<P> Electrical Cardiometry is a non-invasive method similar to Impedance cardiography; both methods measure thoracic electrical bioimpedance (TEB). The underlying model differs between the two methods; Electrical cardiometry attributes the steep increase of TEB beat - to - beat to the change in orientation of red blood cells . Four standard ECG electrodes are required for measurement of cardiac output . Electrical Cardiometry is a method trademarked by Cardiotronic, Inc., and shows promising results in a wide range of patients . It is currently approved in the US for use in adults, children and babies . Electrical cardiometry monitors have shown promise in postoperative cardiac surgical patients, in both haemodynamicially stable and unstable cases . </P> <P> Velocity - encoded phase contrast Magnetic Resonance Imaging (MRI) is the most accurate technique for measuring flow in large vessels in mammals . MRI flow measurements have been shown to be highly accurate compared to measurements made with a beaker and timer, and less variable than the Fick principle and thermodilution . </P> <P> Velocity - encoded MRI is based on the detection of changes in the phase of proton precession . These changes are proportional to the velocity of the protons' movement through a magnetic field with a known gradient . When using velocity - encoded MRI, the result is two sets of images, one for each time point in the cardiac cycle . One is an anatomical image and the other is an image in which the signal intensity in each pixel is directly proportional to the through - plane velocity . The average velocity in a vessel, i.e., the aorta or the pulmonary artery, is quantified by measuring the average signal intensity of the pixels in the cross-section of the vessel then multiplying by a known constant . The flow is calculated by multiplying the mean velocity by the cross-sectional area of the vessel . This flow data can be used in a flow - versus - time graph . The area under the flow - versus - time curve for one cardiac cycle is the stroke volume . The length of the cardiac cycle is known and determines heart rate; Q can be calculated using equation (1). MRI is typically used to quantify the flow over one cardiac cycle as the average of several heart beats . It is also possible to quantify the stroke volume in real - time on a beat - for - beat basis . </P> <P> While MRI is an important research tool for accurately measuring Q, it is currently not clinically used for haemodynamic monitoring in emergency or intensive care settings . As of 2015, cardiac output measurement by MRI is routinely used in clinical cardiac MRI examinations . </P>

What are two ways to increase cardiac output