Brachial Cuff

• US 20110275944A1
• Filed: 05/05/2011
• Published: 11/10/2011
• Est. Priority Date: 05/07/2010
• Status: Active Grant

• Current Assignee: Atcor Medical Pty Ltd (CardieX Ltd.)
• Original Assignee: Atcor Medical Pty Ltd (CardieX Ltd.)
• Inventors: Qasem, Ahmad M.
• Granted Patent: US 9,314,170 B2
• Time in Patent Office: Days
• US Class Current: 600/493
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/0225 the pressure being controlled by electric signals, e.g. derived from Korotkoff sounds
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/7253 characterised by using transforms
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: G16H 10/40 for data related to laboratory analysis, e.g. patient specimen analysis
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass

Abstract

A method for determining a calibrated aortic pressure waveform from a brachial cuff waveform involves the use of one or more generalized transfer functions. The one or more generalized transfer functions are specific for predetermined brachial cuff pressure ranges, such as below diastolic pressure, between diastolic and systolic pressure, and above systolic pressure. The brachial cuff is inflated to a pressure within the pressure range appropriate for the generalized transfer function to be applied to the brachial cuff waveform to generate the aortic pressure waveform. In some circumstances, it may be necessary to use a calibration transfer function to generate a calibrated aortic waveform. In other circumstances, the calibration transfer function is not necessary.

Claims

1. In a blood pressure measuring system, a method for determining a calibrated aortic pressure waveform, the method comprising the steps:

inflating a brachial cuff around a patient'"'"'s upper arm to a pressure within a predetermined pressure range;

using the brachial cuff to record the patient'"'"'s brachial cuff waveform;

using at least two of systolic pressure (SP), mean pressure (MP) and diastolic pressure (DP) to calibrate the brachial cuff waveform; and

using one or more generalized transfer functions to convert the calibrated brachial cuff waveform to a calibrated aortic pressure waveform;

wherein each of the one or more generalized transfer functions are determined specifically for application to a brachial cuff waveform measured by the brachial cuff inflated to a pressure within the predetermined pressure range.

2. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the brachial cuff waveform is a volumetric displacement waveform.

3. A method of determining a calibrated aortic pressure waveform as recited in claim 1 further comprising the step of using a generalized calibration transfer function when converting the calibrated brachial cuff waveform to a calibrated aortic pressure waveform.

4. A method as recited in claim 1 wherein the calibrated aortic pressure waveform is displayed as a trace or otherwise on a computer display screen.

5. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the one or more generalized transfer functions includes a generalized transfer function that mathematically transforms the calibrated brachial cuff waveform to an aortic pressure waveform.

6. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein one or more generalized transfer functions comprise at least:

a first generalized transfer function that mathematically transforms the calibrated brachial cuff waveform to an intermediate artery pressure waveform and a second generalized transfer function that mathematically transforms the intermediate artery pressure waveform to an aortic pressure waveform.

7. A method as recited in claim 1 wherein the brachial cuff used to record the patient'"'"'s brachial cuff waveform is also used to determine the patient'"'"'s systolic (SP) and diastolic (DP) pressures.

8. A method for determining the calibrated aortic pressure waveform as recited in claim 1 wherein the predetermined pressure range is one of less than DP, between DP and SP, and above SP.

9. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the predetermined pressure range is 10-90% of the diastolic pressure (DP).

10. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the step of using at least two of SP, MP and DP to calibrate the brachial cuff waveform uses MP and DP, SP and DP, or MP and SP to calibrate the brachial cuff waveform.

11. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the one or more generalized transfer functions are estimated from simultaneously recorded data for a general population.

12. A method for determining a calibrated aortic pressure waveform as recited in claim 1 wherein the one or more generalized transfer functions operate in the frequency domain.

13. A method for determining a calibrated aortic pressure waveform as recited in claim 1 wherein the one or more generalized transfer functions operate in the time domain.

14. A method for determining a calibrated aortic pressure waveform as recited in claim 1 wherein at least one of the one or more generalized transfer functions are embodied in a filter.

15. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the brachial cuff is part of a device that comprises a brachial cuff, a tube, a pressure pump with a pressure control system, a pressure sensor that provides an analog signal and a digital signal processor that receives the analog signal from the pressure sensor and outputs a digital brachial cuff signal.

16. A method of determining a calibrated aortic pressure waveform as recited in claim 15 wherein a USB cable connects the digital signal processor of the brachial cuff device to a computer.

17. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the one or more generalized transfer functions are implemented by software on a computer.

18. A method for determining a calibrated aortic pressure waveform as recited in claim 11 wherein the simultaneously recorded data for the central aortic pressure waveform is determined in the general population using a non-invasive technique to determine equivalent aortic pressure waveform.

19. A method of determining a calibrated aortic pressure waveform as recited in claim 11 wherein the simultaneously recorded data for the central aortic pressure waveform is determined in the general population using a catheter to directly measure central aortic pressure.

20. A method for determining a calibrated aortic pressure waveform as recited in claim 1 wherein the blood pressure measuring system includes multiple generalized transfer functions each being based on cuff pressures within a predetermined pressure range.

21. A method for determining a calibrated aortic pressure waveform as recited in claim 1 wherein the predetermined pressure range is between SP and DP and piece of cuff is defined by the following equation

P_Cuff=(K %)(SP_B−

DP_B)+DP_B

where K % is chosen to be between 10 and 90%.

22. A method of determining a calibrated aortic pressure waveform as recited in claim 1 wherein the predetermined pressure range is above SP and the cuff pressure is in the following range

P_Cuff=[(K %)+1]SP_B

where K % ranges from 10 to 90%.