Defibrillation controller that advises regarding shock impedance before delivering a shock

Abstract

A defibrillator using an ECG analyzer and a shock impedance advisor for improving defibrillation of a patient's heart by a defibrillation discharge circuit associated with the defibrillator. In operation, the ECG analyzer derives a shock delivery decision from detecting a shockable rhythm in the patient's ECG waveform in response to a shock delivery decision, and the shock impedance advisor measures the non-shock impedance of the defibrillation discharge circuit, estimates a pre-shock impedance of the defibrillation discharge circuit from the measured non-shock impedance of the defibrillation discharge circuit, and communicates a lower shock impedance advisory to a responder operating the defibrillator when the pre-shock impedance of the defibrillation discharge circuit exceeds a shock impedance threshold.

Description

[Technical Field]

[0001] The present disclosure relates generally to cardiac arrest treatments including defibrillation of a patient's heart, and more particularly to improving defibrillation of a patient's heart by a defibrillator-associated defibrillation discharge circuit. [Background technology]

[0002] 1 shows a CPR monitor 30 positioned on the sternum of a patient 10, with a responder 20 placing one hand on top of the other to deliver chest compressions in a traditional two-handed manner. However, rather than placing hands directly on the patient 10, the responder's 20 hands are placed on the CPR monitor 30, delivering chest compressions to the patient 10 via the CPR monitor 30. Chest compressions are delivered by the responder 20 to the heart of the patient 10 as prescribed by a traditional CPR protocol. As is known in the art, the CPR monitor 30 monitors the quality of the CPR delivered by the responder 20 to the heart of the patient 10, e.g., the depth and rate of compressions, chest release and recoil, and the placement of the responder's hands on the chest of the patient 10, to determine whether the CPR is effective or ineffective. Cable 31 is attached to defibrillator 40 to connect CPR quality monitoring to defibrillator 40 and provide audible CPR instructions through the defibrillator 40 speaker.

[0003] FIG. 1 further illustrates a defibrillator 40 attached to the patient 10 by electrodes 41 a and 41 b. Defibrillators 40, as known in the art, are used to deliver defibrillation shocks to the patient 10 as needed during CPR. More specifically, the defibrillator 40 operates to deliver high-voltage impulses to the heart of the patient 10 to restore normal rhythm and contractile function in patients experiencing arrhythmias without spontaneous circulation (e.g., ventricular fibrillation (VF) or ventricular tachycardia (VT)). During operation, the defibrillator 40 automatically analyzes the electrocardiogram (ECG) rhythm of the patient's 10 heart to determine whether defibrillation is necessary. If necessary, the defibrillator 40 prompts the responder 20 to terminate CPR and press a shock button to deliver a defibrillation shock to the patient when a shock is advised by the defibrillator 40. Summary of the Invention [Problem to be solved by the invention]

[0004] As illustrated illustratively in Figure 1, the field of resuscitation is focused on improving the quality of care by identifying and delivering optimal CPR / shock therapy to patients experiencing cardiac arrest. [Means for solving the problem]

[0005] The present disclosure is directed to improving existing defibrillators (e.g., automated external defibrillators and advanced life support defibrillators) by providing a shock impedance lowering advisory when the estimated pre-shock impedance of the defibrillation discharge circuitry associated with the defibrillator exceeds a shock impedance threshold.

[0006] The present disclosure can be embodied as (1) a defibrillation controller and (2) a defibrillation method.

[0007] Various exemplary embodiments of the defibrillator of the present disclosure include an ECG analyzer and a shock impedance advisor for improving defibrillation of a patient's heart by a defibrillator discharge circuit associated with the defibrillator. The ECG analyzer is configured to derive a shock delivery decision from detecting a shockable rhythm in the patient's ECG waveform. In response to the shock delivery decision, the shock impedance advisor is configured to (1) measure the non-shock impedance of the defibrillator discharge circuit, (2) estimate the pre-shock impedance of the defibrillator discharge circuit from the measured non-shock impedance of the defibrillator discharge circuit, and (3) communicate a lower shock impedance advisory to a responder operating the defibrillator when the pre-shock impedance of the defibrillator discharge circuit exceeds a shock impedance threshold.

