Oximetry Signal, Pulse-Pressure Correlator

• US 20150051463A1
• Filed: 07/17/2014
• Published: 02/19/2015
• Est. Priority Date: 08/16/2013
• Status: Abandoned Application

• Current Assignee: Guy P. Curtis And Frances L. Curtis Trust
• Original Assignee: Guy P. Curtis And Frances L. Curtis Trust
• Inventors: Curtis, Guy P.
• Application Number:
  US14/334,335
• Publication Number:
  US 20150051463A1
• Time in Patent Office: Days
• US Class Current: 600/324
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2560/0238 Means for recording calibration data
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence
• CPC Class Codes: A61B 5/02208 using the Korotkoff method
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B

Abstract

A system and method are provided for using an oximeter to take blood pressure readings for an extended period of time. Calibration of the oximeter for this purpose requires use of a sphygmomanometer to determine a sequence of blood pressure readings taken for a patient over a sphygmomanometer duty cycle. During the duty cycle, readings for both blood pressure (sphygmomanometer) and blood flow amplitude (oximeter) are taken simultaneously at predetermined time intervals (e.g. patient pulse rate). These readings then determine an operational ratio between the two that can be used to translate pulse magnitude readings of the oximeter for presentation as blood pressure readings. Operationally, variations from the patient'"'"'s systolic pressure can then be continuously monitored in real time.

Claims

1. A system for continuously monitoring blood flow in the vasculature of a patient which comprises:

a sphygmomanometer for measuring a blood pressure pulse magnitude p_s for each pulse of the patient'"'"'s heart during a sphygmomanometer duty cycle, wherein the sphygmomanometer duty cycle extends between a systolic pressure p_s(systolic) and a diastolic pressure p_s(diastolic);

an oximeter for measuring a blood flow pulse amplitude p_o for each pulse of the patient'"'"'s heart during the sphygmomanometer duty cycle, wherein p_s and p_o are measured simultaneously for each pulse;

a computer for establishing an operational ratio p_o/p_s based on contemporary measurements of p_s and p_o, and for identifying a base amplitude signal p_o(base) to correspond with the systolic pressure p_s(systolic) of the patient; and

a monitor connected to the computer for continuously comparing pulse amplitude signals p_o from the oximeter with the base amplitude p_o(base), in real time, to detect variations therebetween as an indicator of changes in blood pressure and blood flow.

2. A system as recited in claim 1 further comprising an alarm initiated by the computer for indicating when a pulse amplitude p_o, measured by the oximeter, varies from the base amplitude by a predetermined value.

3. A system as recited in claim 2 wherein the predetermined value is based on the operational ratio p_o/p_s with a positive change of more than 60 mmHg and a negative change of more than 40 mmHg in blood pressure p_s.

4. A system as recited in claim 1 wherein the oximeter is connected to the patient at a selected pulse pressure location of the patient.

5. A system as recited in claim 1 wherein, for an n number of pulses during a sphygmomanometer duty cycle, successively different blood pressure measurements p_sn are taken by the sphygmomanometer and corresponding blood flow measurements p_on are taken by the oximeter to establish the operational ratio p_o/p_s.

6. A system as recited in claim 5 wherein, over the duty cycle, an average change in blood pressure pulse magnitude Δ

p_s [Δ

p_s=(Σ

Δ

p_sn)n] is compared with an average change in pulse amplitude Δ

p_o[Δ

p_o=(Σ

Δ

p_on)n] over the duty cycle to determine an operational ratio Δ

p_o/Δ

p_s for determining a blood pressure value p_s based on changes in pulse amplitude p_o.

7. A system as recited in claim 6 wherein each blood pressure pulse magnitude p_s and each blood flow pulse amplitude p_o is taken at a selected point in each pulse of the patient'"'"'s heart during the sphygmomanometer duty cycle.

8. A system as recited in claim 6 wherein each operational ratio Δ

p_o/Δ

p_s is patient specific.

9. A system as recited in claim 6 wherein the operational ratio Δ

p_o/Δ

p_s is recalculated to recalibrate the oximeter at least every hour.

