Automated Assessment of Peripheral Vascular Condition

• US 20140257062A1
• Filed: 03/08/2013
• Published: 09/11/2014
• Est. Priority Date: 03/08/2013
• Status: Active Grant

• Current Assignee: D. E. Hokanson, Inc.
• Original Assignee: D. E. Hokanson, Inc.
• Inventors: Ciliberti, Molly, Masin, Donald I., Gray, Kyra M.
• Granted Patent: US 9,662,051 B2
• Time in Patent Office: Days
• US Class Current: 600/324
• CPC Class Codes: A61B 2562/0233 Special features of optical sensors or probes classified in A61B5/00
• CPC Class Codes: A61B 5/02141 Details of apparatus construction, e.g. pump units or housings therefor, cuff pressurising systems, arrangements of fluid conduits or circuits A61B5/02233, A61B5/0235 take precedence
• 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
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• 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 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/6829 Foot or ankle
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence

Abstract

An automated assessment of a patient'"'"'s peripheral vascular condition includes using a pulse oximeter to generate at least a perfusion index relative to a limb or digit of the patient. Pressure is applied to the limb or digit, and while increasing or decreasing the pressure, a change in the perfusion index is determined. The change is indicative of a cessation of blood flow or a return of blood flow in the limb or digit. A systolic blood pressure is thereafter determined based on the pressure applied at the time of cessation of blood flow or the return of blood flow in the limb or digit. Using a pulse oximeter to generate a perfusion index may include transmitting light into the limb or digit, detecting light that was transmitted into tissue in the limb or digit, and calculating the perfusion index based on the light transmitted through the tissue.

Claims

1. An automated method of assessing a peripheral vascular condition of a patient, the method comprising, under control of a computing device:

using a pulse oximeter to generate a perfusion index relative to a limb or digit of the patient;

applying pressure to the limb or digit of the patient;

while increasing or decreasing the pressure applied to the limb or digit, determining a change in the perfusion index indicative of a cessation of blood flow or a return of blood flow in the limb or digit; and

determining a systolic blood pressure in the limb or digit based on the pressure applied at the time of cessation of blood flow or the return of blood flow in the limb or digit.

2. The method of claim 1, wherein applying pressure to the limb or digit of the patient comprises using a pressure cuff to compress the limb or digit.

3. The method of claim 2, wherein the pressure cuff inflates or deflates at a controlled rate.

4. The method of claim 1, wherein using a pulse oximeter to generate a perfusion index comprises:

transmitting light into the limb or digit;

detecting light that was transmitted through tissue in the limb or digit; and

calculating the perfusion index relative to the limb or digit based on the light transmitted through the tissue.

5. The method of claim 1, wherein determining a change in the perfusion index comprises identifying when a decrease in the perfusion index occurs, in which the decrease is indicative of a cessation of blood flow in the limb or digit.

6. The method of claim 1, wherein determining a change in the perfusion index comprises identifying when an increase in the perfusion index occurs, in which the increase is indicative of a return of blood flow in the limb or digit.

7. The method of claim 1, further comprising calculating an assessment index for the patient by dividing a systolic blood pressure determined in an ankle of the patient by a systolic blood pressure determined in an arm of the patient.

8. The method of claim 1, further comprising calculating an assessment index for the patient by dividing a systolic blood pressure determined in a toe of the patient by a systolic blood pressure determined in an arm of the patient.

9. The method of claim 1, further comprising, while increasing or decreasing the applied pressure, monitoring a change in oxygen saturation of the blood in the limb or digit indicative of a cessation of blood flow or a return of blood flow in the limb or digit,

wherein the systolic blood pressure in the limb or digit is determined based on the pressure applied when the cessation of blood flow or the return of blood flow occurred as indicated by the change in the perfusion index and by the change in oxygen saturation.

10. The method of claim 1, further comprising, while increasing or decreasing the applied pressure, monitoring a volumetric pulse waveform of the blood in the limb or digit for a change indicative of a cessation of blood flow or a return of blood flow in the limb or digit,

wherein the systolic blood pressure in the limb or digit is determined based on the pressure applied when the cessation of blood flow or the return of blood flow occurred as indicated by the change in the perfusion index and by the change in the volumetric pulse waveform.

