Automated assessment of peripheral vascular condition

• US 9,662,051 B2
• Filed: 03/08/2013
• Issued: 05/30/2017
• Est. Priority Date: 03/08/2013
• Status: Active Grant

• Current Assignee: D. E. Hokanson, Inc.
• Original Assignee: D.E. Hokanson, Inc.
• Inventors: Masin, Donald I., Gray, Kyra M., Ciliberti, Molly
• Primary Examiner(s): KUHLMAN, CATHERINE BURK
• Application Number:
  US13/791,806
• Publication Number:
  US 20140257062A1
• Time in Patent Office: 1,544 Days
• 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 the control of a computing device:

applying pressure to a limb or digit of the patient sufficient to cease blood flow to the limb or digit distal to the applied pressure;

using a pulse oximeter distal to the applied pressure to generate a plurality of pulse oximeter parameters relative to the limb or digit of the patient, wherein the plurality of pulse oximeter parameters comprises a perfusion index, oxygen saturation, and a volumetric pulse waveform;

while increasing or decreasing the pressure applied to the limb or digit, determining a change in each of the plurality of pulse oximeter parameters indicative of a cessation of blood flow or a return of blood flow in the limb or digit;

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 as determined by the change in each of the pulse oximeter parameters; and

assessing the peripheral vascular condition of the patient based on the systolic blood pressure determined 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 plurality of pulse oximeter parameters comprises:

transmitting light into the limb or digit;

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

calculating the plurality of pulse oximeter parameters 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 plurality of pulse oximeter parameters comprises identifying when a decrease in at least one of the plurality of pulse oximeter parameters 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 plurality of pulse oximeter parameters comprises identifying when an increase in at least one of the plurality of pulse oximeter parameters 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, wherein assessing the peripheral vascular condition of the patient based on the systolic blood pressure determined in the limb or digit comprises using systolic blood pressure determined in both an ankle and a toe of the patient.

10. The method of claim 1, wherein using a pulse oximeter distal to the applied pressure to generate a plurality of pulse oximeter parameters relative to the limb or digit of the patient comprises simultaneously generating the plurality of pulse oximeter parameters relative to the limb or digit of the patient.

11. 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;

a pulse oximeter configured to generate a plurality of pulse oximeter parameters of the patient at a position on the limb or digit distal to the pressure cuff, wherein the plurality of pulse oximeter parameters comprises a perfusion index, oxygen saturation, and a volumetric pulse waveform; and

a processor configured to;

cause the pressure cuff to controllably apply or release a pressure to the limb or digit of the patient sufficient to cease blood flow to the limb or digit distal to the pressure cuff,

monitor the plurality of pulse oximeter parameters generated by the pulse oximeter relative to the limb or digit and determine a change in each of the plurality of pulse oximeter parameters indicative of a cessation of blood flow or a return of blood flow in the limb or digit, and

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 as determined by the change in each of the plurality of pulse oximeter parameters.

12. The apparatus of claim 11, 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.

13. The apparatus of claim 11, further comprising one or more optical devices configured to transmit and detect light when attached to the patient, wherein the plurality of pulse oximeter parameters are generated by the pulse oximeter using the one or more optical devices.

14. The apparatus of claim 13, wherein the pulse oximeter is configured to transmit light into or onto the limb or digit and detect light transmitted through or reflected from tissue in the limb or digit, and wherein the processor is configured to monitor the plurality of pulse oximeter parameters by the pulse oximeter based on the light transmitted through or reflected from the tissue.

15. The apparatus of claim 14, wherein the pulse oximeter comprises an optical source configured to transmit light at specific wavelengths and a photodiode configured to detect light transmitted at the specific wavelengths.

16. The apparatus of claim 11, 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.

17. The apparatus of claim 11, 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.

18. The apparatus of claim 11, wherein the pulse oximeter is configured to simultaneously generate the plurality of pulse oximeter parameters of the patient at a position on the limb or digit distal to the pressure cuff.

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

applying pressure to a limb or digit of the patient;

using a pulse oximeter to generate a plurality of pulse oximeter parameters relative to the limb or digit of the patient, wherein the plurality of pulse oximeter parameters comprises a perfusion index, oxygen saturation, and a volumetric pulse waveform;

while increasing or decreasing the pressure applied to the limb or digit, determining a change in each of the plurality of pulse oximeter parameters indicative of a change in blood flow in the limb or digit;

determining a systolic blood pressure in the limb or digit based on the pressure applied at the time of change in blood flow in the limb or digit as determined by the change in each of the plurality of pulse oximeter parameters; and

assessing the peripheral vascular condition of the patient based on the systolic blood pressure determined and pulse oximeter parameter changes in the limb or digit.