Abstract:
There is disclosed a system for monitoring a prenatal condition of a patient and reporting the monitored condition. The system includes a monitor which may be worn by the patient and which generates an electrical signal representing uterine electrical activity of the patient. A microprocessor is configured for analyzing a characteristic of the electrical signal to generate data indicative of the condition and a transmitter transmits the generated data to a receiver, separated from the monitor. The receiver receives the transmitted data and includes a display for displaying the received data.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is generally directed to a system and method for providing long-term monitoring of uterine activity of an animal. The present invention is more particularly directed to such a system and method wherein a monitor is wearable by a patient and provides long-term monitoring and trending of uterine activity during the prenatal period 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. 
     Preterm delivery, or delivery before 37 weeks of gestation, occurs in over 10% of births and also contributes directly to neonatal morbidity and mortality. For infants born between 25 and 30 weeks gestation, the mortality rates are between 10% and 20%. The morbidity of the surviving infants correlates directly with the degree of prematurity. Common problems for the infant include respiratory distress syndrome (RDS) which may require chronic oxygen therapy, intra-ventricular hemorrhage (IVH) which is a harbinger of cerebral palsy, necrotizing enterocolitis (NEC) which can lead to short gut and chronic malnutrition, and patent ductus arteriosus (PDA) which contributes to pulmonary edema and respiratory distress. The incidence of these complications for infants born at 28 and 32 weeks gestation are summarized in Table I below. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE I 
               
               
                   
                   
               
               
                   
                 28 Weeks 
                 32 Weeks 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 RDS 
                 64% 
                 28%  
               
               
                 IVH 
                  4% 
                 1% 
               
               
                 NEC 
                 25% 
                 6% 
               
               
                 PDA 
                 43% 
                 9% 
               
               
                   
               
             
          
         
       
     
