Abstract:
The present invention provides a system for enabling the sensing of changes in pressure in response to uterine muscle tone changes relating to contractions, and for enabling the evaluation of contractions based thereon. The system enables a portion thereof to effectively and efficiently project at least partially below the non-compressed abdominal surface, and provides electrical isolation of the system elements. It enables ease of use and enhanced patient comfort. It also enables maximized sensitivity and minimized system loading retention pressure.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a division of application Ser. No. 11/123,862 filed May 6, 2005 now U.S. Pat. No. 7,862,521, which was a continuation-in-part of a co-pending application Ser. No. 10/113,890 filed on Mar. 27, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is generally related to devices for sensing uterine contractions during labor, and more particularly, to a system and method for sensing the frequency and duration of contractions, and for estimating the relative intensity thereof. 
     2. General Background and State of the Art 
     During a contraction, the muscle tone of the uterus increases. This increase in muscle tone applies pressure to the abdomen. The abdomen hardens and the shape changes due in part to the muscles surrounding the anterior ligament of the uterus pulling the abdomen forward. 
     It is known to provide systems for estimating the force of uterine contractions during labor, generally known as tocodynamometers, which sense, in relative terms, the increase and decrease in abdominal pressure relating to uterine contractions, and enable evaluation thereof. Such systems have typically included a cantilevered beam as a sensor, and a button as a force collector, which is connected to the sensor by a link pin. The output from the system is sent to a. fetal monitor, which displays the relative pressure in the form of a digital reading and strip chart recording. The clinician, in reviewing the chart recording, can observe the progress of labor in terms of contraction frequency and duration, and can obtain a rough indication of the relative intensity of the contractions. 
     However, such systems are relatively large and bulky, require relatively large devices to hold them in place, and are expensive. Further, they are relatively difficult to use, require relativly high belt tension which is uncomfortable, and tend to migrate and require repositioning. 
     It would therefore be desirable to provide a sensing system which would sense the frequency and duration of uterine contractions during labor, and estimate the relative intensity thereof, in a manner which would maximize the sensitivity of the system and enhance ease of use and patient comfort. It would further be desirable to enable unique leveraging thereof, for loading onto the abdomen with the exertion of substantially minimal retention pressure. It would still further be desirable to enable support of the system so as to project into the abdomen wall to efficiently reside below the non-compressed abdominal surface. Moreover, it would be desirable to provide electrical isolation of the patient, to prevent the flow of current thereto 
     Therefore, there has been identified a continuing need to provide a sensing system which will effectively sense uterine contraction frequency and duration during labor, for enabling efficient estimation of the relative intensity thereof. 
     INVENTION SUMMARY 
     Briefly, and in general terms, the present invention, in a preferred embodiment, by way of example, is directed to a system for sensing the frequency and duration, of uterine contractions during labor and estimating the relative intensity thereof. The system is able to sense changes in pressure in response to uterine muscle tone changes relating to contractions, and to enable a fetal monitor to be connected thereto for evaluation of contractions. The system includes a pressure sensor, for sensing changes in pressure responsive to uterine muscle tone changes, positionable against the exterior abdominal wall proximate the uterine muscle, connectable to a fetal monitor for evaluation of contractions during labor, and supportable so as to project into the abdominal wall to reside at least partially below the noncompressed surface of the abdomen. The system also includes a supporting element, for supporting the pressure sensor such that the pressure sensor projects into the abdominal wall to reside at least partially below the non-compressed surface of the abdomen. 
     In accordance with another aspect of the invention, the supporting element may include extending portions which extend from the opposed sides thereof, which include attachment portions and attachment points at the opposed ends thereof, for enabling a securing element to be connected to the attachment portions and attachment points in the opposed ends of the extending portions, to secure the system about the abdomen. The system further includes a force collector, which includes edges thereof. The leveraging provided by the extending portions including the attachment portions, and a leveraging ratio of the distance from the attachment points through the force collector edges, is sufficiently flexible to enable deflection with the tension exerted by the securing element thereon, so that the supporting element conforms to the natural curvature of the abdomen. 
