Patent Publication Number: US-2009217982-A1

Title: Adjustable flow controllers for real-time modulation of flow rate

Description:
BACKGROUND 
     This disclosure relates to flow regulators designed to ensure substantially constant flow rate through a conduit, tube, or pipe, etc. 
     SUMMARY 
     Clamps to be used in conjunction with real-time or about real-time measurement of the flow rate of a fluid through a lumen. The clamps allow for more precise control over the flow rate and therefore over the volume of fluid. When the flow rate is determined to be too fast, the clamps are expanded, which slow down the flow rate. Conversely, when the flow rate is determined to be too slow, the clamps are contracted, which increases the flow rate. Additionally, if an error state is observed, the clamps may arrest flow, thereby preventing further delivery of fluid. 
     According to a feature of the present disclosure, a device is disclosed comprising a vessel for transporting a fluid, an expandable member disposed with the vessel for transporting the fluid, a pressure controller for modulating the pressure within the expandable member, and a microprocessor for calculating a calculated flow rate. The pressure in the pressure in the expandable member is modulated to control the flow rate of the fluid through the vessel. Moreover, the modulation is determined at least based on data provided from the calculated flow rate. 
     According to a feature of the present disclosure, a method is disclosed comprising providing a vessel for transporting a fluid, an expandable member disposed with the vessel for transporting the fluid, a pressure controller for modulating the pressure within the expandable member; and a microprocessor for calculating a flow rate of the fluid. The pressure in the expandable member is modulated to control the flow rate of the fluid through the vessel and the modulation is determined at least based on data provided from the calculated flow rate. 
     According to a feature of the present disclosure, a method is disclosed comprising measuring the flow rate of a fluid within a vessel for transporting the fluid in about real time and modulating the expansion of an expandable member disposed with the vessel for transporting the fluid to change to flow rate of the fluid through the vessel based at least in part on the measured flow rate. 
    
    
     
       DRAWINGS 
       The above-mentioned features and objects of the present disclosure will become more apparent with reference to the following description taken in conjunction with the accompanying drawings wherein like reference numerals denote like elements and in which: 
         FIG. 1  is side sectional view of embodiments of the devices of the present disclosure disposed within a vessel connected to a pressure controller; 
         FIG. 2A  is a side sectional view of embodiments of the devices of the present disclosure introduced into a lumen through an auxiliary lumen; 
         FIG. 2B  is a side sectional view of embodiments of the devices of the present disclosure introduced into a lumen from an auxiliary lumen where an expandable member is build directly into the auxiliary lumen; 
         FIG. 2C  is a side sectional view of an embodiment of the device of  FIG. 2B  illustrating expansion of an expandable member to prevent flow through the lumen; 
         FIGS. 3A and 3B  are top sectional views of an embodiment of the device of  FIG. 1  disposed within a vessel in an unexpanded state ( FIG. 3A ) and an expanded state ( FIG. 3B ); 
         FIG. 4  is a side sectional view of an embodiments of a clamp of the present disclosure disposed around a lumen whereby expansion of the clamp causes the lumen to compress against a block thereby restricting flow; 
         FIG. 5A through 5C  are graphs of embodiments of theoretical and actual flow volume of a finite fluid source over time in which the balloon clamp is in operation; and 
         FIG. 6  is a flow diagram of embodiments of use of balloon clamps in a system measuring about real time flow rates of fluids flowing through a lumen. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of embodiments of the invention, reference is made to the accompanying drawings in which like references indicate similar elements, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical, biological, electrical, functional, and other changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. As used in the present disclosure, the term “or” shall be understood to be defined as a logical disjunction and shall not indicate an exclusive disjunction unless expressly indicated as such or notated as “xor.” 
     As used in the present disclosure, the term “real time” shall be defined as real time or lagging real time only by the time taken to compute a measurement, provided the measurement computed reasonably approximates the state of at the beginning of the measurement process and at the end of the measurement process. 
