Patent Publication Number: US-11389660-B2

Title: Defibrillator that monitors CPR treatment and adjusts protocol

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/855,487 filed Apr. 2, 2013, now U.S. Pat. No. 9,636,510, which a division of U.S. patent application Ser. No. 11/095,305 filed Mar. 31, 2005, now U.S. Pat. No. 8,433,407. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to defibrillators. More particularly, the present invention relates to defibrillators that monitor CPR treatment and adjust treatment protocols based on the monitored results. 
     BACKGROUND 
     A cardiac arrest is a life-threatening medical condition in which a person&#39;s heart fails to provide enough blood flow to support life. During a cardiac arrest, the electrical activity may be disorganized (ventricular fibrillation), too rapid (ventricular tachycardia), absent (asystole), or organized at a normal or slow heart rate (pulseless electrical activity). A person treating a cardiac arrest victim may apply a defibrillation pulse to the patient in ventricular fibrillation (VF) or ventricular tachycardia (VT) to stop the unsynchronized or rapid electrical activity and allow a perfusing rhythm to commence. External defibrillation, in particular, is provided by applying a strong electric pulse to the patient&#39;s heart through electrodes placed on the surface of the patient&#39;s body. The brief pulse of electrical current is provided to halt the fibrillation, giving the heart a chance to start beating with a more normal rhythm. If a patient lacks a detectable pulse but has an ECG rhythm of asystole or pulseless electrical activity (PEA), an appropriate therapy includes cardiopulmonary resuscitation (CPR), which causes some blood flow. 
     The probability of surviving a cardiac arrest depends on the speed with which appropriate medical care is provided to a patient experiencing the cardiac arrest. To decrease the time until appropriate medical care is provided, it has been recognized that those persons who are first to arrive at the scene, “first responders,” should be provided with an automated external defibrillator (AED). An AED that provides adequate instructions to the first responder improves the overall success rate of treating cardiac arrest patients, AEDs are generally designed for use by the first responder, who can be an emergency medical services worker, a firefighter or a police officer, or who can be a layperson with minimal or no AED training. The AED and the first responder work together to deliver resuscitative therapies to the cardiac arrest patient. 
     Typically, the AED is a small, portable device that analyzes the heart&#39;s rhythm and prompts a user to deliver treatment to the patient. Once the AED is activated, it can guide the first responder through each step of the treatment by providing audible and/or visual prompts, that may include CPR treatment and/or a defibrillation pulse, if it determines the desirability for such a pulse. Protocols have been developed for AEDs that typically provide instructions in time intervals, based on medical standards. These protocols generally call for CPR to be administered by the first responder in time intervals of a pre-programmed length, such as “do one minute of CPR”. 
     Unfortunately, under the pressures of an emergency situation, it can difficult for a first responder to accurately judge time intervals designated by the AED for CPR treatment. In addition, different first responders may differ in technique and may not consistently provide adequate CPR treatment during the time period designated by the AED. 
     Accordingly, it is desirable to provide a method and apparatus that quickly, accurately, and automatically prompts a first responder to provide CPR treatment or defibrillation, as appropriate, in an emergency situation. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. 
     BRIEF SUMMARY 
     A defibrillator is disclosed that specifies treatment protocols in terms of number of chest compressions instead of time intervals. The defibrillator includes a connection port that is configured to attach with a plurality of electrodes that are capable of delivery of a defibrillation shock and/or sensing one or more physical parameters. An energy storage device capable of storing a charge is attached to the plurality of electrodes. A controller is coupled to the plurality of electrodes and the energy storage device, the controller is configured to provide CPR chest compression instructions in terms of the numbers of CPR chest compressions. The defibrillator may also monitor the patient during periods of CPR and count chest compressions as they are administered and then use the information it gathers on compressions to gate and/or adjust its protocol. 
     A defibrillator is disclosed that includes a means for selecting a CPR treatment protocol from a plurality of stored CPR treatment protocols. The selected CPR treatment protocol includes at least the number of CPR chest compressions. And a means for communicating the number of CPR chest compressions. 
