Abstract:
An electrode package for use with a defibrillator, the electrode package comprising an outer shell providing a vapor barrier between an interior space inside the outer shell and an exterior environment, a breakaway connection element positioned at the perimeter of the outer shell, one or more defibrillation electrodes positioned in the interior space inside the outer shell, a further electrical element positioned in the interior space inside the outer shell, electrical paths extending from the further electrical element through the breakaway element to the exterior environment, wherein the breakaway element and electrical paths are configured so that, when the outer shell is opened and the defibrillation electrodes are removed, the electrical paths are disconnected within the breakaway element.

Description:
TECHNICAL FIELD 
     This invention relates to electrode packages for defibrillators. 
     BACKGROUND 
     There is a growing trend toward the replacement of multiple use defibrillator paddles with single-use disposable therapeutic electrodes for defibrillation, external transthoracic pacing, or the combination of both. This trend is driven by numerous factors including, but not limited to: (1) convenience related to not having to apply a conductive media (e.g., gel), (2) speed of care when switching from delivering a defibrillation shock to a pacing current, (3) caregiver safety in that contact with the patient can be avoided as the therapy can be delivered remotely from the host device, and (4) increased use of defibrillators incorporating algorithms that analyze the presented ECG rhythm for appropriateness of therapeutic (shock) delivery. These applications typically work only with single-use, disposable therapeutic electrodes. 
     Defibrillation of cardiac arrest is a time sensitive matter. It is well documented that for every minute delivery is delayed, the chance of survival falls 7 to 10 percent. One way manufacturers have addressed the time to shock issue, has been to create electrodes that can be pre-connected to a defibrillator. If electrodes are not pre-connected or present, valuable time will be lost, and chance of survival diminished as responders must address this matter. 
     Owing to many factors both chemical and environmental in nature, single-use therapeutic electrodes have a finite shelf life. Manufacturers typically label individual electrodes with specific dates of expiration beyond which therapeutic delivery cannot be insured. It is incumbent on the operator to read the electrode labeling prior to use to insure a non-expired electrode is deployed for therapy. 
     Electrode packaging is designed to be both airtight and watertight. This is to minimize environmental fluctuations that might shorten the useful life of an electrode. Should an electrode package be breached, chemical reactions will be accelerated and shelf life shortened. 
     SUMMARY 
     In a first aspect, the invention features an electrode package for use with a defibrillator, the electrode package comprising an outer shell providing a vapor barrier between an interior space inside the outer shell and an exterior environment, a breakaway connection element positioned at the perimeter of the outer shell, one or more defibrillation electrodes positioned in the interior space inside the outer shell, a further electrical element positioned in the interior space inside the outer shell, electrical paths extending from the further electrical element through the breakaway element to the exterior environment, wherein the breakaway element and electrical paths are configured so that, when the outer shell is opened and the defibrillation electrodes are removed, the electrical paths are disconnected within the breakaway element. 
     Preferred implementations of the invention may incorporate one or more of the following. The breakaway element and electrical paths may be so configured as to also include defibrillation current electrical paths, and on removal of the defibrillation electrodes the breakaway elements may be removed with the electrodes and the electrical paths connected to the further electrical element may be disconnected upon its removal. The breakaway element may be a gasket element. 
     In a second aspect, the invention features an electrode package for use with a defibrillator, the electrode package comprising an outer shell providing a vapor barrier between an interior space inside the outer shell and an exterior environment, a gasket element positioned at the perimeter of the outer shell, wherein the gasket element is shaped and positioned so that one surface of the gasket element is exposed to the interior space within the outer shell and the other surface of the gasket element is exposed to the exterior environment, and wherein the gasket element comprises a plurality of internal electrical paths extending from the one surface to the other surface, including at least a first, second, and third internal electrical path, one or more defibrillation electrodes positioned in the interior space inside the outer shell, a defibrillation current path extending from each defibrillation electrode to one of the first and second internal electrical paths within the gasket element, a further electrical element positioned in the interior space inside the outer shell, a further electrical path extending from the further electrical element to the third internal electrical paths within the gasket element, wherein the gasket element, defibrillation current paths, further electrical path, and first, second, and third internal electrical paths are configured so that, when the outer shell is opened and the defibrillation electrodes are removed for application on the patient, the gasket element and the first and second internal electrical paths remain connected to the defibrillation current paths and the gasket element and the third internal electrical path is disconnected from the further electrical path within the gasket element. 
