Abstract:
A plurality of electrodes are adapted to be attached on a living body. An electric pulse is output through the electrodes as an electric stimulation to the living body. An analyzer is operable to detect a waveform of the electric pulse and to analyze a parameter of the waveform. A display displays the parameter together with one of the waveform and a model waveform which is an invariable waveform representative of the electric pulse.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to an electric stimulator for providing electrical stimulation to a living body, and more particularly, to a technique for displaying various waveforms such as a result of analysis of an electrical waveform output from a defibrillator. 
   Devices, such as a defibrillator or low-frequency therapy equipment, have hitherto been utilized in the field of medical care as electric stimulators for providing electrical stimulation to a living body. 
   Japanese Patent Publication No 2001-245992A (corresponding to U.S. Patent Application Publication 2002/0022867A1) discloses a technique characterized by an electrical circuit capable of outputting a multiphasic waveform as a waveform of electric stimulation output from a defibrillator. 
   The defibrillator is a device for resuscitating the heart of a patient whose heart is fibrillating by providing electrical stimulation (electric energy) to the patient. When the patient&#39;s heart has changed to fibrillation, the defibrillator must be capable of being put into operation immediately and providing electrical stimulation (i.e., electric energy) at an appropriate timing. For this reason, maintenance is required to ensure that the defibrillator is capable of outputting desired electrical stimulation even when not used for actual treatment. 
   When the defibrillator is used for actual treatment, it is desirable to be able to verify that an operation for outputting electrical stimulation is normal, during or after treatment. 
   Such a necessity also applies not only to the defibrillator, but also to another electric stimulator which provides electrical stimulation to a living body. 
   Japanese Patent Publication No. 54-112589A discloses a defibrillator which displays an output voltage waveform applied to a living body (cf., page  2 , upper right column, lines  40 - 41  and  FIG. 3 ). This technique enables checking of a voltage waveform output to the living body. However, specific values, such as electric energy, resistance existing between electrodes, and a time period during which the electric energy has been supplied, are unknown. Hence, there is no way of knowing whether or not an electric pulse applied to the patient in defibrillation is appropriate 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to provide an electric stimulator and a defibrillator which enable checking of appropriateness of an electric pulse by analyzing an output electric pulse and displaying an analysis result and a model waveform or output waveform. 
   In order to achieve the above object, according to the invention, there is provided an electric stimulator for applying electric stimulation to a living body, comprising: 
   a plurality of electrodes, adapted to be attached on the living body, and through which an electric pulse is output as the electric stimulation; 
   an analyzer, operable to detect a waveform of the electric pulse and to analyze a parameter of the waveform; and 
   a display, which displays the parameter together with one of the waveform and a model waveform which is an invariable waveform representative of the electric pulse. 
   According to the invention, there is also provided an electric stimulator for applying electric stimulation to a living body, the electric stimulator comprising: 
   a plurality of electrodes, adapted to be attached on the living body, and through which an electric pulse is output as the electric stimulation; 
   an energy charging element, in which an electric energy to be supplied to the electrodes is charged, the energy charging element having terminals; 
   an analyzer, operable to detect a voltage waveform between the terminals as a waveform of the electric pulse to be output, and to analyze a parameter of the waveform; and 
   a display, which displays the parameter together with one of the waveform and a model waveform which is an invariable waveform representative of the electric pulse. 
   In the above configurations, the analysis result can be ascertained while being compared with the actual waveform or the model waveform. 
   Preferably, the display displays an index mark corresponding to the parameter. 
   In such a configuration, the analysis result can be ascertained while being compared with the index mark provided with the waveform. 
   Preferably, the parameter includes at least one of a discharge start voltage of the electric pulse, an electric energy output by the electric pulse, a duration of the electric pulse and a resistance between the electrodes. 
   In such a configuration, information pertaining to the waveform of the electric pulse can be ascertained. 
   Preferably, the electric stimulator further comprises a storage, which stores at least one of the waveform and the parameter. 
   In such a configuration, the waveform data can be read later from the storage and ascertained. 
