Method and apparatus for sensing lead and transthoracic impedances
First Claim
1. An apparatus for use with medical diagnostic and therapeutic apparatus employing electrodes attached to a patient'"'"'s skin for sensing the integrity of lead connections and patient transthoracic impedance comprising:
- (a) a carrier signal source means coupled to a first lead having a first lead impedance and coupled to a plurality of second leads having a plurality of second lead impedances;
(i) for producing a first carrier signal having a lead impedance frequency component and an impedance respiration frequency component and for applying said first carrier signal to said first lead; and
,(ii) for producing a second carrier signal having said lead impedance frequency component and said impedance respiration frequency component and for applying said second carrier signal to said plurality of second leads;
(b) a receiver means coupled to said first lead and said plurality of second leads for receiving;
(i) a first lead voltage produced by said first carrier signal and said first lead impedance; and
,(ii) a plurality of second lead voltages produced by said second carrier signal and said plurality of second lead impedances;
(c) amplifying means, coupled to receive a plurality of combinations of said first lead voltage with one of said plurality of second lead voltages, for amplifying the difference between said first and second lead voltages in each of said combinations and producing;
(i) a plurality of first stage output voltages, one of said first stage output voltages being produced for each of said combinations of said first and second lead voltages; and
,(ii) a plurality of second stage output voltages, one of said second stage output voltages being produced for each of said combinations of said first and second lead voltages; and
,(d) a signal separator means coupled to said amplifying means for receiving said plurality of first stage output voltages and for producing;
(i) a plurality of lead impedance-related voltages related to said lead impedance frequency component of said first and second carrier signals; and
,(ii) at least one impedance respiration-related voltages related to said impedance respiration frequency component of said first and second carrier signals.
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Accused Products
Abstract
A method and apparatus for use with medical electrode systems that sense the integrity of lead connections and patient transthoracic impedance is provided. In an ECG electrode application, a carrier circuit (12) produces two carrier signals (SC1 and SC2) that are out of phase with each other. The SC1 signal is applied to an RA lead through a terminating impedance (Z1). The SC2 signal is applied to LA, LL and V leads through terminating impedances (Z2, Z3, and Z4). Each of the SC1 and SC2 carrier signals comprises a lead impedance frequency component (SLI) and an impedance respiration frequency component (SIR). First stage amplifiers (A1, A2, and A3) located in an ECG preamplifier (13) amplify the difference between a lead voltage on the RA lead (VRA) and lead voltages on the LA, LL, and V leads (VLA, VLL and VV). High pass filters (F1, F2 and F3) remove patient ECG signals from the outputs of A1, A2 and A3 to produce first stage output voltages (V1, V2 and V5). The V1, V2 and V5 voltages are demodulated by a demodulator circuit (18). Lead impedance demodulators (DM1, DM2 and DM3) are clocked by a lead impedance control signal (SA) that has the same frequency as the SLI component so that the outputs of DM1, DM2 and DM3 are lead impedance-related voltages (VL1, VL2 and VL5). V2 is also demodulated by an impedance respiration demodulator (DM4). DM4 is clocked by an impedance respiration control signal (SB) that has the same frequency as the SIR component so that the output of DM4 is a transthoracic impedance-related voltage VT. VT is amplified by an operational amplifier (OA10) to produce an impedance respiration-related voltage (VR). The ECG preamplifier (13) and the demodulator circuit (18) include fast DC restoration circuits (66, 68, 70 and 71) that use switched capacitor integrators (76) to restore ECG outputs (VE1, VE2, and VE5) and the VR voltage to nominal values when a DC offset has occurred.
78 Citations
18 Claims
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1. An apparatus for use with medical diagnostic and therapeutic apparatus employing electrodes attached to a patient'"'"'s skin for sensing the integrity of lead connections and patient transthoracic impedance comprising:
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(a) a carrier signal source means coupled to a first lead having a first lead impedance and coupled to a plurality of second leads having a plurality of second lead impedances; (i) for producing a first carrier signal having a lead impedance frequency component and an impedance respiration frequency component and for applying said first carrier signal to said first lead; and
,(ii) for producing a second carrier signal having said lead impedance frequency component and said impedance respiration frequency component and for applying said second carrier signal to said plurality of second leads; (b) a receiver means coupled to said first lead and said plurality of second leads for receiving; (i) a first lead voltage produced by said first carrier signal and said first lead impedance; and
,(ii) a plurality of second lead voltages produced by said second carrier signal and said plurality of second lead impedances; (c) amplifying means, coupled to receive a plurality of combinations of said first lead voltage with one of said plurality of second lead voltages, for amplifying the difference between said first and second lead voltages in each of said combinations and producing; (i) a plurality of first stage output voltages, one of said first stage output voltages being produced for each of said combinations of said first and second lead voltages; and
,(ii) a plurality of second stage output voltages, one of said second stage output voltages being produced for each of said combinations of said first and second lead voltages; and
,(d) a signal separator means coupled to said amplifying means for receiving said plurality of first stage output voltages and for producing; (i) a plurality of lead impedance-related voltages related to said lead impedance frequency component of said first and second carrier signals; and
,(ii) at least one impedance respiration-related voltages related to said impedance respiration frequency component of said first and second carrier signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for sensing the integrity of lead connections and patient transthoracic impedance comprising the steps of:
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(a) producing a first carrier signal having a lead impedance frequency component and an impedance respiration frequency component, and producing a second carrier signal having said lead impedance frequency component and said impedance respiration frequency component, wherein said first carrier signal is out of phase with said second carrier signal; (b) applying said first carrier signal to a first lead having a first lead impedance and applying said second carrier signal to a plurality of second leads having a plurality of second lead impedances; (c) receiving a first lead voltage produced by said first carrier signal and said first lead impedance and receiving a plurality of second lead voltages produced by said second carrier signal and said plurality of second lead impedances; (d) amplifying the difference of a plurality of combinations of said first lead voltage and one of said plurality of second lead voltages and producing a plurality of first stage output voltages and a plurality of second stage output voltages; and
,(e) producing a plurality of lead impedance-related voltages and at least one impedance respiration-related voltage from said plurality of first stage output voltages. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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Specification