Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2000-04-12
2001-07-31
Layno, Carl H. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S007000
Reexamination Certificate
active
06269267
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an electrotherapy apparatus and method for delivering an electrical pulse to a patient's heart. This invention also relates to an apparatus and method for selectively configuring an electrotherapy apparatus by adjusting criteria used to determine shock and no-shock conditions based upon categories of detected heart rhythms such that a level of operator judgment is enabled commensurate with the skill level of an intended operator.
BACKGROUND OF THE INVENTION
A frequent consequence of heart attacks is the development of cardiac arrest associated with a heart arrhythmia, such as ventricular fibrillation. Electrotherapy can be performed by delivering an electrical pulse to a patient's heart in order to treat ventricular fibrillation. More particularly, ventricular fibrillation may be treated by applying an electric shock to the patient's heart through the use of a defibrillator. The chances of surviving a heart attack decrease with time after the attack. Quick response to a heart attack by administration of a defibrillating shock as soon as possible after the onset of ventricular fibrillation is therefore often critically important.
In order to be effective, a defibrillation shock must be delivered to a patient within minutes of the onset of ventricular fibrillation. Studies have shown that defibrillation shocks delivered within one minute after ventricular fibrillation may approach up to 100% survival rate. The survival rate falls to approximately 30% if six minutes have elapsed before the shock is administered. Beyond twelve minutes, the survival rate approaches zero.
One way of decreasing the time required to deliver a defibrillation shock to a patient is to greatly increase the availability of defibrillators in proximity with potential patients. Recently, the development of lightweight, relatively low-cost defibrillators has enhanced availability and contributed to decreasing the response time for patients needing treatment. More particularly, low-cost lightweight defibrillators manufactured by Heartstream, Inc. of Seattle, Wash., utilize an impedance-compensating biphasic waveform which has reduced size and cost, thereby increasing the availability of such devices to persons in outside-of-hospital settings. For example, such defibrillators have been deployed on first-response vehicles and to locations where large groups of individuals are gathered, such as in office buildings, corporate campuses, airplanes, health clubs, stadiums, and theaters. Such deployment to many environments contributes to greatly shortening the time from a patient's collapse to the delivery of a first shock.
With greatly increased deployment of such portable external defibrillators, the response time to shock a patient is being greatly reduced. However, an expanded first-response force needs to be trained so as to include a broad range of physician-authorized personnel, such as fire service and ambulance personnel, police officers, flight attendants, security guards, safety officers, and any other health care professional or appropriately trained individual with a duty to respond. Presently, such attempts are being undertaken.
One problem associated with expanding the use of defibrillators to physician-authorized personnel has been the varying degrees of training and skill that such personnel possess. Depending upon the environment in which an external defibrillator is employed, it might be desirable to control the functionality of such defibrillator so that it is tailored to match the level of skill and training that an intended operator possesses. Only through a dramatic improvement in defibrillator access, accompanied by appropriate training and delivered functionality, will sudden cardiac arrest lose its distinction as one of the nation's leading killers.
Prior art electrotherapy devices are known for producing electric shock to treat patients for a variety of heart arrhythmias. For example, manual external defibrillators provide relatively high-level shocks to a patient, usually through electrodes attached to the patient's torso, to convert ventricular fibrillation to a normal sinus rhythm. Similarly, external cardioverters, which are also manual defibrillators, can be used to provide shocks to convert atrial fibrillation to a more normal heart rhythm. Manual defibrillators require a significant amount of training, whereas automatic defibrillators tend to be expensive and invasive. One type of defibrillator is an implantable defibrillator which is relatively expensive, invasive, and requires a reduced level of shock delivery because of a direct current path to a patient's heart. Another type of defibrillator is an automatic external defibrillator (AED) which automatically analyzes patient heart rhythms and delivers electrotherapeutic pulses to a patient's heart indirectly, through the patient's skin and rib cage. Hence, external defibrillators tend to operate at higher energies, voltages, and/or currents.
Hardware and/or software electrocardiogram (ECG) analysis devices and analysis implementations are known within prior art defibrillators, both implantable and external, for detecting heart function so as to characterize a patient's heart condition. Furthermore, such prior art defibrillators are known for generating defibrillator waveforms that are characterized according to the shape, polarity, duration, and number of pulse phases. Typically, such heart function detection and defibrillator waveform generation are carried out via an ECG arrhythmia analysis algorithm and a discharge controller having discharge circuitry, respectively.
One approach for detecting patient heart function is shown in U.S. Pat. No. 5,014,697 to Pless, et al. (incorporated herein by reference). The Pless, et al, patent discloses a two-channel defibrillator having a programmable stimulator. The stimulator provides an assessment of lethal ventricular tachyarrhythmias in determining defibrillation thresholds during implantable defibrillator procedures. An initial test defibrillation shock is delivered to a patient, after which an automatic charging circuit and dual-channel, high-voltage capacitor circuits operate to reduce the time in which a rescue shock can be delivered to a patient. A microprocessor-controlled display system includes an operator interface that provides information parameters regarding the defibrillation shocks being delivered.
Another approach for detecting patient heart function is shown in U.S. Pat. No. 5,620,471 to Duncan (incorporated herein by reference). The Duncan patent discloses an apparatus for applying atrial and ventricular therapies to a patient's heart using an implanted cardiac stimulating device. Atrial and ventricular heart rates are monitored with the device to determine whether the patient is suffering from atrial or ventricular arrhythmia, and to then determine what type of therapy is appropriate for application to the patient's heart. Atrial and ventricular heart rates are compared via an algorithm to determine if the ventricular heart rate exceeds the atrial heart rate and to determine whether the ventricular heart rate is stable. According to one implementation, an early atrial stimulation pulse can also be applied to determine whether the ventricular heart rate follows the atrial heart rate. Therapy is applied to the patient's heart based upon determinations between atrial and ventricular heart rates.
Yet another approach to monitoring and defibrillating a patient's heart is provided by U.S. Pat. No. 5,474,574 to Payne, et al. (incorporated herein by reference). The Payne, et al., patent discloses a cardiac monitoring and defibrillation system configurable as a bedside or an ambulatory unit. Amplification and processing circuitry receives and conditions inputs from sensing apparatus such as electrocardiograms, blood oxygenation sensors, blood pressure monitors, and a cardiac acoustical transducer. Noise and artifact discrimination is implemented to prevent erroneou
Bardy Gust H.
Lyster Thomas D.
Agilent Technologie,s Inc.
Layno Carl H.
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