Systems And Methods For Noninvasively Monitoring Baroreflex Response And Nominal Blood Volume

• US 20070213619A1
• Filed: 01/17/2007
• Published: 09/13/2007
• Est. Priority Date: 01/17/2006
• Status: Active Grant

• Current Assignee: The Trustees of Dartmounth College (Dartmouth College)
• Original Assignee: The Trustees of Dartmounth College (Dartmouth College)
• Inventors: Linder, Stephen
• Granted Patent: US 8,485,978 B2
• Time in Patent Office: Days
• US Class Current: 600/481
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/6814 Head
• CPC Class Codes: A61B 5/6816 Ear lobe
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips

Abstract

Systems and methods for noninvasively monitoring baroreflex response and nominal blood volume are disclosed herein. Software and methods for evaluating morphological features of a photoplethysmogram (PPG) obtained using a pulse oximeter allow for the affirmative detection and quantification of the baroreflex response from data obtained during orthostatic stress tests, lower body negative pressure chamber tests and treadmill stress tests.

Claims

1. A software product comprising instructions, stored on computer-readable media, wherein the instructions, when executed by a computer, perform steps for detecting the presence of a baroreflex response, comprising:

instructions for obtaining photoplethysmographic (PPG) data;

instructions for determining one or more of the following parameters;

(a) a normalized peak width of each cardiac cycle;

(b) an amplitude of the pulsatile component of each cardiac cycle in the PPG data derived from an ear sensor; and

(c) an instantaneous pulse rate;

instructions for determining a median value for the one or more parameters using a representative sample of cardiac cycles; and

instructions for providing a result indicative of the presence of the baroreflex response when one or more of the following is observed;

(d) an increase in the normalized peak width of 5% or more relative to the median normalized peak width;

(e) a two-fold decrease in the amplitude of the pulsatile component relative to the median pulsatile amplitude; and

(f) an increase in the instantaneous pulse rate of at least 20% relative to the median pulse rate.

2. The software product of claim 1, further comprising instructions for providing a result indicative of the absence of detection of the baroreflex response when none of (d), (e) and (f) is observed.

3. The software product of claim 1, further comprising instructions for recording and saving data to memory.

4. A software product comprising instructions, stored on computer-readable media, wherein the instructions, when executed by a computer, perform steps for detecting the presence of a baroreflex response, comprising:

instructions for obtaining photoplethysmographic (PPG) data;

instructions for determining a normalized peak width of each cardiac cycle;

instructions for determining a median normalized peak width using a representative sample of cardiac cycles; and

instructions for providing a result indicative of the presence of the baroreflex response when an increase in the normalized peak width of 5% or more relative to the median normalized peak width is detected.

5. The software product of claim 4, further comprising instructions for providing a result indicative of the absence of detection of the baroreflex response when an increase in the normalized peak width of 5% or more relative to the median normalized peak width is not detected.

6. The software product of claim 4, further comprising:

instructions for determining an amplitude of the pulsatile component of each cardiac cycle in the PPG data derived from an ear sensor;

instructions for determining a median pulsatile amplitude using a representative sample of cardiac cycles from the PPG data derived from the ear sensor; and

instructions for providing a result indicative of the presence of the baroreflex response when a two-fold decrease in the amplitude of the pulsatile component relative to the median pulsatile amplitude is detected.

7. The software product of claim 6, further comprising instructions for providing a result indicative of the absence of detection of the baroreflex response when a two-fold decrease in the amplitude of the pulsatile component relative to the median pulsatile amplitude is not detected.

8. The software product of claim 4, further comprising:

instructions for determining an instantaneous pulse rate;

instructions for determining a median pulse rate using a representative sample of cardiac cycles; and

instructions for providing a result indicative of the presence of the baroreflex response when an increase in the instantaneous pulse rate of at least 20% relative to the median pulse rate is detected.

9. The software product of claim 8, further comprising instructions for providing a result indicative of the absence of detection of the baroreflex response when an increase in the instantaneous pulse rate of at least 20% relative to the median pulse rate is not detected.

10. The software product of claim 4, further comprising instructions for recording and saving data to memory.

11. A method of detecting the presence of a baroreflex response, comprising:

obtaining photoplethysmographic (PPG) data; and

detecting one or more of the following;

(a) an increase in a normalized peak width of 5% or more relative to a median normalized peak width;

(b) a two-fold decrease in an amplitude of a pulsatile component relative to a median pulsatile amplitude of the PPG data derived from an ear sensor;

(c) an increase in an instantaneous pulse rate of at least 20% relative to a median pulse rate;

(d) a height of a top RIV envelope that is greater than a difference between a minimum value of the top RIV envelope and a maximum value of a bottom RIV envelope;

(e) a synchronous rise of a top RIV envelope and a bottom RIV envelope by a significant proportion of a peak amplitude;

(f) a synchronous fall of a top RIV envelope and a bottom RIV envelope by a significant proportion of a peak amplitude; and

(g) a PPG spindle wave.

12. A method of quantifying a baroreflex response, comprising:

obtaining photoplethysmographic (PPG) data;

determining an instantaneous value and a sustained value for one or more of the following parameters;

(a) a normalized peak width of each cardiac cycle;

(b) an amplitude of the pulsatile component of each cardiac cycle in the PPG data derived from an ear sensor; and

(c) an instantaneous pulse rate;

determining a ratio of the instantaneous value to the sustained value for one or more of (a), (b) and (c); and

comparing the ratio to a library of known ratios.

13. A software product comprising instructions, stored on computer-readable media, wherein the instructions, when executed by a computer, perform steps for detecting the presence of a baroreflex response, comprising:

instructions for obtaining photoplethysmographic (PPG) data;

instructions for determining one or more of the following parameters;

(a) a normalized peak width of each cardiac cycle;

(b) an amplitude of the pulsatile component of each cardiac cycle in the PPG data derived from an ear sensor; and

(c) an instantaneous pulse rate;

instructions for determining a median value for the one or more parameters using a representative sample of cardiac cycles; and

instructions for providing a result indicative of the presence of the baroreflex response when a statistically significant change in the median value is detected using a statistical threshold of p<

0.01.