Abstract:
A novel enhanced stopcock is disclosed, as well as related methods, that safely controls flow of flow materials from a pump. Pump fills a first chamber, from which a second chamber is filled. Flow material is dispensed from the second chamber when the stop cock is moved to a different position wherein it is no longer in fluid communication with the first chamber. Pressure sensors disposed in fluid communication with first and second chambers are used to determine the volume of flow material dispensed.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the Paris Convention priority and incorporates by reference U.S. Provisional Patent Application Ser. No. 61/097,492, filed Sep. 16, 2008 and entitled “Flow Regulating Stopcocks and Related Methods.” 
     
    
     BACKGROUND 
       [0002]    This disclosure relates to devices and methods for the regulation of the flow of flow materials, as well as features to prevent undesired flow. 
       SUMMARY 
       [0003]    A novel enhanced stopcock is disclosed, as well as related methods, that safely controls flow of flow materials from a pump. A pump fills a stopcock, which then dispenses to a target. Flow material is dispensed from the second chamber when the stop cock is moved to a different position wherein it is no longer in fluid communication with the first chamber. Pressure sensors disposed in fluid communication with first and second chambers are used to determine the volume of flow material dispensed. 
         [0004]    According to a feature of the present disclosure, a device is disclosed comprising a stopcock device having a first chamber, a first compressible member disposed in the first chamber, a stopcock having a second chamber for holding aliquots of flow material to be dispensed, a second compressible member disposed in the second chamber, and a first pressure sensor. The second chamber is filled with flow material from first chamber when stopcock is in a first position and the stopcock device only dispenses flow material when the stopcock is in the second position that is not in fluid communication with the first chamber. 
         [0005]    According to a feature of the present disclosure, a method is disclosed comprising providing a stopcock device having a first chamber, a first compressible member disposed in the first chamber, a stopcock having a second chamber for holding aliquots of flow material to be dispensed, a second compressible member disposed in the second chamber, and a first pressure sensor. The second chamber is filled with flow material from first chamber when stopcock is in a first position and the stopcock device only dispenses flow material when the stopcock is in the second position that is not in fluid communication with the first chamber. 
         [0006]    According to a feature of the present disclosure, a method is disclosed comprising positioning a stopcock into a first position whereby a first chamber and a second chamber are in fluid communication, positioning the stopcock into a second position whereby the first chamber and the second chamber are not in fluid communication and whereby the second chamber is in fluid communication with a dispensing conduit, measuring the pressure in the second chamber with a first pressure sensor; and calculating the flow rate in about real time. 
     
    
     
