METHOD AND APPARATUS FOR A CONTINUOUS NON-INVASIVE AND NON-OBSTRUSIVE MONITORING OF BLOOD PRESSURE

• US 20090163821A1
• Filed: 12/22/2008
• Published: 06/25/2009
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: CSEM Centre Suisse d'Electronique et de Microtechnique SA Recherche et Développement
• Original Assignee: CSEM Centre Suisse D'Electronique et de Microtechnique SA
• Inventors: SOLA I CAROS, Josep, LOELIGER, Hans-Andrea
• Granted Patent: US 8,585,605 B2
• Time in Patent Office: Days
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• 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 5/0295 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 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]

Abstract

The invention provides a method and an apparatus for a continuous non-invasive and non-obstrusive monitoring of blood pressure. The method comprises the steps of: a) measuring the value (PW) of a Pulse Wave parameter, equal to or derived from the Pulse Wave Velocity (PWV) parameter of a segment of the arterial tree of a subject, b) measuring the value (CO) of the Cardiac Output parameter, and c) determining the value (BP) of the blood pressure that satisfies

$BP=\underset{\mathrm{BP}}{\arg \min }d\left(PW,\left(CO,BP\right)\right),$

where PW is the value measured in step a), (CO, BP) corresponds to a predicted value of the Pulse Wave parameter computed according to a model of the segment of the arterial tree, the value (CO) of the Cardiac Output parameter measured in step b) and an hypothesized value of the blood pressure.

Claims

1. Method for a continuous non-invasive and non-obtrusive monitoring of blood pressure (BP), comprising the steps of:

a) measuring the value (PW) of a Pulse Wave parameter, equal to or derived from the Pulse Wave Velocity (PWV) parameter of a segment of the arterial tree of a subject,

b) measuring the value (CO) of the Cardiac Output parameter, and

c) determining the value (BP) of the blood pressure that satisfies

$\mathrm{BP}=\underset{\mathrm{BP}}{\mathrm{argmin}}<br><br><br><br>d<br><br>\left(\mathrm{PW},<br><br>\left(\mathrm{CO},\mathrm{BP}\right)\right),$

where PW is the value measured in step a), (CO, BP) corresponds to a predicted value of the Pulse Wave parameter computed according to a model of the segment of the arterial tree, the value (CO) of the Cardiac Output parameter measured in step b) and an hypothesized value of the blood pressure.

2. Method according to claim 1, wherein the hypothesized value of the blood pressure used in step c) is determined from an hypothesized value of at least one of geometric and elastic characteristics of the involved vessels in the segment of the arterial tree, and wherein said step c) comprises the steps of:

i) hypothesizing a value of at least one of geometric and elastic characteristics of the involved vessels in the segment of the arterial tree,

ii) from said hypothesized value of said geometric and elastic characteristic, determining an expected value of the Pulse Wave parameter by using a model relating the Pulse Wave parameter, the Cardiac Output parameter and said geometric and elastic characteristic,

iii) computing the distance between said expected Pulse Wave parameter value and said measured Pulse Wave parameter value (PW),

iv) repeating steps i), ii), and iii) until the distance between the expected Pulse Wave parameter value and the measured Pulse Wave parameter value (PW) is minimized in order to determine an estimated value of said geometric and elastic characteristic,

v) from said estimated value of the geometric and elastic characteristic determined in step iv), determining the value (BP) of the blood pressure by using a model relating the blood pressure, said Cardiac Output parameter, and said geometric and elastic characteristic.

3. Method according to claim 1, wherein the Pulse Wave parameter is the Pulse Wave Velocity (PWV) parameter or the Pulse Transit Time (PTT) parameter.

4. Method according to claim 2, wherein said geometric and elastic characteristic is the diameter of the vessels in the segment.

5. Method according to claim 2, wherein the model relating the Pulse Wave parameter, the Cardiac Output parameter and said geometric and elastic characteristic is theoretical.

6. Method according to claim 2, wherein the model relating the blood pressure, the Cardiac Output parameter and said geometric and elastic characteristic is theoretical.

7. Method according to claim 2, wherein the model relating the Pulse Wave parameter, the Cardiac Output parameter, and said geometric and elastic characteristic is empirical.

8. Method according to claim 2, wherein the model relating the blood pressure, the Cardiac Output parameter, and said geometric and elastic characteristic is empirical.

9. Method according to claim 1, wherein the Pulse Wave parameter measured in step a) is measured only by means of optic and electric sensing technologies.

10. Method according to claim 9, wherein the optic technology is Photoplethysmography (PPG) and the electric technologies are Electrocardiography (ECG) and Impedance Pleythysmography (IPG).

11. Method according to claim 1, wherein the Cardiac Output parameter measured in step b) is measured only by means of electric sensing technologies, by measuring the Heat Rate (HR) parameter and the Stroke Volume (SV) parameter.

12. Method according to claim 11, wherein the electric technologies are Electrocardiography (ECG) and Impedance Pleythysmography (IPG).