[0008] Various additional exemplary embodiments of a defibrillation controller of the present disclosure include a non-transitory machine-readable storage medium encoded with instructions for execution by one or more processors to improve defibrillation of a patient's heart by a defibrillation discharge circuit associated with a defibrillator. In response to a decision to deliver a shock, the non-transitory machine-readable storage medium includes instructions to: (1) measure a non-shock impedance of a defibrillation discharge circuit; (2) estimate a pre-shock impedance of the defibrillation discharge circuit from the measured non-shock impedance of the defibrillation discharge circuit; and (3) communicate a lower shock impedance advisory to a responder operating the defibrillator when the pre-shock impedance of the defibrillation discharge circuit exceeds a shock impedance threshold.

[0009] Various exemplary embodiments of a defibrillation method according to the present disclosure include improving defibrillation of a patient's heart with a defibrillator associated with a defibrillator. The defibrillation method includes the defibrillator deriving a shock delivery decision from detecting a shockable rhythm in the patient's ECG waveform. In response to the shock delivery decision, the defibrillator further includes the defibrillator (1) measuring a non-shock impedance of the defibrillation discharge circuit, (2) estimating a pre-shock impedance of the defibrillation discharge circuit from the measured non-shock impedance of the defibrillation discharge circuit, and (3) communicating a lower shock impedance advisory to a responder operating the defibrillator when the pre-shock impedance of the defibrillation discharge circuit exceeds a shock impedance threshold.

[0010] The above-described exemplary embodiments and other embodiments of the present disclosure, as well as various features and advantages of the present disclosure, will become more apparent to those skilled in the art from the following detailed description of various embodiments of the present disclosure, read in conjunction with the accompanying drawings. The detailed description and drawings are illustrative of the present disclosure, rather than limiting, the scope of which is defined by the appended claims and equivalents thereof. [Brief explanation of the drawings]

[0011] The present disclosure is set forth in detail in the following description of exemplary embodiments with reference to the following figures: [Figure 1] FIG. 1 illustrates cardiopulmonary resuscitation administered to a patient's heart by a responder, as known in the art of this disclosure. [Figure 2] FIG. 2 illustrates an exemplary embodiment of a cardiac arrest treatment system according to the present disclosure. [Figure 3] FIG. 3 illustrates an exemplary embodiment of a defibrillation discharge circuit according to the present disclosure. [Figure 4] FIG. 4 illustrates an exemplary embodiment of a defibrillator according to the present disclosure. [Figure 5] FIG. 5 shows a flow chart representative of an exemplary embodiment of a defibrillation method according to the present disclosure. [Figure 6] FIG. 6 illustrates an exemplary embodiment of a defibrillation controller according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present disclosure aims to improve existing defibrillators (e.g., automated external defibrillators and advanced life support defibrillators) by providing an end of resuscitation (TOR) advisory and assisting responders in determining TOR while administering cardiopulmonary resuscitation (CPR) to a patient's heart.

[0013] To facilitate understanding of the present disclosure, the following description of Figure 2 teaches an exemplary embodiment of a cardiac arrest treatment system according to the present disclosure. From the description of Figure 2, those skilled in the art will understand how to apply the present disclosure to make and use further embodiments of a cardiac arrest treatment system according to the present disclosure.

[0014] Referring to FIG. 2, an exemplary cardiac arrest treatment system of the present disclosure uses a CPR monitor 20a and a defibrillator 40a.

[0015] In fact, the CPR monitor 20a is any device known or hereinafter contemplated in the art of the present disclosure for analyzing the quality of CPR administered to the heart 11 of the patient 10a by a responder (not shown).

[0016] In a first exemplary embodiment, the CPR monitor 20a is configured as a CPR coaching device in accordance with U.S. Patent No. 8,532,765 B2, entitled "CPR Coaching Device with Reduced Sensitivity to Motion," inventors Ochs et al., the contents of which are incorporated herein by reference.

[0017] In a second exemplary embodiment, the monitor 20a is a CPR machine that incorporates the CPR analysis principles described by Ochs et al.

[0018] Still referring to FIG. 2, defibrillator 40a may, in fact, be any type of defibrillator known in the art or hereinafter contemplated that incorporates the inventive principles of the present disclosure for assisting a responder in determining TOR while administering cardiopulmonary resuscitation (CPR) to a patient's heart.

[0019] During operation, the defibrillator 40a receives CPR feedback (CFB) 22 from the CPR monitor 20a as a basis for monitoring the administration of CPR by a responder to the patient's heart.