     As used in the present disclosure, the term “expansion” shall be defined as the ability of the expandable members of the present disclosure to increase or decrease in volume. 
     As used in the present disclosure, the term “contract” shall be defined as the decrease in volume of the expandable members of the present disclosure. 
     As used in the present disclosure, the term “modulate” shall be defined as changing the volume of an expandable member to effect a change in volume of the expandable member to a desired, determined, calculated, or predetermined volume. “Modulate” encompasses both increases in volume as well as decreases in volume. 
     According to embodiments of the present disclosure and as shown in  FIG. 1 , clamp system  100  is shown. Clamp system  100  comprises, according to embodiments, expandable member  110  which is disposed substantially within vessel lumen  122  of vessel for transporting fluid  120 . Expandable member  110  is connected to pressure controller  114  via conduit  112 . 
     According to embodiments, vessel for transporting fluid  120  comprises piping or tubing. For example and according to embodiments, vessel for transporting fluid  120  may comprise surgical tubing used to deliver to patients pharmacological agents and other similar excipients. 
     Expandable member  110  is a compliant material, such as a balloon. When a gaseous or liquid substance is added to or removed from expandable member  110 , expandable member  110  increases or decreases in volume, respectively due to pressure changes. Expandable member  110  may be made from silicon, urethane, polyisoprene, or rubbers, for example. 
     According to embodiments, expandable member  110  is substantially enclosed within lumen  122  of vessel for delivering fluid  120 , except where pressure controller  112  connects with expandable member  110 . The interior of expandable member  110 , conduit  112 , and pressure controller  114  are in fluid or gaseous communication. Conduit  112  comprises tubing, piping, or other similar devices that allow pressurized gas or fluid to be transferred from pressure controller  112  to expandable member  110 . According to embodiments, conduit  112  is pressurizable tubing. Artisans will readily appreciate that the choice of material for conduit  112  may be nearly any device that facilitates the movement of pressurized gas or liquid. 
     Conduit  112  crosses through the wall(s) of vessel for transporting fluid  120  and connects to expandable member  110 . Vessel for transporting fluid  120  is sealed at the point where pump conduit  112  crosses through the wall(s) to prevent the fluid being delivered through vessel for transporting fluid  120  from leaking out of vessel for transporting fluid  120 , according to embodiments. A sealant, for example silicon or other biocompatible sealants known to artisans, may be applied to seal the wall(s) of vessel for delivering fluid  120  against leakage at the point where conduit  112  crosses. 
     According to embodiments, and as illustrated in  FIG. 2A , a ‘Y’ valve may be used instead of causing conduit  112  to pass through the wall of vessel for transporting fluid  120 , whereby expandable member  110  is introduced at the junction of the ‘Y’ and conduit  112  is disposed in one of the “arms” of the ‘Y.’ For example, as illustrated in  FIG. 2A , expandable member  110  and conduit  112  are inserted through one of the arms of the ‘Y.’ Through the other arm of the ‘Y’ and through the stem of the ‘Y’ the fluid flows through vessel for transporting fluid  120 . 
     According to variant embodiments and as illustrated in  FIG. 2B , expandable member  110  is directly connected to the lumen wall(s) one of the arms of the ‘Y.’ The arm of the ‘Y’ therefore comprises at least a portion of conduit  112  rather than a separate conduit as illustrated in  FIG. 2A . 
     According to embodiments, clamp system  100  provides for a “clamping” action within lumen  112  of vessel for transporting fluid  120  as illustrated generally in  FIGS. 2-3 . Specifically as illustrated in  FIG. 3A , expandable member  110  is in an state whereby fluid being transported through vessel  120  is relatively unimpeded because it occupies a relatively small cross-section of lumen  122 . Artisans will appreciate that expandable member  110  may be hooked to a vacuum source, whereby the volume of expandable member  110  is minimized when in a contracted state by reducing the volume as much as possible, thereby allowing a greater volume of fluid to flow by expandable member  110  through vessel for transporting fluid  120 . 
