Detection of parameters in cardiac output related waveforms

• US 8,771,197 B2
• Filed: 06/24/2013
• Issued: 07/08/2014
• Est. Priority Date: 02/11/2009
• Status: Active Grant

• Current Assignee: Edwards Lifesciences Corporation
• Original Assignee: Edwards Lifesciences Corporation
• Inventors: Hatib, Feras, Roteliuk, Luchy
• Primary Examiner(s): DIETRICH, JOSEPH M
• Application Number:
  US13/925,349
• Publication Number:
  US 20130289427A1
• Time in Patent Office: 379 Days
• Field of Search: 600/509, 600/513, 600/519, 600/526
• US Class Current: 600/526
• 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 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• 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 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence

Abstract

Methods for detecting parameters in cardiac output related waveforms are described. The methods include methods for detecting individual heart beat cycles in a cardiac output related waveform, methods for detecting an error in an assigned starting point for an individual heart beat cycle in a cardiac output related waveform, methods for detecting a dichrotic notch for an individual heart beat cycle in a cardiac output related waveform, and methods for detecting an error in an assigned dichrotic notch for an individual heart beat cycle in a cardiac output related waveform. The identification of these parameters is important for a clinician as these parameters form the basis for the calculation of many other cardiac output related parameters.

Claims

1. A method for detecting an error in an assigned starting point for a first individual heart beat cycle in a cardiac output related waveform, the method comprising:

providing cardiac output related waveform data for the first individual heart beat cycle to a processing system, the first individual heart beat cycle having a predetermined starting point;

using the processing system to determine a maximum value of the cardiac output related waveform data;

using the processing system to determine a first point in the cardiac output related waveform, the first point being the first point on the cardiac output related waveform prior to the maximum value that has a value equal to one-half the maximum value;

using the processing system to search the portion of the first individual heart beat cycle between the starting point and the first point for a local maximum,

wherein if a local maximum is found, using the processing system to search the portion of the first individual heart beat cycle between the first point and the local maximum for a local minimum point, and reassigning the starting point for the first individual heart beat as the local minimum point.

2. The method of claim 1, further comprising using the processing system to find the starting point of the next individual heart beat, wherein the starting point of the next individual heart beat is the ending point for the first individual heart beat cycle.

3. A method for detecting a dichrotic notch for an individual heart beat cycle in a cardiac output related waveform, the method comprising:

providing cardiac output related waveform data for an individual heart beat cycle to a processing system, the individual heart beat cycle having a previously determined starting time point;

using the processing system to calculate a first derivative function for the waveform data;

using the processing system to determine a first time point and a second time point from the first derivative function, the first time point being the first zero crossing after the starting time point for the first derivative function and the second time point being the second zero crossing after the starting time point for the first derivative function;

using the processing system to calculate a second derivative function for the waveform data;

using the processing system to determine a third time point and a fourth time point from the second derivative function, the third time point being the first zero crossing after the second time point for the second derivative function and the fourth time point being the second zero crossing after the second time point for the second derivative function; and

using the processing system to search the portion of the second derivative function between the third time point and the fourth time point for a local maximum, the local maximum occurring at a fifth time point,

wherein the fifth time point corresponds to the time point at which the dichrotic notch is located in the cardiac output related waveform data for the individual heart beat cycle.

4. The method of claim 3, further comprising filtering the second derivative function using a low-pass filter.

5. A method for detecting an error in an assigned dichrotic notch for an individual heart beat cycle in a cardiac output related waveform, the method comprising:

providing cardiac output related waveform data for an individual heart beat cycle to a processing system, the individual heart beat cycle having a previously determined dichrotic notch time point, a previously determined starting time point, a previously determined cardiac output maximum point, and a previously determined ending time point;

using the processing system to calculate a first derivative function for the waveform data;

using the processing system to determine all the local maximums between the cardiac output maximum point and a search time point in the first derivative function, the search time point being at the starting time point plus two-thirds of the time between the starting time point and the ending time point,

wherein if more than one local maximum is found, the dichrotic notch is assigned to the time point at the second local maximum.