Non-invasive method for measuring tissue perfusion state

• US 9,943,240 B2
• Filed: 02/05/2014
• Issued: 04/17/2018
• Est. Priority Date: 02/05/2013
• Status: Active Grant

• Current Assignee: Assistance Publique - Hopitaux De Paris
• Original Assignee: Assistance Publique - Hopitaux De Paris
• Inventors: Vallee, Fabrice, Mateo, Joaquim, Payen De La Garanderie, Didier
• Primary Examiner(s): Thomson, William
• Assistant Examiner(s): HUH, VYNN V
• Application Number:
  US14/766,098
• Publication Number:
  US 20150374241A1
• Time in Patent Office: 1,532 Days
• Field of Search: 600300, 600301
• CPC Class Codes: A61B 5/026 Measuring blood flow A61B3/1233, A61B3/1241 take precedence
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/1477 non-invasive
• CPC Class Codes: A61B 5/1491 Heated applicators
• CPC Class Codes: A61B 5/412 Detecting or monitoring sepsis
• CPC Class Codes: A61B 5/4884 inducing physiological or psychological stress, e.g. applications for stress testing
• CPC Class Codes: A61B 5/6816 Ear lobe
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence

Abstract

A non-invasive method for determining the tissue perfusion state in a patient, by measuring the variations in the skin CO₂ pressure and in the perfusion index of the patient during the conducting of a localized hyperthermia test.

Claims

1. A non-invasive method for determining the microcirculatory perfusion state of a patient, comprising the following steps:

carrying out the following measurements;

measuring of cutaneous CO₂ pressure (PcCO₂) of the patient;

measuring of perfusion index (PI) of the patient;

wherein said measurements are carried out using one or more sensor(s) which are maintained at an initial temperature chosen between 30°

C. and 37°

C. or of a non-heated, ambient temperature,

performing a hyperthermia challenge consisting of;

starting with increasing the temperature of the sensor(s) from said initial temperature to a heating temperature chosen between 40°

C. and 48°

C.;

maintaining said sensor(s) at said heating temperature for a period of between 3 and 15 minutes, and bringing the temperature of the sensor(s) to said initial temperature, wherein said hyperthermia challenge ends when the temperature of the sensor(s) have recovered said initial temperature, and

measuring a PcCO_{2_start}, wherein PcCO_{2_start} is the cutaneous CO₂ pressure at a start of said hyperthermia challenge;

measuring a PcCO_{2_heated}, wherein PcCO_{2_heated} is the cutaneous CO₂ pressure at five minutes into said heating temperature of said hyperthermia challenge;

determining a PcCO<sub>2_heated−

start</sub> by calculating a difference PcCO_{2_heated}−

PcCO<sub>2—

start</sub>;

measuring the perfusion index of the patient during said hyperthermia challenge, and determining a maximum value of the perfusion index obtained during said hyperthermia challenge;

interpreting the functionality of vascular endothelium at the level of the microcirculatory network;

indicating that the vascular endothelium at the level of the microcirculatory network of the patient is functional when PcCO<sub>2_heated−

start</sub> is a non-positive value, accompanied by a ratio between the maximum value of the perfusion index obtained during said hyperthermia challenge and the perfusion index (PI) of the patient at said initial temperature being greater than a predetermined threshold of between 2 and 4; and

indicating that the microcirculatory network of the patient is affected when PcCO<sub>2_heated−

start</sub> is a positive value, accompanied by a ratio between the maximum value of the perfusion index obtained during said hyperthermia challenge and the perfusion index (PI) of the patient at said initial temperature being lesser than a predetermined threshold of between 2 and 4.

2. The method as claimed in claim 1, wherein the cutaneous CO₂ pressure and the perfusion index are measured by a sensor placed on an earlobe.

3. The method as claimed in claim 1, further comprising the measurement of the time elapsed between the end of the hyperthermia challenge and the moment when the sensor again begins to consume energy in order to maintain its temperature at 37°

C.

4. The method as claimed in claim 1, further comprising the measurement of the energy consumed by the sensor in order to increase the temperature thereof to the temperature chosen for the hyperthermia challenge or to maintain its temperature at 37°

C. for a predetermined period of time beginning at the end of the hyperthermia challenge.

5. The method of claim 1, further comprising:

obtaining information relating to the prognosis for the chances of survival at 28 days for a patient in a state of shock by determining the microcirculatory perfusion state of the patient and interpreting the indication of the vascular endothelium at the level of the microcirculatory network being functional as a good prognosis for this patient or the indication of the microcirculatory network of the patient being affected as a poor prognosis.