     In another aspect of the invention, the force collector is secured to the pressure sensor, and a protective cover extends over the force collector for protectively covering the force collector. The protective cover may have a vent hole therein, for enabling the venting of trapped air therethrough, and for preventing zero shifts which might occur due to thermal effects. The protective cover enables the force collector to slide over the patient&#39;s skin, and prevents sticking upon repositioning thereof, which might otherwise cause negative pressure readings when the pressure cover is unloaded and returns to its natural state. 
     In still another aspect of the invention, the force collector includes an outer section and an inner section, and the coefficient of thermal expansion of the outer section of the force collector is substantially similar to the coefficient of thermal expansion of the inner section of the force collector, to prevent a zero shift in the pressure reading as the system warms on the patient&#39;s skin. 
     In a further aspect of the invention, the force collector further includes an outer portion of the outer section, and an inner portion of the outer section, and the average thickness of the outer portion of the outer section of the force collector is less than the average thickness of the inner portion of the outer section of the force collector, to overcome slight differences in coefficients of thermal expansion of the outer portion and the inner portion of the outer section of the force collector. The outer portion of the outer section is retained firmly against a non-moving surface, keeping the thickness of the outer portion down in this area, and allowing the outer section to move more freely over the inner portion of the outer section, so as to negate at least a portion of any expansion differences. 
     In still further aspects of the invention, the supporting member includes a plurality of contact pads, and the system further includes a cable for connecting to a fetal monitor at one end thereof, a plurality of connectors extending from the opposite end of the cable and secured to the plurality of contact pads, and a plurality of wires extending from the sensing member to the contact pads. The plurality of connectors may each comprise solid unstranded telephone cable, and the cable which is connectable to the fetal monitor may include an extended venting lumen for enabling venting therethrough, and for enabling underwater use thereof. Solid wire makes it less labor intensive to solder to the contact pads, as there is no twisting and trimming of strands. 
     In accordance with other aspects of the invention, the plurality of connectors in the cable which is connectable to the fetal monitor are able to be soldered directly to the contact pads, for providing a secure connection thereof. In still further aspects of the invention, the programming element comprises a user interface module, includes a processor, and is programmable for a time within the period of the minimum time required to complete a flush of the toilet to the maximum time required to drain all of the water from a toilet tank. It is positionable at a user-accessible location. 
     In other aspects of the invention, the opposed ends of the extending portions of the supporting element include slots and posts, and the securing element includes opposed ends and has buttonholes. The opposed ends of the securing element are able to extend directly over the post, and each of the buttonholes is able to stretch over and interlock with the post to engage therewith for securing the system about the abdomen. 
     In another aspect of the invention, the opposed ends of the extending portions of the supporting element include slots, and the securing element includes opposed ends, each of which includes interengageable elements. The opposed ends of the securing element are able to extend through the slots in the opposed ends of the extending portions and fold thereover, and the interengageable elements are able to interengage for securing thereof. 
     In still other aspects of the invention, the system further includes a cover, for covering the supporting member, the sensing member, and a portion of the cable which is connectable to the fetal monitor. The cover includes a pair of posts, one on each of the opposed ends thereof, the securing element includes opposed ends, and has buttonholes, and each of the buttonholes in the securing element is able to stretch over and interlock with one of the posts to engage therewith for securing the system about the abdomen. 
