Abstract:
A portable system for analysis of blood or other bodily fluids removable from a patient is disclosed. The system includes a temperature sensing device and a temperature control circuit. The temperature sensing device senses a temperature of a surface of a sensor substrate of a cartridge having an electrical heater device without direct contact with the cartridge or direct exposure to the heating device. The temperature sensing device also generates an electrical signal related to the sensed temperature. The temperature control circuit controls an electrical input to the heater device based on the sensed temperature and a designed control temperature.

Description:
FIELD 
     A portable diagnostic system is generally related to portable diagnostic systems based on electrochemical determinations in biological samples, and is more particularly related to a portable diagnostic system that can be connected to a larger diagnostic system having improved operating characteristics. 
     BACKGROUND 
     Methods and devices utilized for determining concentrations of electroactive species in solutions using electrochemical or electrolytic methods are well known. These instruments typically include a pair of electrochemical half cells, one of which is used as the sensor or sample half cell and the other as a reference electrode or a reference half cell. As is the case with any concentration determination of dissolved gaseous species in a liquid, the temperature at which the electrochemical determination is made needs to be known. Traditionally, blood gas determinations, for example, have been made utilizing permanently installed laboratory instrumentation to which samples are brought for analysis. Of course, in such instruments the temperature at which the sample is analyzed can be readily controlled, for example, by a constant temperature oven. These types of methods have disadvantages for portable devices. One such disadvantage is that portable devices cannot contain constant temperature ovens. Known temperature control systems for portable devices also have disadvantages. One such disadvantage is that they typically have limited operating temperature ranges. Another disadvantage is that such systems are susceptible to outside interferences. Therefore, improvements are desirable. 
     SUMMARY 
     In accordance with the present disclosure, the above and other problems are solved by the following: 
     In one aspect of the present disclosure, a portable system for analysis of blood or other bodily fluids removable from a patient is disclosed. The system includes a temperature sensing device and a temperature control circuit. The temperature sensing device senses a temperature of a surface of a sensor substrate of a cartridge having an electrical heater device without direct contact with the cartridge or direct exposure to the heating device. The temperature sensing device also generates an electrical signal related to the sensed temperature. The temperature control circuit controls an electrical input to the heater device based on the sensed temperature and a designed control temperature. The temperature control circuit includes capacitors arranged and configured to dampen radio frequency interference and electro static discharge. 
     In another aspect of the present disclosure, a portable system for analysis of blood or other bodily fluids removable from a patient is disclosed. The system includes a temperature sensing device and a temperature control circuit. The temperature sensing device senses a temperature of a surface of a sensor substrate of a cartridge having an electrical heater device without direct contact with the cartridge or direct exposure to the heating device. The temperature sensing device also generates an electrical signal related to the sensed temperature. The temperature control circuit controls an electrical input to the heater device based on the sensed temperature and a designed control temperature. The temperature control circuit is calibrated to operate at an ambient temperature at least below 14 degree Celsius. 
     In another aspect of the present disclosure, a portable system for analysis of blood or other bodily fluids removable from a patient is disclosed. The system includes a temperature sensing device and a temperature control circuit. The temperature sensing device senses a temperature of a surface having an analytical cell of a sensor substrate of a cartridge having an electrical heater device without direct contact with the cartridge or direct exposure to the heating device. The temperature sensing device also generates an electrical signal related to the sensed temperature. The temperature control circuit controls an electrical input to the heater device based on the sensed temperature and a designed control temperature. 
     In another aspect of the present disclosure, a portable system for analysis of blood or other bodily fluids removable from a patient is disclosed. The system includes a temperature sensing device and a temperature control circuit. The temperature sensing device senses a temperature of a surface, in fluid communication with an analytical cell, of a sensor substrate of a cartridge having an electrical heater device without direct contact with the cartridge or direct exposure to the heating device. The temperature sensing device also generates an electrical signal related to the sensed temperature. The temperature control circuit controls an electrical input to the heater device based on the sensed temperature and a designed control temperature. 