     A method is disclosed of operating a defibrillator in conjunction with the delivery of an injected medication. The method includes selecting a CPR treatment protocol from a plurality of CPR treatment protocols corresponding to the injected medication. The CPR treatment protocol includes at least chest compression and defibrillator pulse instructions. Communicating at least the number of chest compressions of the CPR treatment protocol. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in conjunction with the following figures, wherein like reference numbers refer to similar elements throughout the figures. 
         FIG. 1  is a simplified schematic view of an AED connected to a patient in accordance with an exemplary embodiment of the invention; 
         FIG. 2  is a simplified block diagram of an AED in accordance with one embodiment of the invention; 
         FIG. 3  is a flowchart for the method of operating the AED of  FIG. 1  in accordance with one embodiment of the present invention; 
         FIG. 4  is a flowchart for the method of determining the number of users of the AED of  FIG. 1  in accordance with one embodiment of the present invention; and 
         FIG. 5  is a flowchart for the method of operating the AED of  FIG. 1  in conjunction with a drug injection in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     The invention may be described herein in terms of functional and/or logical block components and various processing steps. It should be appreciated that such block components may be realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. For example, an embodiment of the invention may employ various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, look-up tables, or the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices. In addition, those skilled in the art will appreciate that the present invention may be practiced in conjunction with any number of defibrillator implementations and that the system described herein is merely one exemplary application for the invention. 
     For the sake of brevity, conventional techniques related to defibrillator devices, related control signal processing, data transmission, and other functional aspects of the systems (and the individual operating components of the systems) may not be described in detail herein. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent example functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical embodiment. 
     It is sometimes difficult for a user, or “first responder”, and an external defibrillating system to work effectively together to efficiently deliver resuscitative therapies. Current protocols have been developed that specify time intervals for the application of CPR. While the external defibrillating system is good at measuring time intervals, a stressed first responder may be poor at judging the length of time intervals and cannot reliably anticipate when that time interval will conclude. Furthermore, with different first responders having different training and techniques, specifying a time interval may result in drastically different CPR therapies, since the benefit does not come solely from the time interval but comes from actively compressing the chest enough times during that interval. 
     The invention described herein is a method and apparatus that includes an algorithm that makes it possible to specify treatment protocols in terms of number of chest compressions instead of time intervals. The external defibrillating system disclosed may also monitor the patient during periods of CPR treatment and count chest compressions as they are administered and then use the information it gathers on chest compressions to gate and/or adjust the treatment protocol. 
     The invention is directed to an external defibrillating system that may be an Automated or Automatic External Defibrillator (AED) or a manual monitor/defibrillator. While many of the exemplary embodiments of the invention apply to all types of external defibrillators, some of the embodiments are only for specific types, such as embodiments only for automated defibrillators or only for manual monitor/defibrillators 
       FIG. 1  shows one embodiment of an external defibrillating system  100  configured to be able to deliver a CPR treatment protocol, including a defibrillation pulse if needed, to a patient. The system  100 , includes, but is not limited to, a defibrillator  105  having a connection port  110  that is configured to electrically connect the defibrillator  105  to one or more electrodes  115 , 116 . The defibrillator  105  can be any number of external defibrillators in accordance with the present invention. 
