Method and apparatus for monitoring cardiac output of a patient in a home environment

• US 9,326,735 B2
• Filed: 04/23/2013
• Issued: 05/03/2016
• Est. Priority Date: 05/15/2012
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Muhlsteff, Jens
• Primary Examiner(s): Koharski, Christopher D
• Assistant Examiner(s): CAREY, MICHAEL JAMES
• Application Number:
  US14/399,759
• Publication Number:
  US 20150126820A1
• Time in Patent Office: 1,106 Days
• Field of Search: 600/526, 600/508, 600/509
• US Class Current: 1/1
• CPC Class Codes: A61B 2505/07 Home care
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• 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 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/486 Bio-feedback A61B5/375 takes precedence
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: A61B 5/7475 User input or interface means, e.g. keyboard, pointing device, joystick
• CPC Class Codes: A61B 7/00 Instruments for auscultation
• CPC Class Codes: A61B 7/006 Detecting skeletal, cartilage or muscle noise A61B7/003 and A61B7/008 take precedence
• CPC Class Codes: A61B 7/045 Detection of Korotkoff sounds A61B5/0225 takes precedence; measuring blood pressure A61B5/021

Abstract

There is provided a method of determining a measure of the cardiac output, CO, of a patient, the method comprising obtaining measurements of one or more physiological characteristics of the patient, the physiological characteristics including at least the heart rate, HR, of the patient, the systolic blood pressure, S, of the patient and the diastolic blood pressure, D, of the patient; and processing the measurements to determine a measure of the cardiac output of the patient; wherein the measure of the cardiac output of the patient is derived using the relationship

$\mathrm{CO}=K_1\left(\mathrm{HR}\frac{S-D}{S+D}\right),\mathrm{CO}=K_2\mathrm{HR}\left(S-D\right){\left(\mathrm{PTT}\right)}^2,\mathrm{and}/\mathrm{or}$$\mathrm{CO}=K_2\mathrm{HR}\left(S-D\right){\left(\mathrm{PAT}-\mathrm{PEP}\right)}^2$
where K₁ and K₂ are patient-specific calibration factors, PAT is the pulse arrival time, PEP is the pre-ejection period and PTT is the pulse transit time, the time taken for a pulse wave to travel between two points in the body of the patient.

Claims

1. A method of determining a measure of the cardiac output, CO, of a patient with a monitoring apparatus, the monitoring apparatus comprising a hardware processing unit and one or more physiological sensors, the method comprising:

obtaining, with the processing unit, measurements of one or more physiological characteristics of the patient from the one or more physiological sensors, the physiological characteristics including at least the heart rate, HR, of the patient, the systolic blood pressure, S, of the patient and the diastolic blood pressure, D, of the patient; and

processing, with the processing unit, the measurements to determine a measure of the cardiac output of the patient;

wherein the measure of the cardiac output of the patient is derived using the relationship;

2. A method as claimed in claim 1, wherein K₁ and/or K₂ are determined by the processing unit from a reference measurement of the cardiac output of the patient.

3. A method as claimed in claim 1, wherein the measure of the cardiac output of the patient is a measure of the change in the cardiac output from an earlier cardiac output measurement or a reference measurement for cardiac output, and the measure of the change in the cardiac output is given by

4. A method as claimed in claim 1, wherein the step of obtaining measurements comprises obtaining, from the one or more physiological sensors, an electrocardiogram signal, a photoplethysmogram signal, and at least one of heart sounds and an impedance cardiogram signal;

and wherein the step of processing comprises processing the electrocardiogram signal and photoplethysmogram signal to determine the pulse arrival time, and processing the at least one of the heart sounds or the impedance cardiogram signal and the electrocardiogram signal to determine the pre-ejection period.

5. A method as claimed in claim 1, further comprising the steps of:

comparing, with the processing unit, the measure of the cardiac output of the patient or measure of the change in the cardiac output of the patient to one or more threshold values; and

providing, with the processing unit, an output indicating the result of the step of comparing.

6. A method as claimed in claim 1, the method further comprising the steps of:

obtaining, with the processing unit, measurements of acceleration acting on the patient during the measurement of the physiological characteristics of the patient;

processing, with the processing unit, the measurements of acceleration to determine the posture of the patient;

comparing, with the processing unit, the determined posture of the patient to a predetermined posture for the patient; and

providing, with the processing unit, feedback to the patient regarding their posture if the determined posture is not the same or sufficiently close to the predetermined posture.

7. A method as claimed in claim 6, wherein the predetermined posture corresponds to the posture of the patient during a previous set of measurements of the physiological characteristics of the patient.

8. A method as claimed in claim 1, further comprising the step of:

processing, with the processing unit, the measurements to determine a measure of the systemic vascular resistance, SVR, of the patient from the measure of the cardiac output of the patient using the relationship;

SVR=MAP/CO

where MAP is the mean arterial blood pressure and is given by;

MAP=S/3+2D/3.

9. An apparatus for use in monitoring the cardiac output, CO, of a patient, the apparatus comprising:

a hardware processing unit configured to;

receive measurements of one or more physiological characteristics of the patient from one or more physiological sensors, the physiological characteristics including at least the heart rate, HR, of the patient, the systolic blood pressure, S, of the patient and the diastolic blood pressure, D, of the patient; and

process the measurements to determine a measure of the cardiac output of the patient;

wherein the measure of the cardiac output of the patient is derived using the relationship;

10. An apparatus as claimed in claim 9, wherein the measure of the cardiac output of the patient determined by the processing unit is a measure of the change in the cardiac output from an earlier cardiac output measurement or a reference measurement for cardiac output, and the processing unit is configured to process the measurements to determine the measure of the change in the cardiac output using:

11. An apparatus as claimed in claim 9, wherein the processing unit is further configured to:

compare the measure of the cardiac output of the patient or measure of the change in the cardiac output of the patient to one or more threshold values; and

provide an output indicating the result of the comparison.

12. An apparatus as claimed in claim 9, further comprising the one or more physiological sensors, the one or more physiological sensors including:

a blood pressure monitor, a heart rate sensor, an electrocardiogram sensor, a photoplethysmogram sensor, an impedance cardiogram sensor and one or more microphones.

13. An apparatus as claimed in claim 12, wherein the one or more physiological sensors are integrated into an item of clothing to be worn by the patient.

14. An apparatus as claimed in claim 9, wherein the processing unit is further configured to receive measurements of the acceleration acting on the patient and to process the measurements of the acceleration to determine the posture of the patient.