13. Method according to claim 1, further comprising a step d) of storing and/or displaying the value (BP) of the blood pressure determined in step c).

14. Method according to claim 1, further comprising a step e) of determining the Total Peripheral Resistance (TPR) parameter from the value (BP) of the blood pressure determined in step c).

15. Method according to claim 14, further comprising a step f) of simultaneously storing and/or displaying several cardiovascular parameters selected from the group comprising the determined Total Peripheral Resistance (TPR), the determined value (BP) of the blood pressure, the value (CO) of the Cardiac Outpout parameter.

16. Apparatus for a continuous non-invasive and non-obstrusive monitoring of blood pressure, wherein said apparatus comprises:

means for measuring the Pulse Wave parameter, equal to or derived from the Pulse Wave Velocity (PWV) parameter of a segment of the arterial tree of a subject, and for providing at least one signal representative of said Pulse Wave parameter,

means for measuring the Cardiac Output parameter, and for providing at least one signal representative of said Cardiac Ouput parameter, and

means for determining the value of blood pressure (BP) that satisfies

$\mathrm{BP}=\underset{\mathrm{BP}}{\mathrm{argmin}}<br><br><br><br>d<br><br>\left(\mathrm{PW},<br><br>\left(\mathrm{CO},\mathrm{BP}\right)\right)$

where PW is the measured value of the Pulse Wave parameter, (CO, BP) corresponds to a predicted value of the Pulse Wave parameter computed according to a model of the segment of the arterial tree, the measured value (CO) of the Cardiac Output parameter and an hypothesized value of the blood pressure.

17. Apparatus according to claim 16, wherein the hypothesized value of the blood pressure is determined from a hypothesized value of at least one of geometric and elastic characteristics of the involved vessels in the segment of the arterial tree, and wherein said apparatus further comprises:

processing means for hypothesizing a value of at least one of geometric and elastic characteristics of the involved vessels in the segment and, from said hypothesized value of said geometric and elastic characteristic, determining an expected value of the Pulse Wave parameter by using a model relating the Pulse Wave parameter, the Cardiac Output parameter and said geometric and elastic characteristic,

processing means for comparing said expected Pulse Wave parameter value to said signal representative of the measured Pulse Wave parameter value and computing the distance between said expected Pulse Wave parameter value and said measured Pulse Wave parameter value (PW),

processing means for repeating the determination of an expected value of the Pulse Wave parameter from a hypothesized value of said geometric and elastic characteristic and the comparison of said expected Pulse Wave parameter value to said signal representative of the measured Pulse Wave parameter value, until the distance between the Pulse Wave parameter value and the measured Pulse Wave parameter value is minimized in order to determine an estimated value of said geometric and elastic characteristic,

computing means for determining the value (BP) of the blood pressure from said estimated value of said geometric and elastic characteristic by using a model relating the blood pressure, said Cardiac Output parameter, and said geometric and elastic characteristic,

means for storing and/or displaying the determined value (BP) of the blood pressure.

18. Apparatus according to claim 16, wherein the Pulse Wave parameter is the Pulse Wave Velocity (PWV) parameter or the Pulse Transit Time (PTT) parameter.

19. Apparatus according to claim 17, wherein said geometric and elastic characteristic is the diameter of the vessels in the segment.

20. Apparatus according to claim 17, wherein the model relating the Pulse Wave parameter, the Cardiac Output parameter, and said geometric and elastic characteristic is theoretical.

21. Apparatus according to claim 17, wherein the model relating the blood pressure, the Cardiac Output parameter and said geometric and elastic characteristic is theoretical.

22. Apparatus according to claim 17, wherein the model relating the Pulse Wave parameter, the Cardiac Output parameter, and said geometric and elastic characteristic is empirical.

23. Apparatus according to claim 17, wherein the model relating the blood pressure, the Cardiac Output parameter, and said geometric and elastic characteristic is empirical.

24. Apparatus according to claim 16, wherein means for measuring the Pulse Wave parameter use only optic and electric sensing technologies.

25. Apparatus according to claims 24, wherein the optic technology is Photoplethysmography (PPG) and the electric technologies are Electrocardiography (ECG) and Impedance Pleythysmography (IPG).

26. Apparatus according to claim 16, wherein means for measuring the Cardiac Output parameter use only electric sensing technologies.

27. Apparatus according to claim 26, wherein the electric technologies are Electrocardiography (ECG) and Impedance Pleythysmography (IPG).

28. Apparatus according to claim 16, wherein it further comprises means for computing the Total Peripheral Resistance (TPR) parameter from the determined value (BP) of the blood pressure.

29. Apparatus according to claim 28, wherein the means for storing and/or displaying the determined value (BP) of the blood pressure comprise means for simultaneously storing and/or displaying several cardiovascular parameters selected from the group comprising the determined Total Peripheral Resistance (TPR), the determined value (BP) of the blood pressure, the value (CO) of the Cardiac Outpout parameter.