Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-03-25
2001-03-27
Kamm, William E. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S062000
Reexamination Certificate
active
06208898
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to an electrotherapy method and apparatus for delivering an electrotherapy waveform to a patient's heart. In particular, this invention relates to a method and apparatus to deliver an electrotherapy waveform to a patient's heart through electrodes attached to the patient.
BACKGROUND OF THE INVENTION
Defibrillators apply pulses of electricity to a patient's heart to convert ventricular arrhythmias, such as ventricular fibrillation and ventricular tachycardia, to normal heart rhythms through the processes of defibrillation and cardioversion, respectively. There are two main classifications of defibrillators: external and implanted. Implantable defibrillators are surgically implanted in patients who have a high likelihood of needing electrotherapy in the future. Implanted defibrillators typically monitor the patient's heart activity and automatically supply electrotherapeutic pulses directly to the patient's heart when indicated. Thus, implanted defibrillators permit the patient to function in a somewhat normal fashion away from the watchful eye of medical personnel.
External defibrillators send electrical pulses to the patient's heart through electrodes applied to the patient's torso. External defibrillators are useful in the emergency room, the operating room, emergency medical vehicles or other situations where there may be an unanticipated need to provide electrotherapy to a patient on short notice. The advantage of external defibrillators is that they may be used on a patient as needed, then subsequently moved to be used with another patient. However, because external defibrillators deliver their electrotherapeutic pulses to the patient's heart indirectly (i.e., from the surface of the patient's skin rather than directly to the heart), they must operate at higher energies, voltages and/or currents than implanted defibrillators.
The time plot of the current or voltage pulse delivered by a defibrillator shows the defibrillator's characteristic waveform. Waveforms are characterized according to the shape, polarity, duration and number of pulse phases. Most current external defibrillators deliver monophasic current or voltage electrotherapeutic pulses, although some deliver biphasic sinusoidal pulses. Some prior art implantable defibrillators, on the other hand, use truncated exponential, biphasic waveforms. Examples of biphasic implantable defibrillators may be found in U.S. Pat. No. 4,821,723 to Baker, Jr., et al.; U.S. Pat. No. 5,083,562 to de Coriolis et al.; U.S. Pat. No. 4,800,883 to Winstrom; U.S. Pat. No. 4,850,357 to Bach, Jr.; and U.S. Pat. No. 4,953,551 to Mehra et al. Because each implanted defibrillator is dedicated to a single patient, its operating parameters, such as electrical pulse amplitudes and total energy delivered, may be effectively titrated to the physiology of the patient to optimize the defibrillator's effectiveness. Thus, for example, the initial voltage, first phase duration and total pulse duration may be set when the device is implanted to deliver the desired amount of energy or to achieve the desired start and end voltage differential (i.e., a constant tilt).
In contrast, because external defibrillator electrodes are not in direct contact with the patient's heart, and because external defibrillators must be able to be used on a variety of patients having a variety of physiological differences, external defibrillators must operate according to pulse amplitude and duration parameters that will be effective in most patients, no matter what the patient's physiology. For example, the impedance presented by the tissue between external defibrillator electrodes and the patient's heart varies from patient to patient, thereby varying the intensity and waveform shape of the electrotherapy waveform actually delivered to the patient's heart for a given initial pulse amplitude and duration. Pulse amplitudes and durations effective to treat low impedance patients do not necessarily deliver effective and energy efficient treatments to high impedance patients.
A continuing challenge in applying an optimal electrotherapy waveform to the patient is to compensate for patient to patient impedance variations with the application of the initial electrotherapy waveform. A need exists for a defibrillation method and apparatus which will permit the delivery of an optimal electrotherapy waveform on the initial as well as subsequent applications of electrotherapy waveforms.
SUMMARY OF THE INVENTION
Accordingly, in an electrotherapy apparatus including an energy source, a method for applying electrotherapy to a patient includes measuring a first parameter relating to an impedance of the patient and configuring the energy source based upon the first parameter. The method further includes coupling the energy source to the patient and measuring a third parameter related to energy delivered to the patient by the energy source. The method also includes decoupling the energy source from the patient based upon the third parameter.
An electrotherapy apparatus for performing electrotherapy on a patient through a first electrode and a second electrode includes an energy source to deliver energy to the patient through the first electrode and the second electrode. The electrotherapy apparatus further includes a sensor configured to measure a first parameter related to the energy delivered to the patient. Additionally, included in the electrotherapy apparatus is a first connecting mechanism configured to couple and decouple the energy source to and from, respectively, the first electrode and the second electrode. The electrotherapy apparatus also includes a measuring device configured to measure a second parameter, that varies with patient impedance, through the first electrode and the second electrode. The electrotherapy apparatus further includes a controller coupled to the first connecting mechanism and the energy source and arranged to receive the first parameter from the sensor. The controller is configured to actuate the first connecting mechanism to couple the energy source to the first electrode and the second electrode. The controller is also configured to actuate the first connecting mechanism to decouple the energy source from the first electrode and the second electrode based upon the first parameter. The controller is arranged to receive the second parameter from the measuring device to configure the energy source based upon the second parameter.
A defibrillator for delivering a multi-phasic waveform through a first electrode and a second electrode to a patient for defibrillation includes a capacitor for storing charge for delivery to the patient through the first electrode and the second electrode. The capacitor includes a first terminal and a second terminal. The defibrillator also includes a power supply for charging the capacitor. The defibrillator further includes a first connecting mechanism coupled between the first terminal and the second terminal of the capacitor and the first electrode and the second electrode to permit the first terminal of the capacitor to couple and decouple to and from one of the first electrode and the second electrode. The first connecting mechanism also permits the second terminal of the capacitor to couple and decouple to and from one of the first electrode and the second electrode. The defibrillator also includes a sensor for measuring a first parameter related to the energy supplied by the capacitor. The defibrillator further includes a circuit to measure a second parameter that varies with patient impedance. The circuit is configured for measuring the second parameter through the first electrode and the second electrode. The defibrillator also includes a controller coupled to the first connecting mechanism and arranged to receive the first parameter. The controller is configured to actuate the first connecting mechanism to decouple the first terminal and the second terminal of the capacitor from the first ele
Gliner Bradford E.
Lyster Thomas D.
Agilent Technologie,s Inc.
Kamm William E.
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