Patent Publication Number: US-2021186403-A1

Title: Printed Electrocardiogram Leads for Medical Applications

Description:
RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Application No. 62/953,131, filed Dec. 23, 2019. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     In general, the present invention relates to the structure of electrocardiogram lead elements that interconnect a patient to medical analysis equipment. The present invention also relates to methods of forming electrocardiogram lead elements using printing manufacturing techniques. 
     2. Prior Art Description 
     Many medical testing and monitoring systems require that various probes and sensors be attached to the body of a patient. For example, to perform an electrocardiogram, multiple sensors are attached to the torso and limbs. A common type of electrocardiogram (ECG) is the 10-lead ECG. The 10-lead ECG gives a tracing of the heart from multiple directions using a series of ten electrodes. Each of the ten electrodes picks up electrical activity from a different position on the heart muscle. This allows an experienced interpreter to see the heart from many different angles. The actual electrocardiogram is a graphic record of the direction and magnitude of the electrical activity generated by the depolarization and repolarization of the atria and ventricles of the heart. This electrical activity is readily detected by the ten electrodes attached to the skin. 
     An ECG utilizes electrodes of opposite polarity (one positive and one negative) or one positive surface electrode and a reference point. Two electrodes of opposite polarity are called a bipolar leads. A lead composed of a single positive electrode and a reference point is a unipolar lead. A ten-lead ECG consists of various bipolar limb leads, unipolar limb leads, and unipolar chest leads, which are also called precordial or V leads. 
     In each case, the wire leads attach to disposable electrodes that adhere to the limbs and torso of a patient. The wire leads are difficult to manage as ten electrodes are applied to the body. Furthermore, ten wire leads must be properly attached to the correct electrodes. The wire leads often become entangled, therein causing an error during the application. 
     Wire leads for medical equipment, such as electrocardiograms, are complicated assemblies that are rarely replaced. Rather, many hospitals, clinics and physicians&#39; offices only use disposable electrodes and repeatedly reuse the wire leads that connect the electrodes to the medical equipment. This, of course, presents problems with patient-to-patient contamination. Wire leads come into contact with a patient&#39;s skin and clothing. As such, wire leads can be contaminated with bacteria, viruses, blood and/or other bodily fluids after one use. As a consequence, healthcare providers are required to balance the risks and costs associated with replacing or reusing wire leads. Healthcare providers must either absorb the large expense of replacing or sterilizing wire leads after each use, or they must assume the dangers and complications of potentially cross-contaminating patients by reusing the wire leads. 
     Another disadvantage of traditional wire leads is that the connectors at the ends of the wire leads wear out over time. As the connectors wear, they often become loose and create weak electrical connections with the probe or sensor to which it is attached. Loose connections create noise and disruptions in the electrical signals being sensed. As such, one or more loose connections can invalidate an electrocardiogram test. 
     In the prior art, attempts have been made to replace expensive wire leads with less expensive elements, such as printed flexible substrates. Such prior art is exemplified by U.S. Pat. No. 6,006,125 to Kelly. One problem associated with such printed substrates, is that they are printed in one size in the hope that one size will fit all people. This is clearly not accurate. An infant is obviously very different in size than a full-grown adult. Wire leads can be manipulated to accommodate people of different sizes. However, printed leads are fixed on a substrate. As such, the premanufactured printed leads must be produced in a wide variety of sizes and styles to accommodate people of different ages, sizes, shapes and genders. This requires preprinted substrates of many different sizes and lengths to be held in the inventory of a hospital or clinic. The consequence is that large sums of money must be spent on inventory. This negates the cost savings of not using traditional lead wires. 
     In an attempt to produce a low cost wiring harness that can be used on patients of most any size, wire leads have been printed on substrates where each wire lead is separate and distinct. This enables each of the wire leads to be independently positioned on a patient&#39;s body. Such prior art is exemplified by U.S. Patent Application Publication No. 2011/0054286 to Crosby. A problem with such printed leads is that the leads must be connected to electrodes at one end and the medical equipment cable at the opposite end. As such, if each lead has two connections and there are ten leads, a 10-lead ECG system has twenty separate electrical connections that must be maintained during a procedure. If one or more connections become loose, the electrocardiogram test is compromised. Furthermore, it takes a long period to diagnose the connections and find the bad connection before the procedure can be restarted. 
     In the prior art, there are wiring harnesses, where the wire leads are premanufactured to be connected to the electrodes. As such, there is no chance of a poor connection between the wire leads and the electrodes. Such prior art is exemplified by U.S. Pat. No. 4,353,372 to Ayer. The problem with such prior art systems is that the integration of the wire leads within the electrodes creates a complicated structure that cannot be simply printed on a printing machine. The complicated structure increases the complexities and costs of manufacture. The more expensive a system is, the less likely such a system will be purchased as disposable. 