[0020] Furthermore, during operation, the defibrillator 40a monitors the ECG waveform of the patient's 10a's heart 11 via electrodes 41a and 41b attached to the patient 10a, as known in the art of the present disclosure, and analyzes the ECG waveform to detect any shockable rhythms in the patient's 10a's heart 11, as known in the art of the present disclosure.

[0021] When the defibrillator 40a derives a shock delivery decision from analysis of the ECG waveform, the defibrillator 40a measures the non-shock impedance of the defibrillation discharge circuit 46, as shown in FIG. 3, as a basis for estimating whether the pre-shock impedance of the defibrillation discharge circuit 46 is above a shock defibrillation threshold, as described further in this disclosure.

[0022] Referring to FIG. 3, defibrillation discharge circuit 46 includes capacitor C40a, switch S40a, inductor L40a and resistor R40a of defibrillator 40a, and resistor R10 representing the impedance of patient 10.

[0023] To further facilitate understanding of the present disclosure, the following description of Figure 5 teaches an exemplary embodiment of a defibrillator according to the present disclosure. From the description of Figure 5, one skilled in the art will understand how to apply the present disclosure to make and use further embodiments of a defibrillator according to the present disclosure.

[0024] 4, a defibrillator 40b of the present disclosure uses a pair of electrode pads / paddles 41a and 41b, an optional ECG lead 46, an ECG monitor 50 (internal or external), a shock source 60, and a defibrillation controller 70. Also shown is a CPR coaching device 20a communicatively coupled to the defibrillation controller 70.

[0025] Electrode pads / paddles 41 a and 41 b are structurally configured to be conductively affixed to patient 10 a in a precordial-apical position as shown in FIG. 1 , or alternatively in a precordial-posterior position (not shown), as known in the art. Electrode pads / paddles 41 a and 41 b conduct defibrillation shocks from a shock source 60 to patient 10 a's heart 11 as controlled by a defibrillation controller 70, as known in the art, and conduct electrical activity of patient 10 a's heart 11 to an ECG monitor 50, as known in the art. Alternatively, or simultaneously, ECG leads 46, as known in the art, can be connected to patient 10 a and conduct electrical activity of patient 10 a's heart 11 to ECG monitor 50.

[0026] As is known in the art, the ECG monitor 50 is structurally configured to generate an ECG waveform of the heart 11 of the patient 10a as an indication that the patient 10a is experiencing an organized or unorganized heartbeat. An example of an ECG waveform indicative of an organized heartbeat is an ECG waveform 51a, shown in Figure 4, which represents organized contractions of the ventricles of the heart 11 that are capable of pumping blood. An example of an ECG waveform indicative of the patient 10a is a random ECG waveform 51b, shown in Figure 4, which has zero discernible waves and represents the absence of organized heartbeat activity in the heart 11 of the patient 10a.

[0027] In one exemplary embodiment, ECG monitor 50 uses a digital signal processor (not shown) to stream ECG waveform data 52 to defibrillation controller 70 .

[0028] Shock source 60 is structurally configured to store electrical energy for delivering a defibrillation shock to heart 11 of patient 10a via electrode pads / paddles 41a and 41b as controlled by defibrillation controller 70, as known in the art. In practice, the defibrillation shock may have any waveform known in the art. Examples of such waveforms include, but are not limited to, a monophasic sinusoidal waveform (positive sine wave) 61a and a biphasic truncated waveform 61b, as shown in FIG. 4.

[0029] In one exemplary embodiment, shock source 60 uses a high-voltage capacitor bank (not shown) to store high voltage via a high-voltage charger and power supply upon pressing a charge button. Shock source 60 further uses switching / isolation circuitry (not shown) to selectively apply a charge of electrical energy of a particular waveform from the high-voltage capacitor bank to electrode pads / paddles 41 a and 41 b, as controlled by defibrillation controller 70.

[0030] Defibrillation controller 60 implements an ECG analyzer 80 for analyzing and interpreting ECG waveform data 52 from ECG monitor 50 as known in the art and as discussed below.

[0031] Defibrillation controller 70 further implements shock impedance advisory 90 to conditionally derive lower shock impedance advisory 91 and communicate the advisory to the responder.

[0032] In one embodiment, a flowchart 100, as shown in FIG. 5, is executed by shock impedance advisor 90 upon initiation of CPR by a responder.