     In another aspect of the present disclosure, a method of analyzing blood or other bodily fluids removable from a patient is disclosed. The method includes inserting a cartridge, including a sensor substrate carrying an integral heater device, into a portable system and receiving results of the analysis. The portable system includes characteristics similar to those described above. 
     A more complete appreciation of the present invention and its scope may be obtained from the accompanying drawings, which are briefly described below, from the following detailed descriptions of presently preferred embodiments of the invention and from the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
         FIG. 1  is a fragmentary perspective instrument sub-assembly view; 
         FIG. 2  is an exploded view of the sub-assembly of  FIG. 1 ; 
         FIG. 3  is an enlarged, sectional view of a portion at the system of  FIG. 1 ; 
         FIG. 4  is a sectional view taken substantially along line  4 — 4  of  FIG. 5 ; 
         FIG. 5  is a top view of the system of  FIG. 1 ; 
         FIG. 6  is a plot depicting the temperature control of a sample solution in an electrochemical cell of a cartridge; 
         FIG. 7  is a block diagram illustrating the electrical system of the system of  FIG. 1 ; 
         FIG. 8  is an electrical schematic of a portion of the electrical system of  FIG. 7 ; and 
         FIG. 9  is an electrical schematic of another portion of the electrical system of FIG.  7 . 
     
    
    
     DETAILED DESCRIPTION 
     In the following disclosure, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is understood that other embodiments may be utilized and changes be made without departing from the scope of the present invention. 
     In general, the present disclosure describes a portable instrument that makes analytical determinations such as blood gas analysis. The instrument operates over a broader temperature range than prior known instruments and uses capacitors to dampen or reduce induced radio frequency (RF) interference and to dampen or reduce electro static discharge (ESD) susceptibility. The instrument can also be connected to a larger, more comprehensive system, such as Philips CMS and V24/V26 monitors. 
     In particular, the instrument uses a removable cartridge that contains a calibrated electrochemical cell designed to receive and electrochemically measure a sample injected into a sample port associated with the cartridge. The integral electrochemical cell of the cartridge is carried on a sensor chip and includes a resistive heating element also preferably formed on the sensor chip member. Electric input to the heating element is thermostatically controlled by a non-contact temperature sensitive device, such as a scanning infrared probe, that monitors the temperature of the outer surface of the sensor chip and controls input to the resistive heating element through conventional temperature control circuitry. Of course, the particular embodiment shown is merely illustrative of the several unique features and principles that may be more broadly applied by those skilled in the art. 
     Referring now to  FIGS. 1 and 2 , an instrument sub-assembly is integral with a larger device and housing and includes a removable cartridge and cartridge receiving retaining device together with a temperature control system for the removable cartridge. The system includes an instrument sub-assembly housing, shown generally at  10 , that may be fastened to the main body of a larger portable instrument (not shown) by utilizing openings or holes  12  in the housing. Referring now to  FIG. 2 , the housing  10  further contains a recess  14  and a connecting block  16  for receiving and retaining, as by screws (not shown), an electrical connector or terminal block  18 . The connector  18  includes a plurality of electrical input/output terminals  20  that physically retain and electrically connect a removable cartridge system, depicted generally at  22 , with the main portion of the analytical instrument (not shown) as required. 
     The connector element  18  is shown schematically connected to conventional temperature control circuitry, that operates in a well-known manner and is designated by the box  24 , using a pair of conductors  26  and  28 . The temperature sensing input for the temperature control system is provided by a non-contact temperature sensor  29 . Preferably the temperature sensor  29  is an infrared scanning thermocouple device or probe  30  that senses temperature rapidly and accurately. The temperature probe  30  is connected to the temperature control circuitry  24  by a conduit  32 . The signal received from the temperature probe  30  is processed by the temperature control circuitry  24  and compared with a value corresponding to a fixed designated set point control temperature determined by the application involved, typically about 37 degrees Celsius, which is equivalent to body temperature. 