       DRAWINGS 
         [0007]    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: 
           [0008]      FIG. 1  is a schematic view of an embodiment of the stopcock device of the present disclosure; 
           [0009]      FIG. 2  is a perspective view of an embodiment of the stopcock device of the present disclosure as a first chamber is being filled; 
           [0010]      FIG. 3  is a cross-sectional view of an embodiment of the stopcock of the present disclosure as a second chamber is filled with a flow material; 
           [0011]      FIG. 4  is a cross-sectional view of an embodiment of a stopcock of the present disclosure in a closed position; 
           [0012]      FIG. 5  is a cross-sectional view of an embodiment of a stopcock of the present disclosure in a dispensing position whereby flow material is dispensed; 
           [0013]      FIG. 6  is a flow diagram of an embodiments of a method for dispensing flow materials using the stopcock device of the present disclosure; and 
           [0014]      FIG. 7  is a block diagram of an embodiment of a processing system of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    In the following detailed description of embodiments of the present disclosure, 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 present disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present disclosure, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical, functional, and other changes may be made without departing from the scope of the present disclosure. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present disclosure 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.” 
         [0016]    As used herein, the term “real time” shall be understood to mean the instantaneous moment of an event or condition, or the instantaneous moment of an event or condition plus short period of elapsed time used to make relevant measurements, optional computations, etc., and communicate the measurement, computation, or etc., wherein the state of an event or condition being measured is substantially the same as that of the instantaneous moment irrespective of the elapsed time interval. Used in this context “substantially the same” shall be understood to mean that the data for the event or condition remains useful for the purpose for which it is being gathered after the elapsed time period. 
         [0017]    As used herein, the term “compressible member” shall be understood to mean devices that cause a gas or fluid to be compressed when a gas or fluid is placed into a chamber where the compressible member is disposed. Examples of compressible members include, for example, closed cell foams, elastomeric diaphragms, pistons, and secondary chambers charged with a fixed volume of gas, wherein when a gas or fluid is placed into the chamber in which the compressible member is disposed, the gas or fluid in the compressible member compresses. 
         [0018]    The present inventor has discovered a device and method for preventing inadvertent flow of flow materials from a pump. The device comprises a stopcock having a chamber built in that is charged with aliquots of flow material. The stopcock is moved from a first position that is used for charging (filling) the stopcock into at least a second position that is configured for dispensing the stored aliquots of flow material. One or more pressure sensors are disposed to measure, in real time, the pressure of the chambers holding the flow materials, thereby deriving the volume of flow material dispensed from the stopcock device. Because flow volumes and the elapsed time are also know, the flow rate of the dispensed flow material may be calculated, according to embodiments. Temperature sensors may similarly be disposed to improve the accuracy of the calculations used to measure the flow volume or rate. 
         [0019]    According to embodiments, stopcock device  100  is illustrated generally in  FIG. 1 . Stopcock device  100  comprises first chamber  110 , stopcock  150 , and conduits placing first chamber  110  and stopcock  150  into fluid communication and allowing for dispensing of the flow material. Stopcock is connected to positioning device  158 , which positions stopcock  150  into one of a plurality of positions for at least charging chambers within stopcock with flow material and into position for dispensing flow material. Within stopcock  150  is at least one second chamber  152  and corresponding second chamber conduit  154 . According to embodiments, first pressure sensor  120  and second pressure sensor  122  are disposed at locations in stopcock device  100  that allow for the accurate measurement of the pressure of first chamber  110  and second chamber  152 , thereby allowing calculation of flow volume and flow rates of flow materials based on change of pressure calculations, as described in detail below. 
         [0020]    A computer performs the relevant calculations. The computer comprises at least a timing device for measuring elapsed time, which may comprise a clock or a timer, for example; devices to receive input from the pressure sensors, temperature sensors, and users; and a processor for performing the calculations disclosed herein. 
         [0021]    First chamber  110  is a chamber of known volume. According to embodiments, first chamber  110  volume comprises first chamber  110  and first chamber/stopcock conduit  132 . According to embodiments, first pressure sensor  120  is disposed such that it is in at least gas communication with first chamber  110  or first chamber/stopcock conduit  132 , depending on the components of the present disclosure comprising first chamber  110 . Fill conduit  130  comprises a conduit for filling first chamber  110  with a flow material. Conduits may comprise any conventional device used to sealably transport gases or flow materials, for example pipes, tubes, or other conduits defined by a sealed body terminating in one or more open ends through which a flow material or gas enters and exits the interior of the sealed body. 
         [0022]    According to embodiments, first chamber  110  comprises a chamber having a quantity of gas contained in a compressible member. Filling of first chamber  110  does not displace gas; in other words, the net number of gas molecules remains constant as flow material fills first chamber  110 , thereby pressurizing the gas as the volume of the gas decreases. This may be accomplished by installing a one way value, such as a check valve, as part of fill conduit  130 . The exact amount of gas does not need to be known, provided the differential pressure can be measured and the total volume of first chamber is known. 
         [0023]    According to embodiments, gas in first chamber  110  may be contained in a secondary chamber (i.e., the compressible member). The secondary chamber comprises, according to various embodiments, a gas “pillow” formed from a flexible diaphragm that compresses when flow material fills first chamber  110 ; a movable, sealed divider (e.g., a piston) that compresses when flow material fills first chamber  110 , etc. According to embodiments, gas may also be contained in a closed cell foam that occupies substantially all or part of first chamber  110 . 