[0033] Referring to FIG. 5, in response to receiving a shock delivery decision in stage S102 of flowchart 100, shock impedance advisor 90 proceeds to stage S104 to measure the non-shock impedance of defibrillation discharge circuit 46 (of FIG. 3) and proceeds to stage S106 to estimate the pre-shock impedance of defibrillation discharge circuit 46.

[0034] In one embodiment of stage S104, shock impedance advisor 90 delivers a small signal to defibrillation discharge circuit 46 using, for example, 32 kHz or 12.8 kHz, at an energy level low enough to induce a shock to the heart of patient 10, and measures the non-shockable impedance of defibrillation discharge circuit 46 as known in the art of the present disclosure.

[0035] In one embodiment of stage S104, the shock impedance advisor 90 implements a supervised learning model that is trained on the correlation between the pre-shock impedance of the defibrillation discharge circuit 46 and the non-shock impedance of the defibrillation discharge circuit 46, thereby estimating the pre-shock impedance from the measured non-shock impedance.

[0036] If the pre-shock impedance exceeds a shock impedance threshold (e.g., 80-100 ohms) in stage S108 of flowchart 100, shock impedance advisor 90 derives and communicates a lower shock impedance advisory 93 in stage S110 of flowchart 100 and returns to stage S102. In one embodiment, lower shock impedance advisory 93 may instruct a change in pad placement on the patient's chest, and the responder may change the pad configuration from anterior / anterior chest (A / A) to anterior / posterior (A / P). Another action the responder may take is to press down on the pads to ensure they are firmly attached to the patient and reassess the shock impedance. A new defibrillation vector with a lower estimated shock impedance may deliver more current and improve the defibrillation shock.

[0037] When the pre-shock impedance falls below a shock impedance threshold (e.g., 80-100 ohms) in stage S108 of flowchart 100, shock impedance advisor 90 communicates a decision to deliver a shock in stage S112 of flowchart 100. Once the shock is delivered in stage S114, shock impedance advisor 90 begins measuring the post-shock impedance of the defibrillation discharge circuit and returns to stage S102.

[0038] In practice, this estimated shock impedance can be communicated to the responder by visual indicators (e.g., numbers, colors, symbols, etc.) and / or audio (e.g., simulated voice, pitch, alert, etc.).

[0039] According to exemplary embodiments of the present disclosure, the non-shock impedance is used to estimate the shock impedance before the shock is delivered. When the shock is delivered, the actual shock impedance can be measured. Both the estimated and actual shock impedance can be used for feedback to indicate to the responder whether the impedance is (too) high or (too) low.

[0040] As discussed above, non-shock impedance is useful before any shock is administered (e.g., to prompt the responder to take action to lower impedance before administering a shock). A combined (estimated and actually measured) impedance determination can be used to inform and assist the responder to take action to lower impedance after delivering a shock and before another shock is advised and administered / delivered.

[0041] The actual measured impedance may also be used to alert the responder to (significant) discrepancies / variances between the estimated impedance (e.g., based on a small signal) and the actual impedance (i.e., based on the impedance measured during the delivery of the shock) and to adjust future estimated impedances (e.g., by adjusting the small signal used, and / or by adjusting the estimated results after small measurements are made based on actual impedance measurements and / or combined impedance measurements (i.e., based on both the estimated shock impedance and the true / actual shock impedance), and / or to address other factors that may affect the estimated shock impedance measurements).

[0042] The average shock impedance should typically be between 80 and 100 ohms. If the patient's shock impedance is (very) high, defibrillation success may be reduced. For example, the responder can use paddles or compress the patient's chest with a rolled-up towel to (1) squeeze air out of the chest and (2) improve pad adhesion to the patient's chest, thereby lowering the shock impedance.

[0043] Shock impedance is primarily important if / when a patient has a shockable rhythm. If / when a patient has a non-shockable rhythm, exemplary devices, systems, and / or methods can continue to analyze the patient's impedance while monitoring the patient's electrocardiogram and cardiac rhythm. Even when a non-shockable rhythm is detected, exemplary embodiments of the present disclosure can still alert and communicate to the responder that the impedance is high and that certain action (e.g., changing pad position) should be considered, so that the responder can take appropriate action when and before a shockable rhythm is detected and a shock is advised and administered / delivered.