     These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings, which illustrate by way of example the features of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded top perspective view of a sensing system in accordance with aspects of the present invention; 
         FIG. 2  is a bottom perspective view of a sensing member, wires, and contacts in a supporting member; 
         FIG. 3  is a bottom partly fragmentary plan view of the sensing system; 
         FIG. 4  is a top plan view of a pressure sensor and a supporting element in the sensing system; 
         FIG. 5  is an elevational partly sectional view of a pressure sensor, a force collector, and a supporting element in the sensing system; 
         FIG. 6  is an elevational cross-sectional view of a pressure sensor and a force collector in the sensing system;  FIG. 6  is an underside perspective view of a converting element in the present invention; 
         FIG. 7  is an elevational partly fragmentary view of the system including a ridge area in the supporting element; 
         FIG. 8  is an elevational partly fragmentary view of the system including a counterbore area in the supporting element; 
         FIG. 9  is an elevational view of a supporting element and a securing element in accordance with aspects of the present invention; and 
         FIG. 10  is a perspective view of a cover for the supporting element and a securing element. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, in which like reference numerals refer to like or corresponding parts, the system according to the invention senses the frequency and duration of uterine contractions during labor and estimates the relative intensity thereof. The system is able to sense changes in pressure in response to uterine muscle tone changes relating to contractions, and to enable a fetal monitor to be connected thereto for evaluation of contractions. 
       FIG. 1  presents a sensing system  10  in accordance with the invention, which enables the sensing and monitoring of uterine contractions. The sensing system  10  according to the invention includes a pressure sensor  12 , for sensing changes in pressure responsive to uterine muscle tone changes. The pressure sensor  12  is positionable against the exterior abdominal wall proximate the uterine muscle, and is connectable to a fetal monitor for evaluation of contractions during labor. It is supportable so as to project into the abdominal wall to reside at least partially below the non-compressed surface of the abdomen. The system  10  further includes a supporting element  14 , for supporting the pressure sensor  12 , such that the pressure sensor  12  projects into the abdominal wall to reside at least partially below the non-compressed surface of the abdomen. Also, the system includes a force collector  16 , secured to the pressure sensor  12  so as to bear against the exterior abdominal wall proximate the uterine muscle. The force collector  16  projects into the abdominal wall to reside at least partially below the non-compressed surface of the abdomen. The force collector  16  moves responsive to uterine muscle tone changes, as by displacing or compressing so as to exert pressure responsive thereto relative to the pressure sensor  12 . Further, as seen in  FIG. 3 , the system includes a securing element  18 , for enabling the securing of the pressure sensor  12 , the supporting element  14 , and the force collector  16  in position against the exterior abdominal wall proximate the uterine muscle. 
     The pressure sensor  12  is generally small and lightweight, and the supporting element  14  is generally low profile and lightweight. The pressure sensor  12  is further able to be actuated by an excitation voltage from a fetal monitor, and to send a signal voltage back to the fetal monitor responsive to changes in pressure. The pressure sensor  12  may comprise a piezo-resistive pressure sensor. It includes a supporting member  20 , and a sensing member  22  for sensing changes in pressure responsive to uterine muscle changes relating to contractions, and for enabling a fetal monitor to be connected thereto. The sensing member  22  is supported in the supporting member  20 . 
     There is shown in  FIG. 6  a cross-sectional view of the supporting member  20  which is able to be formed as a supporting part, and which is extendable between the pressure sensor  12  and the supporting element  14 . The supporting member  20  may for example include a gel cup  24  which includes a wall portion  26 , and a base portion  28 . The gel cup  24  is comprised of generally molded plastic material, and is able to be filled with a non-conductive silicone gel to form a portion of the force collector  16 . The supporting member  20  further includes a bonding element  30 , for bonding the force collector  16  to the gel cup  24 , and a ceramic chip substrate  32 . The supporting member  20  may alternatively for example comprise a gel, cup  24 , comprised of generally molded plastic material, and a ceramic chip substrate  32 , or for example may comprise a ceramic chip substrate  32 . 
