Non-invasive vascular waveform transducer and apparatus

• US 4,295,471 A
• Filed: 05/25/1979
• Issued: 10/20/1981
• Est. Priority Date: 05/25/1979
• Status: Expired due to Term

• Current Assignee: William J. Kaspari
• Original Assignee: William J. Kaspari
• Inventors: Kaspari, William J.
• Primary Examiner(s): HOWELL, KYLE
• Application Number:
  US06/042,415
• Time in Patent Office: 879 Days
• Field of Search: 128/670, 128/675, 128/687, 128/715, 179/1 ST, 179/139, 73/774, 73/777
• US Class Current: 600/488
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 5/02208 using the Korotkoff method
• CPC Class Codes: A61B 7/045 Detection of Korotkoff sounds A61B5/0225 takes precedence; measuring blood pressure A61B5/021

Abstract

Apparatus is disclosed herein for non-invasively monitoring arterial waveforms, such as the waveform produced by blood flow through the brachial artery in a human subject. The invention includes a unique transducer which senses both a pressure wave proportional to blood flow in the artery and an acoustical signal proportional to the turbulence created by blood flow through a partially occluded artery. The transducer may be cuff mounted for attachment to the subject, and the cuff may be automatically inflated in accordance with the invention.

Claims

1. A transducer for noninvasively monitoring a vascular waveform comprising

a housing forming two independent cavities therein,

a pair of support members, one disposed in each of said cavities,

a pair of sensing elements, one resting on each of said first support members in said cavities,

a pair of retaining members, one disposed on top of each said sensing element in said cavities,

a pair of retaining caps, each cap having an orifice therethrough, said retaining caps being affixed to said housing to cause each of said sensing elements to be positioned between said support member and said retaining members,

pressure-transmitting means within each of said orifices for causing pressure waves impinging thereupon to be transmitted to the associated sensing element, each sensing element being responsive only to pressure waves entering its associated orifice.

2. The transducer of claim 1 wherein said support members are formed integrally with said housing.

3. The transducer of claim 2 wherein said retaining members are O-rings.

4. The transducer of claim 1 wherein said pressure-transmitting means is rubber and fills substantially all of said cavity accessible through said orifice.

5. A transducer adapted for use in differential measurement comprising first and second pressure sensitive elements disposed parallel to one another, a plate member disposed between the first and second pressure sensitive elements for isolating the pressure sensitive elements from one another such that movement of one of the pressure sensitive elements does not cause movement in the other pressure sentitive element, first support means disposed between the first pressure sensitive element and the plate member, second support means disposed between the second pressure sensitive element and the plate member, the first and second support means configured to support at least the periphery of the respective pressure sensitive elements while permitting substantially free movement of the interior thereof, and retainer means associated with at least the first and second pressure sensitive elements for firmly maintaining the position of the first and second pressure sensitive elements with respect to the plate member and the first and second support means.

6. The transducer of claim 5 wherein the pressure sensitive elements are piezoelectric elements.

7. The transducer of claim 5 wherein the pressure sensitive elements are coated by a pressure-transmitting means.

8. The transducer of claim 5 wherein the first and second support means are O-rings.

9. The transducer of claim 6 wherein the plate member is affixed to the retainer means.

10. The transducer of claim 9 wherein the plate member is part of a housing, and the retainer means attaches to the housing.

11. A transducer adapter for use in differential measurement comprising a first piezoelectric disc, a second piezoelectric disc of substantially the same dimensions as the first piezoelectric disc and disposed substantially parallel thereto, a rigid circular plate of substantially the same diameter as the piezoelectric disc disposed between the first and second piezoelectric discs for isolating the first piezoelectric disc from the second piezoelectric disc, a pair of O-rings for supporting only the periphery of the piezoelectric elements, one O-ring disposed between the first piezoelectric disc and the circular plate and the other O-ring disposed between the second piezoelectric disc and the circular plate, retainer means for firmly positioning the first O-ring between the first piezoelectric disc and the circular plate and also firmly positioning the second O-ring between the second piezoelectric disc and the circular plate, and output means for providing output signals representative of the movement of the first piezoelectric disc and the second piezoelectric disc.