     The defibrillator  105  preferably includes a user interface  125  having a display  130  configured to visually present to the user various measured or calculated parameters associated with the patient  102  and/or other information to a user of the defibrillator  105 . For example, the display  130  can be configured to visually present the ECG and/or other physiological signals indicating the physical status of the patient  102 , or instructions and/or commands, including prompts to perform cardiopulmonary resuscitation (CPR) treatment or other treatment instructions, to the user. The display  130  can also be configured to present visual alerts, flashing lights or warnings to the user. The user interface  125  also includes an audio system  135  that provides an audio signal to aurally communicate with the user voice prompts that deliver instructions or commands, monotonal, ascending, descending or quickening tones to indicate alerts or warnings, or any other suitable audio signals for communicating with the user. The user interface  125  can also include one or more input devices (e.g., switches or buttons)  140  that are configured to receive commands or information from the operator, such as, in the case of automated or manual defibrillators, a shock command. Additionally, the visual display  130  and audio system  135  may be configured to cooperate with one another 
     The defibrillator  105  is configured to generate a charge that is delivered to the patient  102  as a defibrillation pulse with one or more electrodes  115 ,  116 . The one or more electrodes  115 ,  116  may also be configured to sense one or more physiological and/or physical parameters of the patient  102  and supply signals representative of these parameters to the defibrillator  105 . The one or more physiological and/or physical parameters of the patient can include information about the patient&#39;s heart, blood, temperature and/or the like. More particularly, the sensed physical parameter can also be ECG data, heart rhythm data, heart rate data, cardiac output data, blood flow data, a patient&#39;s level of perfusion, respiration data and/or any other physical parameter that is used in the art to assess the physical condition of a patient. As shown in phantom in  FIG. 1 , the defibrillator  105  may additionally include one or more sensing electrodes  120 ,  121  to sense the physiological and/or physical parameters. In either configuration, the signals provided by the one or more electrodes  115 ,  116  and/or one or more sensing electrodes  120 ,  121  are preferably evaluated by the defibrillator  105  to evaluate and determine, among other things, selection of an appropriate CPR treatment protocol from a plurality of CPR protocols stored in the defibrillator  105 . It can also determine whether a defibrillation pulse should be applied to patient  102  in accordance with techniques known to those of ordinary skill in the art. The defibrillator  105  can also evaluate the signals provided by the one or more electrodes  115 , 116  and/or one or more sensing electrodes  120 ,  121  to determine the waveform parameters (e.g., voltage, current, energy and/or duration), as well as magnitude and duration of the defibrillation pulse. 
     Counting chest compressions may be accomplished by a number of different physiological or physical signals. One or more of the physiological or physical signals could also provide a count of breaths (ventilation), which would augment the information provided by the compression counter. In one embodiment, chest compressions could be based on the continuous high frequency impedance signal which fluctuates substantially when the chest is compressed. The continuous high frequency impedance signal may be present in the external defibrillating system. In another embodiment, the compression count could be based on an electrocardiogram (ECG) signal, which generally exhibits substantial “artifact” during compression. In still another embodiment, the compression count could be based on an accelerometer or pressure sensor attached to the chest, optionally as part of the defibrillation electrode. In yet another embodiment, the compression count could be based on physiological signals, such as a plethysmographic waveform used by pulse oximeters. 
       FIG. 2  shows one embodiment of a simplified block diagram of the circuitry that makes up the defibrillator  105 . The defibrillator  105  preferably includes a controller  145 , the user interface  125  (e.g., switches or buttons  140  and/or display  130  as shown in  FIG. 1 ), a circuit  150 , a charging mechanism  155  that can include a power source  160  and a switch  165  to couple the power source  160  to the one or more energy storage devices (e.g., capacitors)  170  and an energy delivery circuit  175 , which is illustrated as a switch  176  that is configured to selectively couple the one or more energy storage devices  170  to the connection port  110  under the control of the controller  145 . The energy delivery circuit  175  can be implemented with any number of circuit configurations. The controller  145  can be a single processing unit or multiple processing units and can be implemented with software, hardware, firmware, or any combination thereof. The controller  145  is configured to at least partially control the operation of the defibrillator  105 . This may include the plurality of treatment protocols and charging the one or more energy storage devices  170 . It will be appreciated that the circuitry depicted in  FIG. 2  is merely exemplary of a particular architecture, and that numerous other circuit architectures may be used to implement the operation of the defibrillator  105 . 
     The controller  145  may include, among other things, a processor  147  and a memory unit  146 . The processor  147  may be any one of numerous known general purpose processors or an application specific processor that operates in response to program instructions, which may be stored in any of various forms of memory storage. It will also be appreciated that the controller  145  may be implemented using various other circuits, not just a programmable processor. The memory unit  146  is in operable communication with processing unit  147 . 
