Biomedical force measuring apparatus

• US 5,218,972 A
• Filed: 09/04/1991
• Issued: 06/15/1993
• Est. Priority Date: 04/29/1988
• Status: Expired due to Fees

• Current Assignee: Matria Healthcare, Inc. (Abbott Laboratories)
• Original Assignee: Healthdyne, Inc. (Abbott Laboratories)
• Inventors: Atkins, John, Gorsuch, Reynolds G.
• Primary Examiner(s): SHAY, RANDY CITRIN
• Application Number:
  US07/754,960
• Time in Patent Office: 650 Days
• Field of Search: 128/632, 128/637, 128/672, 128/673, 128/675, 128/687, 128/689, 128/690, 128/748, 128/774, 128/775, 128/782, 73/721, 73/727, 73/754, 73/706, 73/DIG. 4
• US Class Current: 600/588
• CPC Class Codes: A61B 5/033 Uterine pressure

Abstract

A force transducer usable tokodynamometer for measuring intrauterine pressure and motion, and for measuring other force exerted by human body or other organisms. The tokodynamometer has a cavity filled with an incompressible fluid and closed by a flexible diaphragm disposed for contacting the body portion being studied. A zero-displacement fluid-pressure transducer is in the cavity and provides an electrical signal responsive to pressure in the fluid, as body force acts through the flexible diaphragm to induce pressure in the fluid. Changes in intrauterine pressure or other body forces are thus measured with no significant physical displacement of a transducer or other force-measuring element. The fluid-filled cavity has the shape of a truncated cone with the diaphragm at the larger end and the transducer at the smaller end, increasing the sensitivity of the transducer.

Claims

1. A biomedical apparatus for measuring the amount of force exerted on an external surface of a body in response to activity within the body, comprising:

a housing having a rigid surface operative to be maintained in contact with a selected portion of the body surface, and comprising an interior region beneath the surface;

an opening in the surface of the housing;

a chamber communicating with the opening and containing an incompressible gel;

a flexible yet substantially noncompressible diaphragm disposed on the opening for contact by the portion of the body surface, and in force transfer relation with the gel in the chamber, so that the force exerted against the housing by the body is transferred by the diaphragm to the gel to induce hydrostatic pressure therein;

the chamber being substantially frustoconical in shape and narrowing from a first portion communicating with the opening in the surface to a terminal portion housing a second opening of reduced area relative to the opening in the surface;

a pressure transducer disposed to close the second opening in pressure responsive relation to the hydrostatic pressure in the gel at the second opening and operative to provide a signal corresponding to such pressure;

means associated with the housing holding the transducer rigidly in place relative to the chamber so that the transducer remains stationary notwithstanding changes in the fluid pressure within the chamber;

the means comprising a rigid member secured to the housing and extending behind the terminal portion of the chamber to engage the transducer between the means and the terminal portion; and

an annular rib in radial spaced relation to the chamber and abutting the rigid member for structural rigidity of the housing;

whereby the transducer signal is a function of the force exerted on the body surface and amplified by the ratio of areas of the first-mentioned and second openings.