Method and system for extracting cardiac parameters from plethysmographic signals

• US 20060036183A1
• Filed: 07/08/2004
• Published: 02/16/2006
• Est. Priority Date: 03/26/2002
• Status: Active Grant

• Current Assignee: Adidas AG
• Original Assignee: VivoMetrics, Inc.
• Inventors: Inman, Dana Michael, Sackner, Marvin, Keenan, Desmond Barry
• Granted Patent: US 7,604,603 B2
• Time in Patent Office: Days
• US Class Current: 600/481
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• 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 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/1135 by monitoring thoracic expansion
• CPC Class Codes: A61B 5/6804 Garments; Clothes
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence

Abstract

A method and system for extracting cardiac parameters from a plethysmographic signal is described wherein the plethysmographic signal is passed through a first filter to remove non-cardiac components of the signal. A second filter averages a plurality of cardiac cycles and cardiac parameters are extracted from the averaged cardiac signal.

Claims

10. A method for extracting a cardiac component from a plethysmographic signal, the plethysmographic signal being responsive to cardiac motion, the method comprising the steps of:

performing a frequency domain filtering operation on the plethysmographic signal producing a filtered signal, wherein the frequency domain filtering operation comprises applying a band-pass filter having a lower corner frequency that varies in dependence on current heart rate; and

outputting the filtered signal.

11. The method of claim 10 further comprising, prior to outputting the filtered signal, performing a time domain filtering operation which comprises ensemble averaging timed by the occurrences of electrocardiographic R waves.

12. The method of claim 10 further comprising extracting from the output signal one or more cardiac parameters selected from the group consisting of stroke volume, cardiac output, pre-ejection period, peak ejection rate, and time to peak ejection rate.

13. A system for extracting a cardiac component from a plethysmographic signal, the plethysmographic signal being responsive to cardiac motion, the system comprising a processor coupled to a memory, wherein the memory includes stored instructions for causing the processor to

perform a frequency domain filtering operation on the plethysmographic signal producing a filtered signal, wherein the frequency domain filtering operation comprises applying a band-pass filter having a lower corner frequency that varies in dependence on current heart rate;

and

output the filtered signal.

14. The system of claim 13 wherein the processor further, prior to outputting the filtered signal, performs a time domain filtering operation which comprises ensemble averaging timed by the occurrences of electrocardiographic R waves.

15. The system of claim 13 wherein the processor further extracts from the output signal one or more cardiac parameters selected from the group consisting of stroke volume, cardiac output, pre-ejection period, peak ejection rate, and time to peak ejection rate.

16-1. The system of claim 16 wherein the processor further extracts from the output signal one or more cardiac parameters selected from the group consisting of stroke volume, cardiac output, pre-ejection period, peak ejection rate, and time to peak ejection rate.