Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-10-14
2001-10-16
Getzow, Scott M. (Department: 3737)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06304783
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a defibrillator system which is capable of defibrillation and patient monitoring. When used as a patient monitor, the defibrillator system includes a defibrillator, removable monitoring adapter, and monitoring electrodes. Monitoring electrodes communicate with the monitoring adapter and the defibrillator, providing means to observe the patient's electrocardiogram (“ECG”). A method of detecting the presence of the monitoring adapter by the defibrillator is also included. This invention also relates to the removable monitoring adapter. Defibrillators include manual defibrillators, semi-automatic defibrillators and automatic defibrillators. Semi-automatic defibrillators and automatic defibrillators are collectively referred to as “AEDs.”
2. Description of the Prior Art
Sudden cardiac arrest (“SCA”) is the leading cause of death in the United States. Most sudden cardiac arrest is caused by ventricular fibrillation (“VF”), in which the heart's muscle fibers contract without coordination, thereby interrupting normal blood flow to the body. The only known effective treatment for VF is electrical defibrillation, in which an electrical pulse is applied to the patient's heart. The electrical pulse must be delivered within a short time after onset of VF in order for the patient to have any reasonable chance of survival. Electrical defibrillation may also be used to treat pulseless ventricular tachycardia (“VT”). Accordingly, defibrillation is the appropriate therapy for any shockable rhythm, i.e., VF or pulseless VT.
One way of providing electrical defibrillation uses an external defibrillator. External defibrillators send electrical pulses to the patient's heart through electrodes applied to the patient's torso. External defibrillators are typically located and used in hospital emergency rooms, operating rooms, and in emergency medical vehicles. Of the wide variety of external defibrillators currently available, AEDs are becoming increasingly popular because they can be used by relatively inexperienced personnel. AEDs are also especially lightweight, compact and portable. AEDs are described, for example, in U.S. Pat. No. 5,607,454 to Cameron et al. entitled “Electrotherapy Method and Apparatus” and U.S. Pat. No. 5,591,213 to Morgan entitled “Defibrillator System Condition Indicator,” the specifications of which are incorporated herein.
One example of a defibrillator that provides a mechanism for detecting monitoring electrodes is the Laerdal HeartStart 3000. The Heartstart 3000 measures impedance through the electrodes attached to the patient to determine whether the monitoring pads are attached. The HeartStart 3000 distinguishes between the patient and monitoring electrodes by establishing an impedance threshold for which patient impedances are on one side of the threshold and monitoring electrode impedances are on the other side of the threshold.
AEDs provide a number of advantages, including the availability of external defibrillation at locations where external defibrillation is not regularly expected, and is likely to be performed quite infrequently, such as in residences, public buildings, businesses, personal vehicles, public transportation vehicles, etc. However, many instances of symptomatic patients may occur where defibrillation is not required, or formally permitted, because the patient is not suffering SCA and does not meet the indications for use of an AED. Some AEDs could be used to monitor the patient's ECG using the defibrillation electrodes, but these electrodes are expensive and could represent some risk to a patient who doesn't need defibrillation. Yet, traditional low cost monitoring electrode are not appropriate, because most AEDs are not configured to detect or operate with monitoring electrodes.
What is needed is a simple, low cost and effective way of providing an ECG monitoring function in an AED, while ensuring that the AED does not attempt to send a defibrillation energy pulse through the monitoring electrodes.
SUMMARY OF THE INVENTION
This invention provides a defibrillator system for monitoring or defibrillating a patient, comprising: a defibrillator capable of delivering an electrical pulse to the patient; and a removable monitoring adapter in communication with the defibrillator and a set patient sensors, wherein the monitoring adapter is operable to communicate a patient parameter to the defibrillator, and enable detection of the monitoring adapter by the defibrillator, when the adapter is connected to the defibrillator. An important feature of the invention is that the defibrillator inactivates the defibrillation capability in response to detection of the adapter. The defibrillator detects the adapter based on the interface impedance of the adapter measured by the defibrillator. Specifically, the defibrillator detects the adapter based on the imaginary impedance of the adapter interface greater than zero, measured by the defibrillator. Additionally, the adapter may also be capable of identifying a fault condition to the defibrillator. Typically fault systems that are detected by the system include: low battery condition and disconnected sensors. The monitoring adapter may be configured to removably connect with sensors, such as monitoring electrodes. Alternatively, the adapter may be configured so that the monitoring electrodes are integral with the monitoring device. In a preferred embodiment, the ECG monitoring electrodes also function as a right-leg drive. The monitoring electrode system can include from 2-12 electrodes.
A monitoring adapter is provided that communicates a patient parameter to a medical device which enables detection of the monitoring adapter, when the adapter is connected to the medical device. As a result of detection of the adapter, operation of the medical device is changed. Detection of the adapter is enabled based on the interface impedance of the adapter measured by the medical device. The medical device is a defibrillator and the monitoring adapter communicates with the defibrillator a set of ECG monitoring electrodes. In one specific embodiment, the monitoring adapter is formed integral with the monitoring electrode pads. Alternatively, the monitoring adapter may be configured so that it is removably connected to electrode pads. A fault detector may also be provided within the monitoring adapter to detect a fault condition. The monitoring electrode system can include from 2-12 electrodes.
A monitoring electrode system for use with a defibrillator, comprising: a set of monitoring electrodes; a test impedance, wherein the monitoring detector increases the impedance seen by the a defibrillator to a value greater than would occur in the absence of the monitoring detector. The monitoring electrode system can include from 2-12 electrodes. Typically, the monitoring adapter communicates with a defibrillator a set of monitoring electrode pads. In one embodiment, the monitoring electrode system is formed such that the monitoring adapter is integral with the monitoring electrode pads. Alternatively, the monitoring adapter is removably connectable to monitoring electrode pads. The system may also include a fault detector.
This invention also relates to a method of identifying the presence of a monitoring adapter comprising: measuring impedance at a patient connector. In measuring impedance, the device determines: if the ratio of Z
i
/Z
r
is greater than a first threshold, then the monitor adapter is present; or if the ratio of Z
i
/Z
r
is less than or equal to the first threshold, then the monitor adapter is not present. In the event the monitor adapter is not present, normal device functionality is enabled. However, if the monitor adapter is present, monitoring device functionality is enabled. In determining whether a fault condition exists, the device looks at Z
i
. If Z
i
is greater than a second threshold, a fault condition is present, or if Z
i
is less than the second threshold, a fault condition is not
Bishay Jon M
Lyster Thomas D
Powers Daniel J
Getzow Scott M.
Graybeal Jackson Haley LLP
Heartstream, Inc.
Kaam Matthieu van
Piotrowski Tony E.
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