         [0024]    In each of these embodiments, the compressed gas will exert pressure on the flow material whereby flow material will flow into second chamber  152 , as described below. According to embodiments, in addition to, or instead of pressure, gravity or a pump such as a lead screw may be used to move flow material from first chamber to second chamber  152 , as described below. 
         [0025]    According to embodiments and as illustrated in  FIG. 1 , first chamber  110  has disposed therein compressible member  112 . According to embodiments, compressible member  112  comprises closed cell foam. Compressible member  112  may also comprise rubber or another compressible material that effects a differential gas pressure in first chamber  110  when first chamber  110  is charged with flow material verses when first chamber  110  is not charged with flow material. According to embodiments, compressible member  112  comprises a pocket of air contained within a compressible bag or “pillow.” According to embodiments, compressible member is disposed in first chamber  110  to ensure sufficient pressure to move the last amount of flow material from first chamber  110  to second chamber  152 . 
         [0026]    According to other embodiments, compressible member is not used, as described above. Indeed, as flow material is put into first chamber  110 , the flow material is under pressure or delivered through a one-way valve. Thus, flow material will naturally flow from first chamber  110  to second chamber  152  due to the pressure exerted by the gas that is pressurized as first chamber  110  is filled. 
         [0027]    Because the gas or closed cell foam will tend to equalize flow material moves out of first chamber, the last amount of flow material will be difficult to remove. Removal of this last amount of flow material may be accomplished by placing the gas in first chamber  110  under pressure initially, according to embodiments. According to other embodiments, closed cell foam will mechanically tend to removed this last amount of flow material in much the same way as the foam relaxes into substantially the entire chamber as the flow material flows out. Finally, gravity or a pumping mechanism may be used to remove the last amount of flow material. 
         [0028]    According to embodiments, stopcock device  100  is disposed along a flow path to prevent flow of a flow material except in pre-determined configurations. Stopcocks are well known and understood by artisans, and include any generic two- or three-way valves, for example. According to embodiments, stopcock  150  comprises second chamber  152 , which is a cavity disposed within stopcock  150  and second chamber conduit  154 , which provides fluid communication between second chamber  152  and other components of stopcock device  100 , as detailed herein. According to embodiments, second chamber conduit  154  comprises a plurality of conduits or chambers, whereby the fluid/gas communication features of the present disclosure connect with the different conduits or chambers. According to other embodiments, second chamber conduit  154  is a single conduit wherein each connecting conduit is situated to articulate with second chamber conduit  154  in substantially the same location relative to stopcock  150  depending on the position of stopcock  150 . 
         [0029]    Within second chamber  152 , the amount of gas is constant like with first chamber  110 , and need not be known. The same devices may be used in second chamber with respect to the gas compressible member or secondary chambers may be configured with one or more one-way valves for the filling and dispensing of flow material to prevent back flow, as would be known and understood by artisans. For example, and according to embodiments, second chamber  152  likewise has disposed therein compressible member, such as a closed cell foam. Like compressible member  112 , compressible member compresses when charged with flow material, thereby creating a pressure differential in second chamber  152  when second chamber  152  is charged with flow material versus when second chamber  152  is not charged with flow material. 
         [0030]    According to other embodiments and as shown in  FIG. 2 , second chamber  152  comprises flow material reservoir  152 A and a pressurized reservoir  152 B separated by a flexible or movable separator, such as an elastomeric membrane or piston. As flow material reservoir is charged, the membrane or piston stretches or moves, thereby compressing gas in the pressurized reservoir. The same gas in pressurized reservoir is used as the gas from which second pressure sensor  122  takes measurements. 
         [0031]    Pressure sensor  122  is disposed to be gaseous communication to second chamber  152 . For example, pressure sensor  122  is disposed immediately adjacent to second chamber  152 , as shown in  FIG. 1 . According to alternative embodiments, pressures sensor is separated from second chamber by a pressure sensing conduit. 
         [0032]    According to embodiments, dispensing conduit  134  serves as a conduit from second chamber  152  to a target, for example a patient, where the flow material is intended. According to embodiments, flow regulator  160  may be disposed to modulate flow rate. Flow regulator  160  comprises flow restrictors, for example. 
         [0033]    According to embodiments where it is used, a pressure sensing conduit serves as a conduit between second pressure sensor  122  and second chamber  152  when stopcock  150  is positioned so as to be in gaseous communication with pressure sensing conduit. According to embodiments, pressure sensing conduit comprises a small cavity having a pressure sensor; according to other embodiments, pressure sensing conduit comprises a tube, pipe, or other conduit with second pressure sensor  122  disposed somewhere therein to measure the pressure. In all cases, the total volume of second chamber  152 , second chamber conduit  154 , and pressure sensing conduit is a known volume. 
         [0034]    Repositioning device  158  connects to stopcock  150  and effects repositioning of stopcock. According to embodiments, repositioning device  158  is a motor that rotates stopcock  150 . According to embodiments, repositioning device  158  may also be a device that moves a slideable stopcock back and forth. 
         [0035]    According to embodiments, stopcock  150  occupies one of three positions: a fill position ( FIG. 3 ) where second chamber  152  is in fluid communication with first chamber  110 , but not in communication with dispensing conduit  134 ; a closed position ( FIG. 4 ) where second chamber  152  it is not in fluid communication with either first chamber  110  or dispensing conduit  134 ; and a dispense position ( FIG. 5 ) where second chamber  152  is in fluid communication with dispensing conduit  134 , but not first chamber  100  and in which second pressure sensor  122  is in gaseous communication with second chamber  152 . 
