Dual pressure monitor

• US 6,481,292 B1
• Filed: 12/24/1999
• Issued: 11/19/2002
• Est. Priority Date: 12/24/1999
• Status: Expired due to Fees

• Current Assignee: Apex Medical Corporation
• Original Assignee: Apex Medical Corporation
• Inventors: Reich, Sanford
• Primary Examiner(s): PATEL, HARSHAD R
• Application Number:
  US09/472,708
• Time in Patent Office: 1,061 Days
• Field of Search: 737/30, 737/53, 737/56, 737/14, 737/15--27, 738/624.74, 128/912, 604/27, 604/8-10, 604/164.01, 604/164.09, 604/164.11
• US Class Current: 73/730
• CPC Class Codes: A61B 2560/0257 using atmospheric pressure
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/6865 Access ports
• CPC Class Codes: A61M 60/178 drawing blood from a ventricle and returning the blood to the arterial system via a cannula external to the ventricle, e.g. left or right ventricular assist devices
• CPC Class Codes: A61M 60/216 including a rotating member acting on the blood, e.g. impeller
• CPC Class Codes: A61M 60/531 using blood pressure data, e.g. from blood pressure sensors

Abstract

A remote pressure sensor includes a probe having a chamber for holding a liquid. A flexible membrane is mounted in the probe. A conduit joins a reference cell to the chamber for holding the liquid. And, a reference pressure gauge is operatively joined to the conduit for measuring pressure of the liquid therein for use in referencing a primary pressure sensor through which fluid flows.

Claims

1. An in vivo implantable pressure monitor comprising:

an implant probe having a chamber for holding a liquid, a flexible reference membrane mounted in an opening of a wall of said probe adjoining said chamber for transmitting external pressure to said liquid therein, and a resilient septum spaced from said reference membrane to define in part said chamber for receiving a hypodermic needle to calibrate said monitor; and

a conduit joined in flow communication with said chamber for defining a common reservoir to hold said liquid for transmitting said external pressure therethrough.

2. A monitor according to claim 1 further comprising a reference pressure gauge operatively joined with said conduit for measuring pressure of said liquid therein.

3. A monitor according to claim 2 further comprising:

a tube for channeling a fluid under pressure;

a flexible primary diaphragm mounted in a wall opening of said tube to adjoin said fluid;

a primary gauge adjoining said diaphragm for measuring flexure thereof to determine said fluid pressure;

a processor operatively joined to said primary gauge to determine said fluid pressure from measured flexure of said diaphragm; and

said reference pressure gauge being operatively joined to said processor for providing a reference pressure for said fluid pressure.

4. A monitor according to claim 3 further comprising:

a primary cell joined to said tube outside said primary diaphragm, and being evacuated for increasing pressure difference across said diaphragm;

a reference cell joined to said primary cell at a common wall, and disposed in flow communication with said conduit for defining said common reservoir to hold said liquid therein;

a flexible reference diaphragm mounted in an opening of said common wall between said evacuated primary cell and said secondary cell; and

said reference pressure gauge adjoining said reference diaphragm for measuring flexure thereof to determine pressure of said liquid relative to said evacuated primary cell.

5. A monitor according to claim 4 wherein said primary and reference gauges comprise strain gauges mounted to said primary and reference diaphragms for measuring strain therein under flexure thereof due to pressure thereacross.

6. A monitor according to claim 4 disposed in flow communication with a heart pump for pumping blood as said fluid, and further comprising a controller operatively joined to said primary and reference gauges and said pump, and configured for controlling flow of said blood through said pump in response to pressure of said blood through said tube.

7. A method of using said pressure monitor according to claim 6 comprising:

implanting said heart pump and tube in series in a heart inside a living body for pumping blood therethrough;

filling said probe, conduit, and reference cell with saline liquid; and

implanting said probe subcutaneously in said living body for being responsive to barometric pressure.

8. A method according to claim 7 wherein said reference membrane is water permeable for relaxing following transient changes in barometric pressure.

