Abstract:
Disclosed are several embodiments of a battery-less piezo-electric defibrillation system ( 2 ) comprising external piezo-electric defibrillator ( 4 ) and at least one electrode ( 5 ) connected thereto. The system includes a piezo-electric generator ( 6 ) connected to direct cardiac access—( 5 ), or indirect subcutaneous electrode assemblies ( 30 ). The piezo-electric generator ( 6 ) is energized by a spring-driven striker element ( 8 ) and produces electrical pulse for defibrillation. The direct cardiac access electrodes ( 5 ) engage the heart muscle directly via the intercostal space. Alternatively, indirect subcutaneous electrodes ( 34   a ) are positioned under patient&#39;s skin.

Description:
FIELD OF INVENTION 
     This invention relates in general to cardiac defibrillators, and in particular to external portable defibrillators and systems not requiring a battery source. 
     BACKGROUND OF INVENTION 
     Modern emergency medical practice strives to provide the most advanced and timely diagnosis and treatment as possible, since time factor is often crucial to the successful clinical outcomes. 
     One of the sudden critical health crises is cardiac ventricular fibrillation (VF) which is invariably fatal unless treated promptly. The common way to treat VF is to administer an electric pulse to the heart which shocks the heart muscle and induces it to revert to its normal contraction pattern. This procedure is called defibrillation and is effected by an apparatus called ‘defibrillator’. 
     There are two types of defibrillators: the external and internal, the latter implanted into a patient&#39;s body. 
     External defibrillators are relatively large and contain a large battery pack and a high voltage generator. The weight of an external defibrillator is in the order of 2-3 lbs (1-1.5 kg). The generated high voltage pulse is administered to a patient via two large conductive paddles positioned on his chest and side, respectively. The defibrillator batteries have to be periodically tested and if of the rechargeable type, recharged, which adds to the maintenance labor and expenses for the system&#39;s owner. 
     The implantable defibrillator, being very small and light is permanently surgically implanted into a patient&#39;s body, and its electrical lead is inserted into the heart. The outer case of the device is made of metal and acts as a second electrode to complete the path of electrical current through the heart. The implantable defibrillators are used in patients with chronic cardiac disease and their implantation requires a major surgical procedure in a hospital setting. 
     In an emergency situation providing an external defibrillator in a timely manner can be problematic, since due to its size and weight it presents a carry challenge to first-response medical personnel who are frequently over-burdened with other equipment and may not have an external defibrillator in their medical kit. Also, some first-responders, such as for example motorcycle patrol policemen may not carry a defibrillator due to the limited carry space on their motorcycles. Waiting for the response team with a defibrillator to arrive may spell death for the VF sufferer. On the other hand, to implant a small defibrillator under field conditions and within an extremely short ‘window of opportunity’ is not feasible. 
     Still, having a defibrillation capability ‘on-hand’ in an emergency is very desirable in view of its potential in saving lives. 
     In addition, it would be desirable to have a defibrillator system of the ‘store-and-forget’ type: the one not requiring any service, like periodic testing or re-charging of the batteries. 
     OBJECTIVES OF THE INVENTION 
     Thus, it is the objective of instant invention to provide a small and light defibrillator system which can be easily carried by a first-responder personnel along with other first-aid equipment. 
     Another objective is to provide a defibrillator system which would be easy to maintain and would offer a service-free virtually unlimited storage life. 
     Yet another objective is to provide a defibrillator which would be easy to use even by an untrained personnel. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a miniature battery-less piezo-electric defibrillation system is disclosed. The system consists of a small and light piezo-electric external defibrillator equipped with direct cardiac access-, or indirect subcutaneous electrodes, or both. These types of electrodes provide a low impedance electrical path to the patient&#39;s heart which lowers the energy required for defibrillation and enable compact defibrillator. 
     The direct cardiac access electrodes engage the heart muscle directly, preferably via the left 5 th  intercostal space. 
     The subcutaneous-type electrodes are positioned below the skin near the patient&#39;s sternum and laterally below the left armpit. Their design also facilitates simplified operation by an untrained personnel. 
     PRIOR ART 
     The prior art is comprised by two distinct groups of defibrillators: the external and the implantable ones. The external ones, as was mentioned, are large and heavy for the wide availability in emergencies. The implantable defibrillators, while very small, are unsuitable in the first-response situations. 
