Apparatus and method for enhancing and analyzing signals from a continuous non-invasive blood pressure device

• US 8,814,800 B2
• Filed: 10/29/2010
• Issued: 08/26/2014
• Est. Priority Date: 10/29/2009
• Status: Active Grant

• Current Assignee: CNSystems Medizintechnik AG
• Original Assignee: CNSystems Medizintechnik AG
• Inventors: Fortin, Jrgen, Grllenberger, Rupert
• Primary Examiner(s): Natnithithadha, Navin
• Application Number:
  US12/915,496
• Publication Number:
  US 20110105918A1
• Time in Patent Office: 1,397 Days
• Field of Search: 600500-504, 600/507, 600/473, 600475-481, 600/483
• US Class Current: 600/485
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/02241 of small dimensions, e.g. adapted to fingers
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal

Abstract

A system and method of enhancing a blood pressure signal is disclosed. The volume of an artery in a finger is measured by a photo-plesthysmographic (PPG) system, which produces a PPG signal. This PPG system is placed inside a cuff, and the cuff pressure is controlled by the PPG signal. The portion or component of the PPG signal having a frequency higher than a predefined threshold frequency is then modified or enhanced, such as by multiplying the high frequency component by a calibration factor. A blood pressure signal is then calculated using the cuff pressure and the modified PPG signal. A blood pressure contour curve may then be generated, and a variety of parameters may be calculated using the curve.

Claims

1. A method for determining a blood pressure contour curve comprising:

placing a cuff having a photo-plethysmographic (PPG) system over an artery in a human finger, the PPG system producing a PPG signal based on volume of the artery, the PPG system including at least one light source and at least one light detector;

modifying, by a computing device, a component of the PPG signal having a frequency higher than a predefined threshold frequency by eliminating from the PPG signal an undesired portion of the PPG signal and reconstructing the PPG signal from the remaining portion of the PPG signal;

the cuff pressure being controlled by one or more components of the modified PPG signal; and

calculating, by the computing device, a blood pressure signal using at least the modified component of the PPG signal.

2. The method of claim 1 wherein a new blood pressure is calculated using the cuff pressure and the modified PPG signal.

3. The method of claim 2 wherein modifying a component of the PPG signal having a frequency higher than a predefined threshold frequency further comprises:

separating the PPG signal into a first component having a frequency higher than the predefined threshold frequency and a second component having a frequency lower than the predefined threshold frequency;

modifying the first component; and

adding the modified first component to the second component to create a modified PPG signal;

using the modified PPG signal and the cuff pressure to calculate the blood pressure signal.

4. The method of claim 2 wherein the modification further includes calibrating a component of the blood pressure signal having a frequency higher than a predefined threshold frequency using a value obtained for blood pressure by a sphygmomanometer placed on an artery in a human upper arm.

5. The method of claim 2 wherein the modification further includes multiplying a component of the blood pressure signal having a frequency higher than a predefined threshold frequency by a calibration factor, the calibration factor being calculated from a blood pressure measurement from a sphygmomanometer placed on an artery in a human upper arm.

6. The method according to claim 2, wherein the threshold frequency is about 0.3 Hz.

7. The method according to claim 2, wherein the calculation uses anthropometric parameters.

8. The method according to claim 2, further comprising calculating physiological parameters from the blood pressure contour curve.

9. The method according to claim 8, wherein the parameters are calculated by using multiport algorithms.

10. The method according to claim 8, wherein the parameters are calculated by using one or more markers of input signals.

11. The method according to claim 1, wherein the reconstruction is calculated from the pulsatile part of the remaining portion of the PPG signal.

12. The method according to claim 11, wherein the reconstructed PPG signal is

13. The method according to claim 1, wherein the part of the PPG signal having the undesired portion of the PPG signal is below a predetermined frequency.

19. The device according to claim 12, wherein the computing device receives anthropometric information from the patient.

14. A device for determining a blood pressure contour curve comprising:

a pressure cuff adapted to be placed over an artery in a human finger, the cuff including a PPG system having at least one light source and at least one light detector;

a pressure sensor;

a controller for controlling the pressure in the cuff;

wherein the PPG system produces a PPG signal based on volume of the artery, a pressure signal is calculated by a computing device using the PPG signal, and the pressure signal is continuously applied to the cuff and finger;

wherein the computing device modifies a component of the PPG signal having a frequency higher than a predefined threshold frequency and calculates a blood pressure signal using the cuff pressure and the modified PPG signal; and

wherein the controller uses the one or more components of the modified PPG signal to control the pressure in the cuff.

15. The device according to claim 14, wherein the computing device receives control state information from the controller.

16. The device according to claim 14, wherein the computing device receives information from a calibration device.

17. The device according to claim 14, wherein the computing device receives scaling information from another device.

18. The device according to claim 14, where the computing device receives information from a hydrostatic correction system.

20. The device according to claim 14, wherein the computing device calculates physiological parameters from one or more input signals.