     When the flow rate of the fluid flowing through vessel for transporting fluid  120  is too great, the flow rate may be reduced by increasing the volume of expandable member  110 . As the volume of expandable member  110  increases, the flow rate of the fluid being transported through vessel for transporting fluid  120  decreases as expandable member  110  occupies an increasing percentage of the cross-sectional area of lumen  122 . According to embodiments, flow may be completely impeded by expanding the volume of expandable member  110  to occupy 100% of the cross-sectional area of lumen  122 , as illustrated in  FIG. 3B . 
     Likewise, as pressure controller  114  increases pressure within expandable member  110  of  FIG. 2C , expandable member  110  expands. Expandable member  110 , according to embodiments, is able to occupy relatively little of the cross-sectional diameter of lumen  122  as illustrated in  FIG. 2B  or occupy up to the entire cross-sectional diameter of lumen  122  and arrest flow of fluid through vessel for transporting fluid  120  completely, as illustrated in  FIG. 2C . 
     According to embodiments, pressure controller  114  comprises a pump/valve system. The pump increases pressure in expandable member  110 . A valve system or second pump is used to decrease the pressure in expandable member  110 . Valve systems may have incorporated into them flow restrictors to better regulate the amount of pressure removed from expandable member  110 . 
     According to embodiments, pressure controller  114  comprises a lead screw system. As the screw turns pressure is increased or decreased in expandable member  110 , depending on the direction the screw turns, thereby increasing the volume or decreasing the volume of expandable member  110 , respectively. Lead screws and their application as a pressure controlling mechanism are well known to artisans. 
     Likewise according to embodiments, pressure controller  114  comprises pressurized reserves of gas or fluid together with a valve system. When expandable member  110  needs expansion, a valve is opened between expandable member  110  and a pressurize reservoir, causing expandable member  110  to expand as pressure increases. When expandable member  110  needs to contract, a valve is opened to the ambient environment, allowing pressure in expandable member  110  to decrease, thereby reducing the volume of expandable member  110 . 
     According to embodiments, the clamps of the present disclosure comprise expandable member  110  disposed outside of vessel for transporting fluid  120 . Accordingly, expandable member  110  comprises a collar-like apparatus around vessel for transporting fluid  120 , which operates by reducing cross-sectional area of vessel for transporting fluid  120  for the exterior. According to these embodiments, flow is controlled by reducing the cross-sectional flow area by the wall of lumen  122 —as flow is reduced expandable member  110  is increased in volume, which presses against the wall of lumen  122  thereby “squeezing” the wall in towards the center of lumen  122  and reducing the cross-sectional flow area. Advantageously, disposing expandable member  110  outside of vessel for transporting fluid  120  prevents gas from entering the flow path in the event of a malfunction. 
     According to similar embodiments and as illustrated in  FIG. 4 , within lumen  122  of vessel for transporting fluid  100  is block  130 . Block  130  comprises a member that expandable member  110  may constrict against when expanded to prevent flow of fluid through vessel for transporting fluid  120 . Block  130  may comprise a bearing or other solid implements within vessel for transporting fluid  120  that is able to remain substantially stationary within vessel for transporting fluid  100  and allow flow of fluid around it. 
     According to the embodiment illustrated in  FIG. 4 , as expandable member  110  expands, the cross-sectional diameter of vessel for transporting fluid  120  is reduced as it is constricted by expandable member  110 , thereby reducing flow through vessel for transporting fluid  120 . According to embodiments, expandable member  110  comprises rigid components as well as the compliant expandable components. The rigid components may serve as the external portions of expandable member  110  and the compliant components are disposed against the outer wall of vessel for transporting fluid  120 . Thus, when the pressure of expandable member  110  increases, expansion of the expandable member  110  occurs only at the wall of vessel for transporting fluid  120 , thereby effecting changes to the cross-sectional diameter of vessel for transporting fluid  120  at the site of expandable member  110 . Thus, flow rate of the fluid flowing through vessel for transporting fluid  120  is modulated. According to embodiments, as expandable member  110  further expands, it eventually causes the walls of vessel for transporting fluid  100  to press against block  130 , thereby cutting off or substantially cutting off flow of the fluid through vessel for transporting fluid  120 . 