     The incidence of neonatal morbidity can be significantly reduced if a woman with premature labor receives corticosteroid therapy for one to two days prior to delivery. For example, antenatal glucocorticoid treatment decreases the incidence of RDS, with an odds ratio of 0.31. The incidence of pariventricular hemorrhage and NEC are reduced as well. Clearly, premature labor leading to preterm delivery contributes greatly to neonatal morbidity and mortality, and efforts to delay delivery frequently result in an improved neonatal outcome. 
     Electrical energy applied to the myometrium or uterine muscle has been proposed to inhibit or initiate 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 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. 
     The application of electrical energy to the myometrium as taught in the Karsdon patents is believed to hold great promise in the management of premature labor and prolonged term pregnancies. However, neither of the Karsdon patents addresses the issue of the long-term monitoring of such patients to facilitate a prediction of whether premature labor inhibition or prolonged term pregnancy labor initiation may be required for a patient. 
     SUMMARY OF THE INVENTION 
     The invention therefore provides a monitor for monitoring a prenatal condition of a patient and reporting the monitored conditions. The system includes a monitor adapted to be coupled to the patient including means for generating an electrical signal representing uterine electrical activity of the patient, analyzing means for analyzing a characteristic of the electrical signal to generate data indicative of the condition, and a transmitter for transmitting the generated data. The system further includes a receiver, separated from the monitor, for receiving the transmitted data and including a display for displaying the received data. 
     The invention further provides a monitor for monitoring a prenatal condition of a patient and reporting the monitored condition. The monitor includes electrical signal generating means for generating an electrical signal representing uterine electrical activity of the patient, analyzing means for analyzing a characteristic of the electrical signal to generate data indicative of the condition, and a transmitter for transmitting the generated data to a separate receiver for display. 
     The invention still further provides a monitor for monitoring a prenatal condition of a patient including electrical signal means for generating an electrical signal representing uterine electrical activity of the patient, analyzing means for analyzing a characteristic of the electrical signal to generate data indicative of the condition, and alarm means for providing a perceptible indication when the generated data satisfies predetermined 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 schematic representation of a prenatal uterine monitoring system for providing long-term prenatal uterine monitoring and trending in accordance with a preferred embodiment of the present invention; and 
     FIG. 2 is a block diagram of a monitor embodying further aspects of the present invention and which may be utilized in the system of FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, it schematically illustrates a monitoring system  20  for providing long-term prenatal uterine monitoring of a partially depicted pregnant patient  10 . As will be noted in the figure, the patient has a uterus  11  and a fetus  12  disposed within the uterus  11 . The uterus is enclosed by the abdominal wall  13  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 . 
     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 per burst and which are widely spaced apart by separations of 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, uterine contraction electrical bursts of energy may have durations ranging from, for example, several seconds per bursts with separations on the order of minutes. 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. 
     In accordance with the present invention, the condition of the uterus is monitored long term by ascertaining the durations of uterine electrical bursts and the intraburst separations or burst frequency intervals. At the end of data acquisition periods, for example, at six-hour intervals or four times per twenty-four hour period, the durations and burst frequency intervals for the uterine muscle electrical bursts occurring during the last data acquisition period are averaged. The average burst duration and average burst frequency interval, along with a corresponding time stamp, are then stored for later retrieval. This provides a trend, over time, of the condition of the patient&#39;s uterus. Once retrieved, this data can be very valuable to the physician in evaluating the condition of the patient. For example, it is generally known that normal patients not likely to have premature labor exhibit increased uterine electrical activity at night. The uterine activity burst frequency intervals of these patients are generally less during the day than at night. Conversely, patients likely to have premature labor generally do not exhibit increased uterine activity at night. Hence, for these patients, the uterine activity burst frequency intervals tend to be about the same during the day and at night. As a result, by time stamping the average burst frequency interval every six hours, the physician is provided with a diurnal pattern of uterine activity to assist in predicting potential premature labor. 
     Other features and advantages of the present invention will become apparent as attention is once again directed to FIG.  1 . The monitoring system  20  includes a monitor  40  which is coupled to the patient  10  by electrodes  22  and  24  and leads  26  and  28  respectively. The monitor  40  is dimensioned so as to be readily worn by the patient  10 . The electrodes  22  and  24  as illustrated are surface electrodes of the type well known in the art which make electrical contact with the patient&#39;s abdomen  13 . The leads  26  and  28  are electrically coupled to the electrodes  22  and  24  respectively. As is also well known in the art, the leads  26  and  28  may be detachable from the electrodes  22  and  24  respectively when activity of the patient so dictates. 
     The leads  26  and  28  include connectors  27  and  29  respectively for connection to the monitor  40 . When the electrodes  22  and  24  are coupled to the patient and when the leads  26  and  28  are coupled between the electrodes  22  and  24  respectively and the monitor  40 , internal circuitry of the monitor to be described subsequently generates an electromyographic signal (EMG) representing the electrical activity of the uterus  11 . 