     The housing  10  contains a pair of integral retainers  34  that are configured to fit over and slidably receive the removable cartridge system  22 . The sample cartridge  22  is depicted in exploded view in  FIG. 2 , and includes a top member  40 , sensor chip  42  and a base member  44 . The top member  40  further includes a port  46  that is used to admit a temperature probe (not shown) for experimental verification purposes. A sample receiving port is located at  47 . As illustrated in  FIGS. 3-5 , the top member  40  contains a recess that, with the sensor chip member  42 , defines a volume  48  for containing the sample. The chip  42 , further contains a plurality of electrodes  50  and carries a serpentine resistance-heating element  52  that is electrically connected to the conductors  26  and  28  utilizing the connector  18  that the cartridge  22  is plugged into the recess  54 . The lower member or base member  44  is recessed to receive the chip  42 . The opening  56  aligns with an opening  58  provided through the housing member  10 , giving the probe  30  a direct line of sight to the outer surface  60  of the chip member  42  for the purpose of temperature detection. 
     The probe  30  might be any suitable scanning infrared sensor, or the like. Examples include one known as IR t/c® available from Exergen Corporation of Newton, Mass. Such probes can be produced and pre-calibrated in quantity prior to manufacture of the portable measuring instruments so that they will repeatably, rapidly, and accurately control the temperature of the observed surface  60 , for example, at 37 degrees Celsius±0.2 degrees Celsius. The signal produced by the temperature sensed by the probe  30  is transmitted by the conduit  32  to the control circuitry  24  that, in turn, controls the electric power in conductors  26  and  28  to modulate the energy output of the serpentine resistance element  52  in a well-known manner. 
     In operation, a fresh disposable cartridge  22  is inserted into the portable instrument  10  so that proper electrical connection is made in opening  54  and the cartridge  22  is also retained in place by ears  34 . In connection with this operation, the temperature control system can be automatically activated by the insertion of the cartridge into the receptacle  54 . The system might contain any desired time delay circuits or other activation system. Of course, the device might also be controlled by other means such as an instrument switch (not shown) in a well-known manner. 
       FIG. 6  depicts a computer generated graphical plot illustrating the ability of the temperature control system of the instrument to control the solution temperature of an analytical cell configured for selective conduction of analytical analysis, or the electrochemical cell volume  48 , of a disposable cartridge  22  made in accordance with the preferred embodiment. The probe  30  and temperature control circuitry  24  are designed to control the temperature of the solution in the electrochemical cell  48  at about 37.5 degrees Celsius when stabilized. It is noted that the electrochemical cell does not need to be on the substrate but can be located elsewhere. In such a configuration, the electrochemical cell would be in fluid communications with the substrate. 
     The time-temperature plot of  FIG. 6  illustrates the reaction of the system after activation at approximately 10 seconds into the time plot along the abscissa. The temperature data for the plot of  FIG. 6  was obtained by means of a temperature probe inserted into the cell through port  46 . Actual temperature values sensed by the probe may be mathematically compensated in temperatures in the cell. The time-temperature profile using the inserted temperature probe in any event is quite similar and representative of the control capabilities of the system. 
     As can be seen from  FIG. 6 , the temperature was raised from an ambient temperature of approximately 24 degrees Celsius to the control temperature of approximately 37.5 degrees Celsius at the 32-second mark. At approximately the 71-second mark, the system was shocked by the injection of approximately 5 cc of ice water as through the port  47 . Within about 1-2 seconds the temperature dropped to approximately 11 degrees Celsius, the low point of the cycle. Thereafter, the recovery was again extremely rapid and reached the control point of approximately 37.5 Celsius in about 35 seconds.  FIG. 6  aptly illustrates the rapidity with which the system recovers to the desired control temperature and the accuracy with which that temperature can be maintained in accordance with the invention. 