     Referring to  FIG. 2 , the supporting member  20  includes a plurality of contact pads  34 . A plurality of wires  36  connect the sensing member  22  to the contact pads  34 . In the event of the application of a voltage or current exceeding a limit, the wires  36  connecting the sensing member  22  to the contact pads  34  will fail substantially instantaneously, preventing current from flowing to the patient. The contact pads  34  further are able to receive a plurality of connectors  38 , as seen in  FIG. 1 , which extend in a cable  40  for a fetal monitor. Some baby deliveries are performed in water, requiring a system which is waterproof, as it may be submerged. The sensing member  22  is referenced to atmospheric pressure for proper pressure measurement, whereby for such deliveries a vent is required, which is provided though the cable  40 . The plurality of connectors  38  in the cable  40  may each comprise solid strand telephone cable, and the cable  40  may include an extruded venting lumen  42  for enabling venting therethrough, and for enabling underwater use thereof. The plurality of connectors  38  in the cable  40  may be soldered directly to the contacts pads  34  in the sensing element  12 , for providing a secure connection thereto. The system  10  also includes a cover  44 , for covering the supp supporting member  20 , the sensing member  22 , and a portion of the fetal monitor cable  40 . 
     The sensing member  22  is supported in the supporting member  20  such that the sensing member  22  is able to project into the abdominal wall to reside at least partially below the non-compressed surface of the abdomen. The sensing member  22  comprises the active area of the pressure sensor  1 . 2 . It includes resistors, which may comprise for example thin film resistors deposited thereon, which resistors are able to change the resistance with. changes in applied pressure. The resistors in the sensing member  22  may comprise a balanced resistor network, which may comprise a silicon semiconductor Wheatstone bridge. The sensing member  22  and the supporting member  20  for example may comprise a pressure transducer. Alternatively for example the sensing member  22  and a supporting portion of the supporting element  20  may comprise a pressure transducer, or for example the sensing member  22  and a supporting part of the supporting element  20  may comprise a pressure transducer. The ceramic chip substrate  32  of the supporting member  20  may include compensating resistors therein, for providing compensation for the resistors in the sensing member  22 . 
     As further illustrated in  FIG. 6 , the force collector  16 , which is able to interact with the sensing member  22  by displacing or compressing so as to exert pressure on the sensing member  22  responsive to uterine muscle tone change, is supported in the supporting member  20 . The force collector  16  is formed of a material which is able to be dispensed and formed relative to the gel cup  24 . The gel cup  24  includes the bonding element  30  for providing an adhering portion, to enable the material of which the force collector  16  is formed to adhere thereto. The force collector  16  includes an outer section  46 , an inner section  48 , and an interface  50  ( FIG. 1 ) between the outer section  46  and the inner section  48 . The supporting member  20  supports the sensing member  22  and the inner section  48  of the force collector  16  therein, and supports the outer section  46  of the force collector  16  thereon. The outer section  46 , which may be comprised for example of an ultraviolet-cured flexible adhesive, projects from the supporting element  14 . The inner section.  48  is comprised of compliant material, for example a silicone gel, and contacts the sensing member  22 . The force collector  16  projects from the supporting element  14  and is moveable therein. The supporting member  20  and the inner section.  48  of the force collector  16  are further able to support the pressure sensor  12  so as to isolate the pressure sensor  12  from the external environment, to prevent current from flowing to the patient. The compliant material of the inner section  48  of the force collector  16  is able to be formed in the wall portion  26 , on the base portion  28  of the gel cup  24  and the ceramic chip substrate  32 , and over and about the piezo-resistive pressure sensor  12 . 
     The force collector  16  is generally in the shape of a nipple, and may be comprised of a generally soft and compliant material. The generally compliant material of which the force collector  16  is comprised for example may be a generally compliant polymer material, a generally compliant monomer material, or another generally compliant material such as latex. The force collector  16  may alternatively for example be comprised of a generally noncompliant material which includes compliant material therein, such as an oil. The generally compliant material and the generally non-compliant material may comprise a generally soft low durometer material or a generally non-low durometer non-compliant material. The system  10  may include a protective cover  52 , which extends over the force collector  16  to provide additional protection for the generally low durometer embodiment of the force collector  16 . The protective cover  52  may be thin, may be comprised of polyethylene, and may have a vent hole  54  therein, for enabling the venting of trapped air therethrough. The protective cover  52  also enables the force collector  16  to slide over the patient&#39;s skin, and prevents the force collector  16  from sticking to the patient&#39;s skin, when the clinician wishes to reposition the system  10 . The vent hole  54  prevents the air from expanding as it warms up on the patient&#39;s abdomen, which may otherwise cause a zero shift in the pressure reading. The protective cover  52  is also able to prevent sticking of the force collector  16 , which might otherwise pull on the force collector  16  causing negative pressure readings when the protective cover  16  is unloaded and returns to its natural state. 
