Body worn physiological sensor device having a disposable electrode module
A body worn patient monitoring device includes a flexible substrate having a plurality of electrical connections adapted to be coupled to a skin surface to measure physiological signals. The flexible substrate is adapted to be directly and non-permanently affixed to a skin surface of a patient and configured for single patient use. A communication-computation module, removably attached to an upper surface of the flexible substrate, is configured to receive physiological signals from the flexible substrate and includes a microprocessor that is configured to process and analyze the physiological signals. A series of resistive traces screened onto the flexible substrate are configured as at least one series current-limiting resistor to protect the communication-computation module.
1. A method to improve ECG signal high pass filtering, said method comprising:
providing an ECG monitor having a programmed microprocessor and a plurality of electrical connections to measure patient heartbeat signals;
filtering the measured heartbeat signals with an analog high pass filter having an analog high pass cutoff frequency;
performing a first measurement on the measured heartbeat signals filtered with the analog high pass filter at the analog high pass cutoff frequency;
removing the effects of the analog high pass filter with a digital inverse filter algorithm resulting in substantially unfiltered heartbeat signals;
filtering the substantially unfiltered heartbeat signals digitally using a digital filter having a digital high pass filter cutoff frequency lower than the analog high pass cutoff frequency; and
performing a second measurement on the measured heartbeat signals filtered with the lower digital high pass filter cutoff frequency.
2. The method of claim 1 , wherein the step of filtering the measured heartbeat signals with an analog high pass filter comprises the step of filtering the measured signals with an analog high pass filter having a 0.5 Hz analog high pass cutoff frequency, and the step of filtering the substantially unfiltered heartbeat signals digitally comprises the step of filtering the substantially unfiltered heartbeat signals digitally using a digital filter having a digital 0.05 Hz high pass filter cutoff frequency.
3. The method of claim 1 , wherein the ECG monitor is part of a body-worn monitoring device, the monitoring device comprising a disposable module having a plurality of electrical connections for coupling to a skin surface, a power source to power the body-worn monitoring device, and a computation-communication module, the body-worn monitoring device being adapted to be directly non-permanently affixed to the skin surface.
4. The method of claim 3 , further comprising providing at least one series current-limiting resistor configured to protect the computation-communication module.
5. The method of claim 4 , wherein the step of providing the at least one series current-limiting resistor includes the steps of providing resistive traces on a flexible substrate of the body-worn monitoring device.
6. The method of claim 5 , further comprising providing an insulating material overlaying the at least one series-limiting resistor to prevent arcing.
7. The method of claim 3 , including the step of providing a pacer detection circuit.
8. The method of claim 7 , wherein the pacer detection circuit is provided in the computation-communication module.
9. The method of claim 8 , wherein the pacer detection circuit is configured to produce an interrupt signal when a pacer event has occurred.
10. The method of claim 9 , including the step of determining whether a patient has a pacemaker and only enabling the pacer detection circuit when a pacemaker is present.
11. The method of claim 3 , including the step of implementing the high pass filter in software running on a microprocessor in the computation-communication module.
12. The method of claim 9 , including the step of self-checking the pacer detection circuit by injecting a simulated pacer pulse into a front end amplifier to simulate the presence of a pacemaker.
13. The method of claim 3 , including the step of providing electro-surgical suppression (ESIS) circuits to protect the computation-communication module from external high energy signals.