Abstract:
A system and method for detecting for and initiating contractions of a uterus of a human patient employs a sensor for sensing electrical activity of the uterus of the patient. Data from the sensed electrical activity is stored in memory. A processor accesses the stored data for analysis. Electrical energy is applied to the uterus to initiate a uterine contraction when the analyzed data fails to satisfy predetermined detection criteria.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is generally directed to a system and method for effecting uterine contractions of an animal. The present invention is more particularly directed to such a system and method for detecting and automatically stimulating contractions of the uterus of a human. 
     Prolonged pregnancy, generally classified as a gestational age exceeding 42 weeks of gestation, is associated with increased perinatal morbidity and mortality. Specifically, in addition to the increased neonatal deaths, there is an increase in the meconium aspiration, depressed infant at five minutes, and cesarean section rate. The mortality from meconium aspiration can be as high as 38% for those women managed expectantly. 
     Electrical energy applied to the myometrium or uterine muscle has been proposed to affect uterine contractions. One system and method to this end is disclosed in Karsdon, U.S. Pat. Nos. 5,447,526 and 5,713,940 which are incorporated herein by reference. In accordance with a preferred embodiment disclosed in these patents, a first or positive electrode is placed in surface contact to a woman&#39;s abdomen over the top of the uterus. Four negative electrodes are placed in spaced apart relation in surface contact to the woman&#39;s abdomen over lower portions of the uterus beginning at approximately a mid portion of the uterus. The negative electrodes and the positive electrode are then connected to a muscle controller which generates square wave pulse trains of current between the positive electrode and the negative electrodes. The muscle controller is capable of providing current pulse trains of selectable polarity. The controller is activated to inhibit uterine contractions when they are undesirably present or to initiate uterine contractions when they are undesirably absent. 
     In accordance with a further embodiment disclosed in the above-referenced Karsdon patents, a uterine contraction monitor is added to the system with feedback to the controller. The monitor is disposed for surface contact with the abdomen. The amount of electrical energy applied is thus responsive to the sensed contractions. The feedback may be negative or positive depending upon whether contraction initiation or inhibition is desired. 
     While the contraction monitor of Karsdon represents a significant step forward in the prenatal management of patients, there remains substantial room for improvement. The contraction monitor disclosed in the Karsdon patents is a surface monitor. Such monitors respond to physical movement. 
     As a result, physical movement which is a certainty to occur other than that of real contractions will also be sensed and create a noisy signal environment in which the contraction affecting device must respond. It would be most advantageous to have a contraction monitor which is substantially more specific in detecting uterine contractions. 
     Further, surface monitors must be worn in order to function. Hence, if a patient is to be constantly monitored, the monitor must be worn at all times. This would include times of sleep and other times when such use would either be inconvenient, cumbersome, or confining. 
     In addition, there is no guarantee that such a surface monitor will remain in the same place or that if removed, it will be returned to the same location on the body at a later time. This can result in signals which are variable in amplitude and other characteristics making the application of threshold criterion difficult. 
     Hence, there is a need in the art for an improved uterine contraction detection and stimulation system to initiate uterine contractions. More specifically, such a system must be capable of providing detection signals of good quality, in a low noise environment, and specific to uterine contractions. This would assure that stimulation to initiate uterine contractions will be provided when actually needed and not be provided when such stimulation is not required. The present invention provides such an improved uterine contraction detection and stimulation system. 
     SUMMARY OF THE INVENTION 
     The invention therefore provides a method of detecting for uterine contractions and stimulating a uterus of an animal having a body to initiate uterine contractions when uterine contractions are absent. The method includes the steps of placing first and second electrodes in contact with the body, the first electrode being placed in direct contact with the uterus, sensing electrical activity between the first and second electrodes, detecting for uterine contractions from the sensed electrical activity, and providing electrical current flow between the first and second electrodes when uterine contractions are undetected. 