     Preferred implementations of the invention may incorporate one or more of the following. The further electrical paths may comprise a metallic post and the third internal electrical path may comprise a metallic receptacle into which the metallic post extends and with which the post make electrical contact prior to opening of the electrode package, and wherein upon opening the electrode package the post may break away from contact with the receptacle. The further electrical path and the metallic post may be portions of the same insulated conductive wire, and the insulation may have been removed to provide the post. The receptacle may comprise a generally conical element conductor making a friction fit with the post. 
     Among the many advantages of the invention (some of which may be achieved only in some of its various aspects and implementations) are the following: The invention provides a simple and inexpensive technique for breaking electrical connections when electrodes are removed from an electrode package. This makes it possible, for example, to leave an electrical component inside the package when the electrodes are removed (e.g., a condition sensor that is only used during storage of the package). 
     Other features and advantages of the invention will be found in the detailed description, drawings, and claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a defibrillator implementation of the invention. 
         FIG. 2  is a perspective view of the defibrillator of  FIG. 1  with an electrode package shown removed. 
         FIG. 3  is a side elevation view of the defibrillator of  FIG. 1  looking toward the side with the electrode package. 
         FIG. 4  is a cross-sectional view taken along section  4 - 4  in  FIG. 3 . 
         FIG. 5  is a plan view of the electrode package after being opened to expose its contents. 
         FIG. 6  is a plan view of the two defibrillation electrodes stored inside the electrode package. 
         FIG. 7  is an exploded, cross-sectional view taken along  7 - 7  in  FIG. 6 . 
         FIG. 8  is an exploded, cross-sectional view taken along  8 - 8  in  FIG. 6 . 
         FIG. 9  is a plan view of the condition sensor (electrochemical cell) secured inside the electrode package. 
         FIG. 10  is an exploded, cross-sectional view taken along section  10 - 10  in  FIG. 9 . 
         FIG. 11  is a schematic view of the electrical connections between the contents of the electrode package (electrodes, condition sensor, CPR puck) and the electrode package connector. 
         FIG. 12  is a plan view showing the rigid shell of the electrode package with its removable lid removed and its contents removed. 
         FIG. 13  is a partial cross-sectional view taken along section B-B in  FIG. 12  showing a cross section through an inner end of the gasket element of the electrode package. 
         FIG. 14  is a partial cross-sectional view taken along section A-A in  FIG. 12  showing a cross section through an outer end of the gasket element of the electrode package. 
         FIG. 15  is a plan view of the gasket element. 
         FIG. 16  is an end view of the gasket element. 
         FIG. 17  is a cross-sectional view taken along section  17 - 17  in  FIG. 15 . 
         FIG. 18  is a perspective view of the gasket element. 
         FIG. 19  is another perspective view of the gasket element. 
         FIG. 20  is a block diagram of the electronics and components of the defibrillator of  FIG. 1 . 
         FIG. 21  is a plan view showing the triangular electrode of  FIGS. 6-7  applied to a the chest of a patient. 
         FIG. 22  is a plan view showing an alternative, crescent shaped electrode that could be used in place of the triangular electrode. 
     
    
    
     DETAILED DESCRIPTION 
     There are a great many possible implementations of the invention, too many to describe herein. Some possible implementations that are presently preferred are described below. It cannot be emphasized too strongly, however, that these are descriptions of implementations of the invention, and not descriptions of the invention, which is not limited to the detailed implementations described in this section but is described in broader terms in the claims. 