   Preferably, the electric stimulator further comprising: a plurality of housings, which respectively house the electrodes therein; and a resistor, connected between the housings such that terminals thereof are exposed at the housings. Here, the electrodes are electrically connected via the resistor in a case where the electrodes are housed in the housings. 
   In such a configuration, an electric pulse can be ascertained for maintenance purpose. 
   Preferably, the electric stimulator serves as a defibrillator. 
   According to the invention, there is also provided an electric stimulator for applying electric stimulation to a living body, the electric stimulator comprising: 
   a plurality of electrodes, adapted to be attached on the living body, and through which an electric pulse is output as the electric stimulation; 
   an analyzer, operable to detect a waveform of the electric pulse and to analyze a parameter of the waveform; and 
   a display, which displays the parameter. 
   According to the invention, there is also provided an electric stimulator for applying electric stimulation to a living body, the electric stimulator comprising: 
   a plurality of electrodes, adapted to be attached on the living body, and through which an electric pulse is output as the electric stimulation; 
   an energy charging element, in which an electric energy to be supplied to the electrodes is charged, the energy charging element having terminals; 
   an analyzer, operable to detect a voltage waveform between the terminals as a waveform of the electric pulse to be output, and to analyze a parameter of the waveform; and 
   a display, which displays the parameter. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein: 
       FIG. 1  is a constitutional block diagram showing an electric stimulator (defibrillator) according to the invention; 
       FIG. 2  is an example result of analysis of a waveform displayed on a screen in the electric stimulator (defibrillator) of the invention; 
       FIG. 3  is an external view of the electric stimulator (defibrillator) of the invention; 
       FIG. 4  is an external view of the electric stimulator (defibrillator) of the 
       FIG. 5  is a constitutional block diagram showing the electric stimulator (defibrillator) according to the invention; 
       FIG. 6  is a descriptive view of an electrical path in the constitutional block circuit of the electric stimulator (defibrillator) of the invention employed when a positive-phase waveform is output; 
       FIG. 7  is a descriptive view of an electrical path in the constitutional block circuit of the electric stimulator (defibrillator) of the invention employed when a switch  101  is in a conductive state at the time of output of a negative-phase waveform; 
       FIG. 8  is a descriptive view of an electrical path in the constitutional block circuit of the electric stimulator (defibrillator) of the invention employed when the switch  101  is in a conductive state at the time of output of the negative-phase waveform; 
       FIG. 9  is a descriptive view of an electrical path in the constitutional block circuit of the electric stimulator (defibrillator) of the invention employed when the switch  101  is in a non-conductive state at the time of output of the negative-phase waveform; and 
       FIGS. 10A and 10B  show electrical waveforms of the electric stimulator (defibrillator) of the invention, wherein  FIG. 10A  is a voltage waveform of a capacitor  104  and  FIG. 10B  is the waveform of a voltage developing between electrode pads. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Preferred embodiments of an electric stimulator according to the invention will be described hereinbelow in detail with reference to the accompanying drawings while a defibrillator is taken as an example. 
   As shown in  FIG. 1 , in a defibrillator  10  according to one embodiment of the invention, a control panel  1  has several buttons to be used for performing operations for outputting an electric pulse for defibrillation treatment. When an operator has actuated these buttons, an instruction signal is output from the control panel  1  to a processor  2  in accordance with the operation. 
   Upon receipt of the instruction signal, the processor  2  outputs a signal to a power source  3  for instructing supply of the electric energy charged in the power source  3  to a pulse generator  4 . As a result, the electric energy is supplied to the pulse generator  4 . The processor  2  also outputs, to the pulse generator  4 , a control signal for outputting an electric pulse to electrodes  5   a ,  5   b  (e.g., electrode paddles or the like). 
   Upon receipt of the control signal, the pulse generator  4  configures an electric pulse, to thereby output the thus-configured electric pulse to the electrodes  5   a ,  5   b . The waveform pattern of the electric pulse may be a monophasic waveform, such as a damped sinusoidal curve or a truncated exponential curve used in a monophasic defibrillator, or a biphasic waveform such as a truncated exponential curve used in a biphasic defibrillator. Further, the waveform pattern may be a biphasic waveform or a multiphasic waveform in which a first-phase waveform and a second-phase waveform are alternately and repetitively iterated, as disclosed in Japanese Patent Publication No. 2001-245992A. 
