Wearable cardioverter defibrillator having adjustable alarm time
A wearable cardioverter defibrillator (WCD) having a processor configured to receive a signal indicating a position and/or movement of the ambulatory patient while the ambulatory patient is wearing the support structure receive the ECG signal, determine from an ECG signal whether a shock criterion is met, determine a confirmation time period and/or a response time period based on the position and/or movement of the ambulatory patient, determine from the ECG signal whether the shock criterion is met after the confirmation time period has elapsed, cause the user interface to generate the shock alert signal based on the shock criterion determined after the confirmation time period has elapsed, and control the discharge circuit to discharge the stored electrical charge when a predetermined time period has elapsed after the shock alert signal.
1. A wearable cardioverter defibrillator (WCD), comprising:
a support structure configured to be worn by an ambulatory patient;
an energy storage module configured to store an electrical charge;
a discharge circuit coupled to the energy storage module;
electrodes configured to render an electrocardiogram (ECG) signal of the patient while the ambulatory patient is wearing the support structure;
a user interface configured to output an alarm in response to a shock alert signal;
a motion sensor configured to output a signal indicating a position and/or movement of the ambulatory patient while the ambulatory patient is wearing the support structure; and
a processor configured to:
receive the signal from the motion sensor,
receive the ECG signal,
determine from the ECG signal whether a shock criterion is met;
determine a confirmation time period based on the position and/or movement of the ambulatory patient,
determine from the ECG signal whether the shock criterion is met after the confirmation time period has elapsed,
cause the user interface to generate the shock alert signal based on the shock criterion determined after the confirmation time period has elapsed, and
control the discharge circuit to discharge the stored electrical charge when a predetermined time period has elapsed after the shock alert signal.
2. The WCD of claim 1 , wherein the processor is further configured to:
detect a patient fall in response to the signal from the motion sensor indicating a positional change of the patient from an upright position to a sitting or supine position that violates a positional change threshold, and
determine the confirmation time period based on the detected patient fall.
3. The WCD of claim 2 , wherein the positional change threshold includes a positional change time period or a positional change force, and the patient fall is detected in response to the positional change being less than the positional change time period or greater than the positional change force.
4. The WCD of claim 2 , wherein the processor is further configured to:
detect whether a patient remains motionless based on the signal from the motion sensor after the detected patient fall, and
determine the confirmation time period based on whether the patient remains motionless.
5. The WCD of claim 4 , wherein the confirmation time period is shorter when the patient fall has been detected and the patient has remained motionless after the detected patient fall than when the patient fall has been detected and the patient has not remained motionless after the detected patient fall.
6. The WCD of claim 1 , wherein the predetermined time period is a response time period and the processor is further configured to determine the response time period based on the detected fall and an amount of movement of the patient after the detected fall, and control the discharge circuit to discharge the stored electrical charge when the response time period has elapsed after the shock alert signal and a user response has not been received.
7. The WCD of claim 6 , wherein the response time period is shorter when no movement is detected based on the signal from the motion sensor after the detected fall and the response time period is longer when movement is detected based on the signal from the motion sensor after the detected fall.
8. The WCD of claim 1 , wherein the processor is further configured to detect noise on the ECG signal and determine the confirmation time period based on the detected noise.
9. The WCD of claim 1 , further comprising a transmitter configured to output an alert to a remote center when the confirmation time period has elapsed and a user input has not been received at the user interface.
10. The WCD of claim 1 , wherein the motion sensor is an accelerometer.
11. The WCD of claim 1 , wherein the processor is further configured to determine the confirmation time period by selecting the confirmation time period from a plurality of confirmation time periods based on the position and/or movement of the ambulatory patient.