     As illustrated in  FIGS. 5A and 5B , the clamp devices of the present disclosure provide a platform to ensure relatively constant flow rate from a fluid source. According to embodiments and as shown in  FIG. 5A , a theoretical fluid delivery is illustrated. 
     The devices of the present disclosure allow for relatively constant flow rate by adjusting the volume of the expandable member to either increase or decrease flow rate, as needed to compensate for inherently variable flow rates due to operation or design of pumps, head-heights, or theoretical flow models having variable flow rates, for example or as illustrated in  FIG. 5B . By observing flow rate in real time or about real time, a determination is made as to whether the flow rate is occurring as desired, in which no change to the clamps would be made; flow rate is too slow, in which the balloon clamp would be adjusted to a less expanded state; or flow rate is too fast, in which the balloon claim would be adjusted to a more expanded state. The result of adjusting pressure within the balloon and therefore volume of the balloon is an increase or decrease in the cross-sectional area through which flow occurs. 
     The devices of the present disclosure are able to substantially approximate nearly any desired flow curve or model, including the linear model illustrated in  FIG. 5A . Thus, the devices of the present disclosure are useful for nearly any application whereby flow rate varies over time. 
     According to embodiments, an apparatus, such as a microprocessor may be used to monitor the flow rate and automatically change the volume of the expandable member to adjust the flow rate to model the theoretical flow rate of  FIG. 5A . According to embodiments, such adjustments are shown in  FIG. 5B . According to  FIG. 5B , flow rate assume a step-wise type flow. The “steps” in  FIG. 5B  represent changes in the flow rate of the fluid flowing through the vessel for transporting fluid  112  due to adjustments in the volume of the expandable member  110  depending on whether the observed flow rate is too fast or too slow. If too fast, the volume of the expandable member is increased and if too slow, the volume of the expandable member is decreased. Because the flow rate from the pump source may fluctuate or be non-linear over time, adjustments are made throughout the flow process to achieve a desired degree of flow accuracy. As shown in  FIG. 5B , artisans will readily appreciate that the steps as shown are much larger than is likely in actual practice to illustrate the principle. Moreover, the horizontal and vertical slopes are only exemplary to clearly show in the illustration how step-wise changes can approximate a desired flow curve and is not intended to be limited in any way. 
     Indeed,  FIG. 5C  is exemplary of the use of the clamps and feedback mechanisms of the present disclosure to more closely mimic a desired flow curve. As illustrated in  FIG. 5C , a desired flow rate is illustrated by the broken line. The actual flow rate is shown with a solid line. The dashed lines between the x-axis and the actual flow rate line each represent a period of time. Initially, the actual flow rate was too slow as not enough volume of source fluid is delivered during the first interval as desired. Consequently, the volume of expandable member  110  was reduced, which increased the cross-sectional area of vessel for transporting fluid  120  allowing more fluid to pass expandable member  110  per unit time. 
     Over the second time interval, flow rate closely mirrored the desired flow rate (the slope of the desired and actual flow rates are the same), but the total volume of fluid delivered continued to lag the desired amount of fluid delivered at the end of time interval two (because the actual flow rate line is above the desired flow rate line at the end of time interval two). Thus, the volume of expandable member  110  was again reduced to increase flow rate and move the overall volume delivered towards the desired volume to be delivered. 
     At the end of time interval three, the total volume delivered was the same as the desired total flow volume delivered. It will also be observed, however, that the actual flow rate is greater than the desired flow rate. According to the exemplary embodiment, the measurement of total volume was determinative of whether the volume of expandable member  110  was varied. Thus, according to the exemplary embodiment, no adjustment to expandable member  110  was made at the end of time interval three. Artisans will readily appreciate that flow rate over time interval three or any other arbitrary interval may be used instead of total volume delivered at the end of any time interval to determine adjustments to expandable member  110 . 