   During a period in which the electric pulse is output to the electrodes  5   a ,  5   b , an output waveform analyzer  6  detects a voltage waveform of the electric pulse, to thereby analyze the waveform of the electric pulse. A result of analysis is displayed on a screen  7 . 
   A model waveform (described later) or the detected waveform is also displayed on the screen  7 . The electric pulse and the analysis result are output from the output waveform analyzer  6  and stored in a storage  8  by way of the processor  2 . As required, the analysis result and the electric pulse are read from the storage  8  and displayed on the screen  7  under the control of the processor  2 , through the foregoing operations. Either the electric pulse or the analysis result may be stored in the storage  8 . 
     FIG. 2  shows an example in which a result of analysis of the electric pulse is displayed on the screen  7  when the defibrillator  10  outputs an electric pulse of biphasic waveform. 
   A model waveform is displayed on the left part of the screen  7 . Characteristic values and other values pertaining to the shape of the voltage waveform detected and analyzed by the output waveform analyzer  6  are displayed on the right part of the screen  7 . Displayed items are as follows. 
   “{circle around (1)} Delivered” denotes the quantity of electric energy output from the electrodes  5   a ,  5   b . “{circle around (2)} TTR” denotes resistance existing between the electrodes  5   a ,  5   b . “{circle around (3)} Voltage” denotes a voltage value obtained at the time of commencement of electrical discharge of a first-phase waveform output between the electrodes  5   a ,  5   b . “{circle around (4)} Phase 1” denotes a duration of the first-phase waveform. “{circle around (5)} Phase 2” denotes a duration of a second-phase waveform. 
   Consequently, the detected pulse is analyzed in connection with items {circle around (1)} through {circle around (5)} by the output waveform analyzer  6 . Results of the analysis are displayed on the screen  7  on a per-item basis. In a case where the first phase waveform is produced as a result of discharge of the electric energy charged in a capacitor, computation of the resistance existing between the electrodes pertaining to “{circle around (2)} TTR” can be performed on the basis of the capacitance of the capacitor, a discharge start voltage and discharge end voltage of the first-phase waveform, and a duration of the first-phase waveform. Computation of the amount of electric energy pertaining to “{circle around (1)} Delivered” can be performed on the basis of the energy charged in the capacitor. 
   In relation to computation of the duration of the second-phase waveform defined in “{circle around (5)} Phase 2”, the duration of the second-phase waveform is defined as a period from the time a second-phase amplitude has reached a predetermined percentage of the maximum amplitude until the time the amplitude is attenuated to the same predetermined percentage of the maximum amplitude. 
   Alternatively, the duration of the waveform may be determined by another method. For example, a control time to be used for outputting a second phase may be taken as a second-phase period. Internal resistance of the output waveform analyzer  6  is also taken into consideration at the time of these operations. 
   When the electric pulse has been output to the living body, “{circle around (2)} TTR” corresponds to impedance of the living body. When the electric pulse has been output for maintenance to be described later, “{circle around (2)} TTR” coincides with internal resistance housed between paddle holders  11   a ,  11   b  to be described later. 
   As described the above, the model biphasic waveform is also displayed on the screen  7 . Index marks through {circle around (3)} through {circle around (5)} are provided with the model waveform so that the operator can visually comprehend meanings of the values {circle around (3)} through {circle around (5)}. 
   Here, “{circle around (3)} Voltage” mans a voltage at which discharge of the first-phase waveform to be output between the electrodes  5   a ,  5   b  is to be started. For this reason, {circle around (3)} is provided so as to indicate a waveform portion of the model waveform corresponding to the voltage at which discharge of the first-phase waveform is to be started. “{circle around (4)} Phase 1” means a duration of the first-phase waveform. {circle around (4)} is provided so as to indicate a waveform portion of the model waveform corresponding to the duration of the first-phase waveform. “{circle around (5)} Phase 2” means a duration of the second-phase waveform. Hence, {circle around (5)} is provided so as to indicate a waveform portion of the model waveform corresponding to the duration of the second-phase waveform. 