     OBJECTS AND ADVANTAGES 
     In contrast to the prior art mentioned hereinabove, the present invention provides a miniature external defibrillator, which, together with the specific electrode system delivers the desired defibrillation action. In addition, the defibrillator does not require batteries to operate: the defibrillation energy is generated via mechanical stress on the piezo-electric generator element. 
     My research showed that a great difference exists between the required defibrillation energy while using an external defibrillator and using an implanted defibrillator. An external defibrillator is required to deliver up to 400 Joules of electrical energy per pulse. The need for high energy output for external defibrillation results in large size and weight of the corresponding defibrillators. In contrast, only 10-50 Joules per pulse are delivered by an implanted defibrillator with a direct intra-cardiac electrode, with satisfactory defibrillation results. 
     I determined that the difference in the required pulse energies is due to the high impedance of the human skin and tissues immediately underneath it, which needs to be overcome by the existing external defibrillators in order to deliver sufficient defibrillation energy to the heart. 
     If, however, the heart can be stimulated from within the body, such as done presently with implanted defibrillators, directly to/inside the heart, or from under the skin and thus avoiding its high impedance, the required pulse energy is greatly reduced. 
     Thus, it is possible to use a small external defibrillator if its energy is delivered directly to the heart or indirectly subcutaneously, avoiding high losses in the skin and the immediate underlying tissue. 
     Indeed, an implantable defibrillator, Model S-ICD® introduced recently by Boston Scientific, Inc. of Natick, Mass., USA utilizes an indirect subcutaneous electrode positioned along the sternum, with the defibrillator itself implanted laterally, below left armpit. The metal case of this defibrillator serves as a second subcutaneous electrode to complete the current path through the patient&#39;s heart. The energy generated by this device is relatively low 80 Joules per pulse but it is sufficient for successful defibrillation. This further supports the low-impedance model of subcutaneous electrode operation. 
     Additionally and crucially, the reduced defibrillation energy required, in the order of 50-80 Joules, allows the use of piezo-electric generators instead of batteries. 
     Furthermore, in case of external defibrillators, the external electrode pads by necessity are made quite large in order to decrease impedance and current density and avoid burns to the patient&#39;s skin. In case of subcutaneous electrodes, this requirement is reduced due to lower impedance. 
     Nevertheless, in several embodiments of the instant system, precautions were taken to decrease current density at electrodes to minimize a chance of an electrical burn injury to the patient. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the defibrillator of the instant invention, in the armed configuration. 
         FIG. 2  is a perspective view of the defibrillator of the instant invention, in the fired configuration. 
         FIG. 3  is a perspective view of the defibrillation system positioned on the patient&#39;s thorax and engaging his heart. 
         FIG. 4  is a perspective view of the defibrillation system&#39;s alternate embodiment positioned on the patient&#39;s thorax and engaging his heart. 
         FIG. 5  is a perspective view of a ‘return’ electrode assembly with spike-shaped electrode elements. 
         FIG. 5   a  is a perspective view of an alternate ‘return’ electrode assembly with scimitar-shaped electrode elements. 
         FIG. 5   b  is a partial cross section of the arming lever interfacing with striker shaft. 
         FIG. 6  is an electrical schematic of the system&#39;s output impedance matching and pulse shaping network. 
         FIG. 6   a  is a perspective view of the defibrillation system&#39;s alternate embodiment with direct cardiac and indirect subcutaneous electrodes assemblies positioned on the patient&#39;s thorax. 
         FIG. 6   b  is a perspective view of the direct cardiac electrode assembly. 
         FIG. 7   a  is a perspective view of the defibrillation system&#39;s alternate embodiment with indirect subcutaneous electrode assemblies positioned on the patient&#39;s thorax. 
         FIG. 7  is a perspective view of the subcutaneous electrode assembly in its pre-deployment configuration. 
         FIG. 8  is a perspective view of the subcutaneous electrode assembly deployed. 
         FIG. 9  is a perspective view of the subcutaneous electrode assembly&#39;s alternate embodiment in its pre-deployment configuration. 
         FIG. 10  is a perspective view of the subcutaneous electrode assembly&#39;s alternate embodiment while deployed. 