     Because no adjustment was made to expandable member  110  at the end of time interval three, the flow rate remained the same throughout time interval four. Thus, at the end of time interval four, the total volume delivered was greater than desired due to the more rapid than desired flow rate. Thus, the volume of expandable member  110  was increased to reduce the cross-sectional area of vessel for transporting fluid thereby reducing the flow rate. At each time interval, the flow volume was measured and the volume of expandable member  110  was adjusted accordingly to more closely follow the desired flow volume of time. According to embodiments, depending on the difference between the desired flow rate and the actual flow rate, the amount by which the volume of expandable member  110  is adjusted is variable, thereby allowing the system and method to more rapidly approximate the desired flow at the end of the next time interval. Likewise, if enough computing power is present, a database of flow values may be used to both store and lookup the correct adjustment at any time interval based on the flow rate from the prior time periods; similarly, mathematical algorithms may accomplish the same objective. When the time intervals are small enough, over long periods of time, the desired flow rate is closely approximated by using expandable members  110  of the present disclosure. The principles of closely approximating a theoretical flow rate is more clearly understood in combination with the methods illustrated in  FIG. 6 . 
       FIG. 6  is a flow chart of embodiments of methods of the present disclosure whereby the clamps disclosed herein are utilized together with a pump system having the ability to measure flow rate in real time or about real time. The methods disclosed herein may be automated with a simple microprocessor. In operation  600 , flow rate is measured. The measurement of flow rate may occur in real time or about real time in cases where the fluid cannot be contacted directly to measure flow. For example, the pumps that do not contact the fluid are described in U.S. Pat. No. 7,008,403, the teachings of which are hereby incorporated by reference. 
     According to embodiments, a determination is made as to whether a malfunction state exists. A malfunction state may be, for example, detected if the flow rate is determined to be outside of a range of permissible flow volumes or if the a pump malfunctions thereby causing unpredictable flow of the fluid through vessel for transporting fluid. In drug delivery scenarios, errors occur where unexpected flow of therapeutic agents is a considerable safety concern. For example, the administration of insulin is a particularly sensitive process and must be dosed in a relatively narrow range as a matter of safety. If a malfunction state is detected in operation  602 , pressure in the expandable member  110  is immediately increased to arrest flow or minimize flow of the fluid flowing through vessel for transporting fluid  120  in operation  604 . 
     However, if a malfunction state is not detected, the flow rate is compared to a desired flow rate in operation  606 . If the flow rate as measured in operation  600  is the same as the desired flow rate at a given time interval (actual flow=desired flow rate) no adjustments are made to expandable member  110  and the flow rate is measured again in the next iteration of the method. 
     If the flow rate is measured to be less than the desired flow rate at a given time interval in operation  606 , (actual flow rate&lt;desired flow rate) then the pressure is decreased in expandable member  110  in operation  608 , which causes expandable member  110  to contract. Conversely, if the measured flow rate is greater than the desired flow rate in operation  606 , then the pressure in expandable member  110  is increased to expand and thereby slow the flow rate in operation  610 . The amount of pressure increase or decrease in expandable member  110  may occur in small increments to slowly expand or contract expandable member  110  over a plurality of iterations of the method, according to embodiments. So doing allows fine tune control over the system and, once the desired flow rate is achieved, the small increments allow for adjustments that closely approximate the theoretical or desired flow rate, as illustrated in  FIG. 5C . 
     According to embodiments, the degree to which expandable member  110  is expanded may be determined using a table of lookup values representing pressure changes for expandable member  110  based on the difference between the actual and theoretical flow rates. Thus, if the flow volume is largely divergent of the desired flow volume, the expandable member  110  is expanded by a larger increment, which allows expandable member  110  to arrive at a level of expansion causing the desired flow rate more rapidly. 
