APPARATUS AND METHOD FOR RESPIRATORY RATE DETECTION AND EARLY DETECTION OF BLOOD LOSS VOLUME

• US 20120296219A1
• Filed: 10/20/2010
• Published: 11/22/2012
• Est. Priority Date: 10/20/2009
• Status: Active Grant

• Current Assignee: The Research Foundation for The State University of New York (State University of New York), Worcester Polytechnic Institute
• Original Assignee: Worcester Polytechnic Institute
• Inventors: Chon, Ki H., Selvaraj, Nandakumar
• Granted Patent: US 9,414,753 B2
• Time in Patent Office: Days
• US Class Current: 600/479
• CPC Class Codes: A61B 5/02042 Determining blood loss or bleeding, e.g. during a surgical procedure
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• 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

Abstract

An apparatus and method is provided that provide, in real-time, an accurate detection and warning of dangerous blood or fluid loss to warn of impending hypovolemia, by non-invasive monitoring and processing of photoplethysmography data.

Claims

1. A method for non-invasive monitoring and detection of sudden changes in cardiovascular hemodynamics, the method comprising:

obtaining a photoplethysmography (PPG) signal from a patient;

computing, from the PPG signal, a time-frequency spectrum (TFS);

extracting from the TFS a group of instantaneous modulations from time points defining a curve of prominent frequency oscillations;

comparing the curve to a baseline cardiovascular hemodynamic state; and

detecting impending hypovolemia when the curve formed by the instantaneous modulations statistically deviates from the baseline cardiovascular hemodynamic state.

2. The method of claim 1, wherein the instantaneous modulations are obtained from one of frequency modulations and amplitude modulations.

3. The method of claim 1, wherein the prominent frequency oscillations are obtained from a heart rate of the patient between 0.8 and 1.4 Hz.

4. The method of claim 1, wherein the prominent frequency oscillations are obtained from a respiratory rate of the patient between 0.05 and 0.35 Hz.

5. The method of claim 1, wherein, for a spontaneously breathing patient, an indication of hypovolemia is obtained by monitoring a predominantly arterial signal of the PPG signal.

6. The method of claim 1, wherein, for a mechanically ventilated patient, an indication of hypovolemia is obtained by detecting increases in modulation of venous (DC) components of the PPG signal.

7. The method of claim 6, wherein detection of the DC components is made in a range of 0.15-0.4 Hz

8. A method for non-invasive monitoring and detection of sudden changes in cardiovascular hemodynamics, the method comprising:

obtaining a photoplethysmography (PPG) signal from a patient;

computing, from the PPG signal, a time-frequency spectrum (TFS);

extracting from the TFS, a group of instantaneous modulations from time points defining a curve of prominent frequency oscillations;

computing, using the instantaneous modulations, a peak power spectral density (PSD) sequence; and

identifying blood loss by monitoring instantaneous peak values of following prominent frequency oscillations.

9. The method of claim 8, wherein the instantaneous modulations are frequency modulations.

10. A method of claim 8, wherein the instantaneous modulations are amplitude modulations

11. The method of claim 8, further comprising computing an area under the curve, wherein the curve is from 0.15 Hz to 0.7 Hz of the PSD sequences of the prominent frequency oscillation.

12. The method of claim 8, wherein the prominent frequency oscillation is a heart rate of the patient between 0.8 and 1.4 Hz.

13. The method of claim 8, wherein the prominent frequency oscillation is a respiratory rate of the patient between 0.05 and 0.35 Hz.