Wearable cardioverter defibrillator (WCD) system with isolated patient parameter component
Embodiments are directed to wearable cardioverter defibrillator (WCD) systems that include patient parameter electrodes, such as ECG electrodes, that are at least substantially electrically isolated from other circuits of the WCD system. In embodiments, the WCD system includes a power source, an energy storage module, and a processor each connected to a first circuit ground. A patient parameter sense port, such as an ECG port, is coupled to the patient. A measurement circuit may render a physiological input from the sensed patient parameter received at the patient parameter sense port, and the measurement circuit includes an isolating circuit that electrically isolates the patient parameter sense port from the first circuit ground. The sensing of physiological inputs of the patient can be improved, resulting in fewer erroneous readings and false alarms.
1. A wearable cardioverter defibrillator (WCD) system, comprising:
a support structure configured to be worn by a patient;
a patient parameter sense port;
Electrocardiogram (ECG) electrodes configured to be coupled to the patient parameter sense port and to sense an ECG signal of the patient;
a first circuit ground;
a second circuit ground electrically isolated from the first circuit ground;
a power source connected to the first circuit ground;
an energy storage module electrically connected to the first circuit ground and configured to be charged from the power source to store an electrical charge;
a discharge circuit electrically coupled to the energy storage module;
a measurement circuit configured to render ECG data from the ECG signal received at the patient parameter sense port as sensed by the ECG electrodes, the measurement circuit including an isolating circuit directly coupled to both the first circuit ground and to the second circuit ground, the isolating circuit configured to electrically isolate the patient parameter sense port from the first circuit ground; and
a processor electrically connected to the first circuit ground, operatively coupled to the measurement circuit, and configured to:
determine from the ECG data whether or not a shock criterion is met, and
control the discharge circuit to discharge the stored electrical charge through the patient while the support structure is worn by the patient responsive to the shock criterion being met,
wherein the isolating circuit comprises an isolated side that includes an isolated circuit portion connected to the second circuit ground isolated from the first circuit ground and a non-isolated side that includes a non-isolated circuit portion connected to the first circuit ground.
2. The WCD system of claim 1 , wherein the measurement circuit includes an ECG acquisition circuit coupled to the patient parameter sense port and the isolating circuit, the ECG acquisition circuit being configured to detect the ECG signal.
3. The WCD system of claim 2 , in which the isolating circuit includes an isolated digital data coupler configured to couple a first digital signal representative of the sensed patient parameter from the ECG acquisition circuit to the processor.
4. The WCD system of claim 3 , in which the isolated digital data coupler is configured to couple a second digital signal from the processor to the ECG acquisition circuit.
5. The WCD system of claim 3 , in which the isolating circuit further includes an isolated power supply configured to transfer power from the power source to the ECG acquisition circuit.
6. The WCD system of claim 2 , in which the isolating circuit includes an isolating signal coupler configured to couple a first parameter signal representative of the sensed patient parameter from the patient parameter sense port to the ECG acquisition circuit.
7. The WCD system of claim 2 , in which the ECG acquisition circuit couples the isolating circuit to the patient parameter sense port, and the ECG acquisition circuit is connected to the second circuit ground and isolated from the first circuit ground.
8. The WCD system of claim 1 , in which the isolating circuit includes an isolation barrier electrically isolating the patient parameter sense port from the first circuit ground with at least 100 volts of protection across the isolation barrier.
9. The WCD system of claim 1 , wherein the isolating circuit further includes a voltage-difference reducing circuit configured to reduce a voltage difference between the first circuit ground and the second circuit grounds.
10. The WCD system of claim 9 , in which the voltage-difference reducing circuit includes a resistor connecting the first circuit ground to the second circuit ground.
11. The WCD system of claim 1 , in which the isolating circuit includes an isolating signal coupler configured to couple a signal representative of the sensed patient parameter from the isolated circuit portion of the isolating circuit to the non-isolated circuit portion of the isolating circuit, the isolated circuit portion is isolated from the first circuit ground, and the non-isolated circuit portion is connected to the first circuit ground.
12. The WCD system of claim 11 , in which the isolating circuit further includes an isolated power supply configured to transfer power from the power source to the isolated circuit portion of the isolating circuit.
13. The WCD system of claim 12 , wherein the isolated power supply includes an isolation transformer having a first winding coupled to the first circuit ground and a second winding isolated from the first winding and coupled to the second circuit ground.