source  109 . The time taken for the fluid heated by the thermal source  109  to pass through fixed distance between thermal source  109  and thermal sensor  110  will be measured and the electronic circuitry of the Flow Detection Unit  100  can be designed to have repetitions of such measurements to achieve better accuracy. Since the cross section of the fluid path (i.e. channel  213 ) in the Flow Cell  200  is fixed, the time taken for the thermal pulse to appear at thermal sensor  111 , or to flow cells with more sensors e.g. thermal sensors  112  or  113 , and the amplitude of such a thermal pulse at each of the sensor locations would vary according to the flow rate of the fluid And could be determined. In similar fashion, the approximate volume of fluid delivered can be derived from the flow rate and duration lapsed. Trigger level is a predetermined reference level to ensure that time measurements are consistent, i.e. time is measured when this level is reached. 
         [0066]    Referring to  FIG. 7 , input ports of MCU  130  receive a signal J 1  from thermal sensor  110 , a signal J 2  from thermal sensor  111 , and a signal J 3  from the barcode reading means  114 , a signal J 4  from membrane switch  107  and an alarm reset signal J 5  from alarm button  104 . In embodiments having more thermal sensors, e.g. thermal sensor  112 ,  113 , MCU  130  also receive signals J 6  and  17  from respective thermal sensors  112  and  113 . A display latch and driver controls the display screen  108 . The MCU  130  sends signals O 1  to display screen  108 , O 2  to a buzzer  140  to indicate occlusion, end of infusion and unacceptable flow rate detected; O 3  to trigger thermal source  109  to emit at a desired time interval based on the expected flow rate of the fluid in the channel  213  or alternatively channel  242 . The input signal for the expected flow rate is made possible via the barcode signal J 3 . To conserve power consumption, a signal from the MCU  130  will control the power source  131  to operate intermittently. The power source  131  can be coupled to the MCU  130  via a voltage regulator. 
         [0067]    A software program is stored in a Flash Memory to work with the arithmetic logic unit (ALU) to generate the output signals O 1 , O 2 , O 3  and O 4 . O 4  represents a signal to display patient data when the barcode  212 , tagged to some patient data, is read by the barcode reading means  114 . Signals J 1  and J 2  are compared and a differential is referenced with a predetermined threshold giving an output O 2  when there is an occlusion. In the absence of occlusion, the time taken for J 2  to reach a trigger level will produce a signal O 1  which displays the flow rate in, for example, mL per hour. 
         [0068]    Referring to  FIG. 8 , in a method of detecting flow rate of intravenous fluid delivery system according to one embodiment of the present invention, the Flow Detection Unit  100  is powered on automatically when the Flow Cell  200  is inserted, e.g. inserted into an opening (or slot  103 ) of the Flow Detection Unit  100  or suitably attached to the Flow Detection Unit  100  (step  410 ). The MCU  130  then undergoes a reset (step  411 ) before activating the barcode reading means  114  to decode the nominal flow rate (Q.sub.N) and nominal volume (V.sub.N) at step  412 . The barcode  212  or alternatively  312  is decoded by the barcode reading means  114  to provide nominal flow rate data (Q.sub.N) as well as nominal volume (V.sub.N) for calculations to be performed by the MCU  130 . Data from the barcode  212  or alternatively  312  is decoded by blocking and transmitting IR light from the barcode reading means  114  during Flow Cell  200  insertion into the Flow Detection Unit  100 . Next, the MCU  130  checks whether the reading or data decoded from the barcode  212  or alternatively  312  is valid (step  413 ). For example, the MCU  130  comprises a checksum function to ensure that any dirt or blur on the barcode  212  or alternatively  312  area does not cause wrong readings. In the event such decoding fails or the data is not valid, manual input via the membrane switch  107  will be prompted (step  415 ). Otherwise, the display screen  108  would display automatically a mode selection option (step  414 ) for instantaneous flow rate (step  420 ) or mean flow rate (step  440 ) measurements. User then selects the desired mode by manipulating the membrane switch  107 . 
         [0069]    Referring to  FIG. 9A , the Flow Detection Unit  100  is programmed to display instantaneous flow rate (step  420 ). Next, the MCU  130  sets the initial instantaneous flow rate (Q.sub.i) to “null” (step  421 ) and sets the measurement variables by looking up the nominal flow rate (Q.sub.N) value from a reference table stored in the Flash Memory of the Flow Detection Unit  100  (step  422 ). The measurement variables comprises the duration the thermal source  109  is switched on (T.sub.IRON), the time interval between each measurement (T.sub.INT), the maximum time laps for detecting the presence of an occlusion (T.sub.EXP), the trigger level of temperature difference between T 1  and T 2  (T.sub.DIFF), and the constant for the calculating the instant flow rate (C.sub.Q). In embodiments where the Flow Cell  200  is predisposed with more temperature measurement locations along its fluid channel, additional permutations of T.sub.DIFF could be developed to further improve the accuracy of flow rate determination. 