     An outer section-inner section ratio comprises the ratio of the linear width of the force collector outer section  46  to the linear width of the force collector inner section  48 . The width of the linear width of the outer section  46  of the force collector  16  comprises the linear widest width thereof. The ratio for example is no greater than about three and one-half to one, and may be about two and one-half to one. An interface-inner section ratio comprises the ratio of the cross-sectional area of the width of the force collector interface  50  to the cross-sectional area of the width of the force collector outer section  46 . The interface-inner section ratio of the interface  50  of the force collector  16  to the outer section  46  of the force collector  16  is substantially minimal. The interface-inner section ratio may comprise the ratio of the cross-sectional area of the width of the interface  50  to the cross-sectional area of the width of the inner section  48 . The cross-sectional area of the width of the force collector  16  comprises the cross-sectional area of the widest width thereof. The ratio for example is no greater than about eight to one, and may be about four to one. 
     The coefficient of thermal expansion of the solid non-fluid outer section  46  of the force collector  16  is substantially similar to the coefficient of thermal expansion of the solid non- fluid inner section  48  of the force collector  16 . If there is a difference in the coefficient of thermal expansion between the outer section  46  and the inner section  48  of the force collector  16 , a zero shift in the pressure reading may result as the system  10  warms on the patient&#39;s skin. The average thickness of an outer portion  56  of the outer section  46  of the force collector  16  is less than the average thickness of an inner portion  58  of the outer section  46  of the force collector  16 , to overcome slight differences in coefficients of thermal expansion of the outer portion  56  and the inner portion  58  of the outer section  46  of the force collector  16 . The outer portion  56  of the outer section  46  is retained firmly against a nonmoving surface, thereby keeping the thickness of the outer section.  46  down in this area, and allowing the outer portion  56  of the outer section  46  to move more freely over the inner portion of the outer section  46 , so as to negate at least a portion of any expansion differences. 
     The pressure sensor  1 . 2  is able to be formed such that ratios of the pressure sensor  12  relative to the force collector  16  are substantially minimal so as to maximize the sensitivity of the system  10 . An inner section-sensing member ratio of the inner section  48  of the force collector  16  to the sensing member  22  of the pressure sensor  12  is substantially minimal. The inner section-sensing member ratio comprises the ratio of the area of the width of the force collector inner section  48  to the width of the sensing member  22 . The width of the force collector inner section  48  and the width of the sensing member  22  comprises the width in any direction thereof. The ratio for example is no greater than about three and one-half to one, and may be about two and one half to one. Alternatively, the inner section- sensing member ratio comprises the ratio of the area of the force collector inner section  48  to the area of the sensing member  22 . The ratio for example is no greater than about eight to one, and may be about five to one. 
     The securing element  18  for example comprises a belt, which is comprised of generally elastic material. The generally elastic material may for example comprise an elastic nylon material, or an elastic polyester material. The supporting element  14  also leverages the pressure sensor  12 , so as to enable the securing element  18  to load the pressure sensor  12  onto the abdomen, with substantially minimal retention pressure exerted by the securing element  18  on the pressure sensor  12 . Further, the supporting element  14  is comprised of a flexible material or a non-flexible material, such that, in conjunction with the securing element  18 , the flexible material or the non-flexible material maintains a load on the pressure sensor  12  during abdominal changes in response to contractions. The flexible material of which the supporting element  14  may be comprised is preferably a flexible plastic material, which flexible plastic material may constitute for example a thermoplastic such as polycarbonate. 