[0044] For example, when shock impedance is high, a responder action is to try a different pad configuration. In addition to changing the pad placement on the patient's chest, the responder can change the pad placement from anterior / anterior chest (A / A) to anterior / posterior chest (A / P) and reassess the estimated shock impedance. Another action the responder can take is to press down on the pads to ensure they are firmly adhered to the patient and reassess the shock impedance. A new defibrillation vector with a lower estimated shock impedance may deliver more current and improve the defibrillation shock.

[0045] Exemplary embodiments of the present disclosure may also be used in conjunction with / for dual sequential defibrillation (DSD), which uses multiple shocks delivered in rapid succession from one or more defibrillators with different defibrillation vectors, as will be appreciated by those skilled in the art. The use of estimated shock impedance and / or combined impedance measurements (i.e., based on both estimated and actual shock impedance) by exemplary embodiments of the present disclosure helps to refine and identify / estimate the best and / or optimal (or near-best / optimal) defibrillation vector suitable for future shocks.

[0046] To facilitate a further understanding of the present disclosure, the following description of Figure 6 teaches an exemplary embodiment of a defibrillation controller according to the present disclosure. From the description of Figure 6, those skilled in the art will understand how to apply the present disclosure to make and use additional embodiments of a defibrillation controller according to the present disclosure.

[0047] Referring to FIG. 6, an exemplary embodiment of a defibrillation controller 170 is shown, which includes one or more processors 171, memory 172, a user interface 173, a network interface 174, and storage 175 interconnected via one or more system buses 176.

[0048] Each processor 171 may be any hardware device known in the art of this disclosure or as contemplated below that is capable of executing instructions or processing data stored in memory 172 or other storage device. By way of non-limiting example, processor 171 may include a microprocessor, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or other similar device.

[0049] Memory 172 may include various memories as known in the art or as contemplated below, including, but not limited to, L1, L2, or L3 cache, or system memory. By way of non-limiting example, memory 172 may include static random access memory (SRAM), dynamic RAM (DRAM), flash memory, read-only memory (ROM), or other similar memory devices.

[0050] User interface 173 may include one or more devices known in the art or as contemplated below for enabling communication with a user, e.g., an administrator. By way of non-limiting example, the user interface may include a command line interface or a graphical user interface that may be presented to a remote terminal via network interface 174.

[0051] The network interface 174 may include one or more devices, such as those known in the art or contemplated below, for enabling communication with other components of the medical device. In a non-limiting example, the network interface 174 may include a network interface card (NIC) configured to communicate according to the Ethernet protocol. Furthermore, the network interface 174 may implement a TCP / IP stack for communication according to the TCP / IP protocol. Various alternative or additional hardware or configurations for the network interface 174 will become apparent.

[0052] Storage device 175 may include one or more machine-readable storage media known in the art of this disclosure or as contemplated below, including, but not limited to, read-only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, or similar storage media. In various non-limiting embodiments, storage device 175 may store instructions for execution by processor 171 or data on which processor 171 operates. For example, storage device 175 may store a basic operating system for controlling various basic operations of the hardware.

[0053] The storage device 175 may also store application modules in the form of executable software / firmware for implementing various functions of the methods of FIGS. 4 and 6, as described above in this disclosure.

[0054] In one exemplary embodiment shown, the memory device 175 stores application modules 177 including an ECG analyzer 178 for deriving shock delivery decisions as known in the art of the present disclosure, and a shock impedance advisor 179 for deriving a lower shock impedance advisory as described above in this disclosure, particularly in accordance with flowchart 100 of FIG. 5.

[0055] From the description of Figures 1-6 of the present disclosure, one skilled in the art will appreciate the many advantages of the present disclosure, including, but not limited to, improving defibrillation of a patient's heart by a defibrillation discharge circuit associated with a defibrillator.

[0056] The present disclosure has been described with reference to preferred embodiments. Modifications and alterations may occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

[0057] Furthermore, as one skilled in the art will appreciate in view of the teachings provided in this disclosure, the features, elements, components, etc. disclosed and described in this disclosure / specification and / or shown in the accompanying drawings and / or recited in the claims can be implemented in various combinations of hardware and software, providing functionality that can be combined in a single element or multiple elements. For example, the functionality of the various features, elements, components, etc. shown / illustrated / depicted in the figures and / or recited in the claims can be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functionality can be provided by a single dedicated processor, by a single shared processor, or by multiple individual processors, some of which are shared and / or multiplexed. Furthermore, express use of the terms "processor" or "controller" should not be construed to refer exclusively to hardware capable of executing software, but can implicitly include, without limitation, digital signal processor ("DSP") hardware, memory (e.g., read-only memory ("ROM"), random access memory ("RAM"), non-volatile storage that stores software, etc.), and substantially any means and / or machine (including hardware, software, firmware, combinations thereof, etc.) that can perform processing and / or control (and / or be configured to do so).