         FIG. 11  is a perspective view of a subcutaneous electrode assembly&#39;s alternate embodiment in its pre-deployment configuration. 
         FIG. 12  is a perspective view of a subcutaneous electrode assembly&#39;s alternate embodiment while deployed. 
         FIG. 13  is a perspective view of another subcutaneous electrode assembly&#39;s alternate embodiment in its pre-deployment configuration. 
         FIG. 14  is a perspective view of another subcutaneous electrode assembly&#39;s alternate embodiment while deployed. 
         FIG. 15  is a perspective view of a subcutaneous electrode element in pre-deployment configuration. 
         FIG. 15   a  is a perspective view of a subcutaneous electrode element while deployed. 
         FIG. 16  is a perspective partial view of a subcutaneous electrode assembly in pre-deployment configuration. 
         FIG. 16   a  is a perspective partial view of a subcutaneous electrode assembly while deployed. 
         FIG. 17  is a perspective view of a subcutaneous electrode with scimitar-shaped electrode elements. 
         FIG. 18  is prior art of implantable defibrillator with indirect subcutaneous electrode. 
         FIG. 19  is a perspective view of a linear subcutaneous electrode assembly inside the introducer prior to insertion. 
         FIG. 20  is a perspective view of a linear subcutaneous electrode assembly inside the introducer, with introducer being extracted. 
         FIG. 21  is a partial perspective view of a linear subcutaneous electrode assembly inside the introducer, with introducer penetrating tip closed. 
         FIG. 22  is a partial perspective view of a linear subcutaneous electrode assembly inside the introducer, with introducer penetrating tip open during extraction. 
         FIG. 23  is a perspective view of the alternate embodiment of the defibrillation system with indirect linear subcutaneous electrode assemblies positioned in the patient&#39;s thorax. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the foregoing description like components are referenced by the like numerals. The preferred embodiment  2  of the defibrillator system is shown on  FIGS. 1 and 2 . Defibrillator  2  comprises cylindrical case  4  which houses piezo-electric generator  6 , striker  8 , power spring  10 , and direct cardiac access electrode  5 . Electrode  5  is covered with electrically insulating layer  5   a , with the exception of its very tip which is made very sharp for easy penetration into patient&#39;s body. 
     Striker  8  is connected to handle  32  by shaft  7 . On the outside of case  4  there is a hinged lever  9  which at its proximal end interacts with shaft  7 . Lever  9  is sprung by spring  7   b  to enable its ratcheting action against shaft  7 . Trigger  11  is pivotally attached to case  4  and holds striker  8  in armed position prior to its release. 
     Case  4  at its bottom is terminated by a generally annular ‘return’ electrode  13 , which contains a plurality of sharp penetration spikes  13   a  on its bottom surface, as shown on  FIG. 5 . 
     One output of the piezo-electric generator  6  is connected to the electrode  13  and the other to the direct cardiac access electrode  5 . An optional impedance-matching and output pulse shaping network preferably comprising a transformer  6   a  and passive resistor-inductor-capacitor (“R-L-C”)-type network  6   b  is electrically interposed between generator  6  and electrodes  5  and  13 . The primary and secondary windings of the transformer are labeled ‘P’ and ‘S’ respectively and contain equal or different number of wire turns, depending on the determined impedance match requirements. 
     Piezo-electric generator  6  can be realized with a number of piezo-electric materials, such as BaTiO 3 , LiNbO 3 , PMN-PT, PZT, PZN-9PT and the like, preferably as a stack of individual metallized elements. Such piezoelectric stacks used primarily for precision actuators and high voltage pulse generation are well-known in the art. The maximum conversion efficiency of power conversion from mechanical to electrical energy in piezo-electric materials occurs with maximum force and lowest frequency. Our preferred embodiment design calls for a significant force exerted on the piezo-electric stack by a striker  8  driven by the power spring  10 . The short duration of the strike generates an impulse with wide frequency content which aids in coupling of the mechanical energy into electricity within the piezo-electric material. 
     OPERATION 
     Prior to operation, the defibrillator is armed by either pulling shaft  7  by the handle  32  directly or working the lever  9  and ratcheting shaft  7  and striker  8  attached to it into the armed position while compressing power spring  10 . In the armed position spring  10  is held in compression by trigger  11  which arrests the movement of striker  8 . 