     The invention further provides a system for detecting for uterine contractions and stimulating a uterus of an animal having a body to initiate uterine contractions when uterine contractions are absent. The system includes a first electrode, a first anchor for anchoring the first electrode to the uterus of the animal, and return current path establishing means for establishing a return current path within the body, the return current path including the first electrode. The system further includes a sense amplifier coupled to the first electrode for sensing electrical activity of the body, a detector coupled to the sense amplifier for detecting for contractions of the uterus from the sensed electrical activity and a source of electrical energy coupled to the first electrode and responsive to the detector failing to detect uterine contractions for providing electrical energy to the body along the return current path for initiating contractions of the uterus. 
     The invention still further provides a system for detecting for uterine contractions and stimulating a uterus of an animal having a body to initiate uterine contractions when uterine contractions are absent wherein the system includes first and second electrodes for establishing a return current path within the body, an anchor for releasably anchoring at least one of the electrodes to the uterus of the animal, a detector coupled to the first and second electrodes for detecting for uterine contractions, and a source of electrical energy responsive to the detector failing to detect uterine contractions for applying electrical energy to the first and second electrodes for initiating contractions of the uterus. 
     The present invention further provides a system for detecting for uterine contractions and stimulating a uterus of an animal to initiate contractions when uterine contractions are absent, the system including a sensor for sensing electrical activity of the uterus, a processor for analyzing the electrical activity of the uterus, and an energy source for applying electrical energy to the uterus responsive to the processor when the electrical activity of the uterus fails to satisfy predetermined detection criteria. 
     The invention further provides a system for detecting for uterine contractions and stimulating a uterus of an animal to initiate contractions when uterine contractions are absent, the system including a sensor for sensing electrical activity of the uterus, means for storing data associated with the sensed electrical activity of the uterus, a processor for analyzing the stored data, and an energy source for applying electrical energy to the uterus to initiate contractions of the uterus responsive to the processor when the analyzed data fails to satisfy predetermined detection criteria. 
     The invention further provides a method of detecting for uterine contractions and stimulating a uterus of an animal to initiate uterine contractions when uterine contractions are absent. The method includes the steps of sensing electrical activity of the uterus, analyzing the electrical activity of the uterus, and applying electrical energy to the uterus to initiate contractions of the uterus when the analyzed electrical activity of the uterus fails to satisfy predetermined detection criteria. 
     The invention still further provides a method of detecting for uterine contractions and stimulating a uterus of an animal to initiate uterine contractions, wherein the method includes the steps of sensing electrical activity of the uterus, generating data associated with the sensed electrical activity, storing the data associated with the sensed electrical activity; analyzing the stored data, and applying electrical energy to the uterus to initiate contractions of the uterus responsive to the analyzed data failing to satisfy predetermined detection criteria. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof may best be understood by making reference to the following description taken in conjunction with the accompanying drawings, in the several figures of which like reference numerals identify identical elements, and wherein: 
         FIG. 1  is a side view, partly cut away, of a pregnant patient and a system for detecting and initiating uterine contractions having a pair of electrodes in direct contact with the patient&#39;s uterus in accordance with a preferred embodiment of the present invention; 
         FIG. 2  is a schematic diagram of a uterine contraction detection and initiation unit embodying further features of the present invention; 
         FIG. 3  is a partial side view to an enlarged scale and partly in cross section illustrating a first step in placing an electrode in direct contact with a uterus of a patient; 
         FIG. 4  is a partial side view to an enlarged scale and partly in cross-section illustrating a further step in placing an electrode in direct contact with a uterus of a patient; 
         FIG. 5  is a partial side view to an enlarged scale and partly in cross-section illustrating an electrode in direct contact with the uterus of a patient in accordance with a preferred embodiment of the present invention; and 
         FIG. 6  is a side view, partly cut away of a pregnant patient and another uterine contraction detection and initiation system embodying the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1 , it schematically illustrates a pregnant patient  10  having a uterus  11  and a fetus  12  disposed within the uterus  11 . The uterus  11  is enclosed by the abdominal wall  18  of the patient and includes an amniotic cavity  14  which is defined by the uterine wall  15 . The uterine wall  15  is primarily comprised of the uterine muscle or myometrium  16 . As is well known, the fetus  12  is disposed within amniotic fluid contained within the amniotic cavity  14 . 
