Telemetric differential pressure sensor with the improvement of a conductive shorted loop tuning element and a resonant circuit

• US 4,385,636 A
• Filed: 02/05/1981
• Issued: 05/31/1983
• Est. Priority Date: 05/23/1978
• Status: Expired due to Term

• Current Assignee: Integra Lifesciences Corporation (Integra LifeSciences Holdings Corporation)
• Original Assignee: Eric R. Cosman
• Inventors: Cosman, Eric R.
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): Sykes, Angela D.
• Application Number:
  US06/231,707
• Time in Patent Office: 845 Days
• Field of Search: 128/748, 128/673-675, 128/630, 128/645-652, 128/660
• US Class Current: 600/561
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/031 Intracranial pressure

Abstract

An improvement in design of an implantable telemetric differential pressure sensing device enabling thinner, more compact, and simplified construction for the device; increased pressure sensitivity and range of measurement; and a wider class of applications for such pressure sensing devices in diagnostic medicine and clinical monitoring. The implanted device includes a thin, planar, closed, conductive loop which moves with a flexible diaphragm, the diaphragm moving upon changes in the difference of two bodily pressures on its opposite sides. The position of the conductive loop relative to a resonant circuit fixed in the device determines the resonant frequency of the resonant circuit. The resonant frequency is detected telemetrically outside the body, and its value is used to determine the difference in the two bodily pressures.

Claims

1. An in vivo pressure sensor adapted for in vivo calibration, said sensor comprising:

(a) a flexible housing defining a chamber therein;

(b) inlet means allowing the entrance into said chamber of a bodily fluid the pressure of which is to be sensed when said sensor is implanted in the living body, said flexible housing being so adapted that when the sensor is implanted beneath the skin, at least a portion of the outside of said flexible housing is positioned to be adjacent to and facing an interior portion of skin whereby said outside portion of the housing is in mechanical pressure communication with the skin and whereby pressures external to the body and applied to the skin can be mechanically communicated across the skin to the outside of said flexible housing and so that changes in the differences in pressures inside said chamber and outside said housing will cause a distortion of said flexible housing;

(c) mechanical stop means located within said flexible housing for preventing further distortion of the flexible housing when the pressure outside of the flexible housing equals or exceeds the pressure inside said chamber by a predetermined relationship;

(d) means located within said flexible housing having a preselected parameter that is detectable by apparatus located outside the living body, said means having a preselected parameter being at least in part cooperatively connected to said flexible housing so that said preselected parameter will change with the movement of said flexible housing, said parameter being detectable at least when said flexible housing is at said mechanical stop means and said parameter changing upon at least a distortion of said flexible housing from said mechanical stop means whereby when said sensor is implanted beneath the skin, said flexible housing can be driven to said mechanical stop means by a pressure external to the living body applied to the skin adjacent to said sensor and said preselected parameter can be determined at said mechanical stop means after implantation, and whereby the magnitude of the external pressure applied to the skin required to drive said single diaphragm means to said mechanical stop means is a function of the pressure in said internal bodily region.

2. The sensor of claim 1 wherein said means having a preselected parameter comprises electronic circuit means with said preselected parameter being a characteristic response parameter of said electronic circuit means which is detectable by electromagnetic coupling to the electronic apparatus located external to said living body.

3. The sensor of claim 1 wherein said electronic circuit means is a resonant electronic circuit with an element of said resonant electronic circuit being at least in part cooperatively connected to said flexible housing so that a change of said distortion of said flexible housing will cause a change in said resonant frequency.

4. The sensor of claim 1 wherein said stop means prevents further distortion of said flexible housing when said pressure outside said flexible housing is equal to or greater than the pressure in said chamber.

5. An in vivo pressure sensor adapted for in vivo calilbration, said sensor comprising:

(a) a flexible housing having means defining a chamber therein;

(b) inlet means allowing the entrance into said chamber of a bodily fluid the pressure of which is to be sensed when said sensor is implanted in the living body, said flexible housing being so adapted that when the sensor is implanted beneath the skin, at least a portion of the outside of said flexible housing is positioned to be adjacent to and facing an interior portion of skin whereby said outside portion of the housing is in mechanical pressure communication with the skin and whereby pressures external to the body and applied to the skin can be mechanically communicated across the skin to the outside of said flexible housing so that changes in the difference in pressures inside said chamber and outside said housing will cause a distortion of said flexible housing;

(c) mechanical stop means located within said flexible housing for preventing further distortion of the flexible housing when the pressure outside of the flexible housing equals or exceeds the pressure inside said chamber by a predetermined relationship;

(d) means located within said flexible housing having a preselected, detectable variable parameter that is detectable by apparatus outside the living body, said preselected, detectable variable parameter changes as a known function of the pressures inside said chamber and outside said flexible housing; and

whereby the sensor can be calibrated in vivo by driving said flexible housing into contact with said stop means by pressing on the skin adjacent to said sensor at which point the value of said preselected, detectable variable parameter can be determined, and whereby the change in said preselected, detectable variable parameter is a measure of the pressure of said bodily fluid.

6. The sensor of claim 5 wherein said preselected parameter comprises electronic circuit means with said preselected parameter being a characteristic response parameter of said electronic circuit means which is detectable by electromagnetic coupling to the electronic apparatus located external to said living body.

7. The sensor of claim 5 wherein said electronic circuit means is a resonant electronic circuit with an element of said resonant circuit being at least in part cooperatively connected to said flexible housing so that a movement of said distortion of said flexible housing will cause a change in said resonant frequency.

8. The sensor of claim 5 wherein said stop means prevents further distortion of said flexible housing when said pressure outside said flexible housing is equal to or greater than the pressure in said chamber.

9. An in vivo pressure detecting system comprising in combination:

(a) a differential pressure sensor adapted for implantation in a living body and for in vivo calibration after implantation, said sensor comprising;

(1) a housing which defines a chamber therein at least a portion of the wall of said housing being flexible so that changes in the pressure inside said chamber and outside said housing will cause movement of said flexible portion of said housing walls, said housing being adapted so that when implanted beneath the skin in the living body, said flexible portion of said housing wall can be placed in mechanical pressure communication with an interior portion of skin and whereby pressures external to the body can be communicated mechanically across the skin to said flexible portion of said housing wall;

(2) inlet means to said chamber allowing the entrance into said chamber of a bodily fluid, the pressure of which is to be measured when the sensor is implanted in the body;

(3) stop means within said housing adapted to make contact with, and thereby stop the movement of said flexible portion of said housing wall for a predetermined pressure relationship between pressures inside said chamber and outside said housing;

(4) means within said housing having a preselected, detectable, variable parameter that is detectable by apparatus outside the living body, the preselected, detectable variable parameter changes as a known function of the pressures inside said chamber and outside said housing; and

whereby the sensor can be calibrated in vivo by driving said flexible portion of wall into contact with said stop means by pressing on the skin adjacent to said sensor at which point the value of said preselected, detectable variable parameter can be determined, and whereby the change in said preselected, detectable variable parameter is a measure of the pressure of said bodily fluid;

(b) means for detecting said value of said preselected, detectable variable parameter at said mechanical contact reference position and any variation therefrom when said sensor is implanted in a living body, said detecting means being located externally of the living body and without any connection to said sensor which requires a break in the skin of the living body.