   In place of or in addition to the model waveform, the waveform of an electric pulse detected by the output waveform analyzer  6  may be displayed on the screen  7 . As a result, the waveform of an electric pulse to be actually output can be visually checked, hereby enabling a check as to whether or not an output is normal. Incidentally, the above index marks may be provided with the waveform of an actual electric pulse. 
     FIGS. 3 and 4  are external views of the defibrillator. A range selector  1   a  is to be used for controlling the quantity of electric energy of the electric pulse to be output. A button  1   b  is to be used for instructing the pulse generator  4  to be charged with electric energy supplied from the power source  3 . A button  1   c  is to be used for instructing the electrode paddles  5   a ,  5   b  to output an electric pulse for defibrillation purpose. The range selector  1   a  and the buttons  1   b ,  1   c  belong to the control panel  1  shown in  FIG. 1 . The defibrillator  10  has paddle holders  11   a ,  11   b  for housing the electrode paddles  5   a ,  5   b , respectively. 
   The structure of the defibrillator  10  required to test discharge of an electric pulse for maintenance will now be described. As shown in  FIG. 3 , a built-in resistor (not shown) is provided between the paddle holders  11   a ,  11   b , and terminals  12   a ,  12   b  of the resistor are provided while being exposed in the respective paddle holders  11   a ,  11   b.    
   Consequently, when the electrode paddles  5   a ,  5   b  are housed in the paddle holders  11   a ,  11   b  as shown in  FIG. 4 , the electrode paddles  5   a ,  5   b  come into contact with the terminals  12   a ,  12   b . As a result, the electrode paddles  5   a ,  5   b  are electrically connected together by way of the built-in resistor. 
   In order to check the waveform of the electric pulse for maintenance purpose, an electric pulse is output between the electrode paddles  5   a ,  5   b  through actuation of the control panel  1  while the electrode paddles  5   a ,  5   b  are housed in the paddle holders  11   a ,  11   b . The output waveform analyzer  6  is caused to analyze the electric pulse, and the result of analysis can be displayed on the screen  7 . 
   When the electric pulse is being analyzed for maintenance purpose, a message “Basic Checks,” for example, is displayed on the screen  7  by the processor  2 . In contrast, when the electric pulse actually output for defibrillating a patient is being analyzed, a message “Actual Treatment,” for example, is displayed on the screen  7  by the processor  2 . Thus, the two cases may be distinguished from each other. 
   Moreover, there may be stored a mark or flag to be used for distinguishing a case where the electric pulse has been analyzed for maintenance by establishing a link to the electric pulse to be stored in the storage  8  and the analysis result thereof, from a case where the analysis result of the electric pulse actually output for defibrillating a patient has been made. As a result, when the stored data are read, the case for which the data have been acquired can be determined. 
   A time at which the electric pulse is output may be stored while being linked with the electric pulse to be stored in the storage  8  and the result of analysis thereof. As a result, when the stored data are read, a time at which maintenance has been performed or a time at which the defibrillation is performed can be checked. 
   A discharge test may be performed during the course of an operation to be performed daily for checking basic operations. The test result may be read from the storage  8  after completion of testing of all items and displayed on the screen  7 . Storage of such data into the storage  8  is considerably important for verifying whether or not maintenance action and clinical treatment have been performed appropriately. 
   In this embodiment, as shown in  FIG. 1 , the output waveform analyzer  6  is designed to detect a voltage waveform developing between the electrodes  5   a ,  5   b . However, the output waveform analyzer  6  may be an electrical element provided in the pulse generator  4  and may detect a voltage of an energy charging element (e.g., a capacitor) which temporarily charging the electric energy supplied from the power source  3 . 
   Such an example will be described with reference to an electrical circuit for outputting a biphasic waveform, which is disclosed in Japanese Patent Publication No. 2001-245992A.  FIG. 5  shows a defibrillator employing the electrical circuit. 
