System and method for noninvasively measuring ventricular stroke volume and cardiac output

• US 10,405,762 B2
• Filed: 08/01/2016
• Issued: 09/10/2019
• Est. Priority Date: 04/22/2009
• Status: Active Grant

• Current Assignee: Vital Metrix Inc.
• Original Assignee: Vital Metrix Inc.
• Inventors: Teixeira, Rodrigo E.
• Primary Examiner(s): Borin, Michael L
• Application Number:
  US15/225,803
• Publication Number:
  US 20170119261A1
• Time in Patent Office: 1,135 Days
• Field of Search: None
• 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 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• 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 5/6826 Finger
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7267 involving training the classification device
• CPC Class Codes: A61B 5/7405 using sound
• CPC Class Codes: A61B 5/7455 characterised by tactile indication, e.g. vibration or electrical stimulation
• CPC Class Codes: G06F 18/2321 using statistics or function optimisation, e.g. modelling of probability density functions
• CPC Class Codes: G06F 2218/08 Feature extraction

Abstract

A system for non-invasively measuring cardiac output, stroke volume, or both comprises a pulse oximeter, a data processor, and means for generating an output reporting measured one or more CO or SV values to a user. A method for non-invasively measuring cardiac output, stroke volume, or both comprises collecting plethysmographic waveform data of a patient, providing the plethysmographic waveform to a data processor, and calculating measured values for CO or SV. The data processor comprises a mathematical model of the cardiovascular system integrated in a dynamic state space model (DSSM).

Claims

1. A system for non-invasively measuring left ventricular stroke volume (SV) and/or cardiac output (CO) of a patient, said system comprising:

a pulse oximeter, a data processor, and means for generating an output reporting a measured SV or CO value to a user wherein;

the pulse oximeter is configured to collect plethysmographic waveform data of the patient and to transmit the plethysmographic waveform data to the data processor;

the data processor is configured to receive said plethysmographic waveform data and comprises software that calculates the measured value for SV and/or CO using said plethysmographic waveform data and reports the measured value for SV and/or CO to the user;

the software that calculates a measured value for SV and/or CO from plethysmographic waveform data comprises a probabilistic processor and a mathematical model of a cardiovascular system integrated in a dynamic state space model (DSSM); and

the mathematical model of the cardiovascular system comprises aortic pressure, radial pressure, peripheral resistance, aortic impedance, heart rate, stroke volume, and blood density as state or model parameters.

2. The system of claim 1, wherein the pulse oximeter is configured to collect plethysmographic waveform data of the patient and to transmit the plethysmographic waveform data to the data processor in real time.

3. The system of claim 1, wherein the software calculates the measured value for SV and/or CO in real time.

4. The system of claim 1, wherein the DSSM is integrated with a dual estimation processor engine or a joint estimation processor engine.

5. The system of claim 1, wherein the means for generating an output reporting measured SV or CO values to a user comprises means for generating an electronic display, a hard copy display, an audible sound, a visual display, or a tactile output.

6. The system of claim 1, wherein the pulse oximeter is a fingertip pulse oximeter.

7. The system of claim 1, wherein the mathematical model of a cardiovascular system includes model and/or state parameters that correspond directly to one or more of peripheral blood oxygen saturation (SpO₂), heart rate (HR), respiratory rate (RR), and blood pressure (BP).

8. The system of claim 7, wherein the data processor is additionally configured to receive data from a direct measurement of one or more of SpO₂, HR, RR, and BR.

9. The system of claim 1, further comprising a blood pressure measuring device that transmits blood pressure data to the processor and wherein the processor receives said blood pressure data to be used as input into the cardiovascular model.

10. The system of claim 1, wherein the processor comprises a processing engine within an executable program that is configured to receive digital data from the pulse oximeter and to output stroke volume data and/or cardiac output data to a display.

11. The system of claim 1, wherein:

the DSSM receives first probability distributions for state and model parameters to produce a first probability distribution function (PDF) representing a first state;

data for a time t1 from the pulse oximeter and the first PDF are combined using a Bayesian statistical process to generate a second PDF that represents a state at time t1;

expectation values for the second PDF are calculated and, using the expectation values, updated state parameters for time t1 are combined with pulse oximeter data for time t1 to update the model parameters for time t2 in the DSSM;

expectation values are also entered into the DSSM as the state, in the form of a vector of state parameters;

after the state parameters and model parameters for the DSSM are updated to time t1, the process is repeated with pulse oximeter data for time t2 to produce updated parameters for time t2;

and the processor is configured to process the parameters to generate an output related to ventricular stroke volume.

12. The system of claim 11, wherein the state parameters and model parameters are concatenated into a single vector that is transformed by the DSSM.