Method and apparatus for assessing hemodynamic parameters within the circulatory system of a living subject

• US 8,328,727 B2
• Filed: 05/18/2006
• Issued: 12/11/2012
• Est. Priority Date: 03/23/2000
• Status: Expired due to Fees

• Current Assignee: Tensys Medical Inc. (Recorders & Medicare Systems Pvt Ltd.)
• Original Assignee: Tensys Medical Inc. (Recorders & Medicare Systems Pvt Ltd.)
• Inventors: Miele, Frank R., Mucci, Ronald, Gallant, Stuart L.
• Primary Examiner(s): Natnithithadha, Navin
• Application Number:
  US11/437,197
• Publication Number:
  US 20060206032A1
• Time in Patent Office: 2,399 Days
• Field of Search: 600/481, 600/483, 600/437, 600/449
• US Class Current: 600/481
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 5/0053 by applying pressure, e.g. compression, indentation, palpation, grasping, gauging
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/0858 involving measuring tissue layers, e.g. skin, interfaces

Abstract

An improved method and apparatus for non-invasively assessing one or more hemodynamic parameters associated with the circulatory system of a living organism. In one aspect, the invention comprises a method of measuring a hemodynamic parameter by measuring a non-calibrated value of the parameter non-invasively, and inducing a stress of the circulatory system while measuring a second parameter. The response of the circulatory system to the stress is determined directly from the subject, and a calibration function is derived from the response and applied to the non-calibrated measured value to produce a calibrated measure of the actual value of the hemodynamic parameter. Methods of using backscattered acoustic energy for determination of hemodynamic markers are also disclosed.

Claims

1. An apparatus for locating a blood vessel having a lumen, said apparatus comprising:

a transducer element adapted to transmit acoustic energy into said blood vessel; and

a processor element adapted to;

determine a power of backscatter energy from said transmitted energy as a function of depth within said blood vessel;

identify at least one artifact associated with a location of said lumen;

compute a power function in a first dimension relative to said location; and

compute a power function in a second dimension relative to said location;

wherein said computations substantially determine a location of said blood vessel.

2. The apparatus of claim 1, wherein said identification is performed via a method that identifies at least one plateau.

3. The apparatus of claim 1, wherein said identification is performed via a method that specifies at least one interval.

4. A method of locating a blood vessel having a lumen, comprising:

transmitting acoustic energy into said blood vessel via a transducer;

receiving a signal related to backscattered energy derived from said transmitted acoustic energy at said transducer; and

processing said backscattered energy to identify at least one artifact associated with said lumen at a processor associated with said transducer, said at least one artifact comprising a substantially flat portion of a power profile corresponding to said lumen.

5. The method of claim 4, wherein said identification of said substantially flat portion comprises:

determining a power metric as a function of depth;

integrating said power metric and normalizing said integrated power metric; and

detecting a plateau associated with said lumen based at least in part on said acts of determining and integrating.

6. Apparatus adapted to detect the location of a blood vessel, comprising:

an acoustic transducer;

a signal transceiver operatively coupled to said acoustic transducer; and

a processor operatively coupled to said signal transceiver, said processor adapted to perform computations on data received by said signal transceiver in order to compute the location of said blood vessel;

wherein said processor is further adapted to;

baseband said received acoustic energy data; and

square said basebanded data to produce envelope-squared data.

7. The apparatus of claim 6, wherein said acoustic transducer comprises an ultrasonic transducer.

8. The apparatus of claim 6, wherein said processor basebands said received acoustic energy data by:

multiplication of the received acoustic energy data by a sine and cosine function; and

application of a lowpass filter to said multiplied data to produce said basebanded data.

9. The apparatus of claim 6, wherein said processor is further adapted to decimate said envelope-squared data to a predetermined sampling rate, and apply a depth-dependent gain to said decimated envelope-squared data.

10. The apparatus of claim 9, wherein said depth-dependent gain is non-linear.

11. An apparatus for locating a position of a blood vessel having a lumen, said apparatus comprising:

a means for transmitting acoustic energy into said blood vessel;

a means for determining power of backscatter energy from said transmitted energy as a function of depth within said blood vessel;

a means for identifying at least one artifact associated with a location of said lumen; and

a means for calculating;

a power function in a first dimension relative to said location; and

a power function in a second dimension relative to said location;

wherein said means for calculating are utilized to substantially determine a location of said blood vessel.

12. The apparatus of claim 11, wherein said means for identifying at least one artifact comprise means for identifying at least one plateau.

13. The apparatus of claim 11, wherein said means for identifying at least one artifact comprise means for identifying at least one interval.

14. A method of locating a blood vessel having a lumen, comprising:

transmitting acoustic energy into said blood vessel via a transducer;

receiving, at said transducer, backscattered energy produced from said transmitted acoustic energy; and

processing, at a processor in signal communication with said transducer, said received backscattered energy to identify at least one artifact associated with said lumen;

wherein said identification of said at least one artifact comprises identification of a substantially flat portion of a power profile corresponding to said lumen.

15. The method of claim 14, wherein said identification of said substantially flat portion comprises:

determining a power metric as a function of depth;

integrating said power metric and normalizing said integrated power metric; and

detecting a plateau associated with said lumen based at least in part on results from said acts of determining and integrating.

16. The method of claim 15, wherein:

said identification of said substantially flat portion further comprises dividing said normalized integrated power metric into a number of intervals; and

said detecting said plateau is based at least in part on said acts of determining, integrating and dividing.

17. The method of claim 16, wherein said dividing is performed in substantially equally spaced intervals.

18. The method of claim 16, wherein said dividing is performed in substantially non-equally spaced intervals.

19. The method of claim 14, wherein said processing is performed using an interval-based method.