[0058] Moreover, all statements herein reciting principles, aspects, and exemplary embodiments of the present disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, such equivalents are intended to include both currently known equivalents and equivalents now or in the future developed (e.g., any elements developed that can perform the same or substantially similar function, regardless of structure). Thus, for example, in light of the teachings provided in this disclosure, those skilled in the art will understand that any block diagrams presented herein may represent a conceptual view of the components and / or circuitry of illustrative systems embodying the principles of the invention. Similarly, in light of the teachings provided in this disclosure, those skilled in the art will understand that any flowcharts, flow diagrams, etc., may be substantially represented on a computer-readable storage medium and may represent various processes performed by a computer, processor, or other device having processing capabilities, whether or not such a computer or processor is explicitly shown.

[0059] While preferred and exemplary embodiments of the present disclosure have been described, it should be noted that these embodiments are intended to be illustrative and not limiting, and modifications and variations may be made by those skilled in the art in view of the teachings provided in this disclosure, including the accompanying drawings and claims. Thus, it should be understood that changes can be made in the preferred and exemplary embodiments of the present disclosure that are within the scope of the disclosure and exemplary embodiments disclosed, described, and taught in this disclosure.

[0060] Moreover, corresponding and / or related systems incorporating and / or implementing the devices, or the like used / implemented with devices according to the present disclosure, are also contemplated and considered to be within the scope of the present disclosure. Furthermore, corresponding and / or related methods for making and / or using devices and / or systems according to the present disclosure are also contemplated and considered to be within the scope of the present disclosure.

Claims

1. 1. A defibrillation controller for improving defibrillation of a patient's heart by a defibrillation discharge circuit associated with a defibrillator, the defibrillation controller comprising: an ECG analyzer configured to derive a shock delivery decision from detecting a shockable rhythm in the patient's ECG waveform; Shock Impedance Advisor and wherein the shock impedance advisor, in response to the shock delivery decision, measuring a non-shock impedance of the defibrillation discharge circuit; estimating a pre-shock impedance of the defibrillation discharge circuit from the measurement of the non-shock impedance of the defibrillation discharge circuit; and issuing a lower shock impedance advisory to a responder operating the defibrillator when the pre-shock impedance of the defibrillation discharge circuit exceeds a shock impedance threshold. a defibrillation controller configured to:

2. The shock impedance advisor communicating the decision to deliver the shock to a responder operating the defibrillator when the pre-shock impedance of the defibrillation discharge circuit falls below the shock impedance threshold.

3. The defibrillation controller of claim 2, further configured to:

3. the shock impedance advisor is further configured to measure a post-shock impedance of the defibrillation discharge circuit in response to delivery of a shock by the defibrillator; The shock impedance advisor, in response to a determination by the ECG analyzer to deliver a second shock after delivery of the shock by the defibrillator, measuring a second non-shock impedance of the defibrillation discharge circuit; estimating a second pre-shock impedance of the defibrillation discharge circuit from the second non-shock impedance measurement of the defibrillation discharge circuit and the post-shock impedance measurement of the defibrillation discharge circuit; and and communicating a second shock impedance reduction advisory to a responder operating the defibrillator when the second pre-shock impedance of the defibrillation discharge circuit exceeds the shock impedance threshold.

3. The defibrillation controller of claim 2, further configured to:

4. 4. The defibrillation controller of claim 3, wherein the shock impedance advisor is further configured to communicate a second shock delivery decision to a responder operating the defibrillator when a second pre-shock impedance of the defibrillation discharge circuit falls below the shock impedance threshold.

5. 10. The defibrillation controller of claim 1, wherein the shock delivery decision is for one of a monophasic sine wave defibrillation of the patient's heart or a biphasic truncated waveform of the patient's heart.