     In accordance with the present invention, a system  19  detects for and initiates contractions of the uterus  11 . More specifically, the system  19  includes a detection and initiation unit  20  including a uterine contraction detector  31  and a source of electrical energy  33 . The system  19  further includes first and second leads  22  and  24  having first and second electrodes  26  and  28  respectively. The first and second electrodes are coupled directly to the uterus  11  to establish a current return path between the electrodes within the myometrium  16 . As will be seen with respect to  FIG. 2 , the electrodes  26  and  28  are coupled to both the detector  31  and energy source  33  of unit  20 . 
     As can be clearly seen in  FIG. 1 , the electrodes  26  and  28  of leads  22  and  24  respectively are in direct contact with the myometrium  16 . The electrodes  26  and  28  are also preferably configured so as to be releasably anchored within the myometrium  16  as will be more particularly described subsequently. 
     In the detection of contractions of the uterus  11 , the electrodes  26  and  28  provide an electromyographic signal (EMG) representing the electrical activity of the myometrium  16 . Because the electrodes  26  and  28  are within the myometrium  16 , the EMG is very specific to the electrical activity of the myometrium  16 . When the EMG satisfies a predetermined criteria to be explained subsequently, uterine contractions are determined to be present. Conversely, when the EMG fails to satisfy a predetermined criteria, uterine contractions are considered to be sufficiently absent to require uterine stimulation for uterine contraction initiation. 
     When contractions of the uterus  11  are to be initiated, the electrical energy source  33  is activated by the detector  31  to provide, for example, trains of square wave voltage pulses. The electrical energy is applied directly to the myometrium  16  along the aforementioned current return path within the myometrium by virtue of the electrodes  26  and  28  being directly in contact with the myometrium  16 . Because the electrodes  26  and  28  are fixedly anchored within the myometrium  16 , they will not be dislodged by the uterine contractions to enable the therapy to have its complete therapeutic effect. However, because the electrodes are releasably anchored, they may be readily removed in a noninvasive manner when no longer needed. 
     To lend further understanding of the present invention, the electrical activity of the uterus can exhibit two distinct forms of activity. One form is that of a uterine contracture which is exhibited long before actual labor. Contractures are represented by bursts of electrical activity which can last on the order of several minutes and which are widely spaced apart by separations of about an hour or more. Contractures are disorganized muscle activity of the myometrium causing minimal, if any, physical manifestations of the myometrium. 
     The other form is that of a uterine contraction. Contractions are represented by relatively short bursts of electrical energy with the bursts being relatively closely spaced apart. For example, during labor, the uterine contraction electrical bursts of energy may have durations of thirty seconds or less with separations on the order of twenty minutes or less. Contractions, as compared to contractures, are organized muscle activity of the myometrium causing pronounced physical manifestations of the myometrium. It is the occurrence of contractions that is most identified as labor. 
     The electrical energy bursts of both contractures and contractions are made up of electrical waves having separations of, for example, three hundred milliseconds to nine hundred milliseconds (300 ms to 900 ms). As will be seen subsequently, one or more characteristics of the EMG electrical bursts are used to identify actual contractions or the lack thereof in need of initiation. 
     Referring now to  FIG. 2 , it illustrates in schematic form, the uterine contraction detection and initiation unit  20  of FIG.  1 . The unit  20  includes the contractions detector  31  and energy source  33  within an enclosure  30 . The unit  20  is turned on by a switch  50  which connects a battery  51  to the various components of the unit  20  when contractions are to be initiated or maintained. 
     Within the enclosure  30  is also a microprocessor  32  which, in a manner well known in the microprocessor art, operates on operating instructions stored in an internal memory  52  or an external memory (not shown). As a result of such operation, the microprocessor  32  implements the contractions detector  31  including burst duration stage  39 , a first timer  41 , an inhibit stage  45  and a second timer  47 . Also, stored in memory portion  53  of memory  52 , are preprogrammed contraction detection parameters or criteria. 