         [0036]    According to embodiments and as illustrated in  FIGS. 3-5 , when stopcock  150  is in a fill position ( FIG. 3 ), an aliquot of flow material is moved from first chamber  110  into second chamber  152 , wherein second chamber  152  is filled with a flow material. Once filled, flow material is ready to be dispensed to a target, according to embodiments. 
         [0037]    After second chamber  152  is filled with an aliquot of flow material, stopcock  150  is positioned in a closed position ( FIG. 4 ) wherein second chamber  152  is sealed. According to embodiments, the pressure is measured in first chamber  110  or second chamber  152  to determine the volume of the aliquot transferred from first chamber  110  to second chamber  152 . Artisans will note that pressure cannot be sensed for first chamber while first chamber  110  and second chamber  152  are in fluid or gas communication. 
         [0038]    When stopcock is positioned in a closed or dispensing position ( FIGS. 4 and 5 ), second chamber  152  is in gaseous communication with pressure sensor  122 , but not with first chamber  110 . In these positions, the pressure of the gas in second chamber  152  is sensed with pressure sensor  122 . The total volume of second chamber  152  is known, thereby allowing the amount of flow material dispensed or remaining in second chamber  152  to be calculated based on the change in pressure of second chamber  152 . 
         [0039]    According to embodiments, after filling second chamber  152  with an aliquot of flow material or after dispensing flow material, stopcock  150  is positioned in the closed position, the pressure is measured, and the flow material volume calculated (because the total volume of second chamber  152  when stopcock  150  is in the pressure sensing position is known). 
         [0040]    To dispense flow material, stopcock  150  is positioned in its dispense position ( FIG. 5 ) for a period of time. According to embodiments, stopcock  150  is then rotated to the closed position ( FIG. 4 ) for a period of time that is used to measure the pressure. 
         [0041]    According to embodiments, pressure measurements are taken in the dispense position ( FIG. 5 ) to determine the flow rate in about real time without changing the position of stopcock  150 . Because the volume of the aliquot of flow material that filled second chamber  152  is calculated from the pressure in first chamber  110  or second chamber  152 , and because the total volume and initial values for the pressure of second chamber  152  are known, according to embodiments, stopcock need not be positioned in the closed position prior to dispensing the flow material, according to embodiments. 
         [0042]    According to alternate embodiments, stopcock  150  occupies one of four positions: a fill position ( FIG. 3 ) wherein second chamber  152  is in fluid communication with first chamber  110 , but not in communication with dispensing conduit  134 ; a closed position ( FIG. 4 ) where second chamber  152  is not in fluid communication with either first chamber  110  or dispensing conduit  134 ; a pressure sensing position, wherein second chamber  152  is in gaseous communication with second pressure sensor  122  and the pressure of second chamber may be measured; and a dispense position where second chamber  152  is in fluid communication with dispensing conduit  134 , but not first chamber  100 . 
         [0043]    According to embodiments and as illustrated in  FIG. 6 , a method is disclosed for effecting flow of flow material from a source and through stopcock device  100 . During the fill operation, according to embodiments, stopcock  150  is initially positioned into the closed position ( FIG. 4 ), wherein it is not in fluid communication with either first chamber  110  or second chamber  152 . In this position, an initial pressure measurement of first chamber  110  is made in operation  702 . According to alternate embodiments, no initialization is necessary as the system will be in a known state prior to filling (for example, known volume of flow material in first chamber  110  and known initial volume of first chamber  110 ). In operation  704 , first chamber  110  is filled with flow material to a desired level and a second pressure measurement is taken in operation  706 , from which the total amount of flow material in first chamber  110  is calculated. After charging first chamber  110  with flow material, fill conduit  130  is closed and substantially sealed. 
         [0044]    According to embodiments, the filling of first chamber  110  may be omitted where the device comprises a disposable that is discarded when the flow material in first chamber is spent. 
         [0045]    In operation  704 , according to embodiments, flow material enters through fill conduit  130  and into first chamber  110 . 
         [0046]    Flow of flow material into first chamber  110  via fill conduit  130  may be effected from any conventional pump, including specialized infusion pumps, for example those disclosed in U.S. Pat. Nos. 7,008,403; 7,341,581; and 7,374,556, which are hereby incorporated by reference in their entirety. As flow material enters first chamber  110 , compressible member  122  or gas is compressed. Thus, compressible member  122  or the gas stores the energy that will later be used to effect movement of an aliquot of flow material from first chamber  110  to second chamber  152 . 
         [0047]    After first chamber  110  is filled, flow material is ready to be dispensed from first chamber  110  to second chamber  152 . Prior to filling second chamber  152  with and aliquot of flow material, an initial pressure measurement of second chamber  152  is taken, according to embodiments in operation  708 . 
         [0048]    Stopcock  150  is positioned into the fill position in operation  710 , whereby flow material flows from first chamber  110 , through first chamber/stopcock conduit  132  and second chamber conduit  154 , and into second chamber  152 . As flow material enters into first chamber  110 , it compresses compressible member, according to various embodiments. According to embodiments, only a small aliquot of flow material moves from first chamber  110  into second chamber  152  as second chamber  152  charges. For example, first chamber  110  may have a volume of 3 ml and second chamber  152  may have a volume of 0.3 ml. The small aliquot of flow material transferred is the max amount of flow material that can be inadvertently delivered in the event of an error. 