10. A method for continuously monitoring blood flow in the vasculature of a patient which comprises the steps of:

measuring a blood pressure pulse magnitude p_s, with a sphygmomanometer, for each pulse of the patient'"'"'s heart during a sphygmomanometer duty cycle, wherein the sphygmomanometer duty cycle extends between a systolic pressure p_s(systolic) and a diastolic pressure p_s(diastolic);

measuring a blood flow pulse amplitude p_o, with an oximeter, for each pulse of the patient'"'"'s heart during the sphygmomanometer duty cycle, wherein p_s and p_o are measured simultaneously for each pulse;

establishing an operational ratio p_o/p_s based on contemporary measurements of p_s and p_o;

identifying a base amplitude signal p_o(base) to correspond with the systolic pressure p_s(systolic) of the patient; and

continuously comparing pulse amplitude signals p_o from the oximeter with the base amplitude p_o(base), in real time, to detect variations therebetween as an indicator of changes in blood pressure and blood flow.

11. A method as recited in claim 10 further comprising the step of initiating an alarm when a pulse amplitude p_o, measured by the oximeter, varies from the base amplitude by a predetermined value.

12. A method as recited in claim 11 wherein the predetermined value is based on the operational ratio p_o/p_s with a positive change of more than 60 mmHg and a negative change of more than 40 mmHg in blood pressure p_s.

13. A method as recited in claim 10 wherein, for an n number of pulses during a sphygmomanometer duty cycle, successively different blood pressure measurements p_s, are taken by the sphygmomanometer and corresponding blood flow measurements p_on are taken by the oximeter to establish the operational ratio p_o/p_s.

14. A method as recited in claim 13 wherein, over the duty cycle, an average change in blood pressure pulse magnitude Δ

p_s [Δ

p_s=(Σ

Δ

p_sn)n] is compared with an average change in pulse amplitude Δ

p_o [Δ

p_o=(Σ

Δ

p_on)n] over the duty cycle to determine an operational ratio Δ

p_o/Δ

p_s for determining a blood pressure value p_s based on changes in pulse amplitude p_o.

15. A method as recited in claim 14 wherein each blood pressure pulse magnitude p_s and each blood flow pulse amplitude p_o is taken at a selected point in each pulse of the patient'"'"'s heart during the sphygmomanometer duty cycle.

16. A method as recited in claim 10 further comprising the step of recalculating the operational ratio Δ

p_o/Δ

p_s to recalibrate the oximeter at least every hour.

17. A method as recited in claim 10 wherein the establishing step and the identifying step are accomplished by a computer.

18. A method as recited in claim 10 wherein the comparing step is accomplished by a computer with input from a monitor.

19. A non-transitory, computer-readable medium having executable instructions stored thereon that direct a computer system to perform a process that comprises:

measuring a blood pressure pulse magnitude p_s, with a sphygmomanometer, for each pulse of the patient'"'"'s heart during a sphygmomanometer duty cycle, wherein the sphygmomanometer duty cycle extends between a systolic pressure p_s(systolic) and a diastolic pressure p_s(diastolic), measuring a blood flow pulse amplitude p_o, with an oximeter, for each pulse of the patient'"'"'s heart, wherein p_s and p_o are measured simultaneously for each pulse;

establishing an operational ratio p_o/p_s based on contemporary measurements of p_s and p_o;

identifying a base amplitude signal p_o(base) to correspond with the systolic pressure p_s(systolic) of the patient; and

continuously comparing pulse amplitude signals p_o from the oximeter with the base amplitude p_o(base), in real time, to detect variations therebetween as an indicator of changes in blood pressure and blood flow.

20. A medium as recited in claim 19 wherein the process further comprises:

taking successively different blood pressure measurements p_sn and corresponding blood flow measurements p_on, for an n number of pulses during a sphygmomanometer duty cycle, to establish the operational ratio p_o/p_s; and

comparing an average change in blood pressure pulse magnitude Δ

p_s [Δ

p_s=(Σ

Δ

p_sn)/n] with an average change in pulse amplitude Δ

p_o [Δ

p_o=(Σ

Δ

p_on)/n] over the duty cycle to determine the operational ratio Δ

p_o/Δ

p_s for determining a blood pressure value p_s based on changes in pulse amplitude p_o.