     The chip member  42  is normally fabricated of a ceramic with a fairly low thermal capacity for easy temperature control and quick recovery. The serpentine resistive heating element together with connecting conductors is normally deposited on the surface of the chip  42  using screen printing film or one of many well-known metalizing techniques. Such resistive heaters may be made of any conventional materials such as permalloy (an alloy having a preferred composition of 80% nickel and 20% iron). The material may be deposited as a thick or thin film in any desired configuration. The chip  42  itself may be any ceramic or other convenient dielectric material that meets the criteria for both the electrochemical cell and lends itself to temperature control utilizing the heating system of the invention. 
     Attention is directed to  FIGS. 7-9 .  FIG. 7  is a block diagram illustrating in more detail the probe  30 , the cartridge system  22 , and the control circuitry  24 . The control circuitry  24  includes a thermocouple pre-amplifier assembly (TPA) board  100  and an analog board  110 .  FIG. 8  is an electrical schematic of the TPA board  100 , and  FIG. 9  is an electrical schematic of the analog board  110 . Referring to  FIG. 7 , the overall system  200  includes a controller  205 , or central processing unit. The controller  205  controls a A/D converter  206  and a DacTemp  207 . The controller  205  also controls a port  210 . The port  210  can be used to connect to a larger, more comprehensive system, such as Philips CMS and V24/V26 monitors. 
     Referring now to  FIG. 8 , the TPA board  100  is typically connected to the probe  30  by first, second, and third electrical connections  112 ,  114 ,  116 . The TPA board  100  is also typically connected to the Analog board  110  by fourth, fifth, sixth, and seventh electrical connections  118 ,  120 ,  122 ,  124 . The TPA board  100  includes decoupling capacitors  130 ,  132 ,  134 ,  136 ,  138 ,  140 ,  142 ,  144 . These decoupling capacitors  130 ,  132 ,  134 ,  136 ,  138 ,  140 ,  142 ,  144  are arranged and configured to absorb energy to dampen or reduce induced RF interference and ESD. These decoupling capacitors  130 ,  132 ,  134 ,  136 ,  138 ,  140 ,  142 ,  144  are advantageous because they improve overall performance of the control circuitry  24  and enable operation in a wider variety of conditions. On example is that the capacitors  132 ,  134 ,  136 ,  138 ,  140 ,  142 ,  144  eliminate the need for shielding in the shell or case of the instrument. 
     Referring now to  FIG. 9 , likewise, the analog board  110  includes decoupling capacitors  160 ,  162 ,  164 ,  166 ,  168 . These decoupling capacitors  160 ,  162 ,  164 ,  166 ,  168  are arranged and configured to absorb energy to dampen or reduce induced RF interference and ESD, eliminating the need for shielding in the shell or case of the instrument. One skilled in the art will recognize that the number, placement, and capacitance of the decoupling capacitors could be varied to achieve similar results or improved energy absorption. 
     Referring back to  FIG. 7 , the overall system  200  is calibrated prior to use. Data is gathered over the range of the operating temperature to establish constants to be employed during a test of a cartridge  22 . The constants are used to control the system  200  to between 36 degrees Celsius and 38 degrees Celsius, the typical temperature of the cartridge  22  during testing. The system  200  can be calibrated for an external, or ambient, operating temperature range of 12 degrees Celsius to 30 degrees Celsius, or a temperature range of at least below 14 degrees Celsius inclusive. This temperature range is advantageous because the system can be used in a larger variety of external environments having different temperature conditions. 
     The various embodiments described above are provided by way of illustration only and should not be construed to limit the invention. Those skilled in the art will readily recognize various modifications and changes that may be made to the present invention without following the example embodiments and applications illustrated and described herein, and without departing from the true spirit and scope of the present disclosure which is set forth in the following claims.