         [0049]    After second chamber  152  is charged with flow material, the pressure of second chamber  152  is measured in operation  712 . The volume of the aliquot transferred to second chamber may be calculated either from the change in pressure from first chamber  110  or by measuring the change in pressure in second chamber  152 . For example, first pressure sensor  120  again measures the pressure of first chamber  110 . Because flow material has been removed from first chamber  110  into second chamber  152 , the volume of compressible member  112  or the gas is increased, thereby reducing the pressure. Thus, because the total volume of first chamber  110  is known, the amount of flow material transferred to second chamber  152  may be calculated, as shown below. Similarly, the volume of the aliquot of flow material in second chamber  152  may be calculated from the difference in pressure in second chamber measured before the aliquot of flow material is transferred and after the aliquot of flow material is transferred to second chamber  152 . According to embodiments, both calculations may be used and an average value taken. 
         [0050]    Once the volume of flow material in second chamber  152  is known, according to embodiments, stopcock  150  is positioned in its dispense position in operation  714 . Because second chamber  152  also has disposed therein compressible member  112  or gas that is pressurized, flow material in second chamber  152  is dispensed due to the pressure exerted on it by compressible member  112  or the gas. According to embodiments, dispensing conduit  134  has disposed therein flow regulator  160 , which is, for example, a flow restrictor or clamping device designed to regulate the flow rate of flow material. 
         [0051]    Second pressure sensor  122 , according to embodiments, measures the change in pressure as flow material is dispensed in operation  716 . According to embodiments in which stopcock  150  has a pressure sensing position, stopcock  150  is alternated between a dispensing position ( FIG. 5 ) and a pressure sensing position to determine the volume of flow material that has been dispensed. According to embodiments in which stopcock does not have a pressure sensing position, the pressure changes are sensed in real time in the dispense position ( FIG. 5 ). Thus, the pressure change of the gas in second chamber  152  is gradual and predictable, allowing for a flow rate to be calculated. Because the volume of second chamber  152  is known, the rate of flow may be calculated, as shown below. 
         [0052]    According to embodiments, the aliquot of flow material in second chamber  152  is small enough that determination of the flow from second chamber  152  is not required. In other words, because the aliquot size is so small, a flow rate with an acceptable level of error may be determined from the number of aliquots delivered over a period of time. 
         [0053]    According to embodiments, gas from first chamber  110  and second chamber  152  is not dispensed with the flow material. Thus, the number of gas molecules in each respective chamber remains constant, as is required for the exemplary equations below to be true. Artisans will readily appreciate that these exemplary equations illustrate the principles by which the volume of flow material dispensed is calculated. 
         [0054]    According to embodiments, stopcock device  100  is configured as an accessory to other pump devices whereby sterility of the flow material is maintained, but volumes of flow material are determined in about real time accurately. 
         [0055]    For example, the present disclosure is provided as an accessory to infusion pumps. The pumps may be conventional or nonconventional pumping devices. Specialized pumps may also be used, including those with two, three, or more chambers, for example as disclosed in U.S. Pat. Nos. 7,008,403; 7,341,581; and 7,374,556, and U.S. Utility patent application Ser. Nos. 11/744,819 filed May 4, 2007 and 12/020,498, filed Jan. 25, 2008 (the contents of each above listed patent and patent application are incorporated by reference). Indeed, the devices of the present disclosure may be provided as accessories for pumps that are able to measure flow rate in about real time. 
         [0056]    The devices of the present disclosure are also useful as safety devices for any pump, whereby upon an error state the maximum flow material that can be delivered to a patient upon a given error state is the small volume contained in second chamber  152  at the time of the error. 
         [0057]    According to embodiments and as illustrated in  FIG. 7 , stopcock device  100  also comprises computer  810  for controlling and performing the functions disclosed herein. Computer may be any computer that is capable of being configured to receive input from users  822  or pressure sensors or temperature sensors  824 . Computer also calculates flow volumes and flow rates  832 , checks for and detects error states  836 , and repositions stopcock  834 , and output audiovisual content  836 . 
         [0058]    According to embodiments, the ideal gas law is used to calculate the dispensed volumes of flow material. Generally, the ideal gas law is expressed as: 
         [0000]      PV=nRT 
         [0000]    where P is the pressure of the gas in the chamber, V is the volume of the chamber, T is the temperature of the chamber, n is the number of moles of gas, and R is the universal gas constant. 
         [0059]    According to embodiments, first chamber  110  is of known total volume, containing a volume of gas. Similarly, second chamber  152  is of known total volume, containing a volume of gas. As disclosed earlier, first and second chambers  110 ,  152  may not have gas according to some embodiments, but other mechanical devices such as closed cell foam having therein a known volume of gas and a known compression profile, whereby the pressure readings of first chamber  110  are useful for the purposes of calculating a volume of flow material held in first chamber  110 . The following exemplary calculations may be adapted for such embodiments without undue experimentation. 
         [0060]    According to embodiments, because the total volume of first chamber  110  is known, the volume of flow material filling first chamber  110 , as well as the volume of aliquots of flow material dispensed into second chamber  152  may be calculated. Likewise, because the total volume of second chamber  152  is known, the volume of flow material dispensed out of stopcock device  100  may be calculated. The exemplary calculations illustrate an embodiment whereby the volume of flow material dispensed is calculated. 
         [0061]    Assuming constant temperature, the initial pressure of first chamber  110  is known or measured using first pressure sensor  120 . Additionally, the total volume of first chamber  110  (V 1 ) and second chamber  152  (V 2 ) are known. Accordingly, an initial volume of flow material is placed in first chamber  110 , thereby increasing the pressure of first chamber  110 . The amount of flow material in first chamber  110  (V FlowMaterial ) is calculated: 
         [0000]    
       
