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USCOM is the only method of cardiac output measurement to have achieved equivalent accuracy to the implantable flow probe. The method can be applied with equal accuracy to patients of all ages for the development of physiologically rational haemodynamic protocols. USCOM has been validated from 0.12 L/min to 18.7 L/min in new-born babies, children and adults. Real-time, automatic tracing of the Doppler flow profile allows beat-to-beat right-sided and left-sided Q measurements, simplifying operation and reducing the time of acquisition compared to conventional echocardiography. In comparison to the echocardiographic method, USCOM significantly improves reproducibility and increases sensitivity of the detection of changes in flow. It uses anthropometry to calculate aortic and pulmonary valve diameters and CSAs, allowing right-sided and left-sided Q measurements. Ultrasonic Cardiac Output Monitor (USCOM) uses continuous wave Doppler to measure the Doppler flow profile VTI. In the manner used in clinical practice, precision of SV and CO is of the order of ☒0%. Although it is in wide general use, the technique is time-consuming and is limited by the reproducibility of its component elements.

An alternative that is not necessarily more reproducible is the measurement of the pulmonary valve to calculate right-sided CO. 2D measurement of the aortic valve diameter is one source of noise others are beat-to-beat variation in stroke volume and subtle differences in probe position. It is said to require extensive training and skill, but the exact steps needed to achieve clinically adequate precision have never been disclosed. Although used in clinical medicine, it has a wide test-retest variability. The result is then multiplied by the heart rate (HR) to obtain cardiac output. 2D measurement of the diameter (d) of the aortic annulus allows calculation of the flow cross-sectional area (CSA), which is then multiplied by the VTI of the Doppler flow profile across the aortic valve to determine the flow volume per beat ( stroke volume, SV). Two-dimensional (2D) ultrasound and Doppler measurements are used together to calculate cardiac output. Echocardiography Įchocardiography is a non-invasive method of quantifying cardiac output using ultrasound.

VTI is the velocity time integral of the trace of the Doppler flow profile.īeing non-invasive, accurate and inexpensive, Doppler ultrasound is a routine part of clinical ultrasound it has high levels of reliability and reproducibility, and has been in clinical use since the 1960s.

CSA is the valve orifice cross sectional area,.

In cardiac physiology, cardiac output ( CO), also known as heart output and often denoted by the symbols Q Major factors influencing cardiac output – heart rate and stroke volume, both of which are also variable.