   A positive terminal of the capacitor (energy charging element)  104  is connected to an inductor  105  by way of a switch  101 . The other terminal of the inductor  106  is connected to the negative terminal of the capacitor  104  by way of a switch  103 . The other terminal of the inductor  105  is also connected to one electrode paddle  112   a  for applying an electric pulse to a living body  113  (an impedance  113   a  of the living body), by way of an inductor  110  through a switch  102 . Another electrode paddle  112   b  is connected to the negative terminal of the capacitor  104 . 
   Diodes  108 ,  109  for preventing backflow of an electric current are connected in series between the switch  101  and the inductor  110 , with the inductor  110  being taken as an anode side and the switch  101  being taken as a cathode side. The capacitor  106  and the resistor  107  for smoothing a waveform are interposed between the two diodes; that is, between the cathode of the diode  109  and a node which is located between the inductor  105  and the switch  102 . Further, a protective resistor  111  is interposed between the electrode paddles  112   a ,  112   b.    
   The capacitor  104  is charged by a charging circuit  115 . Diodes  117 ,  118  for preventing backflow of an electric current are interposed between the respective electrodes of the capacitor  104  and the charging circuit  115 . A voltage detection circuit  114  is connected across both electrodes of the capacitor  104 , to thereby detect a voltage to be used for charging the capacitor  104 . A voltage signal  122  for transmitting the thus-detected voltage is output to a microprocessor  116 . 
   The voltage detected by the voltage detection circuit  114  is also transmitted to a capacitor voltage analyzer  6   a  as a voltage signal  122 . The capacitor voltage analyzer  6   a  analyzes the received voltage signal  122 , and the result of analysis is transmitted to and displayed on the screen  7 . The voltage signal  122  is also transmitted to and stored in the storage  8 . The result of analysis performed by the capacitor voltage analyzer  6   a  is also transmitted to and stored in the storage  8 . 
   Connection is established such that opening and closing actions of the switches  101 ,  102 , and  103  are respectively controlled by a drive circuit  119  of the switch  101 , a drive circuit  120  of the switch  102 , and a drive circuit  121  of the switch  10 . The drive circuits  119 ,  120 , and  121  are controlled by control signals  124 ,  125 , and  126  output from the microprocessor  116 . The microprocessor  116  controls the charging circuit  115  by a control signal  123 . 
   Preferably, the switches  101 ,  102 , and  103  are constituted of semiconductor switches formed from an insulated gate bipolar transistor (IGBT). 
   In  FIG. 5 , portions corresponding to the pulse generator  4  and the processor  2  are enclosed by dashed lines for reference purposes. 
   A method for controlling an output of electric pulse from the defibrillator will now be described. First, an operation for charging the capacitor  104  with electric energy will be described. 
   A charging start instruction is input to the microprocessor  116  (Step  1 - 1 ). The microprocessor  116  outputs control signals  124 ,  125 , and  126  to drive circuits  119 ,  120 , and  121  of the respective switches such that the switches  101 ,  102 , and  103  become a continuous non-conductive state (Step  1 - 2 ). The switches  101 ,  102 , and  103  become the continuous non-conductive state (Step  1 - 3 ). 
   The microprocessor  116  outputs a control signal  123  to the charging circuit  115  to start charging (Step  1 - 4 ). The charging circuit  115  starts charging the capacitor  104  with energy (Step  1 - 5 ). The microprocessor  116  receives the voltage signal  122  from the voltage detection circuit  114 . When the voltage of the capacitor  104  detected by the voltage detection circuit  114  has increased to a predetermined voltage, the microprocessor  116  outputs a control signal  123  to the charging circuit  115  to stop charging (Step  1 - 6 ). The charging circuit  115  stops charging the capacitor  104  with energy (Step  1 - 7 ). 
   Next, in relation to an operation for outputting electric energy to the electrode paddles  112   a ,  112   b  for applying an electric pulse from the capacitor  104  to the living body (patient)  113 , an operation to be performed at the time of output of a positive-phase waveform will be described by reference to  FIG. 6 . 
