Apparatus and method for respiratory rate detection and early detection of blood loss volume

• US 9,414,753 B2
• Filed: 10/20/2010
• Issued: 08/16/2016
• 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: The Research Foundation for The State University of New York (State University of New York), Worcester Polytechnic Institute
• Inventors: Chon, Ki H., Selvaraj, Nandakumar
• Primary Examiner(s): Le, Long V
• Assistant Examiner(s): PONTIUS, KEVIN LANE
• Application Number:
  US13/503,075
• Publication Number:
  US 20120296219A1
• Time in Patent Office: 2,127 Days
• Field of Search: 600/479, 600/481, 600/483, 600/484, 600/500, 600/501, 600/502, 600/507, 600/529
• US Class Current: 1/1
• 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 for non-invasive monitoring and detection of sudden changes in cardiovascular hemodynamics, in which a PPG signal is obtained from a patient, a time-frequency spectrum (TFS) is computed from the PPG signal, instantaneous modulations at a plurality of time points defining a curve of a prominent frequency of oscillation are extracted from the TFS, a peak power spectral density sequence is computed using the instantaneous modulations, and instantaneous peak values for following prominent frequency oscillations are monitored.

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), the TFS obtained using Complex Demodulation (CDM);

extracting from the TFS, for a predetermined range of frequencies, time points for the TFS in the predetermined range of frequencies;

wherein the predetermined range of frequencies is at least one range of frequencies selected from a range between 0.8 and 1.4 Hz, referred to as a heart rate range and a range between 0.15 and 0.4 Hz, referred to as a respiratory rate band;

obtaining, from a curve of the time points for the IFS in the predetermined range of frequencies, a curve of instantaneous modulations at the time points in the predetermined range of frequencies, the instantaneous modulations being amplitude modulations;

for the range between 0.8 and 1.4 Hz the instantaneous modulations being referred to as AC components;

for the range between 0.15 and 0.4 Hz the instantaneous modulations referred to as venous components; and

detecting impending hypovolemia by one of either by detecting changes in a ratio of the venous components to the AC components, or, for a mechanically ventilated patient, by detecting increases in the venous components.

2. The method of claim 1, wherein, for a mechanically ventilated patient, an indication of hypovolemia is obtained by detecting increases in the venous components of the TFS signal.

3. The method of claim 1,

wherein an indication of hypovolemia is obtained by detecting changes in a ratio of the venous components to the AC components.

4. The method of claim 3 wherein, for a mechanically ventilated patient, an indication of hypovolemia is obtained by detecting increases in the ratio of the venous components to the AC components.

5. The method of claim 3 wherein, for a spontaneously breathing patient, an indication of hypovolemia is obtained by detecting increases in the ratio of the venous components to the AC components.

6. A system for detecting hypovolemia, the apparatus comprising:

a computer configured to;

compute, from a PPG signal, a time-frequency spectrum (TFS), the TFS obtained using Complex Demodulation (CDM);

extract from the TFS, for a predetermined range of frequencies, time points for the TFS in the predetermined range of frequencies;

wherein the predetermined range of frequencies is at least one range of frequencies selected from a range between 0.8 and 1.4 Hz referred to as a heart rate range and a range between 0.15 and 0.4 Hz, referred to as a respiratory rate band;

obtain, from a curve of the time points for the IFS in the predetermined range of frequencies, a curve of instantaneous modulations at the time points in the predetermined range of frequencies, the instantaneous modulations being amplitude modulations;

for the range between 0.8 and 1.4 Hz the instantaneous modulations being referred to as AC components;

for the range between 0.15 and 0.4 Hz the instantaneous modulations referred to as venous components; and

detecting impending hypovolemia by one of either by detecting changes in a ratio of the venous components to the AC components, or, for a mechanically ventilated patient, by detecting increases in the venous components.

7. The system of claim 6 wherein, for a mechanically ventilated patient, an indication of hypovolemia is obtained by detecting increases in the venous components of the TFS signal.

8. The system of claim 6

wherein an indication of hypovolemia is obtained by detecting changes in a ratio of the venous components to the AC components.

9. The system of claim 8 wherein, for a mechanically ventilated patient, an indication of hypovolemia is obtained by detecting increases in the ratio of the venous components to the AC components.