     The internal circuitry within the monitor as described subsequently analyzes the EMG signal whenever there is a burst of electrical activity of the myometrium  16 . For each such burst, a microprocessor within the monitor  40  determines the duration of the burst and the time span or interval between the starting time of the present or most recent burst and the starting time of the immediately preceding burst. The microprocessor then stores these acquired data or results in a memory. At the end of a data acquisition period, for example, six hours, the microprocessor accesses from the memory the data acquired during the just completed or last data acquisition period. An averaging stage of the microprocessor averages that data to provide averaged data in the form of the average burst duration and the average burst frequency interval. The averaged data is then time stamped by the microprocessor and stored in memory. 
     As also illustrated in FIG. 1, the monitor  40  includes a serial port  42  in the form of a standard telephone jack which is coupled to a standard telephone wall jack  30  within the patient&#39;s home  34  by a telephone cord  32 . The monitor  40  further includes a pushbutton switch  44  which, when depressed, activates a modem within the monitor  40  for transmitting by facsimile the averaged data and corresponding time stamps over a standard telephone system  36 . The depression of the switch  44  also activates an autodialer within the monitor  40  for automatically dialing the facsimile telephone number of the patient&#39;s physician&#39;s office  35 . 
     To that end, and in accordance with the present invention, the monitoring system  20  further includes a receiver  31  within the physician&#39;s office  35  which includes a facsimile machine  33  and a printer  37 . The facsimile machine  33  is coupled to a standard telephone wall jack  39  within the physician&#39;s office  35  by a telephone cord  29 . As a result, the stored averaged data and the corresponding time stamps may be transmitted from the monitor  40  to a distant facsimile machine  33  to enable the physician to receive the transmitted data and evaluate the patient&#39;s condition. Preferably, the facsimile transmission is formatted by the monitor  40  so that the printer  37  may provide a printed display of the received averaged data and time stamps in, for example, a bar graph format to clearly indicate the trend of the electrical activity of the patient&#39;s myometrium  16  or uterus  11 . 
     Lastly, the monitor  40  includes a speaker  46  for emitting a discernable audible alarm signal to advise the patient to call the physician. As will be seen hereinafter, whenever the monitor  40  generates a new burst duration and burst frequency interval, it compares this data to a predetermined criteria. If the data exceeds the predetermined criteria, the speaker  46  will sound an alarm to indicate to the patient that the physician should be consulted. The speaker  46  may further be utilized to remind the patient to transmit the averaged data and corresponding time stamps to the physician. To this end, the speaker  46  may be activated by a clock which periodically indicates to the patient when the stored averaged data and corresponding time stamps should be transmitted to the physician&#39;s facsimile machine  33 . 
     Referring now to FIG. 2, it illustrates, in block diagram form, the monitor  40  of FIG. 1 in accordance with a preferred embodiment of the present invention. In addition to the standard telephone jack  42 , the pushbutton switch  44 , and the speaker  46 , the monitor  40  includes input terminals  48  and  50 , a detector  52  including a current source  54 , and a current detector  56 , a sense amplifier  58 , and capacitors  60  and  62 . The monitor further includes a band pass filter  64 , a threshold detector  66 , a microprocessor  68 , a memory  70 , a modem  72 , and an autodialer  74 . 
     The input terminals  48  and  50  are arranged to receive the connectors  27  and  28  respectively of the leads  26  and  28  respectively as illustrated in FIG.  1 . The input terminals  48  and  50  are capacitively coupled to the sense amplifier  58  by the capacitors  60  and  62 . 
     The detector  52  including the current source  54  and current detector  56  detects when the monitor is coupled to the patient. When the input terminals  48  and  50  are coupled to the patient by the electrodes  22  and  24 , the patient  10  will present to the input terminals  48  and  50  a load of approximately 1,000 ohms. The current source  54  provides a DC current of about, for example, 1 microamp. When the terminals  48  and  50  of the monitor  40  are coupled to the patient, the current detector  56  will detect a current on the order of 1 microamp. This will indicate to the monitor that the patient is coupled to the monitor. Conversely, when the patient is not coupled to the monitor  40  as by, for example, one of the input terminals  48  or  50  not being coupled to the patient, the current detector  56  will detect no current to indicate to the monitor that the patient is not currently connected to the monitor. 
     When the patient is coupled to input terminals  48  and  50 , the sense amplifier  58  will generate an electromyographic (EMG) signal which is bandpassed filtered by the bandpass filter  64 . The bandpass filter  64  preferably has a bandpass from 1 Hertz to 100 Hertz. The bandpass filtered EMG signal is conveyed to the threshold detector  66 . The electrical energy bursts of both contractures and contractions of the electromyographic signal are made up of electrical waves having separations of, for example, 300 milliseconds to 900 milliseconds (300 ms to 900 ms). Whenever an electrical wave of the bandpass filtered EMG signal exceeds a threshold magnitude set by the threshold detector  66 , the threshold detector will provide an output to an interrupt input  76  of the microprocessor  68 . 
     The implementation of the microprocessor  68  in accordance with this embodiment of the present invention results in a plurality of functional stages. The stages include an enable stage  80 , a burst duration stage  82 , a burst frequency interval stage  84 , a timer  86 , and an averaging stage  88 . The functional stages further include an alarm stage  90 , a comparator stage  92 , a clock stage  94 , and a facsimile format stage  96 . The clock stage  94  includes a clock  98  and a time stamp stage including the time of day stage  100  and a date stage  102 . 
     The microprocessor  68  is arranged to operate in conjunction with the memory  70  which may be coupled to the microprocessor  68  by a multiple-bit address bus  104  and a bi-directional multiple-bit data bus  106 . This permits the microprocessor  68  to address desired memory locations within the memory  74  for executing right or read operations. During a right operation, the microprocessor  68  stores data in the memory at memory locations defined by the multiple-bit address bus  104  and conveys the data to the memory over the multiple-bit data bus  106 . During a read operation, the microprocessor  68  accesses the memory at stored location identified by the multiple-bit address bus  104  and receives the data from the memory over the bi-directional data bus  106 . 
