Apparatus and method for enhancing and analyzing signals from a continuous non-invasive blood pressure device
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.
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
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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.
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.
19. The device according to claim 12 , wherein the computing device receives anthropometric information from the patient.
20. The device according to claim 14 , wherein the computing device calculates physiological parameters from one or more input signals.