11. The method of claim 1, further comprising, while increasing or decreasing the applied pressure, monitoring an oxygen saturation and a volumetric pulse waveform of the blood in the limb or digit for a change indicative of a cessation of blood flow or a return of blood flow in the limb or digit,

wherein the systolic blood pressure in the limb or digit is determined based on the pressure applied when the cessation of blood flow or the return of blood flow occurred as indicated by the change in the perfusion index, the change in oxygen saturation, and the change in the volumetric pulse waveform of the blood in the limb or digit.

12. An apparatus for assessing a peripheral vascular condition of a patient, the apparatus comprising:

a pressure cuff configured to apply pressure to a limb or digit of the patient to cause cessation of blood flow in the limb or digit; and

a processor configured to cause the pressure cuff to controllably apply or release a pressure to the limb or digit of the patient,

wherein the processor is configured to monitor a perfusion index calculated by a pulse oximeter relative to the limb or digit and determine a change in the perfusion index indicative of a cessation of blood flow or a return of blood flow in the limb or digit, and

wherein the processor is configured to determine a systolic blood pressure in the limb or digit based on the pressure applied by the pressure cuff when the cessation of blood flow or the return of blood flow occurred.

13. The apparatus of claim 12, wherein the pressure cuff is configured to apply pressure to the limb or digit by inflating and thereby compressing the limb or digit, and wherein the processor is configured to cause the pressure cuff to controllably apply or release a pressure by inflating or deflating the pressure cuff at a controlled rate.

14. The apparatus of claim 12, further comprising one or more optical devices configured to transmit and detect light when attached to the patient, wherein the perfusion index is monitored using data generated by the pulse oximeter using the one or more optical devices.

15. The apparatus of claim 14, wherein the one or more optical devices are configured to transmit light into the limb or digit and detect light transmitted through tissue in the limb or digit, and wherein the processor is configured to monitor the perfusion index calculated by the pulse oximeter based on the light transmitted through the tissue.

16. The apparatus of claim 15, wherein the one or more optical devices comprise an optical source configured to transmit light at specific wavelengths and a photodiode configured to detect light transmitted at the specific wavelengths.

17. The apparatus of claim 14, wherein the one or more optical devices comprise a pulse oximeter sensor, and wherein the processor is configured to read the perfusion index from the pulse oximeter.

18. The apparatus of claim 12, wherein the processor is further configured to calculate an assessment index for the patient by dividing a systolic blood pressure determined in an ankle of the patient by a systolic blood pressure determined in an arm of the patient.

19. The apparatus of claim 12, wherein the processor is further configured to calculate an assessment index for the patient by dividing a systolic blood pressure determined in a toe of the patient by a systolic blood pressure determined in an arm of the patient.

20. The apparatus of claim 12, wherein while causing the pressure cuff to controllably apply or release a pressure to the limb or digit of the patient, the processor is further configured to monitor oxygen saturation of the blood in the limb or digit for a change in oxygen saturation indicative of a cessation of blood flow or a return of blood flow in the limb or digit, and

wherein the processor is configured to determine the systolic blood pressure in the limb or digit based on the pressure applied when the cessation of blood flow or the return of blood flow occurred as indicated by the change in the perfusion index and by the change in the oxygen saturation.

21. The apparatus of claim 12, wherein while causing the pressure cuff to controllably apply or release a pressure to the limb or digit of the patient, the processor is further configured to monitor a volumetric pulse waveform of the blood in the limb or digit for a change indicative of a cessation of blood flow or a return of blood flow in the limb or digit, and

wherein the processor is configured to determine the systolic blood pressure in the limb or digit based on the pressure applied when the cessation of blood flow or the return of blood flow occurred as indicated by the change in the perfusion index and by the change in the volumetric pulse waveform.

22. The apparatus of claim 12, wherein while causing the pressure cuff to controllably apply or release a pressure to the limb or digit of the patient, the processor is further configured to monitor oxygen saturation and a volumetric pulse waveform of the blood in the limb or digit, and

wherein the processor is configured to determine the systolic blood pressure in the limb or digit based on the pressure applied when the cessation of blood flow or the return of blood flow occurred as indicated by the change in the perfusion index, the change in the oxygen saturation, and the change in the volumetric pulse waveform of the blood in the limb or digit.