     The memory  70  includes a plurality of memory locations or portions. These include a data portion  108  for storing data such as burst initiation time stamps, burst completion time stamps, burst durations, and burst frequency intervals. The memory locations or portions of the memory  70  further include a criteria portion  110  for storing alarm criteria, for example, a memory location  112  for storing averaged burst frequency intervals and a further portion  114  for storing averaged burst durations. 
     As previously mentioned, whenever an electrical wave of the bandpass filtered EMG provided by sense amplifier  58  and bandpass filter  64  exceeds a threshold magnitude established by the threshold detector  66 , the threshold detector will provide an output to the interrupt input  76  of the microprocessor  68 . The burst duration stage  82  time stamps each interrupt input and stores each time stamp in memory portion  108  of memory  70 . It also, with timer  86 , starts keeping time from each interrupt input. When the timer  45  has timed a predetermined period of, for example, five seconds without being reset by another interrupt, the burst duration stage  82  considers the current burst to be completed. It then determines the burst duration by accessing the memory  70  at location  108  for the first and last time stamps and computes the time between the first time stamp and the last time stamp as the burst duration. It then stores the burst duration in memory portion  108 . The next interrupt will then represent the beginning of the next burst. 
     Also when a burst is completed, the burst frequency interval stage  84  accesses memory portion  108  of memory  70  for the first time stamp of the just completed burst and the first time stamp of the immediately preceding burst. It then computes the time interval between the first time stamp of the just completed burst and the first time stamp of the immediately preceding burst to determine a burst frequency interval. The burst frequency interval stage  84  then stores the burst frequency interval in memory portion  108  of memory  70 . 
     The foregoing process is carried out for each electrical burst of the myometrium or uterus of the patient. In addition, after each burst is completed, the alarm stage  90  causes the comparator stage  92  to compare the last determined burst duration and burst frequency interval to predetermined criteria. If, for example, the last computed burst duration falls below ninety seconds and the last computed burst frequency interval is less than ten minutes, the alarm  90  responsive to the comparator stage  92  will provide a perceptible indication in the form of an audible alarm from the speaker  46 . This alarm may be used to indicate to the patient that the patient&#39;s physician should be consulted. 
     At spaced apart times, as for example, every six hours or four times per twenty-four hour period, the clock  98  of clock stage  94  causes the microprocessor to generate time stamped trended data. To that end, the clock  98  causes the averaging stage  88  to access memory portion  108  of memory  70  for the burst durations and burst frequency intervals determined during the last data acquisition period. The averaging stage  88  averages the burst durations and the burst frequency intervals to provide trended or averaged burst durations and burst frequency intervals. Each average burst duration and burst frequency interval pair is then stored in memory  70  at memory portions  114  and  112  respectively along with a corresponding time stamp indicating when the average burst duration and average burst frequency interval were determined. The time stamps are provided by the time of day stage  100  and date stage  102 . 
     The detector  52  including the current source  54  and current detector  56 , as previously mentioned, detects when the monitor  40  is coupled to the patient. When the monitor is coupled to the patient, the enable stage  80  responsive to the current detector  56  enables the microprocessor  68 . When the patient is not coupled to the monitor  40 , the enable stage  80  disables the microprocessor burst data gathering activity which then makes note of the time in which the monitor  40  is not coupled to the patient. The times at which the monitor  40  are not coupled to the patient are noted by the clock stage  94  so that an inactive time period of the microprocessor  68  due to the patient not being coupled to the monitor will not be mistaken for an unduly long burst frequency interval. As a result, the integrity of the data generated the microprocessor  68  is assured. 
     As previously mentioned with respect to FIG. 1, occasionally the patient will be called upon to transmit the trended data stored in memory  70  to the physician&#39;s office. As illustrated in FIG. 1, the patient connects the telephone jack  42  to the wall jack  30  to connect the monitor to the telephone system. The patient then depresses switch  44  which causes the autodialer  74  to dial the physician&#39;s facsimile telephone number. Simultaneously, the microprocessor is initiated over a line  116  to cause the facsimile formatting stage  96  to access the trended data in memory portions  112  and  114  of memory  70 , format the data in the form of a facsimile, and convey the data to the modem  72  over a line  118 . The facsimile formatting stage  96  preferably formats the facsimile transmission so that once the facsimile is received by the physician&#39;s facsimile machine, its printer will print out a bar graph of the average burst durations and average burst frequency intervals along with their corresponding time stamps. This will provide the physician with trending data and a diurnal trend of the patient&#39;s uterine electrical activity. The facsimile formatting state  96  may also provide the patient&#39;s name or some other form of patient identification. 
     As can be seen from the foregoing, the present invention provides a monitoring system and method which provides long-term monitoring and trending of uterine activity during the prenatal period of a human. The data generated by the monitor and provided to the physician provides assistance in diagnosing potential prenatal complications and most notably, premature labor. 
     While a particular embodiment of the present invention has been shown and described, modifications may be made, and it is therefore intended to cover in the appended claims all such changes and modifications which fall within the true spirit and scope of the invention.