   The discharge start instruction is input to the microprocessor  116  in response to the operator&#39;s action for pressing the button  1   c  of the control panel  1  to start discharging (Step  1 - 8 ). The microprocessor  116  outputs control signals  124 ,  126 , and  126  to the switch drive circuits  119 ,  120 , and  121  such that the switches  101  and  102  become a continuous conductive state and the switch  103  becomes a continuous non-conductive state (Step  1 - 9 ) The switches  101 ,  102  become a continuous conductive state, and the switch  103  becomes a continuous non-conductive state (Step  1 - 10 ). The voltage of the capacitor  104  decreases. Electric energy is supplied to the living body (patient)  113  in positive polarity (Step  1 - 11 ). 
   In accordance with a predetermined protocol, the microprocessor  116  outputs the control signals  124 ,  125 , and  126  to the respective drive circuits  119 ,  120 , and  121  such that the switches  101 ,  102  become a continuous non-conductive state and the switch  103  becomes a continuous conductive state, until the voltage of the capacitor  104  is attenuated to a predetermined percentage (e.g., 37%) of the initial voltage (Step  1 - 12 ). The switches  101  and  102  become a continuous non-conductive state, and the switch  103  becomes a continuous conductive state (Step  1 - 13 ). Output of electric energy (i.e., output of the positive-phase waveform) to the living body (patient)  113  is completed (Step  1 - 14 ). 
   Operation for outputting electric energy to the electrode paddles  112   a ,  112   b  for applying an electric pulse to the living body (patient)  113  from the capacitor  104  will now be described. Operation for outputting a negative-phase waveform will now be described by reference to  FIGS. 7 through 9 . 
   As shown in  FIG. 7 , when the switch  101  has become conductive (first time) at the time of output of the negative-phase waveform, an electrical current flows along a current path  151  designated by the arrow. The inductor  105  and the capacitor  104  constitute a closed circuit within the device without including the living body. At this time, the electric energy of the capacitor  104  is stored in the inductor  105  as magnetic energy as a result of flow of an electrical current through the current path  151 . Electric energy is not output to the living body (patient)  113  during this step. 
   As shown in  FIG. 9 , when the switch  101  is in a non-conductive state at the time of output of the negative-phase waveform, the electric current flows along the current path  153  designated by the arrow. At this time the diodes  108  and  109  become conductive by a forward bias, whereupon the magnetic energy stored in the inductor  105  is output as electric energy. The electric current flows along the current path  153 . As a result, there is achieved a state in which the electric energy is output to the living body (patient)  113 . Concurrently, the electric current also flows into the capacitor  106 , and consequently the electric energy is stored in the capacitor  106 . 
   As shown in  FIG. 8 , when the switch  101  is conductive (second times or subsequent times) at the time of output of the negative-phase waveform, the electric current flows along the current paths  151 ,  152  designated by the arrows. At this time, the diode  108  is reversely biased and brought into a nonconductive state. The diode  109  remains in a conductive state by a forward bias. Consequently, the electric energy stored in the capacitor  106  is output, whereupon the electric current flows along the current path  152 . As a result, there is maintained a state in which the electric energy is output to the living body (patient)  113 . Simultaneously, as a result of flow of the electric current along the current path  151 , the electric energy stored in the capacitor  104  is stored as magnetic energy in the inductor  105 . 
   The microprocessor  116  outputs a control signal to the drive circuit  119  of the switch  101  for controlling on/off operation of the switch  101  so that an intended waveform can be output through use of a predetermined reference curve (Step  1 - 15 ). The switch  101  performs switching operation for repeating conduction/cutoff operation (Step  1 - 16 ). The voltage of the capacitor  104  decreases. Electric energy is supplied to the living body (patient)  113  in negative polarity (Step  1 - 17 ). 
   In accordance with a predetermined protocol, the microprocessor  116  outputs the control signal  124  to the drive circuit  119  of the switch  101  such that the switch  101  becomes a continuous non-conductive state (Step  1 - 18 ). The switch  101  becomes a continuous nonconductive state (Step  1 - 19 ). Output of the energy (i.e., the negative-phase-waveform output) to the living body (patient)  113  ends (Step  1 - 20 ). 
