Sensor for transcutaneous measurement of vascular access blood flow

• US 6,987,993 B2
• Filed: 12/09/2003
• Issued: 01/17/2006
• Est. Priority Date: 12/29/2000
• Status: Expired due to Fees

• Current Assignee: HEMA Metrics Incorporated
• Original Assignee: HEMA Metrics Incorporated
• Inventors: Miller, David R., Bell, David A., Steuer, Robert R.
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Assistant Examiner(s): Kremer, Matthew
• Application Number:
  US10/730,102
• Publication Number:
  US 20040122330A1
• Time in Patent Office: 770 Days
• Field of Search: 600309-310, 600/322, 600/504
• US Class Current: 600/322
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14535 for measuring haematocrit
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/14557 specially adapted to extracorporeal circuits
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61M 1/361 before treatment
• CPC Class Codes: A61M 1/3612 after treatment
• CPC Class Codes: A61M 1/3656 Monitoring patency or flow at connection sites; Detecting disconnections
• CPC Class Codes: A61M 1/3663 Flow rate transducers; Flow integrators
• CPC Class Codes: G01N 2021/036 transformable, modifiable
• CPC Class Codes: G01N 21/0303 Optical path conditioning in cuvettes, e.g. windows; adapted optical elements or systems; path modifying or adjustment G01N21/031 - G01N21/15 take precedence

Abstract

An optical sensor includes photoemitter and photodetector elements at multiple spacings (d₁, d₂) for the purpose of measuring the bulk absorptivity (α) of an area immediately surrounding and including a hemodialysis access site, and the absorptivity (α_o) of the tissue itself. At least one photoemitter element and at least one photodetector element are provided, the total number of photoemitter and photodetector elements being at least three. The photoemitter and photodetector elements are collinear and alternatingly arranged, thereby allowing the direct transcutaneous determination of vascular access blood flow.

Claims

1. A device for locating the flow of a fluid in a graft or vein in the body of a patient, the device comprising:

a sensor configured to measure the value of a parameter in an area of the skin of a patient including the graft or vein to be located and to measure the value of the parameter in the area of the skin adjacent to the graft or vein to be located;

means for placing the sensor on the skin of the patient near the flow of fluid to be found;

means based on the measurements detected by the sensor for calculating;

(a) the optical attenuation coefficient (α

) in an area of the skin that includes the graft or vein to be located;

(b) the optical attenuation coefficient (α

_o1) in a first area adjacent to the graft or vein to be located;

(c) the optical attenuation coefficient (α

_o2) in a second area adjacent to the graft or vein to be located;

means for measuring a reference ratio between the optical attenuation coefficient (α

_o1) and the optical attenuation coefficient (α

_o2); and

means for monitoring the reference ratio so that when the ratio reaches a certain value a signal indicates that the graft or vein is located.

2. The device of claim 1 wherein the reference ratio is determined by solving the equation (1−

α

_o1/α

_o2) times 100.

3. The device of claim 1 wherein the parameter is Hematocrit.