Central pressure waveform with features preserved

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.

1 - 22 . (canceled) 
     
     
         23 . A blood pressure measuring system for determining a calibrated aortic pressure waveform with cardiovascular waveform features preserved the system comprising:
 a brachial cuff device having a brachial cuff, a tube, a pressure pump with a control unit, and a pressure sensor that provides an analog signal, said brachial cuff device being capable of measuring a patient's brachial systolic pressure (SPB) and brachial diastolic pressure (DPB) by oscillometric technique;   the control unit controlling the inflation of the brachial cuff around a patient's upper arm to a constant pressure within a predetermined pressure range, wherein the predetermined pressure range is one of less than the patient's brachial diastolic pressure DPB as measured by the brachial cuff device by oscillometric technique, between the patient's brachial diastolic pressure DPB and the brachial systolic pressure SPB as measured by the brachial cuff device by oscillometric technique, and above the patient's brachial systolic pressure SPB as measured by the brachial cuff device by oscillometric technique;   a digital signal processor comprising a low pass filter and a high pass filter that receives the analog signal from the pressure sensor when the cuff pressure is maintained at a constant pressure within the predetermined pressure range and outputs a digital brachial cuff signal containing filtered data that preserves cardiovascular waveform features of the patient's brachial cuff volumetric displacement waveform, said preserved cardiovascular waveform features comprising a first shoulder, a second shoulder and an incisura; and   software on a computer that calibrates the brachial cuff volumetric displacement waveform using at least two of the patient's brachial systolic pressure (SPB) as measured by the brachial cuff device by oscillometric technique, the patient's brachial mean pressure (MPB) and the patient's brachial diastolic pressure (DPB) as measured by the brachial cuff device by oscillometric technique, wherein the patient's brachial mean pressure (MPB) if used is calculated by the brachial cuff device based on measured values for the patient's brachial systolic pressure (SPB) and the patient's brachial diastolic pressure (DPB), and the software further converts the calibrated brachial cuff volumetric displacement waveform with cardiovascular waveform features preserved to a calibrated aortic pressure waveform with cardiovascular waveform features preserved by using one or more generalized transfer functions;   wherein each of the one or more generalized transfer functions are determined specifically for application to a calibrated brachial cuff volumetric displacement waveform measured by the brachial cuff inflated to a pressure within the predetermined pressure range, said one or more generalized transfer functions representing the harmonic ratio in amplitude and phase to transform the calibrated brachial cuff volumetric displacement waveform with cardiovascular waveform features preserved to the calibrated aortic pressure waveform with cardiovascular waveform features preserved when the brachial cuff is inflated to a pressure within the selected pressure range.   
     
     
         24 . A blood pressure measuring system as recited in  claim 23  wherein software also uses a generalized calibration transfer function to reduce error in the estimation of aortic systolic pressure, which would be introduced by calibrating the cuff volume pulse with the measured brachial SP B  and DP B  values. 
     
     
         25 . A blood pressure measuring system as recited in  claim 23  wherein the one or more generalized transfer functions includes a generalized transfer function that transforms the calibrated brachial cuff waveform directly to an aortic pressure waveform. 
     
     
         26 . A blood pressure measuring system as recited in  claim 23  wherein one or more generalized transfer functions comprise at least a first generalized transfer function that transforms the calibrated brachial cuff waveform to an intermediate artery pressure waveform and a second generalized transfer function that transforms the intermediate artery pressure waveform to an aortic pressure waveform. 
     
     
         27 . A blood pressure measuring system as recited in  claim 23  wherein the predetermined pressure range is 10-90% of the diastolic pressure (DP B ). 
     
     
         28 . A blood pressure measuring system as recited in  claim 23  further comprising multiple generalized transfer functions each being based on cuff pressures within a predetermined pressure range. 
     
     
         29 . A blood pressure measuring system as recited in  claim 23  wherein the predetermined pressure range is between SP B  and DP B  and cuff pressure 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%. 
     
     
         30 . A blood pressure measuring system as recited in  claim 23  wherein the predetermined pressure range is above SP B  and the cuff pressure is in the following range
     P   Cuff =[( K  %)+1]SP B    
 
       where K % ranges from 10 to 90%. 
     
     
         31 . A blood pressure measuring system as recited in  claim 23  wherein the calibrated brachial cuff waveform that is converted using one or more generalized transfer functions to the calibrated aortic pressure waveform with its cardiovascular waveform features preserved comprises an average of multiple recorded and calibrated brachial cuff waveforms measured by the inflated cuff around the patient's upper arm.