     The memory unit  146  may contain the operating system, software routines and a plurality of CPR treatment protocols. The CPR treatment protocols may include at least chest compression and defibrillator pulse treatment instructions. The CPR treatment protocols may also include predetermined parameters based on the sensed physical parameters such things as the administration of oxygen therapy, drug therapy, or, checking the patient for a pulse or for normal breathing, monitoring SaO 2 , monitoring end tidal CO 2 , or blood pressure levels, or any other non-electric treatment known in the art that is appropriately administered to a patient with an arrhythmic heart condition. The memory  146  can also receive and store the patient&#39;s sensed physical parameters, historical data, lengths of time and rate of CPR treatments and defibrillation pulses previously discharged to the patient. 
     It will be appreciated that the above-mentioned scheme is merely exemplary of one scheme for storing operating software and software routines, and that various other storage schemes may be implemented. It will be appreciated that the memory unit  146  could be integrally formed as part of the controller  145  and/or processing unit  147 , or could be part of a device or system that is physically separate from the defibrillator  105 . 
     In use, the defibrillator  105  makes treatment determinations based on the sensed physical parameters by comparing the sensed physical parameters to predetermined CPR treatment protocols stored in the memory unit  146 . The defibrillator  105  determines which of the stored CPR treatment protocols should be used to deliver the appropriate chest compressions and/or rate based on the sensed physical parameters and whether a patient should receive a defibrillation pulse, such as a shock. The appropriate CPR treatment protocol is then communicated to the user. The controller  145  is configured to automatically update and/or continuously sense the sensed physical parameters and adjust the CPR treatment protocol accordingly. 
     The CPR treatment protocols described herein are specified in terms of numbers of chest compressions and communicated to the user in that fashion. With this approach, the defibrillator  105  instructs the user to deliver a certain number of chest compressions, rather than provide CPR for a certain time interval. There are many different ways that the desired number of chest compressions may be conveyed to the user. For example, the defibrillator  105  may count the number of chest compressions with the user. This may be used to pace the chest compression rate. The defibrillator  105  may communicate total chest compression count, such as “apply 100 chest compressions”. The defibrillator may communicate updated compression information, such as “20 more compressions starting now”. The defibrillator may communicate a “pre-shock” sprint before a defibrillation pulse is applied, such as “do 50 compressions and then press the defibrillate button”. 
       FIG. 3  shows one method of operating a defibrillator according to the present invention, such as defibrillator  105  shown in  FIG. 1 . The defibrillator is coupled to a patient at step  200 . At step  202 , one or more physical parameters of the patient are obtained from the patient via the one or more electrodes  115 ,  116 ,  120 ,  121 . It will be appreciated that any number of physical parameters can be sensed. Once the defibrillator  105  receives the signals at step  204 , the one or more physical parameters are analyzed and compared to a plurality of CPR treatment protocols stored in the memory unit  146  of the controller  145  to determine whether or not the patient&#39;s physical parameters indicate a condition that should be treated with chest compressions or a defibrillation pulse. The controller  145  then selects the appropriate CPR treatment protocol based in the one or more physical parameters at step  206 . The appropriate CPR treatment protocol is then aurally communicated to the user at step  208 . The aurally communicated information includes at least chest compression and defibrillator pulse treatment instructions. The appropriate CPR treatment protocol may also be displayed on the display  130 . 
     The controller  145  is configured to automatically update and/or continuously sense the sensed physical parameters at step  210  to determine the number of chest compressions and/breaths being given the patient. For example, in one embodiment of the invention, counting the number chest compressions may be based on an electrocardiogram (ECG) signal. In other embodiments, counting the number chest compressions may be based on high frequency impedance, an acceleration sensor signal, a pressure sensor signal, or an impedance plethysmographic waveform. The controller  145  then adjusts the CPR treatment protocol accordingly based on the monitored information at step  212 . 