       FIGS. 1-4  show an external defibrillator  10  (e.g., a hospital crash cart defibrillator, such as the R Series manufactured by ZOLL Medical of Chelmsford, Mass.). User interface elements (graphical display, speaker, microphone, input buttons and dials) are provided on the front face of the defibrillator. Attached to the right side of the defibrillator is an electrode package  12 , which is removable from the defibrillator, as shown in  FIG. 2 , and normally electrically connected to the defibrillator by cable  14  even when the defibrillator is not in use. The multi-conductor cable  14  emerging from the electrode package passes through a connector (not shown in  FIG. 1-4 , but shown in the schematic of  FIG. 11 ) and divides into two cables  11 ,  13  which attach to the back of the defibrillator. A removable lid  16  is removed (by grasping tab  18 ) to open the defibrillator package. 
     The electrode package  12  includes a rigid base (or tray)  20  (polypropylene), which with the removable lid  16  (foil lined paper) constitutes the outer shell of the package. The base and lid provide a moisture barrier to prevent the gel layers of the electrodes from drying out during the shelf life of the package. The lid is heat sealed to the perimeter of the base (tray). The rigid base (a molded polymer part) is removable snapped into the receptacle  22  on the side of the defibrillator also used to secure a defibrillator paddle. Upper and lower flexible clips  24 ,  26  snap into engagement with mating elements of the receptacle  22 . Engagement of the flexible clips  24 ,  26  is shown in the cross section of  FIG. 4 , which shows the electrode package snapped into place on the side of the defibrillator. 
       FIG. 5  shows the electrode package with lid  16  peeled back to expose the contents of the package. A first defibrillation electrode  28  (generally square in this plan view) for the back (posterior) of the patient&#39;s chest is adhered to a release liner (not shown) secured to the inside face of lid  16 . Electrode  28  is peeled off of the release liner and adhered to the back of the chest. 
     A second defibrillation electrode  30  (generally triangular in this plan view) for the front (anterior) of the patient&#39;s chest is adhered to another release liner (not shown) secured to the rigid based of the electrode package. Electrode  30  is an assembly of a defibrillation electrode and three ECG monitoring electrodes, and is described in co-pending U.S. patent application Ser. No. 11/055,572, filed on Feb. 11, 2005, hereby incorporated by reference. 
     A device for assisting CPR, known as a CPR puck or pad  32 , is also stored within the electrode package. A similar CPR pad is described in U.S. Pat. No. 6,782,293, hereby incorporated by reference. It includes an accelerometer for measuring movement of the chest during CPR. 
     The fourth element within the electrode package is a condition sensor  34  that assists the defibrillator in determining whether the liquid-containing (gel) layers of the defibrillation electrodes are still sufficiently moist to function properly. The condition sensor  34  is not intended to be removed from the package, as it is not used during defibrillation. 
     Various electrical conductors pass into the electrode package to connect the contents with the defibrillator. These conductors pass through a gasket element  36  that is sealed between the rigid base  20  and removable lid  16  of the package. When the electrodes and CPR puck are removed from the package, the gasket element is also removed, as the electrical conductors for the electrodes and CPR puck extend through the gasket element. 
       FIGS. 6-8  show the two defibrillation electrodes  28 ,  30  in greater detail. The triangular front electrode  30  is shown in  FIGS. 6-7 . The construction of the electrode is shown in exploded, cross-sectional view in  FIG. 7 . A conductive liquid-containing layer  40  (solid gel) contacts the patient&#39;s skin, and conveys electrical current from the metallic layer  42  (tin plate or other metallic material such as silver chloride) to the patient. The gel and tin layer are supported on foam layer  44 , which carries adhesive to secure the electrode to the patient. The metallic layer is connected to wire  46  through which the defibrillation pulse is delivered from the defibrillator. A foam insulator layer  48  covers the area where the metallic layer and wire emerge from the electrode. A label  50  is applied over the foam layer  44 . 
