Method and apparatus for non-invasive monitoring of central venous pressure, and improved transducer therefor

• US 5,040,540 A
• Filed: 04/17/1990
• Issued: 08/20/1991
• Est. Priority Date: 08/24/1988
• Status: Expired due to Term

• Current Assignee: VivoMetrics, Inc.
• Original Assignee: NIMS Incorporated
• Inventors: Sackner, Marvin A.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/510,456
• Time in Patent Office: 490 Days
• Field of Search: 128/672, 128/675, 128/680, 128/681, 128/687, 128/688, 128/691, 128/693, 128/, 128/694, 128/713, 128/714, 128/380, 128/639, 128/644, 128/734, 128/721, 128/402
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02108 from analysis of pulse wave characteristics
• CPC Class Codes: A61B 5/02152 specially adapted for venous pressure
• CPC Class Codes: A61B 5/1073 Measuring volume, e.g. of limbs
• CPC Class Codes: A61B 5/412 Detecting or monitoring sepsis

Abstract

A method and apparatus for measuring central venous pressure (CVP) is disclosed, along with an improved transducer (50) for measuring CVP in infants. Changes in CVP may also be monitored by employing the method and apparatus of the invention.

Claims

1. A transducer for monitoring cardiopulmonary events in a subject comprising:

a cap formed by a tube of stretchable material closed at one end, the other end of said tube being dimensioned for a close fit about the head of the subject;

a conductor comprising a conductive loop;

means for securing said conductive loop in a flexible configuration about said other end of said stretchable tube for fitting said conductive loop about the head of said subject and for expansion and contraction of said conductive loop with said subject'"'"'s head in response to said cardiopulmonary events with changes in the configuration of the loop as a result of said expansion and contraction resulting in corresponding changes in the inductance of said loop; and

means for insulating said conductor for preventing contact between said subject and said conductor.

2. The transducer of claim 1, wherein said other end of said tube is folded back on itself to define a hem, and wherein said means for securing said conductive loop comprises means for threading said conductive loop in a flexible configuration to said hem.

3. The transducer of claim 2, wherein said conductive loop comprising said conductor is threaded in a flexible configuration which extends in an up-and-down fashion about a width of said hem for accommodating expansion and contraction of said conductive loop.

4. The transducer of claim 1, wherein said tube comprises a stretchable cloth material.

5. The transducer of claim 1, further comprising an LC oscillator, and wherein the inductance of said conductive loop comprising said conductor changes in conjunction with changes in the configuration of the loop as a result of expansion and contraction thereof, and wherein said conductor is incorporated as an inductance element in said oscillator such that changes in the inductance of the conductive loop comprising the conductor effect corresponding changes in the variable frequency of the oscillator.

6. The transducer of claim 5, further comprising means for converting the variable frequency output from the oscillator to a corresponding variable voltage signal.