     A need therefore exists for a new construct and method of manufacture that enables a wiring harness to be made using only low-cost printing manufacturing techniques, wherein the wiring harness contains both electrodes and the wire leads that connect the wire leads to a medical machine. A need also exists for a wiring harness with electrodes and wire leads that is highly reliable, yet inexpensive enough to be replaced after every use. These needs are met by the present invention as described and claimed below. 
     SUMMARY OF THE INVENTION 
     The present invention is an electrocardiogram lead package that contains low-cost printed constructs and the associated method of manufacturing the printed constructs. The electrocardiogram lead package contains a first and second printed construct. The first printed lead construct includes a first plurality of electrodes, a first lead hub, and a first plurality of printed wire leads that electrically interconnect the first plurality of electrodes to the first lead hub. The first plurality of electrodes contains a first set of printed contact heads. The first lead hub contains a first set of printed contact pads. The first plurality of printed wire leads contains a first set of printed conductive pathways. 
     The second printed lead construct has a second plurality of electrodes, a second lead hub, and a second plurality of printed wire leads that electrically interconnect the second plurality of electrodes to the second lead hub. The second plurality of electrodes contains a second set of printed contact heads. The second lead hub contains a second set of printed contact pads. The second plurality of printed wire leads contains a second set of printed conductive pathways. The first and second sets of printed contact heads, the first and second sets of printed contact pads, and the first and second sets of printed conductive pathways are all formed from conductive ink that is printed onto a common segment of flexible substrate. 
     On the flexible substrate, the first plurality of electrodes is linearly aligned, and interposed with, the second plurality of electrodes. When separated from the electrocardiogram lead package, the first and second printed constructs provide all the electrodes and leads needed to perform an electrocardiogram. After one use, the printed constructs are thrown away. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention, reference is made to the following description of an exemplary embodiment thereof, considered in conjunction with the accompanying drawings, in which: 
         FIG. 1  shows the present invention being used to connect a patient to an electrocardiogram machine; 
         FIG. 2  is a top view of printed constructs on a common substrate; 
         FIG. 3  is a cross-sectional view of a section of a printed construct; 
         FIG. 4  shows and enlarged section of an electrode with an alternate construction of a printed wire lead; and 
         FIG. 5  shows printed constructs separated and ready for use; and 
         FIG. 6  is a block diagram outlining the method of manufacture. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Although the present invention system and method can be embodied in many ways, only one exemplary embodiment is shown. This embodiment is selected in order to set forth one of the best modes contemplated for the invention. The illustrated embodiment, however, is merely exemplary and should not be considered a limitation when interpreting the scope of the appended claims. 
     Referring to  FIG. 1 , an application  10  is shown where printed constructs  12  are used to interconnect an electrocardiogram machine  14  to a patient. During an electrocardiogram, two such printed constructs  12  would be used. One is shown for simplicity. The printed constructs  12  each contain five electrodes  20  that are integrated with five printed wire leads  16 . As such, two printed constructs  12  would contain ten electrodes  20  and ten printed wire leads  16 , wherein the two printed constructs  12  can be utilized to perform a multi-lead electrocardiogram. 
     Each electrode  20  present on a printed construct  12  has its own independent printed wire leads  16 . The printed wire leads  16  connect the electrodes  20  to a common lead connection hub  18 . The lead connection hub  18  enables each of the printed constructs  12  to interconnect to a multi-lead cable  22 . The multi-lead cable  22  interconnects the printed constructs  12  to the electrocardiogram machine  14 . As will be explained, it is only the printed constructs  12  that contact the body  25  of the patient. The multi-lead cable  22  can be kept away from the body  25  of the patient or can be sheathed in a disposable plastic sleeve  23 . Accordingly, the printed constructs  12  are for single use applications and the multi-lead cable  22  can be used repeatedly. 
     Referring to  FIG. 2  in conjunction with  FIG. 1 , it can be seen that two printed constructs  12  are printed upon a single segment of flexible substrate  24  to form a complete ECG lead package  27 . The two printed constructs  12  in the ECG lead package  27  include a first printed construct  12 A and a second printed construct  12 B. As a result, each ECG lead package  27  contains ten electrodes  20 , ten printed wire leads  16 , and two lead connection hubs  18  that are all formed on a common segment of flexible substrate  24 . In this manner, the ECG lead package  27  is manufactured and packaged as a unit for single use by a healthcare professional. A healthcare professional removes the ECG lead package  27  from sterile packaging (not shown) and separates the two printed constructs  12  from the remaining flexible substrate  24 . The printed constructs  12  are then applied to the body  25  of the patient for use in performing an electrocardiogram. As will be explained, the positioning of the printed constructs  12  are variable and are governed by the size and shape of the patient&#39;s body  25 . After use, the printed constructs  12  are removed from the body  25  and discarded. 