       FIG. 21  shows the triangular electrode in place on the chest of the patient. The triangular shape greatly facilitates application of the electrode to the chest in the vicinity of a breast. The front electrode is adhered at the edge of the patient&#39;s breast, and the triangular shape has an advantage over circular or square electrodes in this location. These other shapes tend to fold or roll back on themselves. E.g., with a square electrode in this location, one corner of the electrode rides up on the breast, and will tend to roll back off the breast. This also tends to occur with circular electrodes. But with the triangular shape the problem is usually avoided. Another shape that will work well is a crescent shape, as shown in  FIG. 22 , with the smaller radius of the crescent closest to the breast. It is the lateral perimeter of the electrode that has the triangular or crescent shape. 
     Three ECG monitoring electrodes are built into the three corners of the electrode. Each monitoring electrode includes a solid gel layer  52  for contacting the patient, a conductive stud  54  (Ag/Cl) in contact with the gel layer, and conveying electrical potentials from the gel layer to the snap conductor  56  (Ni/Brass) to which a monitoring wire is connected. Alternatively, the snap conductor can be eliminated, and the ECG monitoring wires connected directly to the conductive studs  54 . 
     The square defibrillation electrode  28  is shown in exploded, cross-sectional view in  FIG. 8 . It includes most of the same layers as the other defibrillation electrode (identified in the figure by using the same reference numeral for corresponding parts). 
       FIGS. 9-10  show the condition sensor  32 , which functions as an electrochemical cell producing an electrical potential that is measured by the defibrillator to determine whether the moisture in the aqueous layer of the sensor has dried out. As the aqueous layer dries out (because moisture has escaped from the electrode package, e.g., because the package has been damaged), the potential of the electrochemical cell will fall off in magnitude. Once it falls below a threshold, indicating that the aqueous layer of the sensor has dried out, the defibrillator concludes that there is a high probability that the liquid-containing layers of the defibrillation electrodes have also dried out, and a warning prompt is delivered and the defibrillator may not deliver a defibrillation pulse to the electrodes. 
     Various other alternative tests could be applied to decide that the electrode is no longer suited for its intended use. E.g., the potential could be sampled frequently enough to establish a rate of change, and too high a rate of change could be a basis for deciding that something is wrong with the electrode. Depending on the circuitry used to measure the potential, a problem with the electrode could be detected by a voltage exceeding a threshold, and there could be multiple limits that the measured voltage is tested against. 
       FIG. 10  shows an exploded, cross-sectional view of the condition sensor. At the top of the stack of layers is a styrene release liner  60 , which is removed when the sensor is installed in the electrode package, to expose adhesive on the vinyl mask layer  62 , which is adhered to an interior surface of the electrode package to secure the condition sensor within the package. A aqueous layer  64  (gel) is positioned below the vinyl mask. A first metallic layer (metallic element)  66  (tin) is in contact with the gel. That is followed by an insulator layer  68  that is larger in area than the tin layer. Following the insulator layer is a second metallic layer (metallic element)  70  (aluminum) that is also in contact with the gel along its periphery outside of the extent of the insulator layer  68 . A foam backing layer  72  and foam cover  74  complete the sandwich of layers. A wire  76  (electrical conductor) is connected to each of the metallic layers (both shown in  FIG. 9 ; one shown in  FIG. 10 ). A bridging resistor  78  (approximately 100K ohms) is connected across the two metallic layers to control the rate of the electrochemical reaction (the size of this resistor will vary with the metals and gels used in the electrochemical cell and with other factors well known to those skilled in the art). The wires  76  are connected to the metallic layers with rings  80  and sockets  82 . A foam insulator layer  84  and length of tape  86  are positioned between the aqueous layer  64  and the first metallic layer  66 . 
       FIG. 11  is an electrical schematic of the electrode package  12 . Defibrillator electrodes  28 ,  30 , condition sensor  32 , and CPR puck  34  are shown within the electrode package. Cables connecting these elements tot the defibrillator pass out of the package through gasket element  36  (shown diagrammatically as a dashed rectangle in the schematic). Each defibrillation electrode has a single electrical conductor  90  configured to carry a high voltage signal. Three shielded wires  92  connect to the three ECG monitoring electrodes (designated by the snap conductors  56  at the locations of the monitoring electrodes. Two wires  94  connect to the condition sensor  32  (although in a preferred embodiment the electrical conductors connecting to the condition sensor are shared with other wires (e.g., one or more of the CPR puck wires). Eight wires  96  connect to the CPR puck. 
