Method for determining the perfusion

• US 4,867,165 A
• Filed: 08/13/1987
• Issued: 09/19/1989
• Est. Priority Date: 06/03/1987
• Status: Expired due to Term

• Current Assignee: Philips Electronics North America Corporation (Koninklijke Philips N.V.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Noller, Friedemann, Forstner, Klaus
• Primary Examiner(s): Wayner, William E.
• Application Number:
  US07/085,594
• Time in Patent Office: 768 Days
• Field of Search: 128/633, 128/694, 128/666, 128/774, 356/39, 356/382, 356/381
• US Class Current: 600/328
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips

Abstract

A method is proposed for determining the perfusion by evaluation of the light emitted by at least one light source and influenced by the arterial blood, by use of optical measuring means which measure the intensity variation as a consequence of the variation in arterial blood volume. According to this method, the perfusion is either displayed as variation in thickness from the sum of the parallel tissue enlargements d or as normalized volume. The perfusion is derived by one or more measurements of light intensity. According to the invention, for the first time a method for determining perfusion as a quantitative value is provided.

Claims

1. A method for determining the perfusion of blood in a body member comprising:

passing light having the isobestic wavelength through a member of the body,

measuring the variation, in intensity, Δ

I, of light emerging from said body member due to arterial blood volume variation, and

deriving from Δ

I one of the variations in thickness, Δ

d/d, of the body member or the variation in volume Δ

V/V.

2. A method according to claim 1 wherein the light intensity variation (Δ

I) is converted into a current variation by optoelectronic means and is determined as relative variation in current (Δ

I/Imax), and that the perfusion thickness Δ

d or the normalized perfusion Δ

V/V is determined by a substitution of the known determined quantities in;

##EQU5## Δ

I/Imax being the relative variation in intensity at the isobestic wavelength λ

_i, c₁ to c_n being the molecular concentrations of hemoglobin, oxihemoglobin or other substances,

E_1i to E_ni being the extinction coefficients for hemoglobin, oxihemoglobin or other substances at wavelength λ

_i.

3. A method according to claim 2 characterized in that measurements of the relative intensity variation (Δ

I/Imax) are carried out at a number of different wavelengths and that these measurements are used to determine a corresponding number of unknown equation parameters such as hemoglobin concentration, oxygen saturation and perfusion.

4. A method for determining the perfusion of blood in a body member comprising:

passing light, of two different wavelengths which both differ from the isobestic wavelength, through a member of the body;

measuring the variation in intensity, Δ

I, of light emerging from said body member due to arterial blood volume variation; and

deriving from Δ

I one of the variations in thickness, Δ

d/d, of the body member or the variation in volume Δ

V/V.