         [0070]    When the measurement cycle starts (step  423 ), the thermal source  109  will be turned ON and OFF intermittently to emit heat pulses to the fluid in the channel  213 . In one embodiment, the thermal source  109  turns on for the duration of T.sub.IRON then turns off. The temperature difference (T.sub.DIFF) between the readings at thermal sensors  110  (T 2 ) and  111  (T 1 ) is measured and a timer starts to count time interval (T.sub.INT) for the start of the next measurement cycle (step  424 ), which helps to ensure that the measurements are taken at equal intervals. At step  425 , the measured temperature difference (T 2 −T 1 ) is compared against a predetermined trigger level (T.sub.DIFF) to confirm the existence of fluid flow versus occlusion. In other words, the MCU  130  checks whether the temperature difference between T 1  and T 2  exceeds the trigger level (T.sub.DIFF). 
         [0071]    If there is occlusion, the difference in the temperature readings taken by thermal sensors  110  and  111  will be below the trigger level (T.sub.DIFF), which activates the buzzer/alarm on the Flow Detection Unit  100 . A suitable display indicator, e.g. “OCCLUSION” will be shown on the display screen  108  (step  427 ). In one embodiment, the MCU  130 , at step  426 , checks whether the number of time laps, from the time the thermal source  109  turned on, has reached the maximum laps for occlusion detection (T.sub.EXP) before activating the buzzer at step  427 . In other words, the buzzer activates after the maximum waiting time had lapsed without the temperature difference (T 2 −T 1 ) reaching or exceeding the trigger level (T.sub.DIFF). 
         [0072]    In the absence of occlusion ( 430 ), the time taken for the temperature difference (T 2 −T 1 ) to reach the predetermined trigger level (T.sub.DIFF) will be measured (step  431 ) and stored as T.sub.LAP (step  431 ), and subsequent readings of this duration are taken (see  FIG. 9B ). In other words, the MCU  130  records the time lapsed or time duration from the moment the thermal source  109  is turned on until the temperature difference (T 2 −T 1 ) reached the trigger level (T.sub.DIFF), and sets the time lapsed as T.sub.LAP. Next, at step  432 , the instantaneous flow rate (Qi) is calculated as Qi=T.sub.LAP.times.C.sub.Q. The number of measurement cycle completed is represented as N=N+1, where initially N is defined as zero. A timer in the Flow Detection Unit checks whether the measurement time has reached the selected T.sub.INT (step  433 ), which helps to control the measurement interval. If the interval has reached a preset value of T.sub.INT, the measurement cycle restarts at step  423  in  FIG. 9A . The measurement intervals are optimized to the timing of the pulses emitted by thermal source  109 , and different nominal flow rate (Q.sub.N) entry registered by the MCU will result in different measurement intervals. 
         [0073]    Referring to  FIG. 10A , the Flow Detection Unit  100  is programmed to display mean flow rate (Q.sub.M) (step  440 ). Next, at step  441 , the nominal volume (V.sub.N) is defined either by reading the barcode  212  or alternatively barcode  312  at step  412  ( FIG. 8 ) or manually input by the user at step  442 . Furthermore, manual input allows user to set the nominal volume (V.sub.N) in case of an invalid reading of the barcode  212  by the barcode reading means  112 . The MCU  130  then sets the variables at step  443 , which comprises the number of completed measurements (N), nominal time (T.sub.N), total volume delivered (V.sub.D), volume delivered within one completed measurement cycle (Vi), instant flow rate (Qi), mean flow rate (Q.sub.M) and the accumulated instant flow rate (Q.sub.ACC). Subsequently, the MCU  130  sets the measurement variables T.sub.IRON, T.sub.INT, T.sub.EXP, T.sub.DIFF, C.sub.Q, and C.sub.V (constant value for calculating the volume delivered within one completed measurement cycle), which are retrieved by looking up T.sub.N from a reference table stored in the Flash Memory of the Flow Detection Unit  100  (step  444 ). The algorithm developed is clearly not restricted to the use of the measurement of variables described above. The presence of more sensors and their locations relative to the heat source or sources will allow other permutations in the development of the algorithm for flow rate detection. For example, the determination of flow rates could be realized by comparing the variables or its derivatives or combinations of such resulting from a specific fluid flow with predetermined values established for known flow rates in a table. Referring to  FIG. 6E , a 20 m L/hour fluid flow would manifest varying T.sub.Lap as well as temperature amplitudes, when measured at different sensor locations in a flow cell using four thermal sensors which, generate four temperature readings T 1 , T 2 , T 3  and T 4 . These recordings could form inputs for developing an algorithm. For example, in situations where the flow rate is relatively fast, e.g. 100 mL/Hour, or relatively slow, e.g. 1 mL/Hour, it is possible that the temperature of the location at which one of the sensors is disposed is too close to or too far from the thermal source, and temperature measurements at this location may not be able to detect a clear signal. Embodiments with more sensors disposed at different locations along the fluid channel, provide solutions to enable temperature measurements at multiple locations. Shown in  FIG. 6E  as an example, multi-location measurement of temperature generates temperature difference comparison curves with respect to a reference location. This provides data to the Flow Detection Unit to record temperature measurements with meaningful readings for the purpose of flow rate detection and monitoring. 