     According to other embodiments, expandable member  110  may be designed to have a small plurality of predetermined expansion states. Although these expansion states may not be capable of exactly effecting the desired flow rate, the system will expand and contract expandable member  110  rapidly over time based on the real time flow feedback to deliver the fluid on average commensurate with the desired flow rate. Thus, according to these embodiments, by expanding and contracting expandable member  110  rapidly, the desired flow rate is approximated, for example as shown by the graph in  FIGS. 5B and 5C . 
     As illustrated in  FIG. 5C , as the actual flow rate (solid line) is compared to the theoretical flow rate (dashed-solid line) at time intervals shown by the vertical dotted lines (operation  606  of  FIG. 6 ), the actual flow rate is observed to be greater than the theoretical flow rate (for example, time interval  1 ), equal to the theoretical flow rate (for example, time interval  3 ), or less than the theoretical flow rate (for example, time interval  4 ). 
     Correspondingly, along the x-axis there is shown the action taken based on the comparison of operation  606 . Where there exists a dash (-), the actual flow rate is determined to be approximately the same as the desired flow rate and no adjustment is made to the volume of expandable member  110 . In cases with an down arrow (↓), the actual flow rate is too slow compared to the desired flow rate and pressure in expandable member  110  is decreased in operation  610  to increase the actual flow rate. Similarly, in the cases having a up arrow (↑), the actual flow rate is too rapid compared to the desired flow rate and pressure in expandable member  110  is therefore increased in operation  608  to decrease the actual flow rate. 
     According to embodiments, the microprocessor compares actual volumes delivered over time rather than flow rate, which requires greater processing time and power. At certain time intervals where it is determined the actual flow volume equals the theoretical flow volume, the actual flow rate is in fact different from the theoretical flow rate at these points (see around time interval  2 ) as illustrated by the different slopes of volume over time. However, according to embodiments, the microprocessor only calculates volumes or calculates flow rate from time zero to the chosen interval (e.g., time interval  2  where the flow rate over the entire time is equal in both the theoretical and actual instances because the same volume has been delivered over the same time interval) and is unable to perceive whether the flow rate is too fast or two slow. Therefore, the system “waits” until the next iteration where the actual flow volume is observed to be different from the theoretical flow volume to make an adjustment. According to the graph, in time interval  3 , this change is finally observed and the pressure in expandable member  110  is decreased as the actual rate was too slow through time interval  2 . 
     According to other embodiments, the microprocessor calculates and compares flow rates. Accordingly, expandable member  110  is only unadjusted when the both instantaneous flow rate and the total flow volume equal the desired flow rate and total flow volume at a given interval, respectively. Otherwise, adjustments to expandable member  110  are made. For example, at a given time interval, microprocessor may determine that the flow rate (slope in the graphs of  FIG. 5 ) is equal to the desired flow rate at the given time interval. However, due to previous pump variations and corrections in expandable member, the total volume delivered from the start through that time interval is less than the volume theoretically delivered. Thus, at the given time interval, although the flow rate models the desired flow rate, the flow rate will be increased by adjusting expandable member to make up for the difference between the actual volume delivered and the desired volume to be delivered at that time interval. Similarly, the actual volume delivered may equal the desired flow volume delivered at a given time interval but the flow rate will not equal the desired flow rate (i.e., in the next time interval, both the flow rate and the total volume delivered will be divergent from the desired values unless and adjustment is made to expandable member  110 ). In both cases, adjustments must be made to expandable member  110  to approximate the desired flow over time. 
     According to embodiments, microprocessor may also be configured to determine whether flow is outside a predetermined set of tolerances. For example, as illustrated in  FIG. 5C , flow must remain within the dashed tolerance lines shown parallel to the desired flow rate line. If flow is detected to be outside of these tolerances, microprocessor immediately increases the volume of expandable member to arrest flow. 
     While the apparatus and method have been described in terms of what are presently considered to be the best mode, it is to be understood that the disclosure need not be limited to the disclosed embodiments. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the claims and the principles disclosed herein, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures. The present disclosure includes any and all embodiments of the following claims.