   Through these steps, the status of the current path of the circuit continues from that shown in  FIG. 7 , to that shown in  FIG. 9 , and to that shown in  FIG. 8 , by switching operation for causing the switch  101  to repetitively perform on/off operation. In subsequent steps, the status shown In  FIG. 9  and that shown in  FIG. 7  are repeated. 
   During the duration of the forgoing round of operations, the voltage waveform of the capacitor  104  detected by the voltage detection circuit  114  is analyzed by the capacitor voltage analyzer  6   a . A result of analysis is displayed on the screen  7 . Further, the analysis result is stored in the storage  8 . 
   The voltage waveform of the capacitor  104  and a voltage waveform developing between the electrode paddles  112   a ,  112   b  will now be described by reference to  FIGS. 10A and 10B .  FIG. 10A  Is a voltage waveform of the capacitor  104 , and  FIG. 10B  shows a voltage waveform of the electrode paddles  112   a ,  112   b.    
   The voltage waveform developing during a first-phase period D1, which is depicted in both  FIGS. 10A and 10B , is of a positive phase. The voltage waveform is attenuated in the manner of an exponential function from a voltage V0a to a voltage V1a and from a voltage V0b to a voltage V1b. 
   As shown in  FIG. 10A , the voltage of the capacitor  104  is attenuated in a positive phase during a second-phase period D2. The voltage Vt is the voltage of the capacitor  104  obtained at the end of the second phase. As shown in  FIG. 10B , a voltage between the electrode paddles assumes a negative phase. 
   A method for determining items shown in  FIG. 2  from the voltage waveform of the capacitor  104  will now be described. 
   “{circle around (4)} Phase 1” designates the first-phase period D1, which can be determined from the time required to attenuate the voltage to a predetermined voltage level. 
   “{circle around (5)} Phase 2” designates the second-phase period D2, which can be determined from the time during which the microprocessor  116  has performed control operation for outputting an intended output waveform through use of a predetermined reference curve. 
   The voltage of the first-phase waveform obtained at the initiation of discharge is V0b. “{circle around (3)} Voltage” can be determined from a voltage V0a obtained at the time of initiation of discharge of the capacitor  104 , in consideration of a voltage drop arising in another electrical element. 
   “{circle around (2)} TTR” designates resistance developing between the electrode paddles, which can be determined by the following equation. 
                 TTR   =              -     D1   C       ⁢     1       log   ⁢           ⁢   V0a     -     log   ⁢           ⁢   V1a           -   Rin                  (   1   )               
Here,
     D1: duration of the first phase   C: electrical capacitance of the capacitor  104     V0a: discharge start voltage of the capacitor  104  at the first phase   V1a: discharge end voltage of the capacitor  104  at the first phase   Rin: Internal resistance of a circuit   
   “{circle around (1)} Delivered” designates the quantity of output electric energy, which can be determined by the following equation. 
                 Edelivered   =       (         CV0a   2     2     -       CVt   2     2       )     ⁢     (     TTR     TTR   +   Rloss       )               (   2   )               
Here,
     C: electrical capacitance of the capacitor  104     V0a: discharge start voltage of the capacitor  104  at the first phase   Vt: discharge end voltage of the capacitor  104  at the second phase   TTR: resistance between the electrode paddles  112   a ,  112   b      Rloss: value determined by converting an internal loss of a circuit into resistance   
   As shown in  FIG. 2 , the thus determined values are displayed on the screen  7 . As mentioned above, the model waveform is displayed along with the index marks so that visual confirmation can be facilitated. 
   In the embodiment, the voltage detection circuit  114  detects the voltage of the capacitor  104 . However, the voltage detection circuit  114  may detect and analyze the voltage developing between the electrode paddles  112   a ,  112   b.    
   Although the present invention has been shown and described with reference to specific preferred embodiments, various changes and modifications will be apparent to those skilled in the art from the teachings herein. Such changes and modifications as are obvious are deemed to come within the spirit, scope and contemplation of the invention as defined in the appended claims.