Lawrence Medical Systems, Inc.

Barry D McLaren

Stephen R Barnes

Gary L Tarbox

Lee L Huntsman

Richard S Leard

A method and apparatus for ascertaining the cardiac output of a human patient, said method comprising the steps of: measuring the systolic velocity of the blood flowing through the patient's descending aorta; determining the cross-sectional area of the patient's ascending aorta; and calculating the patient's cardiac output from said systolic velocity and said aortic area. The cardiac output can be converted: (1) to cardiac index by dividing it by the patient's body surface area, and (2) to systemic vascular resistance by dividing a value representing the patient's blood pressure by said cardiac output.

Methods and apparatus for monitoring cardiac output

A method and system for the noninvasive measurement of cardiac output of a mammalian patient on a real time, beat-by-beat basis as a combined function of the cross-sectional area of the ascending aorta and the systolic velocity of blood flow therethrough is comprised of the steps of and apparatus for pulsedly insonifying the ascending aorta of the patient with repetitive, intermittent ultrasonic energy propagating through the patient's cardiac window; receiving pulses of ultrasonic energy reflected from the anatomical structure within the first insonification zone, including energy reflected from the aortic walls and characteristic of the dimensional separation thereof; developing an aortic diameter signal indicative of dimensional separation; computing the cross-sectional area of the ascending aorta therefrom; then continuously insonifying the ascending aorta with uninterrupted ultrasonic energy; receiving a Doppler-shifted ultrasonic energy signal reflected from pulsatile blood flow through the ascending aorta, and characteristic of systolic velocity of blood flow; subjecting the systolic velocity signal to a frequency spectrum analysis at a predetermined signal sampling rate to yield a velocity component profile signal; integrating the velocity component profile signal over time; computing systolic volume as a combined function of cross-sectional area and the systolic velocity integral for each of n cardiac cycles; and, computing cardiac output as the time-averaged sum of systolic volumes for the n periods.

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Auburn, WA, United States of America

Barry D McLaren