     To effect ratcheting of shaft  7  lever  9  engages the corresponding notches  7   a  on shaft  7  as shown on  FIG. 5   b . Spring  7   b  returns lever  9  to its starting position to repeat the ratchet operation. 
     Referring to  FIG. 3 , after arming, the defibrillator&#39;s cardiac electrode  5  is pushed into the patient&#39;s body preferably via the 5 th  intercostal space  15 , between the 5 th  rib denoted  14 , and the 6 th  rib denoted  14   a , respectively and engages patient&#39;s heart  16  with its exposed conductive tip. 
     The length of electrode  5  is made such that when it is fully inserted, electrode  13  contacts the skin and pierces it with its sharp spikes  13   a  thus reducing the electrical impedance for the defibrillation circuit. 
     Defibrillation function is then initiated by applying pressure to the trigger  11  which releases striker  8 . Striker  8  is then propelled by the expanding spring  10  and strikes piezo-electric generator  6  producing an electric pulse which propagates down to patient&#39;s heart  16  via electrodes  5  and  11 . 
     After defibrillation pulse the defibrillator is either withdrawn from the patient&#39;s body, or a subsequent pulse(s) can be delivered in case the first pulse did not succeed. 
     ADDITIONAL EMBODIMENTS 
     In the foregoing description like components are labeled with like numerals. 
     Referring to  FIG. 4  an alternative defibrillator system embodiment  2   a  utilizes a return electrode  17  instead of  13 . Electrode  17  is shown in detail on  FIG. 5   a  where in addition to the central annular portion it contains a number of scimitar-shaped sharp electrode elements  17   a  extending radially from the common center. These elements are inclined with respect to the plane of the device to facilitate their piercing of patient&#39;s skin when the defibrillator body  4  and the attached electrode  17  are placed upon the patient&#39;s skin and rotated, in this embodiment, clockwise. Rotating defibrillator body  4  counter-clockwise removes electrode elements  17   a  from the skin. 
     Referring to  FIG. 6   a  an alternative defibrillator system embodiment  3  utilizes detachable direct cardiac electrode assembly  5   b  and indirect subcutaneous electrode assembly  30 . Direct cardiac electrode assembly  5   b  shown on  FIG. 6   b  is similar in construction to electrode  5  with the addition of the handle  32  and guidance sleeve  5   c  which facilitates precise aiming of the electrode to the heart. 
     An alternative defibrillator system embodiment  3   a  utilizing indirect subcutaneous electrode assemblies  30  is shown on  FIG. 7   a . Subcutaneous electrode assemblies  30  are placed onto patient&#39;s body, one next to the sternum  18  and the other below left armpit, with their blade electrodes piercing the skin to establish a low-impedance current path to the heart. 
     Referring to  FIGS. 7 ,  8 ,  15 ,  15   a ,  16  and  16   a  subcutaneous electrode assembly  30  comprises several electrode sleeves  38  which contain electrode assemblies  34  located in a curved inner channel  35  terminating in electrode exit aperture  35   a . Each assembly  34  contains one or more flexible blade electrodes  34   a  connected to the contact pad  34   b  which in turn is electrically connected to defibrillator  3 . Contact pad  34   b  is also mechanically connected to the deployment handle  32 . Flexible electrode&#39;s  34   a  tip is made to be very sharp to facilitate its easy penetration into the skin. Several sleeve-electrode assemblies are held together by plate  36 . 
     Upon placement on the patient&#39;s skin  19 , handle  32  is pressed downwards toward the skin&#39;s surface by the operator. Sleeves  38  internal curved channels  35  terminating in outwardly and radially pointing apertures  35   a  force blade electrodes  34   a  to emerge at a slant angle with respect to the skin surface  19 , penetrating it. One or more electrodes  34   a  are thus inserted simultaneously under the skin enabling a low-impedance current path for successful defibrillation. 
       FIGS. 9 and 10  show an alternate embodiment of the subcutaneous electrode assembly  40 . It is more compact than assembly  30  and utilizes a single sleeve  38  with assembly  34   c  consisting of two electrodes  34 . To stabilize the assembly on the patient&#39;s skin, it is equipped with a rest  36   a  on its bottom. 
