Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-12-01
2001-09-11
Evanisko, George R. (Department: 3737)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06289243
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of Invention
This invention pertains to an external defibrillator arranged and constructed to provide anti-tachyarrhythmia therapy to a patient on demand. In particular, an automatic external cardioverter/defibrillator is described which has several operational modes including a fully automatic mode in which shocks are delivered without any manual intervention, an advisory mode and a manual mode. Moreover, the invention pertains to a defibrillator with an integral tachyarrhythmia detector which detects an abnormal heart beat and determines whether this abnormal heart beat is amenable to shock therapy.
B. Description of the Prior Art
Defibrillators are devices which apply electric therapy to cardiac patients having an abnormally high heart rhythm. Two kinds of defibrillators are presently available: internal defibrillators which are implanted subcutaneously in a patient together with leads extending through the veins into the cardiac chambers, and external defibrillators which are attached (usually temporarily) to the patient. External defibrillators are used in most instances in case of an emergency, for example, when a patient has either suffered cardiac arrest or where a cardiac arrest is imminent. Typically therefore external defibrillators are manual devices which must be operated by a physician or other trained personal. Internal or implantable defibrillators (and cardioverters) are implanted as a permanent solution for patients having specific well defined cardiac deficiencies which cannot be treated successfully by other means. They generally operate in an automatic mode.
However, there are some instances where an external defibrillator would be very advantageous which could be operated in both automatic and manual modes. For example, presently, it is well known that after a cardiac episode, such as a sudden cardiac arrest, many patients frequently suffer a second episode of similar nature. Therefore, cardiac patients are kept in a hospital under observation. While in the hospital, the patient is attached to a monitor which indicates the patient's heart rate, temperature, respiration rate and other vital signs. Many monitors are provided with an alarm function which is activated when these vital signs fall outside a nominal range. The monitor then generates an audible and visual signal at the bed side of the patient and/or at the remote location such as a nurse station. However, if a cardiac episode does occur, the attending staff has to examine the patient to determine that the patient needs electrical therapy, call the code team, bring a defibrillator to the patient, reconfirm the patient still needs electrical therapy, and then set up and use the defibrillator. All these steps are inherently time-consuming.
Some attempt has been made to overcome some of these problems. For example, some external defibrillators are available which can verify that a patient is suffering from ventricular fibrillation VF and prompt an attendant to activate the defibrillator for the delivery of therapy. However, the algorithms used by these defibrillators to detect VF are very limited. For example, some of defibrillators utilize an algorithm in which the electrocardiogram ECG can be verified only while the patient is unconscious, has no pulse and does not breath. Obviously, these algorithms are not satisfactory since it is important to detect when those conditions happen and apply therapy as soon as those conditions are detected.
Commonly-owned U.S. Pat. No. 5,474,574 discloses an external defibrillator. Commonly-owned U.S. Pat. No. 4,576,170 discloses an external defibrillator that can be worn by a patient.
OBJECTIVES AND SUMMARY OF THE INVENTION
An objective of the present invention is to provide an automatic external cardioverter defibrillator which is capable of recognizing and differentiating between ventricular and supraventricular tachyarrhythmia.
A further objective is to provide a defibrillator capable of performing both amplitude and frequency analyses by using a modulation domain function on a patient's ECG and to use the results of these analyses to categorize or recognize the current condition of the patient.
Yet another objective is to provide an external defibrillator with several modes of operation, including at least one mode in which the modulation domain function is disabled.
Other objectives and advantages of the invention will become apparent from the following description of the invention.
This invention pertains to an automatic external cardioverter defibrillator which can be used to apply anti-tachyarrhythmia therapy in any one of three modes of operation: an automatic mode, an advisory mode, and a manual mode. In the automatic mode, the defibrillator is attached to a patient with risk of sudden cardiac arrest, continuously monitors the patient, automatically detects a cardiac condition for which electrical shocks are indicated (referred herein after as “shockable tachyarrhythmias”) and automatically administers therapy in accordance with a set of parameters without any human intervention. These parameters are determined or set during an initialization process during which the defibrillator is customized by a clinician to match the characteristics and needs of a particular patient.
The therapy delivered by the defibrillator generally includes a series of a predetermined number of defibrillation shocks, delivered at intervals and energy levels that may be individually programmed. At the time a shock is delivered, the defibrillator reconfirm the patient is still in a shockable condition. If the patient is converted, either spontaneously or by other means, to a non-shockable condition, the defibrillator internally disarm the charge and does not deliver the shock to the patient. This feature is called non-committed feature. The defibrillator described in this invention is a non-committed device. Preferably, each shock is synchronized to an intrinsic pulse (R wave), if such a pulse is found within a 2.5 second period. If no intrinsic pulse is detected within that period, then a shock is applied asynchronously. Either defibrillation shocks and anti-tachycardiac therapy may be applied. This automatic synchronization feature eliminates the need for a synchronization button and the need for the operator to select the button position.
After each shock, the defibrillator reexamines patient's cardiac condition. If the shock condition still exists, the defibrillator steps up to the next shock. These successive shocks may have the same or an increased energy level. This process continues until either the patient is converted to a non-shockable condition, or the therapy sequence is completed whichever happens earlier.
However, if the patient is converted to a non-shockable condition after a shock, the programmed therapy sequence resets when the defibrillator detects a period, e.g. 60 seconds, of non-shockable condition. The defibrillator considers the current shockable episode is converted and completed. If defibrillator detects a new shockable episode later, the defibrillator delivers the therapy from the first shock.
The operation of the defibrillator in the advisory mode is very similar to the automatic mode in that the same algorithm is used to detect shockable rhythms. However, in this mode, a visual and aural indication is provided when the defibrillator is ready to apply shocks. The attendant can then activate shock button(s) to deliver the shock. Successive shocks may be delivered in the same manner. These successive shocks may have the same or an increased energy level. The application of the successive shocks continues under the direction of the attendant until either the shockable condition is terminated or the therapy sequence is completed, whichever happens earlier.
If an attendant does not activate the pushbuttons within a preset time period after the defibrillator indicates its readiness (e.g., within about 35 seconds), the defibrillator resets itself and generates a message for the attendant that the therapy has
Lin Dong-ping
Mathur Prabodh
Ybarra Raul
Cardiac Science Inc.
Evanisko George R.
Gottlieb Rackman & Reisman P.C.
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