         
           
             
               
                 P 
                 
                   1 
                    
                   empty 
                 
               
                
               
                 V 
                 
                   1 
                    
                   empty 
                 
               
             
             = 
             
               
                 P 
                 
                   1 
                    
                   Filled 
                 
               
                
               
                 V 
                 
                   1 
                    
                   Filled 
                 
               
             
           
         
       
       
         
           
             
               V 
               
                 1 
                  
                 Filled 
               
             
             = 
             
               
                 
                   P 
                   
                     1 
                      
                     empty 
                   
                 
                  
                 
                   V 
                   
                     1 
                      
                     empty 
                   
                 
               
               
                 P 
                 
                   1 
                    
                   Filled 
                 
               
             
           
         
       
       
         
           
             
               V 
               FlowMaterial 
             
             = 
             
               
                 V 
                 
                   1 
                    
                   empty 
                 
               
               - 
               
                 V 
                 
                   1 
                    
                   Filled 
                 
               
             
           
         
       
     
         [0000]    where the volumes here measuring the initial and final gas volume, not flow material volume. If first chamber  110  is empty, then V 1Initial =V 1 . Otherwise, the computer will keep track of the initial volume of first chamber  110  for each successive aliquot. 
         [0062]    According to embodiments, where closed cell foam is placed in first chamber  110 , the calculation for pressure will account for the physical characteristics imparted by compression of the foam, as well. After filling first chamber  110  with a flow material and calculating the volume of flow material that is in first chamber  110 , fill conduit  130  is sealed. 
         [0063]    Flow material may then flow from first chamber  110  to second chamber  152 . According to embodiments, stopcock  150  is rotated whereby it is in its fill position, as illustrated in  FIG. 3 . The pressure within first chamber  110  causes flow material to move from first chamber  110  to second chamber  152 , according to embodiments. According to other embodiments, gravity or mechanical devices can effect flow material movement from first chamber  110  to second chamber  120 . The volume (V Aliquot ) of flow material that fills second chamber is calculated: 
         [0000]    
       
         
           
             
               
                 P 
                 
                   1 
                    
                   Initial 
                 
               
                
               
                 V 
                 
                   1 
                    
                   Initial 
                 
               
             
             = 
             
               
                 P 
                 
                   1 
                    
                   Flowed 
                 
               
                
               
                 V 
                 
                   1 
                    
                   Flowed 
                 
               
             
