Abstract: 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.

Abstract: An ultrasonic probe for insonifying the ascending aorta of a supine or reclining human patient. The probe has a head housing transducers for insonifying the patient's ascending aorta and for intercepting doppler-shifted energy reflected from the proximate and distal walls of the ascending aorta and from blood flowing through the aorta. The transducer head is integral with and extends below the handle of the probe, facilitating the manipulation of the probe and alignment of the beam of ultrasonic energy propagated by the probe relative to the ascending aorta of the patient. An oval cross-section and trapezoidal profile allow this to be done with a minimum of discomfort to either the patient or the user of the probe, and an L- or T-shaped handle allows the probe to be positioned and manipulated from a position behind the patient's head and with little or no sight of the patient's suprasternal notch.