       FIG. 4  shows one method in which an AED may be able to determine a user&#39;s technique by monitoring the pattern of chest compressions and/or breaths given to the patient. The AED may then adjust the CPR treatment accordingly. Rescuers are often trained to deliver either fifteen compressions followed by two breaths (recommended for CPR with an unsecured airway) or continuous chest compressions with asynchronous ventilation (recommended for CPR with an intubated airway). Based on this information, the defibrillator  105  can optimize the CPR treatment protocol based on the knowledge that the CPR was being administered in a pattern taught for an unsecured or secured airway. In use, the AED is coupled to the patient at step  300 . The number of chest compressions and/or breaths/ventilations is obtained from the patient via the one or more electrodes at step  302  by known means, such as high frequency impedance. Once the AED receives the signals at step  304 , the numbers of chest compressions and/or breaths/ventilations are analyzed and compared to a plurality of CPR treatment techniques stored in the memory unit of the AED to determine compression/ventilation pattern. The AED then adjusts the appropriate CPR treatment protocol based on the compression/ventilation pattern at step  306 . 
     By monitoring the chest compression count given to the patient, the AED can make immediate changes to the CPR treatment protocol. In one embodiment, the AED could use compression count to determine compression rate and provide feedback to the user to speed up or slow down. In another embodiment, the AED is able to detect the slowdown of compressions, which may indicate onset of fatigue by the user and prematurely call the end of the CPR interval in favor of delivering a defibrillation pulse. In another embodiment, the AED could detect if the rate of chest compressions is low or non-existent. For example, if no compressions are detected during CPR treatment, prompts to “start CPR” may be given. Also, if compressions are detected but the rate is so slow to be ineffective, the AED could cut short the CPR treatment segment and defibrillate. 
     In another embodiment, the AED may be able to determine if the user is doing compression-only CPR by monitoring the chest compression count and ventilations given to the patient. Some of the CPR treatment protocols may vary treatments for chest compressions and ventilations. While chest compressions without ventilations may be appropriate for the first few minutes of resuscitation effort, ventilations are best added later in the resuscitation after oxygen has been depleted from the circulating blood. For example, if the AED sensed administration of compression-only CPR, it could advise after a pre-set amount of time or number of chest compressions that ventilations be added to the CPR compressions. 
       FIG. 5  shows one method in which a defibrillator is used with medication injection to assure adequate circulation of injected drugs, such as epinephrine, before delivery of a defibrillation pulse. The coronary perfusion pressure elevating effects of epinephrine during CPR is rather short-lived and there is a “sweet spot” amount of chest compressions that should be delivered between injection of the epinephrine and defibrillation. Often, defibrillation pulse treatments are administered too early or too late. Too early and the heart has not received the boost in circulation; too late and the effects of circulation have worn off. So the CPR treatment protocol selected could optimize the effectiveness of an injection by instructing and counting compressions after injection, and then shocking after an appropriate amount of circulation. The injected drug is communicated to the defibrillator at step  400 . At step  402  the defibrillator counts the chest compressions for the treatment and prompts for delivery of a defibrillation pulse  404 . In terms of compressions after injection of epinephrine, this may be in the neighborhood of 200 compressions. 
     The AED compression count may also be combined with “viability index” information provided by a ventricular fibrillation (VF) analysis algorithm. If the chest compression rate is good and yet the viability index continues to worsen, it would be clear that CPR treatment is not effective. This could indicate the need to improve the CPR chest compressions, such as instruction the user to “Press harder on the chest”, or alter the CPR treatment protocol, for example to administer a peripheral vasoconstrictor drug, such as epinephrine. 
     While the defibrillator described herein instructs the user with CPR treatment protocols based on chest compression count, it is envisioned that an defibrillator could be designed to also instruct the user with time intervals in addition chest compression count. In this way, a single device could be sold to users wanting to continue using time intervals as well as users wanting chest compression counts. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.