     Referring to  FIG. 3 , in conjunction with  FIG. 2  and  FIG. 1 , it will be understood that to create the printed constructs  12 , a single flexible substrate  24  is provided. The flexible substrate  24  is dielectric and can be either polymer-based or paper-based. The preferred flexible substrate  24  is a film of polyethylene terephthalate (PET). However, films of flashspun non-woven high-density polyethylene fiber, such as Tyvek®, can also be used. These films are dielectric, highly flexible, and tear-resistant in tension. 
     In a first printing operation, conductive ink  26  is printed upon the flexible substrate  24 . The conductive ink  26  is printed in a precise pattern to form the conductive features of each printed construct  12 . The conductive features include contact heads  30  within the electrodes  20 , contact pads  32  within the lead connection hubs  18 , and conductive pathways  28  within the printed wire leads  16 . 
     The contact pads  32  for each printed construct  12  are all arranged in parallel in the same areas, therein forming the common lead connector hubs  18 . The contact heads  30  are linearly aligned, but are printed at different distances from the contact pads  32 . The contact heads  30  of the first printed construct  12 A and the contact heads  30  of the second printed construct  12 B are interposed and linearly aligned. In this manner, the density of useful elements on the flexible substrate  24  are maximized. This reduces the area of the flexible substrate  24  needed to support the ECG package  27  and minimizes waste. 
     Since the printed contact heads  30  are all different distances from the printed contact pads  32 , it will be understood that the length of each of the conductive pathways  28  between the contact heads  30  and the contact pads  32  is different. The lengths of the various conductive pathways  28  are designed to be long enough to reach the proper attachment point on the patient&#39;s body  25  during an electrocardiogram, regardless of the size of the patient. Each conductive pathway  28  is electrically isolated from the other conductive pathways  28  printed on the same flexible substrate  24 . Likewise, the contact heads  30  are electrically isolated from one another, as are the contact pads  32 . 
     The contact heads  30 , the contact pads  32  and the conductive pathways  28  are all printed in the same printing operation. As such, the contact heads  30 , conductive pathways  28 , and contact pads  32  are all electrically interconnected without the need of any connections between features. The contact heads  30 , conductive pathways  28  and contact pads  32  are all a common deposit of the conductive ink  26  that is printed upon the material of the flexible substrate  24 . The conductive ink  26  is preferably applied using an industrial grade electronic printer or a 3-D printer. However, alternate printing methods, such as silk-screening, can also be used. Many types of conductive inks can be used in the printing. However, to limit distortion and cracking of the conductive ink, silver-based inks are preferred. The preferred silver-based ink is an Ag/AgCl ink. An Ag/AgCl ink transfers an electrical charge across its boundaries by a reversible redox reaction. Accordingly, an Ag/AgCl ink will not polarize and will not filter or otherwise alter the electrical signal during an electrocardiogram. 
     Depending upon the composition of the flexible substrate  24  and the composition of the conductive ink  26 , the flexible substrate  24  may be coated with an aqueous primer  34  that increases the adhesion between the conductive ink  26  and the flexible substrate  24 . There are many primers commercially available that are used to print ink onto PET or high-density polyethylene fiber. Many of these primers work with silver-based conductive inks and can be incorporated into the present invention. The primer  34  prevents the conductive ink  26  from peeling away from the flexible substrate  24  if the flexible substrate  24  is severely deformed during processing and/or use. The primer  34  is also beneficial in the adhesion of any insulation layer over the flexible substrate  24  and conductive ink  26 . 
     A dielectric insulation layer  36  is applied over some areas of the conductive ink  26  and the flexible substrate  24 . The dielectric insulation layer  36  is not applied over the contact heads  30  or the contact pads  32 . The dielectric insulation layer  36  can be applied in one of two ways. The dielectric insulation layer  36  can simply be a layer of dielectric ink that is printed over the conductive ink  26  and the exposed flexible substrate  24 . The dielectric ink encapsulates the conductive ink  26  so that the conductive ink  26  is interposed between the flexible substrate  24  and the dielectric ink. Alternatively, the dielectric insulation layer  36  can be a curable dielectric polymer that is sprayed or otherwise mechanically applied over the conductive ink  26  and the exposed flexible substrate  24 . In either manufacturing scenario, the conductive ink  26  is interposed between the flexible substrate  24  and the first dielectric insulation layer  36 . Accordingly, the insulated areas of the conductive ink  26  cannot short against the skin or any metallic object that it may inadvertently contact. 
