Defibrillation Current Limiter for Low-Impedance Peak Current Control
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Solution Overview
Problem
Defibrillators face challenges in delivering excessive currents to patients with low impedance, which can cause injury and result in inefficient energy transfer, as existing current limiting solutions dissipate significant energy intended for the patient and affect high impedance patients.
Innovation Solution
A current limiter circuit that activates during excessive current conditions in low impedance patients, using a switching mechanism with a sense resistor, inductor, and filter capacitor to limit peak current without dissipating energy, and remains inactive for high impedance patients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a current limiting impedance is used in series with the patient impedance, then excessive current levels are prevented, but significant energy is dissipated and not delivered to the patient
Solution Approach 1:
The patent employs a dynamic switching mechanism that activates the current limiting impedance only when excessive current conditions are detected during defibrillation pulse delivery. The switching circuit monitors current levels and connects the current limiting impedance into the circuit only when the current exceeds a predetermined threshold, thereby preventing energy dissipation during normal operation while providing protection when needed.
Solution Approach 2:
The invention extracts the current limiting function from a permanently connected impedance and implements it as a separately controllable switching circuit. This allows the current limiting impedance to be isolated and activated only when excessive current conditions occur, rather than being continuously connected and dissipating energy during all defibrillation pulses.
2Object-affected harmful factors
If a current limiting impedance is used, then excessive current is limited, but energy delivery to high impedance patients is affected
Solution Approach 1:
The switching circuit dynamically adjusts the circuit configuration based on real-time current measurements. For high impedance patients where excessive current conditions do not occur, the switching circuit remains open and the current limiting impedance is not inserted into the circuit, allowing full energy delivery without restriction. The system adapts its behavior to match the specific impedance conditions of each patient.
Solution Approach 2:
The current limiter circuit automatically detects excessive current conditions and activates itself without external intervention. The switching circuit monitors the current through the sense resistor and autonomously connects the current limiting impedance when thresholds are exceeded, eliminating the need for manual adjustment or external control for different patient types.
3Reliability
If the defibrillator delivers high voltage impulse to restore normal rhythm, then cardiac resuscitation is achieved, but excessive current can cause patient injury
Solution Approach 1:
The current limiting impedance acts as an intermediary element that is inserted into the circuit only when excessive current conditions are detected. This intermediary component protects the patient from harmful current levels while allowing the defibrillation pulse to effectively restore normal cardiac rhythm by remaining inactive during normal operation and activating only when needed.
Solution Approach 2:
The switching circuit is pre-configured to detect excessive current conditions and activate the current limiting impedance before harmful effects can occur. By monitoring current levels through the sense resistor and having the switching circuit ready to connect the current limiting impedance, the system prevents patient injury before it can happen rather than reacting after damage occurs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively limits peak current to a safe level during the first phase of the biphasic pulse, ensuring therapeutic energy delivery to the patient without wasting energy, while maintaining normal operation for high impedance patients.
Implementation Method 1
A current limiter circuit that activates during excessive current conditions in low impedance patients, using a switching mechanism with a sense resistor, inductor, and filter capacitor to limit peak current
Implementation Method 2
using a switching mechanism with a sense resistor, inductor, and filter capacitor to limit peak current without dissipating energy
Data Source
AI summary
A current limiter for a defibrillation pulse is powered by the defibrillation pulse and switches the current delivery path open and closed when an excessive current condition exists. The excessive current condition is sensed by a sense resistor of the current limiter. The controlled current is delivered by an inductor which delivers a current which varies in a range about a predetermined current level during excessive current conditions. The current limiter dissipates little energy of the defibrillation pulse so that most of the energy produced by the defibrillator is delivered to the patient.