Method for estimating changes of cardiovascular indices using peripheal arterial blood pressure waveform

Abstract

The systems and methods described herein enable reliable estimation of cardiovascular indices on real-time, non-invasive or minimally-invasive, and beat-to-beat basis. Cardiovascular indices which can be estimated include), stroke volume (SV), without being limited to, cardiac output (CO and total peripheral resistance (TPR). In various embodiments, one or more of these indices are estimated continuously, on a beat-to-beat basis, using peripheral arterial blood pressure (ABP) waveforms and certain parameters derived from the peripheral ABP waveforms. The derived parameters are substantially insensitive to distortions of the ABP waveform arising from tapered arterial branches throughout the arterial tree. The methods described herein can provide a more accurate and reliable estimate of hemodynamic parameters than existing techniques.

1 . Method for estimating stroke volume of a cardiac cycle of a heart comprising:
 a. recording an arterial blood pressure signal;   b. processing the arterial blood pressure signal to obtain a plurality of parameters which are insensitive to distortions resulting from the propagation of the arterial pulse through the arterial tree;   c. incorporating the parameters into a formula or algorithm to estimate the stroke volume of the cardiac cycle of the heart.   
     
     
         2 . Method of  claim 1  wherein the parameters include one or more of the following: mean arterial pressure of the cardiac cycle, end-diastolic pressure of the cardiac cycle, end-diastolic pressure of the immediately preceding cardiac cycle, duration of the cardiac cycle, duration of systole of the cardiac cycle. 
     
     
         3 . Method of determining the stroke volumes of a plurality of cardiac cycles of the heart comprising applying the method of  claim 1  to multiple cardiac cycles of the heart. 
     
     
         4 . Method of  claim 1  wherein the formula or algorithm incorporates a model. 
     
     
         5 . Method of  claim 4  wherein the model is a Windkessel type model. 
     
     
         6 . Method of  claim 4  wherein the formula or algorithm incorporates one or more means of fitting the arterial blood pressure signal to one or more models. 
     
     
         7 . Method of  claim 6  wherein the formula or algorithm incorporates one or more means of fitting the arterial blood pressure signal to a Windkessel type model. 
     
     
         8 . Method of  claim 1  wherein the formula or algorithm takes into account the number of dimensionless parameters. 
     
     
         9 . Method of  claim 1  further comprising estimating the characteristic time constant of the cardiac cycle. 
     
     
         10 . Method of  claim 9  further wherein the time constant associated with the cardiac cycle is estimated from time constants estimated for a plurality of cardiac cycles preceding and/or following the cardiac cycle. 
     
     
         11 . Method of  claim 3  further comprising the estimation the cardiac output 
     
     
         12 . Method of  claim 3  further comprising the estimation of the total peripheral vascular resistance. 
     
     
         13 . Method of  claim 1  wherein the arterial pressure signal is obtained from an intra-arterial measurement location. 
     
     
         14 . Method of  claim 1  wherein the arterial pressure signal is obtained from a noninvasive blood pressure measuring device. 
     
     
         15 . Method of  claim 2  wherein the duration of systole parameter involves a measurement of the time elapsed between the onset of systole and the peak arterial blood pressure. 
     
     
         16 . Method of  claim 1  wherein coefficients associated with the formula or algorithm are determined by analyzing a training set of arterial blood pressure signal data for which the associated stroke volumes have been independently measured. 
     
     
         17 . System for estimating stroke volume of a cardiac cycle of a heart comprising:
 a. recording means for recording an arterial blood pressure signal;   b. a processor for processing the arterial blood pressure signal to obtain a plurality of parameters which are insensitive to distortions resulting from the propagation of the arterial pulse through the arterial tree; and   c. computer means for incorporating the parameters into a formula or algorithm to estimate the stroke volume of the cardiac cycle of the heart.   
     
     
         18 . The system of  claim 17 , wherein the parameters include one or more of the following: mean arterial pressure of the cardiac cycle, end-diastolic pressure of the cardiac cycle, end-diastolic pressure of the immediately preceding cardiac cycle, duration of the cardiac cycle, duration of systole of the cardiac cycle. 
     
     
         19 . The system of  claim 17  adapted to determining the stroke volume of a plurality of cardiac cycles of the heart. 
     
     
         20 . The system of  claim 17  wherein the formula or algorithm incorporates a model. 
     
     
         21 . The system of  claim 20  wherein the model is a Windkessel type model. 
     
     
         22 . The method of  claim 20  wherein the formula or algorithm incorporates one or more means of fitting the arterial blood pressure signal to one or more models. 
     
     
         23 . The system of  claim 22  wherein the formula or algorithm incorporates one or more means of fitting the arterial blood pressure signal to a Windkessel type model. 
     
     
         24 . The system of  claim 17  wherein the formula or algorithm takes into account the number of dimensionless parameters. 
     
     
         25 . The system of  claim 17  further comprising means for estimating the characteristic time constant of the cardiac cycle. 
     
     
         26 . The system of  claim 25  wherein the time constant associated with the cardiac cycle is estimated from time constants estimated for a plurality of cardiac cycles preceding and/or following the cardiac cycle. 
     
     
         27 . The system of  claim 19  further comprising means for estimating the cardiac output. 
     
     
         28 . The system of  claim 19  further comprising means for estimating the total peripheral vascular resistance. 
     
     
         29 . The system of  claim 17  wherein the arterial pressure signal is obtained from an intra-arterial measurement location. 
     
     
         30 . The system of  claim 17  wherein the arterial pressure signal is obtained from a non-invasive blood pressure measuring device. 
     
     
         31 . The system of  claim 18  wherein the duration of systole parameter involves a measurement of the time elapsed between the onset of systole and the peak arterial blood pressure. 
     
     
         32 . The system of  claim 17  wherein coefficients associated with the formula or algorithm are determined by analyzing a training set of arterial blood pressure signal data for which the associated stroke volumes have been independently measured.