     The dielectric insulation layer  36  is not applied over the contact heads  30 . A thin layer of tacky adhesive  38  is applied around each contact head  30  in the areas that will form the electrode  20 . If the tacky adhesive  38  is conductive, it can be applied over the contact heads  30 . If the tacky adhesive  38  is not conductive, it is applied around the contact heads  30 . After the tacky adhesive  38  is applied, the tacky adhesive  38  is covered by a peel away protective cover  39 . This prevents the tacky adhesive  38  from becoming contaminated with dust, dirt and oil, prior to use. 
     Referring to  FIG. 4 , it can be seen that an optional shielding layer  40  can be printed atop the first dielectric insulation layer  36 . The shielding layer  40  is made from conductive ink and can be applied either as a solid layer or as a mesh layer. The shielding layer  40  helps prevent the conductive pathways from receiving noise signals from external electromagnetic sources. The shielding layer  40  itself can be covered with a printed second dielectric insulation layer  42  to prevent the shielding layer  40  from receiving any signals from inadvertent contact with metal objects or static discharge. 
     Referring to  FIG. 5  in conjunction with  FIG. 2  and  FIG. 3 , it can be seen that the flexible substrate  24  is stamped to define the peripheries of the first printed construct  12 A and the second printed construct  12 B within the ECG lead package  27 . The stamping can leave small areas of attachment (not shown) that are easily broken by manual manipulation. In this manner, the ECG lead package  27  keeps its shape until it is unpackaged for use. 
     When the flexible substrate  24  is stamped, large bases  46  are left around the contact heads  30 . The bases  46  are the shape of the final electrode  20 . Furthermore, the layer of tacky adhesive  38  is applied across the full area of each base  46 . Accordingly, each electrode  20  is made from a base  46  stamped out of the flexible substrate  24 . In the center of the base  46  is a printed contact head  30 . The base  46  is coated with tacky adhesive  38  and covered in a peel-away cover layer  39 . 
     Likewise, the substrate  24  is not cut in a wide base area  48  surrounding the contact pads  32 . The contact pads  32  printed on the base area  48  form the lead connection hub  18  for each of the printed constructs  12 . Furthermore, tracks  50  are left around the conductive pathways  28  to support the lines of conductive ink  26 . Accordingly, each of the conductive pathways  28  is a stamped track  50  of the flexible substrate  24  that is printed with conductive ink  26  and coated with a first insulation layer  36 . The first insulation layer  36  may have a shielding layer  40  printed upon it and a secondary dielectric insulation layer  42  covering the shielding layer  40 . 
     The printed constructs  12  are printed upside down. Accordingly, the last elements printed lay closest to the patient&#39;s body when applied to the body. Referring to  FIG. 6  in conjunction with all previous figures, it will be understood that to manufacture the ECG lead package  27 , a segment of flexible substrate  24  is provided. See Block  60 . The contact heads  30 , conductive pathways  28  and contact pads  32  are printed onto the flexible substrate  24  in conductive ink  26 . See Block  62 . The conductive ink  26  in the conductive pathways  28  are covered in a first dielectric insulation layer. See Block  63 . Optionally, the first dielectric insulation layer can be printed with a shielding layer and a subsequent second dielectric insulation layer. See Block  64  and Block  66 . 
     The areas surrounding the contact heads  30  are coated with a tacky adhesive  38 . See Block  68 . The tacky adhesive  38  is then covered with a protective peel-away cover layer  39 . See Block  69 . The printed assembly is then stamped to cut along the peripheries of the two printed constructs  12 . See Block  70 . The two printed constructs  12  remain attached to the remaining flexible substrate  24  by a few areas of attachment  44  left after the stamping. The result is an ECG lead package  27  that can packaged, shipped and sold. 
     Once needed, the ECG lead package is removed from its packaging and the printed constructs  12  are removed and detached. To use the printed constructs  12 , the peel-away cover layers  39  are peeled away from the electrodes  20 , therein exposing the tacky adhesive  38 . The electrodes  20  are then attached to a patient&#39;s body  25  in the areas appropriate for an electrocardiogram, give the shape and size of the body  25 . This brings the contact heads  30  into electrical contact with the body  25 . The printed wire leads  16  extend away from the patient and terminate at the lead connector hubs  18 . As shown in  FIG. 1 , the lead connectors  18  are attached to multi-lead cables  22  that extend to the electrocardiogram machine  14 . After use, the printed constructs  12  can be removed from the patient and discarded. 
     It will be understood that the embodiment of the present invention that is illustrated and described is merely exemplary and that a person skilled in the art can make many variations to that embodiment. All such embodiments are intended to be included within the scope of the present invention as defined by the claims.