           
         
       
       
         
           
             
               V 
               
                 1 
                  
                 Flowed 
               
             
             = 
             
               
                 
                   P 
                   
                     1 
                      
                     Initial 
                   
                 
                  
                 
                   V 
                   
                     1 
                      
                     Initial 
                   
                 
               
               
                 P 
                 
                   1 
                    
                   Flowed 
                 
               
             
           
         
       
       
         
           
             
               V 
               Aliquot 
             
             = 
             
               
                 V 
                 
                   1 
                    
                   Initial 
                 
               
               - 
               
                 V 
                 
                   1 
                    
                   Flowed 
                 
               
             
           
         
       
     
         [0064]    After second chamber is charged with an aliquot of flow material, stopcock is changed from its fill position (illustrated in  FIG. 3 ) to another position, for dispensing, pressure measurement, or closed for accurate measurement of the pressure in first chamber  110 . 
         [0065]    To determine an amount of flow material dispensed at a given point, according to embodiments, similar calculation are performed for second chamber  152  to determine the amount of flow material dispensed. The gas volume of second chamber  152  after having receiving an aliquot is first determined: 
         [0000]    
       
         
           
             
               
                 P 
                 
                   2 
                    
                   Initial 
                 
               
                
               
                 V 
                 
                   2 
                    
                   Initial 
                 
               
             
             = 
             
               
                 P 
                 
                   2 
                    
                   Filled 
                 
               
                
               
                 V 
                 
                   2 
                    
                   Filled 
                 
               
             
           
         
       
       
         
           
             
               V 
               
                 2 
                  
                 Filled 
               
             
             = 
             
               
                 
                   
                     
                       P 
                       
                         2 
                          
                         Initial 
                       
                     
                      
                     
                       V 
                       
                         2 
                          
                         Initial 
                       
                     
                   
                   
                     P 
                     
                       2 
                        
                       Filled 
                     
                   
                 
                  
                 
                     
                 
                  
                 or 
                  
                 
                     
                 
                  
                 
                   V 
                   
                     2 
                      
                     Filled 
                   
                 
               
               = 
               
                 
                   V 
                   
                     2 
                      
                     Initial 
                   
                 
                 - 
                 
                   V 
                   Aliquot 
                 
               
             
           
         
       
     
         [0066]    When stopcock  150  is positioned in its dispense position, flow material is dispensed from stopcock  150  by virtue of the pressure within second chamber  152 , gravity, or other mechanical forces, according to embodiments. Accordingly, as flow material is dispensed out of second chamber  152 , the volume dispensed is calculated. The dispensed flow material volume is determined exactly opposite of the method by which the volume filled into first chamber  110  is calculated, according to embodiments. For example: 
         [0000]    
       
         
           
             
               
                 P 
                 
                   2 
                    
                   Filled 
                 
               
                
               
                 V 
                 
                   2 
                    
                   Filled 
                 
               
             
             = 
             
               
                 P 
                 
                   2 
                    
                   Dispensed 
                 
               
                
               
                 V 
                 
                   2 
                    
                   Dispensed 
                 
               
             
           
         
       
       
         
           
             
               V 
               
                 2 
                  
                 Dispensed 
               
             
             = 
             
               
                 
                   P 
                   
                     2 
                      
                     Filled 
                   
                 
                  
                 
                   V 
                   
                     2 
                      
                     Filled 
                   
                 
               
               
                 P 
                 
                   2 
                    
                   Dispensed 
                 
               
             
           
         
       
       
         
           
             
               V 
               Dispensed 
             
             = 
             
               
                 V 
                 
                   2 
                    
                   Filled 
                 
               
               - 
               
                 V 
                 
                   2 
                    
                   Dispensed 
                 
               
             
           
         
       
     
         [0000]    According to embodiments, stopcock  150  is alternated between its dispense position and it pressure sensing position to make pressure measurements. According to other embodiments, stopcock  150  remains in its dispense position and the pressure of chamber two is periodically assayed to determine the volume of flow material dispensed. 
         [0067]    A shortened version of the equations follows, where it isn&#39;t necessary to determine the gas volume in second chamber  152 . 
         [0000]    
       
         
           
             
               V 
               Dispensed 
             
             = 
             
               
                 V 
                 
                   2 
                    
                   Filled 
                 
               
               - 
               
                 V 
                 
                   2 
                    
                   Dispensed 
                 
               
             
           
         
       
       
         
           