     All of wires  90 ,  92 ,  94 , and  96  pass through the gasket element  36 , and extend to an electrode package connector  102  (electrodes end connector), which is plugged into the patient end connector  104  of a cable that runs back to the defibrillator. The two connectors  102 ,  104  are shown mated in  FIG. 11 . 
     An electronic memory device  100  (e.g., a Dallas Maxim semiconductor chip, Part No. DS2431) is built into connector  102 . A variety of information is stored on the chip, including: an authentication code, a configuration code (e.g., whether the package contains ECG monitoring electrodes, a CPR puck, or only defibrillation electrodes), the type of electrodes (adult or pediatric), the expiration date of the electrode package, the serial number, and the date of manufacturing and manufacturing line. Other information (or less information) could be stored on the chip. 
       FIGS. 12-19  show the gasket element through which the electrical conductors extend. The gasket element is shown in perspective view in  FIGS. 18 and 19 . It has gradually tapered extensions  108  extending in the direction in which it is adhered to the perimeter of the seal between the rigid base  20  and removable lid  16  of the package  12 . A bead  110  of silicone adhesive seals one surface of the gasket element to the rigid base  20  of the package. This material is chosen so that the gasket will part from the rigid base when the electrodes are removed from the base. Between the tapered extensions  108  is a central portion  112 . 
     The gasket element has at least one surface exposed to the interior of the electrode package and at least one surface exposed to the exterior of the package. Holes pass through the gasket element from a surface exposed to the interior to a surface exposed to the exterior. Three electrical paths for the monitoring electrodes pass through three holes  120 . Eight smaller holes  122  (or one narrow opening) provide access for the electrical paths connecting the CPR puck. 
     When the gasket releases from the rigid base of the electrode package, certain electrical connections can be broken. For example, a conductive shorting element  130  that shorts across the two high-voltage defibrillation wires  90  (to allow testing of the integrity of these electrical pathways outside of the electrical package) is broken away. A second electrical connection that is broken is the connection to the condition sensor. Wires  94  (or their equivalent) that provide electrical pathways to the metallic layers of the condition sensor are disconnected from the condition sensor. This is necessary because the condition sensor in this implementation remains in the electrode package, as its usefulness as a package condition sensor has ended with the opening of the package. 
     Various techniques could be used to accomplish the disconnection of these electrical connections when the gasket element is removed. In the implementation shown herein, conductive posts  150 , extending upward from the rigid base of the package, and normally received in conductive apertures  152  (conically shaped to receive the posts) in the gasket element, withdraw from the apertures when the gasket is removed. the conductive posts shown are simply the ends of wires, bent 90 degrees to point upwardly, and stripped of insulation (the wider portion of the posts in the drawing is the wire with insulation; the narrower portion of the posts is the wire stripped of insulation). The conductive apertures (into which the posts extend) can be made from plated brass alloy with multiple fingers to engage the posts. 
     A general block diagram of the defibrillator is shown in  FIG. 20 . Processing circuitry and associated software (processing  160 ) is at the heart of the defibrillator. Inputs from sensors  162  such as the accelerometer in the CPR puck and the ECG monitoring electrodes on one of the electrode assemblies are received through signal conditioning and detection circuitry  164 ,  166 . A user interface  168  provides outputs to a display  170  (and possibly to lights that direct the user to graphical images  172 ) and to an audio system  174  with speaker  176  and microphone  178 . 
     Many other implementations other than those described above are within the invention, which is defined by the following claims. As mentioned earlier, it is not possible to describe here all possible implementations of the invention, but a few possibilities not mentioned above include the following: Not all of the features described above and appearing in some of the claims below are necessary to practicing the invention. Only the features recited in a particular claim are required for practicing the invention described in that claim. Features have been intentionally left out of claims in order to describe the invention at a breadth consistent with the inventors&#39; contribution.