SYSTEMS AND METHODS FOR DETERMINING RESPIRATORY EFFORT

• US 20120029361A1
• Filed: 07/30/2010
• Published: 02/02/2012
• Est. Priority Date: 07/30/2010
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Addison, Paul Stanley, Watson, James N.
• Granted Patent: US 8,834,378 B2
• Time in Patent Office: Days
• US Class Current: 600/484
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/02108 from analysis of pulse wave characteristics
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

Systems and methods for calculating a measure of respiratory effort of a subject are provided. The measure of respiratory effort may be calculated based on a differential pulse transit time (DPTT) calculated for received photoplethysmograph signals. The systems and methods may allow for the calculation of respiratory effort in absolute units, and without the need for calibrations from a device that measures blood pressure (e.g., a non-invasive blood pressure cuff).

Claims

1. A method for calculating a measure of respiratory effort of a subject, the method comprising:

receiving at least one (PPG) signal;

calculating, using electronic processing equipment, a differential pulse transit time (DPTT) for each of the at least one PPG signal;

determining, using the electronic processing equipment, a measure of respiratory effort based at least in part on the calculated DPTTs; and

storing, using a storage device, the measure of respiratory effort.

2. The method of claim 1, wherein the determining further comprises:

selecting a plurality of pressure calculation coefficients based on the calculated DPTTs;

selecting a plurality of characteristic DPTTs;

determining, based at least in part on the selected pressure calculation coefficients and selected characteristic DPTTs, a measure of blood pressure; and

calculating, based at least in part on the measure of blood pressure, a measure of respiratory effort.

3. The method of claim 2, wherein the measure of blood pressure is determined solely based on the selected pressure calculation coefficients and selected characteristic DPTTs.

4. The method of claim 2, further comprising:

selecting at least a portion of the calculated DPTTs corresponding to at least one respiratory cycle of the subject; and

selecting a plurality of characteristic DPTTs within the portion of the DPTTs.

5. The method of claim 4, wherein the characteristic DPTTs are selected based on at least a maximum DPTT value and a minimum DPTT value in the portion of the DPTTs.

6. The method of claim 4, further comprising calculating a mean DPTT value corresponding to the at least one respiratory cycle of the subject.

7. The method of claim 2, further comprising:

selecting at least a portion of the calculated DPTTs corresponding to at least two periods of respiratory activity;

calculating a mean DPTT value corresponding to each of the at least two periods of respiratory activity; and

determining, based at least in part on the selected pressure calculation coefficients and calculated mean DPTT values, the measure of blood pressure.

8. The method of claim 7, wherein the at least two periods of respiratory activity correspond to at least one period in which the subject is exercising and at least one period in which the subject is resting.

9. The method of claim 1, wherein the calculation of the measure of respiratory effort is based on a linear relationship between a measure of blood pressure and respiratory effort.

10. A system for calculating a measure of respiratory effort of a subject, comprising:

an input for receiving at least one photoplethysmograph (PPG) signal;

a processor capable of using at least a portion of the at least one PPG signal to;

calculate a differential pulse transit time (DPTT) for each of the at least one PPG signals; and

determine a measure of respiratory effort based at least in part on the calculated DPTTs; and

a storage device for storing the measure of respiratory effort.

11. The system of claim 10, wherein the processor is capable of using at least a portion of the calculated DPTTs to:

select a plurality of pressure calculation coefficients based on the calculated DPTTs;

select a plurality of characteristic DPTTs;

determine, based at least in part on the selected pressure calculation coefficients and selected characteristic DPTTs, a measure of blood pressure; and

calculate, based at least in part on the measure of blood pressure, a measure of respiratory effort.

12. The system of claim 11, wherein the measure of blood pressure is determined solely based on the selected pressure calculation coefficients and selected characteristic DPTTs.

13. The system of claim 11, wherein the processor is capable of using at least a portion of the calculated DPTTs to:

select at least a portion of the calculated DPTTs corresponding to at least one respiratory cycle of the subject; and

select a plurality of characteristic DPTTs within the portion of the DPTTs.

14. The system of claim 13, wherein the characteristic DPTTs are selected based on at least a maximum DPTT value and a minimum DPTT value in the portion of the DPTTs.

15. The system of claim 13, wherein the processor is further configured to calculate a mean DPTT value corresponding to the at least one respiratory cycle of the subject.

16. The system of claim 11, wherein the processor is capable of using at least a portion of the calculated DPTTs to:

select at least a portion of the calculated DPTTs corresponding to at least two periods of respiratory activity;

calculate a mean DPTT value corresponding to each of the at least two periods of respiratory activity; and

determine, based at least in part on the selected pressure calculation coefficients and calculated mean DPTT values, the measure of blood pressure.

17. The system of claim 16, wherein the at least two periods of respiratory activity correspond to at least one period in which the subject is exercising and at least one period in which the subject is resting.

18. The system of claim 10, wherein the calculation of the measure of respiratory effort is based on a linear relationship between a measure of blood pressure and respiratory effort.

19. Computer readable storage media comprising instructions for:

receiving at least one photoplethysmograph (PPG) signal;

calculating at least one differential pulse transit time (DPTT) for each of the at least one PPG signals;

determining a measure of respiratory effort based at least in part on the calculated DPTTs; and

storing the measure of respiratory effort.