             
               V 
               Dispensed 
             
             = 
             
               
                 V 
                 
                   2 
                    
                   Filled 
                 
               
               - 
               
                 
                   
                     P 
                     
                       2 
                        
                       Filled 
                     
                   
                    
                   
                     V 
                     
                       2 
                        
                       Filled 
                     
                   
                 
                 
                   P 
                   
                     2 
                      
                     Dispensed 
                   
                 
               
             
           
         
       
       
         
           
             
               V 
               Dispensed 
             
             = 
             
               
                 
                   
                     P 
                     
                       2 
                        
                       Dispensed 
                     
                   
                    
                   
                     V 
                     
                       2 
                        
                       Filled 
                     
                   
                 
                 
                   P 
                   
                     2 
                      
                     Dispensed 
                   
                 
               
               - 
               
                 
                   
                     P 
                     
                       2 
                        
                       Filled 
                     
                   
                    
                   
                     V 
                     
                       2 
                        
                       Filled 
                     
                   
                 
                 
                   P 
                   
                     2 
                      
                     Dispensed 
                   
                 
               
             
           
         
       
       
         
           
             
               V 
               Dispensed 
             
             = 
             
               
                 
                   V 
                   
                     2 
                      
                     Filled 
                   
                 
                  
                 
                   ( 
                   
                     
                       P 
                       
                         2 
                          
                         Dispensed 
                       
                     
                     - 
                     
                       P 
                       
                         2 
                          
                         Filled 
                       
                     
                   
                   ) 
                 
               
               
                 P 
                 
                   2 
                    
                   Dispensed 
                 
               
             
           
         
       
       
         
           
             
               V 
               Dispensed 
             
             = 
             
               
                 
                   V 
                   
                     2 
                      
                     Filled 
                   
                 
                 
                   P 
                   
                     2 
                      
                     Dispensed 
                   
                 
               
                
               Δ 
                
               
                   
               
                
               
                 P 
                 2 
               
             
           
         
       
       
         
           
             
               V 
               Dispensed 
             
             = 
             
               
                 
                   
                     V 
                     2 
                   
                   - 
                   
                     V 
                     Aliqout 
                   
                 
                 
                   P 
                   
                     2 
                      
                     Dispensed 
                   
                 
               
                
               Δ 
                
               
                   
               
                
               
                 
                   P 
                   2 
                 
                 . 
               
             
           
         
       
     
         [0000]    According to embodiments, temperature sensors may be disposed in substantially the same locations as each pressure sensor to improve the accuracy of the calculations. The application of temperature into the exemplary calculation shown below are will within the skill and understanding of a person of ordinary skill in the art. 
         [0068]    According to embodiments, the above equations are adaptable to a single pressure sensor in chamber two  152 . Such a configuration is possible when knowing the initial volume in chamber one  110  is not necessary or desirable, or when the volume of chamber one  110  is known, for example when the device disclosed herein is a disposable. According, only the volume of each aliquot of flow material is calculated by measuring the pressure differentials in chamber two  152 . For example, the volume of each aliquot (P 2Filled ) may be calculated independent of any calculations related to chamber one  110 : 
         [0000]    
       
         
           
             
               
                 P 
                 
                   2 
                    
                   Initial 
                 
               
                
               
                 V 
                 
                   2 
                    
                   Initial 
                 
               
             
             = 
             
               
                 P 
                 
                   2 
                    
                   Filled 
                 
               
                
               
                 V 
                 
                   2 
                    
                   Filled 
                 
               
             
           
         
       
       
         
           
             
               V 
               
                 2 
                  
                 Filled 
               
             
             = 
             
               
                 
                   
                     P 
                     
                       2 
                        
                       Initial 
                     
                   
                    
                   
                     V 
                     
                       2 
                        
                       Initial 
                     
                   
                 
                 
                   P 
                   
                     2 
                      
                     Filled 
                   
                 
               
               . 
             
           
         
       
     
         [0000]    Knowing the P 2Filled  value allows for the calculation of the dispensed volume as disclosed above. 
         [0069]    According to embodiments, because stopcock  150  eliminates direct fluid communication between the pump and the target of the flow material, it provides a safety mechanism for the pump. If a malfunction of the pump or stopcock device  100  occurs, the maximum unintended amount of flow material that can possibly be dispensed to the target is the small aliquot in second chamber  152 . In certain applications, for example in the delivery of insulin, these types of safety mechanisms are important for preventing unintended delivery of insulin due to malfunction. 
         [0070]    While the apparatus and method have been described in terms of what are presently considered to be the most practical and preferred embodiments, 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, 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.