6. A defibrillation controller having a non-transitory machine-readable storage medium encoded with instructions for execution by at least one processor for improving defibrillation of a patient's heart by a defibrillation discharge circuit associated with the defibrillator, the instructions comprising: The non-transitory machine-readable storage medium, in response to a decision to deliver a shock, measuring a non-shock impedance of the defibrillation discharge circuit; estimating a pre-shock impedance of the defibrillation discharge circuit from the measurement of the non-shock impedance of the defibrillation discharge circuit; and and issuing a lower shock impedance advisory to a responder operating the defibrillator when the pre-shock impedance of the defibrillation discharge circuit exceeds a shock impedance threshold. a defibrillation controller including instructions for:

7. 7. The defibrillation controller of claim 6, wherein the non-transitory machine-readable storage medium further comprises instructions for, in response to the decision to deliver a shock, communicating the decision to deliver a shock to a responder operating the defibrillator when a pre-shock impedance of the defibrillation discharge circuit falls below the shock impedance threshold.

8. In response to delivery of a shock by the defibrillator, the non-transitory machine-readable storage medium further includes instructions for measuring a post-shock impedance of the defibrillation discharge circuit; After delivery of a shock by the defibrillator, in response to a determination by an ECG analyzer to deliver a second shock, the non-transitory machine-readable storage medium: measuring a second non-shock impedance of the defibrillation discharge circuit; estimating a second pre-shock impedance of the defibrillation discharge circuit from the second non-shock impedance measurement of the defibrillation discharge circuit and the post-shock impedance measurement of the defibrillation discharge circuit; and and communicating a second shock impedance reduction advisory to a responder operating the defibrillator when the defibrillator's second pre-shock impedance of the defibrillation discharge circuit exceeds the shock impedance threshold.

8. The defibrillation controller of claim 7, further comprising instructions for:

9. 7. The defibrillation controller of claim 6, wherein, after delivery of a shock by the defibrillator, in response to a decision by an ECG analyzer to deliver a second shock, the non-transitory machine-readable storage medium further includes instructions for communicating the decision to deliver the second shock to a responder operating the defibrillator when a second pre-shock impedance of the defibrillation discharge circuit falls below the shock impedance threshold.

10. 7. The defibrillation controller of claim 6, wherein the shock delivery decision is for monophasic sine wave defibrillation of the patient's heart or a biphasic truncated waveform of the patient's heart.

11. 1. A defibrillation method for improving defibrillation of a patient's heart by a defibrillation discharge circuit associated with a defibrillator, the defibrillation method comprising: the defibrillator deriving a shock delivery decision from detecting a shockable rhythm in the patient's electrocardiogram (ECG) waveform; in response to the decision to deliver a shock, the defibrillator measuring a non-shock impedance of the defibrillation discharge circuit; the defibrillator estimating a pre-shock impedance of the defibrillation discharge circuit from the measurement of the non-shock impedance of the defibrillation discharge circuit; and when the pre-shock impedance of the defibrillation discharge circuit exceeds a shock impedance threshold, communicating a lower shock impedance advisory to a responder operating the defibrillator; A defibrillation method comprising:

12. 12. The defibrillation method of claim 11, further comprising the step of: in response to the decision to deliver a shock, the defibrillator communicating the decision to deliver a shock to a responder operating the defibrillator when a pre-shock impedance of the defibrillation discharge circuit falls below the shock impedance threshold.

13. measuring a post-shock impedance of the defibrillator discharge circuit in response to delivery of a shock by the defibrillator; after delivery of a shock by the defibrillator, in response to a decision by the defibrillator to deliver a second shock; the defibrillator measuring a second non-shock impedance of a defibrillation discharge circuit; the defibrillator estimating a second pre-shock impedance of the defibrillation discharge circuit from a measurement of a second non-shock impedance of the defibrillation discharge circuit and a measurement of a post-shock impedance of the defibrillation discharge circuit; and the defibrillator communicating a second shock impedance reduction advisory to a responder operating the defibrillator when the second pre-shock impedance of the defibrillation discharge circuit exceeds a shock impedance threshold; 13. The defibrillation method of claim 12, comprising:

14. 14. The defibrillation method of claim 13, further comprising the step of: in response to the decision to deliver a second shock, the defibrillator communicating the decision to deliver a second shock to a responder operating the defibrillator when a pre-shock impedance of the defibrillation discharge circuit falls below the shock impedance threshold.

15. 12. The defibrillation method of claim 11, wherein the decision to deliver a shock is for one of monophasic sine wave defibrillation of the patient's heart or a biphasic truncated waveform of the patient's heart.

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