         [0074]    Referring back to  FIG. 10A , at step  445 , the thermal source  109  will be turned ON and OFF intermittently at the start of the measurement cycle. The subsequent steps  446 - 450  shown in  FIG. 10B  are similar to steps  424 - 427  of  FIGS. 9A and 431  of  FIG. 9B , and thus will not be described. 
         [0075]    Next, at step  451 , the volume delivered (V.sub.D) is compared against 75% of the nominal volume (V.sub.N). The mean flow rate (Q.sub.M) is the arithmetic mean of the all instantaneous flow rate (Qi) readings obtained as described above if the volume delivered (V.sub.D) is less than 75% of the nominal volume (V.sub.N) (step  452 ). The total volume delivered (V.sub.D) since the start of the first measured is also calculated. By definition, the mean flow rate (Q.sub.M) shown will change when each subsequent reading of instantaneous flow rate (Qi) changes. 
         [0076]    When the volume delivered (V.sub.D) exceeds 75% of the nominal volume (V.sub.N) (step  453 ), the mean flow rate (Q.sub.M) displayed will be the cumulative volume over time. The cumulative volume is the sum of each unit of volume that is derived from the instantaneous flow rate (Qi) and the time interval (T.sub.INT) between each of these readings. The result of this is that the mean flow rate (Q.sub.M) displayed will approach a value that eventually represents the volume delivered (V.sub.D) over time. The total volume delivered (V.sub.D) since the start of the first measured is also calculated. One of the considerations in selecting a 75% threshold volume is that it corresponds to definition of mean flow rate in the International Organization for Standardization ISO 28620. By definition, averages of instantaneous flow rate (Qi) during the initial 75% of volume delivered (V.sub.D) will show more fluctuations in the readings. It can be appreciated that other threshold volume levels, such as 70% or 80% may be applicable. 
         [0077]    At step  461 , the MCU  130  checks if a DC motor module is attached to the flow rate regulating mechanism  230 . If the DC motor module is available, the MCU checks whether any flow rate adjustment is required (step  462 ) based on Q.sub.M, T.sub.INT, N, and V.sub.D and calculates the number of turns and direction of turns for the DC motor (step  463 ) to, for example, adjust the axle  231  of the flow rate regulating mechanism  230 . 
         [0078]    If no DC motor module is available, the MCU  130  proceeds to determine whether the infusion is complete. For example, at step  464 , the difference between the nominal volume (V.sub.N) and volume delivered (V.sub.D) is compared with a threshold level of, for example, 10 ml. If the difference of V.sub.N and V.sub.D is less than 10 ml, the buzzer is turned on and the display screen  108  indicates “Infusion Completed” (step  465 ). The remaining volume of medication fluid can be considered as residue volume. On the other hand, if the difference is more than 10 ml, the timer checks whether the measurement has reached the selected time interval T.sub.INT (step  466 ), which helps to control the measurement interval. If the interval has reach T.sub.INT, the measurement cycle restarts at step  445  in  FIG. 10A . 
         [0079]    It can be appreciated that the algorithm used may differ according to specific needs as it also relates to the performance characteristics of the fluid pump to which the device is attached and as such does not limit the scope of the invention. Furthermore, several embodiments of the invention have thus been described. However, those ordinarily skilled in the art will recognize that the invention is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims that follow.