Implantable capacitive absolute pressure and temperature monitor system
First Claim
1. A capacitive pressure and temperature sensing system for providing signals representative of magnitude of body fluid absolute pressure at a selected site and ambient operating conditions, including body temperature at the site comprising:
- an elongated implantable lead body having proximal and distal end sections and having first and second electrical conductors extending from the proximal end section to the distal end section, said distal end section adapted to be implanted in a selected body site;
a sensor module formed in the distal end section of the lead body having pickoff and reference capacitor means formed therein and sharing a common charge plate;
sensor circuit means within said sensor module electrically connected to said pickoff and reference capacitor means and said first and second electrical conductors including temperature conversion means for generating a charge current and a discharge current varying with ambient temperature at the selected site, charging and discharging means for alternately charging and discharging said pickoff and reference capacitor means with said charge and discharge currents between selected voltage levels, and pulse generating means for generating pickoff and reference timing pulses separating pressure related and temperature related charge time intervals of said pickoff and reference capacitor means varying as a function of said charge current and capacitance changes of said pickoff capacitor means;
means for providing a bias voltage and current to said first and second electrical conductors for powering said sensor circuit means; and
demodulating means coupled to said first and second conductor means and responsive to said pickoff and reference timing pulses for discriminating and converting said pressure and temperature related time intervals into pressure and temperature signals.
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Accused Products
Abstract
A capacitive pressure and temperature sensing system for providing signals representative of the magnitude of body fluid absolute pressure at a selected site and ambient operating conditions, including body temperature, at the site. An implantable lead having a sensor module formed in its distal end is coupled to a monitor that powers a sensor circuit in the sensor module and demodulates and stores absolute pressure and temperature data derived from signals generated by the sensor circuit. The sensor module is formed with a pickoff capacitor that changes capacitance with pressure changes and a reference capacitor that is relatively insensitive to pressure changes. The sensor circuit provides charge current that changes with temperature variation at the implant site, alternately charges and discharges the two capacitors, and provides timing pulses having distinguishable parameters at the end of each charge cycle that are transmitted to the demodulator. The demodulator detects and synchronizes the timing pulses and derives pressure and temperature analog voltage values representative of the intervals between the timing pulses which are digitized and stored in the monitor. The monitor may also be coupled with other sensors for measuring and storing related patient body parameters, e.g. blood gas, EGM, and patient activity.
524 Citations
18 Claims
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1. A capacitive pressure and temperature sensing system for providing signals representative of magnitude of body fluid absolute pressure at a selected site and ambient operating conditions, including body temperature at the site comprising:
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an elongated implantable lead body having proximal and distal end sections and having first and second electrical conductors extending from the proximal end section to the distal end section, said distal end section adapted to be implanted in a selected body site; a sensor module formed in the distal end section of the lead body having pickoff and reference capacitor means formed therein and sharing a common charge plate; sensor circuit means within said sensor module electrically connected to said pickoff and reference capacitor means and said first and second electrical conductors including temperature conversion means for generating a charge current and a discharge current varying with ambient temperature at the selected site, charging and discharging means for alternately charging and discharging said pickoff and reference capacitor means with said charge and discharge currents between selected voltage levels, and pulse generating means for generating pickoff and reference timing pulses separating pressure related and temperature related charge time intervals of said pickoff and reference capacitor means varying as a function of said charge current and capacitance changes of said pickoff capacitor means; means for providing a bias voltage and current to said first and second electrical conductors for powering said sensor circuit means; and demodulating means coupled to said first and second conductor means and responsive to said pickoff and reference timing pulses for discriminating and converting said pressure and temperature related time intervals into pressure and temperature signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A capacitive pressure and temperature sensing system for providing signals representative of magnitude of body fluid absolute pressure at a selected site and ambient operating conditions, including body temperature at the site comprising:
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an elongated implantable lead body having proximal and distal end sections and having first and second electrical conductors extending from the proximal end section to the distal end section, said distal end section adapted to be implanted in a selected body site; a sensor module formed in the distal end section of the lead body having pickoff and reference capacitor means formed therein and sharing a common charge plate; sensor circuit means within said sensor module electrically connected to said pickoff and reference capacitor means and said first and second electrical conductors including temperature conversion means for generating a charge current and a discharge current varying with ambient temperature at the selected site, charging and discharging means for alternately charging and discharging said pickoff and reference capacitor means with said charge and discharge currents between selected voltage levels, and pulse generating means for generating pickoff and reference timing pulses separating pressure related and temperature related charge time intervals of said pickoff and reference capacitor means varying as a function of said charge current and capacitance changes of said pickoff capacitor means; means for providing a bias voltage and current to said first and second electrical conductors for powering said sensor circuit means; and demodulating means coupled to said first and second conductor means and responsive to said pickoff and reference timing pulses for discriminating and converting said pressure and temperature related time intervals into pressure and temperature signals wherein said sensor module further comprises; pressure deformable pickoff capacitor means having a nominal capacitance at atmospheric pressure for varying in pickoff capacitance in response to variations in fluid pressure at the selected body site having a first plate coupled to said first electrical conductor and a second spaced apart plate; and reference capacitor means having a nominal capacitance as the pickoff capacitor means at atmospheric pressure and not substantially varying in capacitance substantially the in response to variations in fluid pressure at the selected body site and having a first plate coupled to said first electrical conductor and a second spaced apart plate. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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Specification