Surface perfusion pressure monitoring system

• US 6,178,342 B1
• Filed: 05/20/1997
• Issued: 01/23/2001
• Est. Priority Date: 09/09/1993
• Status: Expired due to Term

• Current Assignee: Vasamedics, LLC (Vasamed, Inc.)
• Original Assignee: Vasamedics, LLC (Vasamed, Inc.)
• Inventors: Borgos, John A., Thompson, RIchard John
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US08/859,350
• Time in Patent Office: 1,344 Days
• Field of Search: 600/473-478, 600/310, 600/322, 600/3, 600/328, 600/330, 356/41
• US Class Current: 600/322
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light

Abstract

A blood perfusion pressure monitor which measures blood content within an observation volume as a function of applied pressure, to determine the skin perfusion pressure at a location on a patient.

Claims

1. A perfusion pressure monitor for measuring the blood perfusion of a portion of a patient'"'"'s body, said blood perfusion monitor comprising:

a laser for generating coherent radiant energy;

a laser fiber coupled to said laser for transmitting coherent radiant energy to a portion of said patient'"'"'s body;

a receiver fiber for receiving coherent radiant energy back-scattered back from said patient'"'"'s body;

said laser fiber and said receiver fiber together forming means for defining an observation volume within said patient'"'"'s body;

a photo detector coupled to said receiver fiber for generating a doppler shifted detector signal;

means for measuring the DC component of said detector signal;

means for measuring the AC component of said detector signal;

means for computing the ratio of said AC component to said DC component forming hematocrit measurement data within said observation volume;

pressure cuff means for compressing said patient'"'"'s body at the location of said observation volume;

inflation means coupled to said pressure cuff means for inflating said pressure cuff means;

means for generating pressure data from said pressure cuff means; and

display means for displaying said hematocrit measurement data as a function of said pressure data.

2. The apparatus of claim 1 wherein said display means displays:

a bar graph, said bar graph having a y-axis showing the hematocrit data, said bar graph having an x-axis showing the pressure data.

3. A method for measuring perfusion within a microvascular observation volume at an observation pressure, comprising:

a. defining said microvascular observation volume at said observation pressure;

b. illuminating structures within said microvascular observation volume with a coherent source of radiation;

c. detecting backscattered radiation from said structures and generating a doppler shifted radiation signal from said backscattered radiation;

d. extracting the AC signal component from said radiation signal;

e. extracting the DC signal component from said radiation signal;

f. forming a ratio of said AC signal component to said DC signal component at said observation pressure wherein said ratio is hematocrit measurement data which corresponds to perfusion within said microvascular observation volume;

g. calculating said ratio at a plurality of observation pressures; and

h. displaying said ratio as a function of said observation pressure.

4. The method of claim 3, wherein said step of calculating said ratio at a plurality of pressures calculates the ratio at a plurality of pressures as the pressure values from a higher pressure to a lower pressure.