     Yet another embodiment of the subcutaneous electrode assembly  50  is shown on  FIGS. 11 through 14 . Instead of the flat bottom of the previous assembly, each sleeve  38  terminates in a sharp tip  52 . This construction enables initial penetration of the skin and subcutaneous layers prior to deployment of sharp electrodes  34   a . The plate  36  in addition of holding sleeves  38  serves in this embodiment as their penetration depth limiter. 
     Another embodiment of the subcutaneous electrode assembly  70  is shown on  FIG. 17 . It features scimitar-shaped electrodes  72  extending radially from the common contact pad  34   b  attached to handle  32 . The electrodes are inclined to the plane of the handle/contact pad, so when placed on skin  19 , they pierce it when handle  32  is turned, in this configuration, clockwise. Rotating handle  32  counter-clockwise removes electrodes  72  from the skin. 
     Another embodiment of the subcutaneous electrode assembly  100  is shown on  FIGS. 19 through 23 . A relatively thin and flexible electrode  102  is positioned inside introducer  104  for subcutaneous insertion. Introducer  104  at its distal end has a sharp penetrating tip  106  which consists of several flexible tangs  106   a . During insertion tangs  106   a  are held firmly against each other by skin&#39;s resistance, forming a sharp tip  106 . Referring to  FIG. 23  electrode assemblies  100  of defibrillator system&#39;s embodiment  3   b  are placed under patient&#39;s skin preferably at two locations: one along the patient&#39;s sternum  18  and another laterally below left armpit. These locations are customarily selected for external defibrillator electrode pads placement and also shown in the prior art implantable defibrillator system  80  with indirect electrode  82  and implantable defibrillator  86  whose metal case serves as a second electrode, shown on  FIG. 18 . Afterwards, introducers  104  are withdrawn and electrodes  102  are left in place. Specifically, when an electrode assembly  100  is positioned at the desired location, introducer  104  is withdrawn by the operator&#39;s pulling it back off of the electrode  102 . During this operation the tip of electrode  102  pushes tangs  106   a  of introducer  104  outwards and causes them to flex, clearing electrode  102 . Introducer  104  is then slid off the electrode  102 , leaving it in place inside patient&#39;s body. Electrode  102  is then electrically connected to the defibrillator&#39;s piezo-electric generator  6 . Upon completion of defibrillation electrodes  102  are withdrawn from the patient&#39;s body by simple pulling. 
     Although descriptions provided above contain many specific details, they should not be construed as limiting the scope of the present invention. Several features of distinct embodiments can be combined, for example, the introducer  104  type can be used with direct cardiac contact electrode  5 , with an advantage that a thin electrode can be substituted instead of a more robust one. A thin electrode then can be left in place while chest compressions are performed as part of a cardio-pulmonary resuscitation (CPR) procedures. 
     Various piezo-electric materials can be utilized in the piezo-electric generator  6 , as well as different number and geometry of the individual piezo-electric stack elements. Also, the manner of inducing stress in the generator piezo-electric stack can range between longitudinal compression as in instant invention, via bending by a transverse force, or combination thereof. Also, the behavior of piezo-electric materials depends on the relative direction of the applied stress and material&#39;s crystallographic axes. 
     Additionally, the design of striker  8  itself and case  4  it travels in can be optimized to improve striker&#39;s acceleration by decreasing friction and air resistance. Thus, the inside of case  4  can be polished and striker  8  sides coated with a low-friction material, either temporary like oil or grease, or permanent, such as a fluoropolymer coating like Teflon®. To minimize air compression and resistance longitudinal through holes can be created in the striker to permit air escape. Through holes can be provided in the case  4  wall at its top and bottom to permit air escape in front of the moving striker  8 , and air ingestion behind it. 
     In addition, the compressed spring-type energy storage can be substituted by a compressed air or CO 2  in a compact cylinder. 
     The specific implementations disclosed above are by way of example and for enabling persons skilled in the art to implement the invention only. I have made every effort to describe all the embodiments we have foreseen. There may be embodiments that are unforeseeable or which are insubstantially different. I have further made every effort to describe the invention, including the best mode of practicing it. Any omission of any variation of the invention disclosed is not intended to dedicate such variation to the public, and all unforeseen or insubstantial variations are intended to be covered by the claims appended hereto. Accordingly, the invention is not to be limited except by the appended claims and legal equivalents.