     In the embodiment as seen in  FIGS. 1 ,  3 - 5 , and  7 - 8 , the supporting element  14  further includes extending portions  60  which extend from the opposed sides  62  of the supporting element  14 , which extending portions  60  include opposed ends  64 , to which opposed ends&#39; 66  of the securing element  18  are attachable, to provide leverage for the force collector  16 . The extending portions  60  include the opposed ends  64 , attachment portions  68  at the opposed ends  64  thereof, and an attachment point  70  at which the attachment portions  68  enable the securing element  18  to secure the system  10  about the abdomen. The attachment point  70  is a distance from the force collector  16  such that the extending portions  60  including the attachment portions  68  thereof leverage the force collector  16 . The leveraging provided by the extending portions  60  including the attachment portions  68  is sufficiently flexible to deflect with the tension exerted by the securing element  18  thereon, so that the supporting element  14  conforms to the natural curvature of the abdomen. The force collector  16  includes edges  72  thereof, and a leveraging ratio of the distance from the attachment points  70  through the edges  72  of the force collector  16 , to the width of the force collector  16 , is greater than 1.5 to 1, and may be greater than 13 to 1. 
     The supporting element  14  may include an inhibiting portion  74 , comprising a ridge area  76 , as seen in  FIG. 7 , or a counterbore area  78 , as shown in  FIG. 8 , each of which comprises a detail such as a meniscus, and which is formed relative to the bonding element adhering portion  30 , for inhibiting the material of which the force collector  16  is formed from flowing beyond the adhering portion  30 , so as to prevent the material from affecting the sensitivity of the system. The sensitivity of the active area in the sensing member  22  is affected by the extent of the force collector  16  which is supported thereon which extends beyond the width of the sensing member  22  and is outside the active area thereof. The inhibiting portion  74  reduces the relative surface tension of the supporting element  20  therebeyond for the nipple material of the force collector  16 , so as to resist the nipple material from flowing therebeyond. The ridge area  76  in  FIG. 7 , for example, may be about 0.005 inches high by 0.010 inches wide. 
     In the embodiment shown in  FIG. 9 , the opposed ends  64  of the extending portions  60  of the supporting element  14  include slots  80  and posts  82 , and the securing element  18  may have buttonholes  84  therein, the opposed ends  66  of the securing element  18  are able to extend through the slots  80  in the opposed ends  64  of the extending portions  60  and fold thereover, and wherein each of the buttonholes  84  is able to stretch over and interlock with the post  82  to engage therewith for securing the system  10  about the abdomen. Alternatively, the securing element  18  may include interengageable elements whereby the opposed ends of the securing element  18  extend through the slots  80  and fold back there over, such that the interengageable elements interengage for securing thereof. 
     The  FIG. 10  embodiment illustrates the cover  44  which includes a post  86  on its outer surface  88 , and wherein the securing element  18  may have buttonholes  90  therein, wherein each of the buttonholes  90  is able to stretch over and interlock with the post  86  to engage therewith, for securing the system  10  about the abdomen. In this embodiment, the supporting element  14  does not include extending portions  60 . 
     The supporting element  14  is generally low profile and lightweight. It includes a housing  92  which includes a mounting portion  94  for mounting the pressure sensor  12  therein, is generally semi-spherical in shape, generally in the form of a dome, and includes a recess  96  in the form of a well therein. The pressure sensor  12  is able to project from and be moveable in the recess  96  of the supporting element  14 . The housing  92  further includes a generally rectangular-shaped back portion  98  from which the mounting portion  94  projects. The supporting element  14  may be is comprised of a flexible or non-flexible material, such that the flexible or non-flexible material maintains a load on the pressure sensor  12  during abdominal changes relating to contractions. The flexible material may comprise a flexible plastic material. 
     While the particular sensing system as shown and disclosed in detail herein is fully capable of obtaining the objects and providing the advantages previously stated, it is to be understood that it is merely illustrative of the presently preferred embodiment of the invention, and that no limitations are intended to the details of construction or design shown herein other than as described in the appended claims.