     The contraction detector  31  further utilizes a sense amplifier  35  and a threshold circuit  37 . The sense amplifier  35  has a pair of inputs which are coupled to outputs  68  and  70  of the unit  20 . The outputs  68  and  70  are adapted to be coupled to the first and second electrodes  26  and  28 . 
     The electrodes  26  and  28  provide the EMG representing the electrical activity of the myometrium. The EMG is amplified by the sense amplifier  35 . The amplified EMG is then provided by the sense amplifier  35  to the threshold detector  37 . Whenever an electrical wave from the sense amplifier  35  exceeds a threshold magnitude set by the threshold detector  37 , the threshold detector will provide an output to an interrupt input  43  of the microprocessor  32 . 
     The burst duration stage  39  time stamps each interrupt input and stores each time stamp in memory  52 . It also, with timer  41 , starts keeping time from each interrupt input. When the timer  45  has timed a predetermined time period of, for example, five seconds without being reset by another interrupt, the burst duration stage  39  considers the current burst to be completed. The next interrupt will then represent the beginning of the next burst of electrical activity. 
     The inhibit stage  45  precludes the energy source  33  from stimulating the uterus as long as contractions are sufficiently present. To that end, the second timer  47  starts keeping time from the beginning of each burst as determined by the duration stage  39 . As long as the second timer  47  is reset by the burst duration stage  39  before it times out, the inhibit stage  45  will continue to inhibit the energy source  33 . However, when a next burst fails to begin within the time out time period of the second timer  47 , the inhibit stage  45  activates the energy source  33  for stimulating the uterus to initiate the next contraction. The time out period of timer  47  may be, for example, on the order of two minutes. As a result, if a next burst does not occur within two minutes of its immediately preceding burst, the beginning the contraction detector  31  will consider the contractions to be insufficient and warranting uterine stimulation to initiate the next uterine contraction. Hence, a new contraction will be initiated when a uterine contraction is undetected within a predetermined time from the beginning of an immediately preceding uterine contraction. As can be appreciated by those skilled in the art, the time out period may be tailored to an individual patient. The above time out period is provided as being exemplary only. 
     The energy source  33  includes a charging circuit  34 , an analog to digital converter  36 , a storage capacitor  38 , and an H bridge  40  comprising field effect transistors  42 ,  44 ,  46 , and  48 . 
     The electrical energy source  33  is activated by the inhibit stage  45  of the contractions detector  31  over a line  49  which causes the charge circuit  34  to charge capacitor  38 . The memory  52  has storage locations  54 ,  56 ,  58 ,  60 , and  62  for storing preprogrammed energy delivery parameters such as pulse voltage, pulse polarity, burst duration, pulse interval, and pulse duration respectively. The foregoing parameters including the detection parameters may be stored in the memory  52  with a programming computer (not shown) of the type well known in the art. 
     The charge circuit  34  charges the storage capacitor  38  to the pulse voltage programmed at memory location  54 . The output of the charge circuit  34  is monitored by the analog to digital connector  36  which provides the microprocessor with a digital representation of the output voltage of the charge circuit  34 . In this manner, the microprocessor is capable of regulating or controlling the charge circuit  34  to maintain the preprogrammed pulse voltage across the capacitor  38 . 
     The H bridge  40  is of the type well known in the art which is controlled by the microprocessor  32  over control lines  64  and  66  which are provided with buffers  65  and  67  respectively to accommodate required voltage swings and higher voltage applied to H bridge  40 . The signals provided by the microprocessor over the control lines  64  and  66  cause the energy source  33  to provide a train of output pulses at the output terminals  68  and  70  having the pulse polarity, burst duration, pulse interval, and pulse duration as preprogrammed in memory locations  56 ,  58 ,  60  and  62  respectively of the memory  52 . The output terminals  68  and  70  of the unit  20  are coupled to the leads  22  and  24  respectively as shown in FIG.  1  to provide the electrodes  26  and  28  with the preprogrammed electrical energy. 