9. A method according to claim 7 further comprising calibrating said pressure monitor by comparing barometric pressure with pressure measured by said probe.

10. A method according to claim 9 wherein said calibration further comprises:

inserting a hypodermic needle through said septum of said probe

pressurizing said liquid in said probe to a predetermined pressure; and

measuring strain in said reference diaphragm to determine pressure of said liquid in said reference cell.

11. A monitor according to claim 1 wherein said probe wall laterally surrounds said chamber, said septum is disposed atop said probe for being implanted subcutaneously below skin, and said wall includes a plurality of said flexible reference membranes spaced laterally apart from each other for transmitting external skin pressure through said liquid in said chamber.

12. An in vivo implantable dual pressure monitor comprising:

a primary pressure sensor including a tube for channeling a fluid, a flexible primary diaphragm mounted in a wall of said tube, and a primary gauge adjoining said diaphragm for measuring flexure thereof to determine pressure of said fluid; and

a remote pressure sensor including an implant probe having a chamber for holding a liquid, a flexible reference membrane mounted in a wall of said probe, a reference cell adjoining said primary pressure sensor and including a reference diaphragm mounted in a wall of said cell, a conduit in flow communication between said reference cell and said probe to transmit pressure through said liquid, and a reference gauge adjoining said reference diaphragm for measuring flexure thereof to determine pressure of said liquid for referencing said fluid pressure.

13. A pressure monitor according to claim 12 further comprising:

a primary cell joined to said tube outside said primary diaphragm, and being evacuated for increasing pressure difference across said diaphragm;

said reference cell being joined to said primary cell at a common wall, and disposed in flow communication with said conduit for defining a common reservoir to hold said liquid therein;

said reference diaphragm being mounted in an opening in said common wall between said evacuated primary cell and said reference cell; and

said reference pressure gauge being mounted to said reference diaphragm for measuring flexure thereof to determine pressure of said liquid relative to said evacuated primary cell.

14. A monitor according to claim 13 wherein said primary and reference gauges comprise strain gauges mounted to said primary and reference diaphragms for measuring strain therein under flexure thereof due to pressure thereacross.

15. A monitor according to claim 14 disposed in flow communication with a heart pump for pumping blood as said fluid, and further comprising a controller operatively joined to said primary and reference gauges and said pump, and configured for controlling flow of said blood through said pump in response to pressure of said blood through said tube.

16. A method of using said pressure monitor according to claim 15 comprising:

implanting said heart pump and tube in series in a heart inside a living body for pumping blood therethrough;

filling said probe, conduit, and reference cell with saline liquid; and

implanting said remote probe subcutaneously in said living body for being responsive to barometric pressure.

17. A method according to claim 16 wherein said reference membrane is water permeable for relaxing following transient changes in barometric pressure.

18. An in vivo implantable pressure monitor comprising:

an implant probe having a chamber for holding a liquid;

a flexible reference membrane mounted in a wall of said probe adjoining said chamber for transmitting external pressure to said liquid therein;

a resilient septum spaced from said reference membrane to define in part said chamber for receiving a hypodermic needle to calibrate said monitor;

a conduit joined in flow communication with said chamber for defining a common reservoir to hold said liquid for transmitting said external pressure therethrough;

a reference cell joined in flow communication with said conduit for defining said common reservoir for holding said liquid;

a flexible reference diaphragm mounted in an opening of a wall of said reference cell; and

a reference gauge adjoining said reference diaphragm for measuring flexure thereof to determine pressure of said liquid in said reference cell.

19. A monitor according to claim 18 wherein said probe, conduit, and cell are filled with saline liquid, and said reference membrane is water permeable.

20. A monitor according to claim 18 wherein said probe wall laterally surrounds said chamber, said septum is disposed atop said probe for being implanted subcutaneously below skin, and said wall includes a plurality of said flexible reference membranes spaced laterally apart from each other for transmitting external skin pressure through said liquid in said chamber.