HEMODYNAMIC MONITOR AND METHOD OF HEMODYNAMIC MONITORING

• US 20130006126A1
• Filed: 02/10/2011
• Published: 01/03/2013
• Est. Priority Date: 02/11/2010
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: Lidco Group, PLC (Masimo Corporation)
• Inventors: O'Brien, Terence Kevin, Wolff, Christopher Bancroft, Band, David Marston, Mills, Eric, Douglas, James Arthur
• Granted Patent: US 10,188,303 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 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02108 from analysis of pulse wave characteristics
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence

Abstract

An apparatus and method for determining stroke volume. The apparatus receives an arterial pressure waveform and is arranged to correct a part of the pressure waveform that relates to a heart beat for an influence of an ectopic heart beat, of atrial fibrillation on the pressure waveform or of changes in the pressure waveform'"'"'s baseline. The apparatus also comprising means arranged to calculate the stroke volume from the corrected waveform.

Claims

1. An apparatus for determining stroke volume comprising:

an input for receiving an arterial pressure waveform;

means for defining a start point within the pressure waveform at the beginning of a systolic arterial pressure increase of a ventricular contraction phase of a heart beat;

means arranged to determine an end point of the heart beat by identifying a part or point of the pressure waveform that has substantially the same arterial pressure value as said starting point, and, if said arterial pressure value at said starting point is not regained, extrapolating the pressure waveform to a point where it has substantially the same arterial pressure value as said starting point; and

means for calculating the stroke volume from a part of the pressure waveform or of the extrapolated pressure waveform between the start point and the end point.

4. An apparatus according to claim 1, further arranged to identify a trend in the last half, third, quarter or fifth of a part of the pressure waveform relating to one heart beat and extrapolating the pressure waveform by continuing the identified trend until a value substantially corresponding to the value of the start point is reached.

5. An apparatus according to claim 4, wherein identifying said trend comprises determining a gradient in the said part of the pressure waveform and wherein continuing the trend comprises extending the pressure waveform using the determined gradient.

6. An apparatus according to claim 1, further arranged to apply a non-linear correction to the waveform.

7. An apparatus according to claim 1, further arranged to calculate the stroke volume by determining the pulsatility of the part of the pressure waveform relating to a heart beat between the start point and the end point.

8. An apparatus according to claim 7, further arranged to determine an absolute stroke volume by multiplying the pulsatility with a calibration factor specific to a patient.

9. An apparatus according to claim 1, arranged to determine cardiac output by multiplying stroke volume with a heart rate.

10. An apparatus according to claim 1, arranged to store the stroke volumes or cardiac outputs for a number of heart beats and to provide an indication should a fluctuation in the stroke volume or the cardiac output over time exceed a predetermined value.

11. An apparatus according to claim 1, further arranged to determine a heart rate based on the received pressure waveform by performing autocorrelation on the pressure waveform over a number of consecutive beats.

12. An apparatus according to claim 1, further comprising an output means and arranged to output an indication of at least one of a current stroke volume, a current heart rate, a number of previous stroke volumes and a number of previous heart rates.

13. An apparatus for monitoring patient respiration comprising an apparatus according to claim 1, the apparatus arranged to determine a respiratory rate based on cyclic changes in the stroke volume or cardiac output.

41. An apparatus according to claim 1 arranged to determine a respiratory rate based on cyclic changes in the stroke volume or cardiac output.

2. An apparatus for determining cardiac stroke volume comprising:

an input for receiving an arterial pressure waveform;

means arranged to identify a baseline change in the arterial pressure waveform;

means arranged to identify a part of the pressure waveform relating to a heart beat;

means arranged to correct the identified part to account for said baseline change; and

means arranged to calculate the stroke volume from the corrected part of the pressure waveform.

32. An apparatus according to claim 2, further arranged to identify a trend in the last half, third, quarter or fifth of a part of the arterial pressure waveform relating to one heart beat and extrapolating the arterial pressure waveform by continuing the identified trend until a value substantially corresponding to the value of the start point is reached.

33. An apparatus according to claim 32, wherein identifying said trend comprises determining a gradient in the said part of the arterial pressure waveform and wherein continuing the trend comprises extending the pressure waveform using the determined gradient.

34. An apparatus according to claim 2, further arranged to apply a non-linear correction to the pressure waveform.

35. An apparatus according to claim 2, further arranged to calculate the stroke volume by determining the pulsatility of the part of the pressure waveform relating to a heart beat between the start point and the end point.

36. An apparatus according to claim 35, further arranged to determine an absolute stroke volume by multiplying the pulsatility with a calibration factor specific to a patient.

37. An apparatus according to claim 2, arranged to determine cardiac output by multiplying stroke volume with a heart rate.

38. An apparatus according to claim 2, arranged to store the stroke volumes or cardiac outputs for a number of heart beats and to provide an indication should a fluctuation in the stroke volume or the cardiac output over time exceed a predetermined value.

39. An apparatus according to claim 2, further arranged to determine a heart rate based on the received arterial pressure waveform by performing autocorrelation on the arterial pressure waveform over a number of consecutive beats.

40. An apparatus according to claim 2, further comprising an output means and arranged to output an indication of at least one of a current stroke volume, a current heart rate, a number of previous stroke volumes, or a number of previous heart rates.

3. An apparatus for determining cardiac stroke volume comprising an input for receiving an arterial pressure waveform, the apparatus arranged to correct a part or point of the pressure waveform that relates to a single heart beat for an influence of an ectopic heart beat or of atrial fibrillation or of respiratory changes on the pressure waveform, the apparatus further comprising means arranged to calculate the stroke volume from the corrected part of the pressure waveform relating to the single heart beat.

14-31. -31. (canceled)