       FIGS. 3-5  illustrate a manner in which the electrodes  26  and  28  may be substantially non-invasively placed in direct contact with the uterus  11  through the abdomen  18  and more particularly in direct contact with the myometrium  16  in accordance with a preferred embodiment of the present invention. Referring first to  FIG. 3 , there is illustrated, to an enlarged scale, the abdominal wall  18  and the myometrium  16 . The abdominal wall includes the skin  72  and the abdominal muscle  74 . 
     In an initial step, a removable inner needle  76  is first inserted into an introducer tube  78 . The introducer tube  78  terminates in a conical surface  80  which matches the terminating conical surface  82  of the removable inner needle  76 . With the conical surfaces  82  and  80  aligned as shown in  FIG. 3 , the introducer tube  78  and removable inner needle  76  are moved in unison to pierce the skin  72  and abdominal muscle  74 . Movement of the introducer tube  78  and removable inner needle  76  is terminated when the tip  84  of the needle  76  has entered the space  86  between the abdominal muscle  74  and myometrium  16  to such an extent that the conical surface  80  of the introducer tube  78  is within the space  86 . Once the removable inner needle  76  and introducer tube  78  are positioned as shown in  FIG. 3 , the removable inner needle  76  is withdrawn from the introducer tube  78 . With the removable inner needle  76  thus removed from the introducer tube  78 , the introducer tube  78  is now ready to receive the electrode  26  at the distal end of its lead  22  as illustrated in FIG.  4 . 
     The lead  22  has a cylindrical lead body with an inner electrical conductor  23  which contacts a conductive collar  25  of the electrode  26 . The electrode  26  has a structure  27  secured to the collar  25  by welding, for example. The structure  27  is formed of a relatively rigid conductive wire  29  configured as a screw-in tip. More specifically, the electrode structure  27  is formed in the shape of a helix so that when the lead  22  is introduced through the introducer tube  78  to an extent permitting the electrode  26  to contact the myometrium  16 , rotation of the lead  22  as indicated by the arrow  88  causes the helical screw-in tip  29  of electrode  26  to screw into the myometrium  16 . 
     When the lead  22  has been rotated a sufficient number of turns to fully embed the electrode tip  29  within the myometrium  16 , the lead will be securely, but releasably, anchored within the myometrium  16 . This is illustrated in  FIG. 5  where it can be seen that the helical tip  29  of the electrode  26  is fully embedded within the myometrium  16 . Once this is accomplished, the introducer tube  78  may be removed to thus render the lead  22  passing through the abdominal wall  18  including the skin  72  and abdominal muscle  74  with the electrode  26  securely anchored to the uterus  11  and more specifically, the myometrium  16 . As a result, during the therapy of initiating contractions of the uterus  11 , the contractions of the uterus  11  will not dislodge the electrode  26  from the myometrium  16 . However, when therapy is no longer required and the electrode  26  is no longer needed, it may be readily withdrawn by just rotating the lead  22  in a direction opposite that shown at  88  in FIG.  4  and pulling the lead from the patient when the tip  29  is disengaged from the myometrium. 
     Referring now to  FIG. 6 , it illustrates a further embodiment of the present invention. Here it may be seen that the unit  20  is coupled directly to the myometrium through the lead  22  and electrode  26  as previously described while another lead  90  couples the unit  20  to a surface of the body of the patient  10  with a surface or patch electrode  92 . The patch or surface electrode  92  is in surface contact with a posterior portion of the body of the patient  10  and more specifically, on the back of the patient. With such an arrangement, a return current path is established between the electrodes  26  and  90 . The electrical energy from the energy source  33  of the unit  20  will remain concentrated in the myometrium given the large surface area of electrode  92  compared to electrode  26 . The fetus  12  and the body of the patient  10  will only be exposed to dispersed energy which will be well within safe limits for both the fetus  12  and mother  10 . 
     While particular embodiments of the present invention have been shown and described, modifications may be made, and it is therefore intended to cover in the appended claims all such changes and modification which fall within the true spirit and scope of the invention.